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Mimura K, Kono K, Takahashi A, Kawaguchi Y, Fujii HVascular endothelial growth factor inhibits the function of human mature dendritic cells mediated by VEGF receptor-2. Cancer Immunol Immunother 56:761-770
Abstract
Dendritic cells (DCs) are the most potent antigen-presenting cells and play a central role in the host-antitumor immunity. Since it has been reported that vascular endothelial growth factor (VEGF) inhibits the functional maturation of immature-DCs and impairs DC differentiation, it is important to elucidate the mechanisms of VEGF-induced DC-dysfunction. To investigate the effects of VEGF against human mature DCs, we investigated how VEGF affects mature DCs with regards to phenotype, induction of apoptosis, IL-12(p70) production and the antigen-presenting function evaluated by allogeneic mixed leukocyte reaction (allo-MLR). We generated monocyte-derived DCs matured with lipopolysaccharide, OK-432 or pro-inflammatory cytokine cocktails. As a result, VEGF treatment did not alter the mature DCs with regard to phenotype, IL-12(p70) production and induction of apoptosis. As a novel and important finding, VEGF inhibited the ability of mature DCs to stimulate allogeneic T cells. Furthermore, this VEGF-induced DC dysfunction was mainly mediated by VEGF receptor-2 (VEGF R2). These observations were confirmed by the findings that the VEGF-induced DC dysfunction was recovered by anti-human VEGF neutralizing mAb or anti-human VEGF R2 blocking mAb, and that placenta growth factor (PlGF), VEGF R1-specific ligand, did not have any effect against mature DCs. Some modalities aiming at reversing mature-DC dysfunction induced by VEGF will be needed in order to induce the effective antitumor immunity.
... Mature DCs were harvested and treated with or without 50 ng/ mL recombinant human VEGF-165 (rhVEGF-165; R&D Systems) for 24 hours at 37°C according to the procedures described by Mimura et al. 20 The working concentrations were determined based on previous reports 9,10,15,22 and our preliminary experiments. As an inhibitor for RhoA signaling and BP for P-COF1, 10 μmol/L Y27632 (Sigma) and 1 μg/mL Ser3-P-COF1 BP (ECM Biosciences), as well as the BAs of goat anti-human VEGFR1 mAb (10 μg/mL) and mouse anti-human VEGFR2 mAb (50 ng/ mL), 20 were respectively applied to treat mDCs for 30 minutes before administration of rhVEGF-165. Untreated mDCs and mDCs treated with 50 ng/mL mouse anti-human IgG (Sigma) served as blank and negative controls, respectively. ...
... Dendritic cells at different differentiation stages can express VEGFR1 and VEGFR2 at various levels. 19,20 To identify which VEGFR is involved in RhoA-COF1 signaling, the blocking Abs of VEGFR1 and VEGFR2 were applied to treat mDCs. The results showed that ...
Dendritic cells (DCs) are potent and specialized antigen presenting cells, which play a crucial role in initiating and amplifying both the innate and adaptive immune responses against cancer. Tumor cells can escape from immune attack by secreting suppressive cytokines which solely or cooperatively impair the immune function of DCs. However, the underlying mechanisms are not fully defined. Vascular endothelial growth factor (VEGF) has been identified as a major cytokine in the tumor microenvironment. To elucidate the effects of VEGF on the motility and immune function of mature DCs (mDCs), the cells were treated with 50 ng/ml VEGF and investigated by proteomics and molecular biological technologies. The results showed that VEGF can impair the migration capacity and immune function of mDCs through RhoA-cofilin1 (COF1) pathway mediated by the VEGF receptor 2 (VEGFR2), suggesting impaired motility of mDCs by VEGF is one of the aspects of immune escape mechanisms of tumors. It is clinically important to understand the biological behavior of DCs and immune escape mechanism of tumor as well as how to improve efficiency of anti-tumor therapy based on DCs. This article is protected by copyright. All rights reserved.
... As an example, TNF production by activated DCs induces the synthesis of VEGF in different cell types (including ECs), which influences angiogenesis. In fact, DCs themselves express both VEGFR1 and VEGFR2 (Mimura et al. 2007) and respond to PIGF and VEGF signaling by inhibiting their differentiation into functional DCs (Dikov et al. 2005;Mimura et al. 2007). Tumor-derived VEGF also induces a significant decrease in the number and functionality of spleen and lymph node DCs (Gabrilovich et al. 1996(Gabrilovich et al. , 1998. ...
... As an example, TNF production by activated DCs induces the synthesis of VEGF in different cell types (including ECs), which influences angiogenesis. In fact, DCs themselves express both VEGFR1 and VEGFR2 (Mimura et al. 2007) and respond to PIGF and VEGF signaling by inhibiting their differentiation into functional DCs (Dikov et al. 2005;Mimura et al. 2007). Tumor-derived VEGF also induces a significant decrease in the number and functionality of spleen and lymph node DCs (Gabrilovich et al. 1996(Gabrilovich et al. , 1998. ...
In contrast to mechanisms taking place during resistance to chemotherapies or other targeted therapies, compensatory adaptation to angiogenesis blockade does not imply a mutational alteration of genes encoding drug targets or multidrug resistance mechanisms but instead involves intrinsic or acquired activation of compensatory angiogenic pathways. In this article we highlight hypoxia-regulated and immune-mediated mechanisms that converge in endothelial cell programs and preserve angiogenesis in settings of vascular endothelial growth factor (VEGF) blockade. These mechanisms involve mobilization of myeloid cell populations and activation of cytokine- and chemokine-driven circuits operating during intrinsic and acquired resistance to anti-angiogenic therapies. Particularly, we focus on findings underscoring a role for galectins and glycosylated ligands in promoting resistance to anti-VEGF therapies and discuss possible strategies to overcome or attenuate this compensatory pathway. Finally, we highlight emerging evidence demonstrating the interplay between immunosuppressive and pro-angiogenic programs in the tumor microenvironment (TME) and discuss emerging combinatorial anticancer strategies aimed at simultaneously potentiating antitumor immune responses and counteracting aberrant angiogenesis.
... Therefore, antiangiogenesis-targeted therapy is often combined with immune checkpoint inhibitors in the therapy of metastatic ccRCC. Cabozantinib plus nivolumab, axitinib plus pembrolizumab, and lenvatinib plus pembrolizumab have become standards of care for their maturation, dampening dendritic cell antigen presentation [77]. VEGF recruits Tregs to tumors and promotes the polarization of macrophages into M2 tumor-associated macrophages (TAMs) [78,79]. ...
Typically associated with solid tumors, hypoxia contributes to tumor angiogenesis and lymphangiogenesis through various molecular mechanisms. Accumulating studies indicate that hypoxia-inducible factor is the key transcription factor coordinating endothelial cells to respond to hypoxia in urological cancers, mainly renal cell carcinoma, prostate cancer, and bladder cancer. Moreover, it has been suggested that tumor hypoxia in tumor microenvironment simultaneously recruits stromal cells to suppress immune activities. This review summarizes the mechanisms by which HIF regulates tumorigenesis and elaborates on the associations between HIF and angiogenesis, lymphangiogenesis, and tumor microenvironment in urological cancers.
... Furthermore, the TLS promoting factor transcript levels suggest that Aduro and the highest and lowest dosage of Bevacizumab have immune-supportive effects in DCs. Aduro's effect was expected considering the relevancy of the STING pathway in DCs, while Bevacizumab's effect is consistent with the ability of VEGF to inhibit maturation and differentiation of DCs (25). ...
Tertiary lymphoid structures (TLS) are lymph node-like structures that form at sites of inflammation, and their presence in cancer patients is predictive of a better clinical outcome. One significant obstacle to TLS formation is reduced immune cell infiltration into the tumor microenvironment (TME), resulting from aberrant vasculature within the TME. Recent studies have shown that low doses of vasculature normalizing (VN) agents may override this defect, leading to improved tissue perfusion and increased immune cell entry into the TME. While the effect of VN agents on vascular endothelial cells has been well documented, their effects on immune cell and tumor cell phenotype remain understudied. We hypothesized that treating immune cells with VN agents would induce a pro-inflammatory phenotype in T cells and dendritic cells (DCs), while treating tumor cells would reduce their immunosuppressive phenotype and promote production of chemokines that recruit immune cells and foster TLS formation. To test this, a mouse melanoma cell line, primary murine T cells, and DCs were treated overnight with VN agents. The next day, treated and control cells were harvested for analyses to measure transcript levels of target genes as well as levels of surface markers. Overall, VN agents were observed to have differential but predominantly immune-supportive effects on immune and tumor cell phenotypes. These findings will guide future experiments which may result in an effective clinical treatment.
... Tumors often disturb normal DC activation and maturation to establish tumor tolerance (15)(16)(17). Immunosuppressive cytokines deriving from tumor contexture induce DCs to exhibit an immunosuppressive phenotype that mediates tumor tolerance, thereby restraining T cell priming (15,18). ...
Imbalanced immune homeostasis in cancer microenvironment is a hallmark of cancer. Increasing evidence demonstrated that long non-coding RNAs (lncRNAs) have emerged as key regulatory molecules in directly blocking the cancer immunity cycle, apart from activating negative regulatory pathways for restraining tumor immunity. lncRNAs reshape the tumor microenvironment via the recruitment and activation of innate and adaptive lymphoid cells. In this review, we summarized the versatile mechanisms of lncRNAs implicated in cancer immunity cycle, including the inhibition of antitumor T cell activation, blockade of effector T cell recruitment, disruption of T cell homing, recruitment of immunosuppressive cells, and inducing an imbalance between antitumor effector cells (cytotoxic T lymphocytes, M1 macrophages, and T helper type 1 cells) versus immunosuppressive cells (M2 macrophages, T helper type 2 cells, myeloid derived suppressor cells, and regulatory T cells) that infiltrate in the tumor. As such, we would highlight the potential of lncRNAs as novel targets for immunotherapy.
... Few studies in literature have reported the role of immune response and angiogenesis in oral cancer in the same tissue with survival analysis. VEGF disrupts dendritic cell maturation and function and suppresses T-cell development 11 . The present study aimed to study the relationship between CD3 and VEGF in metastatic and non-metastatic OSCC and the correlation between CD3 and VEGF expression with clinicopathological parameters including the 5-year survival status. ...
Background & objectives:
Oral squamous cell carcinoma (OSCC) is widely prevalent in the Indian subcontinent mainly due to habit-associated aetiologies. Immune regulation and angiogenesis are the part of tumourigenesis that play a crucial role in metastasis and survival. However, the concurrent expression of vascular endothelial growth factor (VEGF) and CD3 (immune regulator receptor on T-lymphocyte) in the same OSCC tissue samples has not been reported in the Indian population. The present study evaluated the expression of CD3+ T-cells and VEGF in OSCC tissue samples and studied the clinicopathological correlation and survival analysis in an Indian population.
Methods:
This was a retrospective study conducted on 30 formalin-fixed and paraffin embedded sections which were histologically diagnosed as OSCC cases comprising of 15 metastatic OSCC and 15 non-metastatic OSCC with available clinical data and survival status.
Results:
Reduced expression of CD3+ T-cells and increased VEGF expression were observed in metastatic OSCC samples. The correlation of expression of CD3+ T-cells and VEGF with clinicopathological parameters showed a significant association between these markers with age, nodal status, site of the lesion and survival.
Interpretation & conclusions:
Reduced expression of CD3+ T-cells in OSCC was found to be associated with a significantly poor survival. VEGF was found to be over expressed in metastatic OSCC as compared to that in non-metastatic OSCC. The study findings suggest that the evaluation of CD3 and VEGF in incisional OSCC biopsies can be considered for predicting the survival outcome and metastasis.
... VEGF interferes with an antigenic presentation by inhibiting the maturation of dendritic cells [81], restricts the migration of lymphocytes into the tumor compartment [82], and favors the recruitment of T-regs, MDSCs and TAMs, contributing to a highly immune- Wound dehiscence (14%), ALP increase (9.3%), AST/ALT increase (9.3%), blood bilirubin increase (9.3%), hypertriglyceridemia (7.0%), anorexia (7.0%), weight loss (7.0%), pneumothorax (7.0%), platelet count decrease (4.7%), diarrhea (4.7%), PPS (4.7%), limb pain (4.7%), leukopenia (4.7%), rash (4.7%), oral mucositis (4.7%), hypertension (4.7%), toothache (4.7%), nausea (4.7%), non-cardiac chest pain ( The first immunotherapy trial with positive results in sarcoma was phase II SARC028 with anti-PD1 pembrolizumab, including a cohort for BS and a cohort for STS [54]. In the BS cohort, there were only two objective responses (one osteosarcoma and one CS). ...
Simple Summary
The systemic treatment of advanced sarcoma remains challenging. Conventional chemotherapy and anti-angiogenic agents, even in the most responsive histologic subtypes, result in short responses and poor clinical outcomes. In a context where new therapeutic approaches are required, several strategies of immunotherapy have emerged as promising options, such as immune checkpoint inhibitors, vaccines, and adoptive cell therapy. In this review, we aim to summarize the current state and challenges of immunotherapy in patients with advanced bone and soft-tissue sarcomas.
Abstract
There is substantial heterogeneity between different subtypes of sarcoma regarding their biological behavior and microenvironment, which impacts their responsiveness to immunotherapy. Alveolar soft-part sarcoma, synovial sarcoma and undifferentiated pleomorphic sarcoma show higher immunogenicity and better responses to checkpoint inhibitors. Combination strategies adding immunotherapy to chemotherapy and/or tyrosine–kinase inhibitors globally seem superior to single-agent schemes. Therapeutic vaccines and different forms of adoptive cell therapy, mainly engineered TCRs, CAR-T cells and TIL therapy, are emerging as new forms of immunotherapy for advanced solid tumors. Tumor lymphocytic infiltration and other prognostic and predictive biomarkers are under research.
... Expression of molecules favouring the selective infiltration of immunosuppressive cells has also been reported, such as CLEVER-1, which promotes selective infiltration of Proangiogenic factors involved in tumour angiogenesis can also promote immunosuppression by direct effects on immune cells. VEGF-A immunosuppressive role has been well described [47][48][49][50]. It inhibits the maturation of dendritic cells, with or without the help of NRP1, thus altering the presentation of tumour antigens. ...
Due to the aberrant hypervascularization and the high immune infiltration of renal tumours, current therapeutic regimens of renal cell carcinoma (RCC) target angiogenic or immunosuppressive pathways or both. Tumour angiogenesis plays an essential role in tumour growth and immunosuppression. Indeed, the aberrant vasculature promotes hypoxia and can also exert immunosuppressive functions. In addition, pro-angiogenic factors, including VEGF-A, have an immunosuppressive action on immune cells. Despite the progress of treatments in RCC, there are still non responders or acquired resistance. Currently, no biomarkers are used in clinical practice to guide the choice between the different available treatments. Considering the role of angiogenesis in RCC, angiogenesis-related markers are interesting candidates. They have been studied in the response to antiangiogenic drugs (AA) and show interest in predicting the response. They have been less studied in immunotherapy alone or combined with AA. In this review, we will discuss the role of angiogenesis in tumour growth and immune escape and the place of angiogenesis-targeted biomarkers to predict response to current therapies in RCC.
... The overexpression of proangiogenic factors not only regulates vascular proliferation but also disrupts the balance between proangiogenic and antiangiogenic processes, leading to abnormal blood vessel proliferation and ultimately creating an immunosuppressive microenvironment of hypoxia and acidosis. Especially by promoting the generation of abnormal blood vessels, VEGF increases the formation of an immunosuppressive microenvironment [20][21][22] that is conducive to immune escape and distant metastasis of tumors. ...
Background:Kidney renal clear cell carcinoma (KIRC) is a highly vascularized and immunogenic tumor that has a high percentage of recurrence and a poor prognosis. Anti-angiogenesis therapies and immunotherapy are critical options to treat KIRC. However, the role of angiogenesis-associated genes (AAGs) in renal cell carcinoma tumorigenesis, prognosis prediction, the influence of the tumor microenvironment (TME) and the response to immunotherapy remains unknown. Identifying potential prognostic markers based on AAGs of KIRC may provide information for the early detection of recurrence and treatment.
Methods: We investigated the expression profiles of 36 AAGs in 536 KIRC patients, including 536 tumors and 72 adjacent nontumor tissues downloaded fromThe Cancer Genome Atlas (TCGA) database. We determined two different clusters based on AAG expression patterns and comprehensively identified the correlation between angiogenesis and patient risk, overall survival, and immune cell proportion in the TME. Next, we assessed the AAG score in different AAG clusters and confirmed the predictive ability in KIRC patients by a risk score model. Finally, we evaluatedthe IC50 of 12 chemotherapy and targeted drugs in different AAG score groups.
Results: We explored the expression levels, CNVs, and mutations of 36 AAGs in KIRC and observed that fifteen differentially expressed genes and VEGFA, TIMP1, VCAN and POSTN were hub genes. Different AAG clusters were divided by theexpression profiles of AAGs, and the survival analysis indicated that the low AAG score and low-risk group demonstrated superior overall survival (OS). We analyzed the correlation between angiogenesis and the TME and found that TME scores in the high AAG score group were higher than those in the low AAG score group. The two clusters had an abundance of metabolic-associated pathways. Next, the clinical viability and OS prediction ability of the AAG score in KIRC patients wereconfirmed by a highly reliable nomogram. Furthermore, different TMB subgroups combined with the AAG_score showed that the low-TMB+low-risk group had greater OS. Additionally, the AAG_score was markedly correlated with chemotherapy and target drug susceptibility.
Conclusion: Our results reveal that as a clinical prognostic signature, AAGs play a significant predictive role in KIRC. The relationship between AAGs and the TME should provide more potent combination therapy options for KIRC patients.
... VEGF also prevents the maturation of DCs and hence antigen presentation [84]. In mature DCs, VEGF promotes PD-L1 expression [85] and suppresses their capacity to activate T cells [86]. Meanwhile in CD8+ T cells, VEGF induces expression of PD-1, CTLA-4, Tim-3 [87] and other inhibitory receptors associated with T cell exhaustion. ...
Over the past decade, immune checkpoint inhibitor (ICI) therapy has been established as the standard of care for many types of cancer, but the strategies employed have continued to evolve. Recently, much clinical focus has been on combining targeted therapies with ICI for the purpose of manipulating the immune setpoint. The latter concept describes the equilibrium between factors that promote and those that suppress anti-cancer immunity. Besides tumor mutational load and other cancer cell-intrinsic determinants, the immune setpoint is also governed by the cells of the tumor microenvironment and how they are coerced by cancer cells to support the survival and growth of the tumor. These regulatory mechanisms provide therapeutic opportunities to intervene and reduce immune suppression via application of small molecule inhibitors and antibody-based therapies against (receptor) tyrosine kinases and thereby improve the response to ICIs. This article reviews how tyrosine kinase signaling in the tumor microenvironment can promote immune suppression and highlights how therapeutic strategies directed against specific tyrosine kinases can be used to lower the immune setpoint and elicit more effective anti-tumor immunity.
... VEGF upregulates programmed death-ligand 1 (PD-L1) in dendritic cells, which results in the inhibition of T-cell expansion and function (26). Furthermore, it inhibits the function of human mature dendritic cells to stimulate T-cells, mediated by VEGFR-2 (27), via the inhibition of NF-κB activation (28). ...
Vascular endothelial growth factor (VEGF) serves a critical role in vasculogenesis, angiogenesis, tumor, inflammatory angiogenesis and lymphangiogenesis. Since 2004, bevacizumab (Avastin), a humanized anti-VEGFA monoclonal antibody, has been approved for the treatment of non-small cell lung, breast, kidney and ovarian cancer in combination with standard chemotherapy. VEGF has been demonstrated to be important in the clinic as a therapeutic target in the anti-angiogenic approach to cancer therapy. The targeting of VEGF, together with immunotherapy, has been reported to be able to reverse the immunosuppressive effects of VEGF. A positive correlation between VEGF expression and the reduced survival rates of patients with cancer has also been demonstrated. Furthermore, increased VEGF expression can lead to immune suppression via the inhibition of dendritic cell maturation, the reduction of T-cell tumor infiltration and the promotion of inhibitory cell types in the tumor microenvironment.
... Vascular endothelial growth factor (VEGF) not only promotes angiogenesis in tumors but also fundamentally programs an immunosuppressive TME by recruiting and inducing immunosuppressive cells including regulatory T cells, tumor-associated macrophages, and myeloid-derived suppressor cells (Kudo, 2020;Morse et al., 2019;Zhu et al., 2011). Furthermore, VEGF inhibits dendritic cell differentiation and maturation as well as effector T cell proliferation, thereby impairing T cell priming and killing of tumor targets Oyama et al., 1998;Mimura et al., 2007). Thus, blocking VEGF signaling may not only inhibit intratumoral angiogenesis to normalize the tumor vasculature but also re-program the immunosuppressive TME into an immune-stimulating one (Fig. 1). ...
Immune-checkpoint inhibitor-based combination immunotherapy has become a first-line treatment for several major types of cancer including hepatocellular carcinoma (HCC), renal cell carcinoma, lung cancer, cervical cancer, and gastric cancer. Combination immunotherapy counters several immunosuppressive elements in the tumor microenvironment and activates multiple steps of the cancer-immunity cycle. The anti-PD-L1 antibody, atezolizumab, plus the anti-vascular endothelial growth factor antibody, bevacizumab, represents a promising class of combination immunotherapy. This combination has produced unprecedented clinical efficacy in unresectable HCC and become a landmark in HCC therapy. Advanced HCC patients treated with atezolizumab plus bevacizumab demonstrated impressive improvements in multiple clinical endpoints including overall survival, progress-free survival, objective response rate, and patient-reported quality of life when compared to current first-line treatment with sorafenib. However, atezolizumab plus bevacizumab first-line therapy has limitations. First, cancer patients falling into the criteria for the combination therapy may need to be further selected to reap benefits while avoiding some potential pitfalls. Second, the treatment regimen of atezolizumab plus bevacizumab at a fixed dose may require adjustment for optimal normalization of the tumor microenvironment to obtain maximum efficacy and reduce adverse events. Third, utilization of predictive biomarkers is urgently needed to guide the entire treatment process. Here we review the current status of clinically approved combination immunotherapies and the underlying immune mechanisms. We further provide a perspective analysis of the limitations for combination immunotherapies and potential approaches to overcome the limitations.
... 27 Additionally, VEGF-targeted therapy can revert the immunosuppressive effects of VEGF. For example, VEGF can inhibit the function and maturation of dendritic cells, 28,29 as well as the infiltration and function of cytotoxic T lymphocytes. 30 As an effective means of tumor treatment, radiotherapy has been shown to have the following effects in HCC: Permanent control of tumor, 31 inhibition of tumor blood vessels, and stimulation of immune cell aggregation. ...
Purpose:
To evaluate the clinical efficacy and safety of apatinib combined with intensity-modulated radiation therapy (IMRT) in patients with unresectable hepatocellular carcinoma (uHCC).
Materials and methods:
Open-label, single-arm, exploratory clinical trial of apatinib combined with IMRT for uHCC patients. Patients aged 18-75 years with adequate hematological, liver, and renal functions and Eastern Cooperative Oncology Group (ECOG) performance status of ≤2 were enrolled in this study from March 2017 to September 2020. Patients were received IMRT (biological effective dose: 46-60 Gy) and continuous apatinib (250-500 mg/day) oral administration until HCC progression or unacceptable toxic effects. The endpoints included progression-free survival (PFS), overall survival (OS), disease control rate (DCR), objective response rate (ORR), and safety. The trial registration number is ChiCTR-OPC-17011890.
Results:
A total of 33 patients have taken part in the study. The median age was 58 years old (range 32-77), 27 (81.9%) patients were ECOG PS 0-1, and 28 (84.9%) patients were male. In addition, 25 (75.7%) patients suffered from hepatitis B, 32 cases (97.0%) were in Barcelona Clinic Liver Cancer (BCLC) Stages B-C, and eight (24.2%) had portal vein involvement. Moreover, 12 (36.4%) and 21 (63.6%) patients received apatinib as first-line and second or later-line therapy, respectively. The average follow-up was 11.4 months, the median PFS was 7.8 months (95% confidence interval: 3.9-11.7). The OS rates at 6 and 12 months were 96.7% and 66.2%. The ORR and DCR were 15.1% and 81.8%, respectively. Hepatic toxicity was the most common treatment-related adverse events in Grades 3-4 (12.1%). No radiation-induced liver disease and Grade 5 toxicity were recorded.
Conclusion:
Apatinib combined with IMRT is a safe and effective method to improve PFS and DCR and has good anti-tumor activity in patients with uHCC.
... For instance, they secrete the immunosuppressive cytokines TGF-β and IL-10, which repress the adaptive anti-tumor immune response [25,26] or polarize tumor-associated macrophages (TAMs) toward an M2 phenotype that has significantly less anti-tumor potential but highly promotes tumor growth and metastasis capacity [27]. Some cancers affect the release of IL-6 [28], IL-10 [29], VEGF [30], or GM-CSF [31] and impair the functions of DC either by inactivating or suppressing maturation. Some tumors induce T regulatory cells to repress tumor-distinct T cell reactions [18]. ...
As a promising alternative platform for cellular immunotherapy, natural killer cells (NK) have recently gained attention as an important type of innate immune regulatory cell. NK cells can rapidly kill multiple adjacent cancer cells through non-MHC-restrictive effects. Although tumors may develop multiple resistance mechanisms to endogenous NK cell attack, in vitro activation, expansion, and genetic modification of NK cells can greatly enhance their anti-tumor activity and give them the ability to overcome drug resistance. Some of these approaches have been translated into clinical applications, and clinical trials of NK cell infusion in patients with hematological malignancies and solid tumors have thus far yielded many encouraging clinical results. CAR-T cells have exhibited great success in treating hematological malignancies, but their drawbacks include high manufacturing costs and potentially fatal toxicity, such as cytokine release syndrome. To overcome these issues, CAR-NK cells were generated through genetic engineering and demonstrated significant clinical responses and lower adverse effects compared with CAR-T cell therapy. In this review, we summarize recent advances in NK cell immunotherapy, focusing on NK cell biology and function, the types of NK cell therapy, and clinical trials and future perspectives on NK cell therapy.
... Another study shows that VEGF inhibits the ability of mature DCs to present antigens to T cells, and the DCs dysfunction induced by VEGF is mainly mediated by VEGFR-2. Blocking mAb by anti-VEGFR-2 can reverse DCs dysfunction [36] . During the exploration of its mechanism, MARTI LC et al. judged that VEGF up-regulated IDO expression in DCs through VEGF/VEGFR pathway, and IDO further inhibited lymphocyte proliferation [37] . ...
Tumor immune therapy, especially anti-programmed cell death ligand-1/programmed cell death-1 (PD-L1/PD-1) treatment, is currently the focus of substantial attention. However, despite its enormous successes, the overall response rate of cancer immunotherapy remains suboptimal. There is an increased interest in combining PD-L1/PD-1 treatment with anti-angiogenic drug Apatinib to enhance antitumor effect. Presently available data seem to suggest that Apatinib may exert immune suppressive effects to make the PD-L1/PD-1 treatment works. Here, we review the extensive tumor microenvironment immune modulatory effects from antiangiogenic agents Apatinib in order to supporting VEGFR2 targettherapies in clinical trials are existing.
... All three receptors are dimers with similar protein organization but different functions [22][23][24]. Both VEGFR1 and VEGFR2 are essential factors in suppressing DC functions [17,25]. The former mainly inhibits DC maturation, and the latter primarily inhibits DC migration. ...
The tumor microenvironment (TME) plays a central role in tumor initiation, development, immune escape, and clinical treatment. Hypoxia, an important characteristic of the TME, mediates vascular endothelial factor (VEGF) signaling through direct or indirect mechanisms. Directly, hypoxia promotes the expression of VEGF through hypoxia-inducible factor (HIF) induction. Indirectly, VEGF inhibits dendritic cell (DC) maturation and function by binding to VEGF receptors (VEGFRs) and co-receptors expressed on cell membranes. Additionally, HIF can bypass VEGF/VEGFR and activate downstream signaling factors to promote tumor development. Currently, DC vaccine, anti-HIF and anti-VEGF therapies are widely used in clinical treatment, but their long-term effects remain limited. Therefore, a further understanding of the effects of hypoxia and VEGF signaling on DCs will help in the development of innovative combination therapies and the identification of new targets.
... One of the first reported immunosuppressive functions of antiangiogenic factors is that tumor-derived VEGF inhibits the maturation of DCs from progenitor cells, which leads to reduced presentation of cancer neoantigens in tumor-draining lymph nodes and thus contributes to immune evasion by tumors [35]. The mechanism of DC dysfunction involves VEGFinduced inhibition of the nuclear factor-κB (NF-κB) signaling pathway in progenitor cells by limiting degradation of an NF-κB inhibitor [36,37]. Compared with mature DCs, immature DCs are more powerful Foxp3 + regulatory T cell (Treg) inducers [38]. ...
Cancer immunotherapy, especially immune checkpoint blockade (ICB), has revolutionized oncology. However, only a limited number of patients benefit from immunotherapy, and some cancers that initially respond to immunotherapy can ultimately relapse and progress. Thus, some studies have investigated combining immunotherapy with other therapies to overcome resistance to monotherapy. Recently, multiple preclinical and clinical studies have shown that tumor vasculature is a determinant of whether immunotherapy will elicit an antitumor response; thus, vascular targeting may be a promising strategy to improve cancer immunotherapy outcomes. A successful antitumor immune response requires an intact “Cancer-Immunity Cycle,” including T cell priming and activation, immune cell recruitment, and recognition and killing of cancer cells. Angiogenic inducers, especially vascular endothelial growth factor (VEGF), can interfere with activation, infiltration, and function of T cells, thus breaking the “Cancer-Immunity Cycle.” Together with immunostimulation-regulated tumor vessel remodeling, VEGF-mediated immunosuppression provides a solid therapeutic rationale for combining immunotherapy with antiangiogenic agents to treat solid tumors. Following the successes of recent landmark phase III clinical trials, therapies combining immune checkpoint inhibitors (ICIs) with antiangiogenic agents have become first-line treatments for multiple solid tumors, whereas the efficacy of such combinations in other solid tumors remains to be validated in ongoing studies. In this review, we discussed synergies between antiangiogenic agents and cancer immunotherapy based on results from preclinical and translational studies. Then, we discussed recent progress in randomized clinical trials. ICI-containing combinations were the focus of this review because of their recent successes, but combinations containing other immunotherapies were also discussed. Finally, we attempted to define critical challenges in combining ICIs with antiangiogenic agents to promote coordination and stimulate collaboration within the research community.
... Chemokines inducing the differentiation to an M2-like macrophage state are interleukin-4 (IL4), IL10, IL13, and CXCL1, however, we did not identify their secretion in our 3Dcc imm system [67]. Further, it has been shown that cancer cells are capable to slow down dendritic cell maturation through the secretion of VEGF [68,69]. ...
Simple Summary
Three-dimensional cancer models have gained interest from pre-clinical testing of single drugs and drug combinations. The research aim of this study was to develop a heterotypic 3D co-culture harboring selected immune cell subsets to evaluate the efficacy of a drug combination for the treatment of renal cell carcinoma. Heterotypic spheroids containing 70% cancer, 20% fibroblasts, and 10% endothelial cells were cultured in a scaffold-free system. Native or immortalized immune cells were added directly or 24 h post spheroid formation, and their infiltration was observed. This infiltration was found to be modulated by various treatment conditions. Our study revealed that heterotypic short-term 3D spheroids complemented with immune cell subsets represent a valuable tool for tumor-immune cell interaction and treatment screening platforms.
Abstract
Two-dimensional cell culture-based platforms are easy and reproducible, however, they do not resemble the heterotypic cell-cell interactions or the complex tumor microenvironment. These parameters influence the treatment response and the cancer cell fate. Platforms to study the efficacy of anti-cancer treatments and their impact on the tumor microenvironment are currently being developed. In this study, we established robust, reproducible, and easy-to-use short-term spheroid cultures to mimic clear cell renal cell carcinoma (ccRCC). These 3D co-cultures included human endothelial cells, fibroblasts, immune cell subsets, and ccRCC cell lines, both parental and sunitinib-resistant. During spheroid formation, cells induce the production and secretion of the extracellular matrix. We monitored immune cell infiltration, surface protein expression, and the response to a treatment showing that the immune cells infiltrated the spheroid co-cultures within 6 h. Treatment with an optimized drug combination or the small molecule-based targeted drug sunitinib increased immune cell infiltration significantly. Assessing the therapeutic potential of this drug combination in this platform, we revealed that the expression of PD-L1 increased in 3D co-cultures. The cost- and time-effective establishment of our 3D co-culture model and its application as a pre-clinical drug screening platform can facilitate the treatment validation and clinical translation.
... TGF-b induces VEGF expression in different cell types, including immune, tumor, and stromal cells, thus creating a positive feedback loop that promotes tumor cell proliferation and immunosuppression.174,181 VEGF impairs T cell anti-tumor responses by promoting T cell exhaustion and blocking dendritic cell (DC) maturation.182,183 Similar to VEGF, TGF-b has immunosuppressive effects by promoting the differentiation of T reg cells in tumors, inhibiting natural killer (NK) anti-tumor activity, and impairing T cell responses.[184][185][186] ...
The liver is endowed with an amazing regenerative capacity that allows it to withstand an enormous amount of damage. Nevertheless, it is precisely this highly regenerative capacity that renders it susceptible to dysplasia and liver cancer. Liver cancer is not only one of the most common cancers but also one of the deadliest. Hepatocellular carcinoma (HCC) is the most common form of liver cancer, accounting for up to 70%–90% of all cases, but treatment options for advanced stages remain scarce. Therefore, a great deal of effort has gone into identifying early diagnostic markers as well as novel therapies, both local and systemic, for the treatment of this deadly disease. In this review, we aim to shed light into the current therapeutic landscape of HCC with an emphasis on the available treatments, ranging from surgical and local-ablative therapy for early and intermediate stages of the disease to systemic therapies for advanced cancer treatments. We will also address the molecular mechanisms and limitations of currently available systemic therapies and the causes of treatment resistance and finally summarize the emerging future avenues and novel concepts that are promising.
... Kaplan-Meier curve showed a higher survival of the combination therapy of vaccine + axitinib when compared to monotherapy (P <0.05) [69]. The inhibition of VEGF activity by anti-VEGF neutralizing antibody or anti-VEGF receptor antibodies overcome the functional inhibition of DCs [70]. The effect of VEGF-A is mediated by its binding to the VEGFR-1 receptor. ...
Angiogenesis plays an important role in tumor growth. Established vasculature provides a supply of nutrients and other necessary survival factors for tumor cell maintenance. In addition, immune factors with capacity to both decrease immune activity leading to cancer suppression and to increase anticancer response are provided via VEGF stimulated angiogenesis. However, VEGF provides more than angiogenesis stimulation; it is itself a growth factor with activity to also decrease the stimulation of dendritic cells (DCs) and T cells involved in anti-cancer mechanisms. As such inhibition of VEGF provides immune therapeutic advantage. This was well demonstrated by IFN-ɣ ELISPOT assay in which T lymphocytes antitumor response was measured against multiple myeloma cells following exposure to myeloma lysate-loaded dendric cells. Block of VEGF lead to enhanced T lymphocyte anticancer immune response. Through stimulation of the immune system angiogenesis inhibitors can work in conjunction with immunotherapy, chemotherapy and/or radiation therapy. Recent clinical trials in advanced renal cell carcinoma, non-small cell lung cancer (NSCLC), and hepatocellular carcinoma have evidenced improved outcomes due to an immune enhancing effect with angiogenesis inhibition and in particular immune checkpoint blockade treatment.
... The current front-line treatment for mCRC patients is often a combination of chemotherapies and biotherapies, the anti-VEGF mAb and anti-EGFR mAb antiangiogenic agents. In the case of bevacizumab, VEGF in the tumor microenvironment drives angiogenesis and contributes to local immune evasion by the tumor (14). Clinical trials have confirmed that regorafenib, a potent inhibitor of angiogenic and oncogenic kinases, in combination of PD1 has encouraging antitumor activity in microsatellite stable (MSS) mCRC patients (15). ...
Background
With the interest in cancer immunotherapy, it may be possible to combine immunotherapy with bevacizumab and chemotherapy. We evaluated whether tumor-infiltrating immune cells are associated with the efficacy of chemotherapy with or without bevacizumab for the treatment of metastatic colorectal cancer (mCRC).
Methods
This study enrolled mCRC patients on standard treatment with available detailed data and tumor tissue at Sun Yat-sen University Cancer Center between July 1, 2005, and October 1, 2017. CD3+ and CD8+ T cell densities examined by immunohistochemistry in both the tumor core (CT) and invasive margin (IM) were summed as the Immunoscore, and the CD8+/CD3+ T cell ratio was calculated. The predictive and prognostic efficacies of tumor-infiltrating immune cells for progression-free survival (PFS) and overall survival (OS) were analyzed with Kaplan-Meier and Cox analyses.
Results
The CD8+/CD3+ T cell ratio in the microenvironment was an independent prognostic factor for OS (28.12 mo vs. 16.56 mo, P = 0.017) among the 108 studied patients. In the chemotherapy only group, patients with a high Immunoscore had a high overall response rate (ORR, 40.0% vs. 60.0%, P = 0.022), those with a low CD8+/CD3+ T cell ratio in the microenvironment had a significantly longer PFS (8.64 mo vs. 6.01 mo, P = 0.017), and those with a high CD3+ T cell density in the CT had a longer OS (16.56 mo vs. 25.66 mo, P = 0.029). In the chemotherapy combined with bevacizumab group, patients with a higher CD8+ T cell density in the IM had a longer PFS (7.62 mo vs. 11.66 mo, P = 0.034) and OS (14.55 mo vs. 23.72 mo, P = 0.033).
Conclusion
Immune cells in primary tumors play an important role in predicting mCRC treatment efficacy. CD8 predicts the effect of bevacizumab plus chemotherapy, while CD3 and CD8/CD3 predict chemotherapy efficacy.
... This lack of DC maturation can prevent the upregulation of MHC and other molecules, ultimately resulting in impaired T-cell activation. VEGF, acting through VEGFR2, has also been shown to inhibit the ability of mature DCs to stimulate T cells (62). VEGFR1 and VEGFRs may have differential roles in regulating DC differentiation where VEGFR1 is the principle mediator of VEGF-induced inhibition of DC maturation (63). ...
Cancer immunotherapy (CIT) with antibodies targeting the programmed cell death 1 protein (PD-1)/programmed cell death 1 ligand 1 (PD-L1) axis have changed the standard of care in multiple cancers. However, durable antitumor responses have been observed in only a minority of patients, indicating the presence of other inhibitory mechanisms that act to restrain anticancer immunity. Therefore, new therapeutic strategies targeted against other immune suppressive mechanisms are needed to enhance anticancer immunity and maximize the clinical benefit of CIT in patients who are resistant to immune checkpoint inhibition. Preclinical and clinical studies have identified abnormalities in the tumor microenvironment (TME) that can negatively impact the efficacy of PD-1/PD-L1 blockade. Angiogenic factors such as vascular endothelial growth factor (VEGF) drive immunosuppression in the TME by inducing vascular abnormalities, suppressing antigen presentation and immune effector cells, or augmenting the immune suppressive activity of regulatory T cells, myeloid-derived suppressor cells, and tumor-associated macrophages. In turn, immunosuppressive cells can drive angiogenesis, thereby creating a vicious cycle of suppressed antitumor immunity. VEGF-mediated immune suppression in the TME and its negative impact on the efficacy of CIT provide a therapeutic rationale to combine PD-1/PD-L1 antibodies with anti-VEGF drugs in order to normalize the TME. A multitude of clinical trials have been initiated to evaluate combinations of a PD-1/PD-L1 antibody with an anti-VEGF in a variety of cancers. Recently, the positive results from five Phase III studies in non-small cell lung cancer (adenocarcinoma), renal cell carcinoma, and hepatocellular carcinoma have shown that combinations of PD-1/PD-L1 antibodies and anti-VEGF agents significantly improved clinical outcomes compared with respective standards of care. Such combinations have been approved by health authorities and are now standard treatment options for renal cell carcinoma, non-small cell lung cancer, and hepatocellular carcinoma. A plethora of other randomized studies of similar combinations are currently ongoing. Here, we discuss the principle mechanisms of VEGF-mediated immunosuppression studied in preclinical models or as part of translational clinical studies. We also discuss data from recently reported randomized clinical trials. Finally, we discuss how these concepts and approaches can be further incorporated into clinical practice to improve immunotherapy outcomes for patients with cancer.
... One of the first described immunosuppressive functions of VEGF would be hindering dendritic cell (DC) maturation [15,170]. This is evident by the defective or reduced numbers of mature DCs reported in several malignancies to be inversely corelated with VEGF plasma concentrations [171][172][173][174]. Inhibition of NF-κB signaling is suggested to be the underlying mechanism that impairs DCs' differentiation and maturation, with various studies indicating this to be a direct consequence of VEGF binding to either VEGFR2 or VEGFR1 on DCs [15,170,[175][176][177]; although NRP1 is also implicated [178], as well as PLGF binding to VEGFR1 [177,179]. Along with directly affecting DCs' maturation, VEGF was also found to upregulate PDL1 on DCs, resulting in inhibition of T-cells' expansion and function [180]. ...
Simple Summary
Although VEGF-A is well characterized as the principal player of cancer angiogenesis, new data on the interplay with other components of the tumor microenvironment emerge. Here we review the effect of VEGF-A on cancer cells and immune cells as well as investigative and established combinational therapies of anti-angiogenic agents with immune checkpoint inhibitors. We thus elaborate the scientific rationale behind the development of these novel combinational approaches.
Abstract
Angiogenesis has long been considered to facilitate and sustain cancer growth, making the introduction of anti-angiogenic agents that disrupt the vascular endothelial growth factor/receptor (VEGF/VEGFR) pathway an important milestone at the beginning of the 21st century. Originally research on VEGF signaling focused on its survival and mitogenic effects towards endothelial cells, with moderate so far success of anti-angiogenic therapy. However, VEGF can have multiple effects on additional cell types including immune and tumor cells, by directly influencing and promoting tumor cell survival, proliferation and invasion and contributing to an immunosuppressive microenvironment. In this review, we summarize the effects of the VEGF/VEGFR pathway on non-endothelial cells and the resulting implications of anti-angiogenic agents that include direct inhibition of tumor cell growth and immunostimulatory functions. Finally, we present how previously unappreciated studies on VEGF biology, that have demonstrated immunomodulatory properties and tumor regression by disrupting the VEGF/VEGFR pathway, now provide the scientific basis for new combinational treatments of immunotherapy with anti-angiogenic agents.
... In addition to its widely studied role in promoting angiogenesis, VEGF can directly affect immune cells of both myeloid and lymphoid lineage and promote immune evasion in different tumor types ( Figure 1). 30 For example, VEGF can impair maturation and function of dendritic cells, which are key antigen-presenting cells, 35,36 and promote accumulation of regulatory T cells and myeloid-derived suppressor cells. 37,38 In addition, VEGF can directly and indirectly inhibit infiltration and function of cytotoxic T lymphocytes, 39,40 and increase PD-1 expression on intratumoral CD8 + T cells. ...
Importance
For more than a decade, sorafenib has been the only systemic treatment option for patients with advanced hepatocellular carcinoma (HCC). However, rapid progress over the past few years led to approval of other angiogenesis inhibitors and several immune checkpoint blockers (ICBs) that have been added to the treatment armamentarium for advanced HCC. Moreover, the recent success of a combination of bevacizumab with atezolizumab signals an important change in the front-line treatment of HCC.
Observations
This review summarizes rapidly emerging clinical data on the promise and challenges of implementing ICBs in HCC and discusses the unmet need of biomarkers to predict response or resistance to therapy. Two strategies to target immunosuppression in tumors are also discussed: one proven (vascular endothelial growth factor pathway inhibition) and one currently under investigation (transforming growth factor-β pathway inhibition). The rationale and preliminary evidence on how their inhibition may reprogram the immunosuppressive milieu and enhance the efficacy of ICBs in HCC are reviewed.
Conclusion and Relevance
The recent successes and failures of angiogenesis inhibitors and ICBs, alone and in combination, have provided important insights into how to implement this novel systemic therapy in HCC and led to new avenues to enhance immunotherapy efficacy in this disease.
... DCs were found inversely correlated with VEGF serum levels (20). Also, experimental data showed that the VEGF-induced DC dysfunction is recovered by both anti-VEGF and anti-VEGFR2 antibodies (20)(21)(22)(23)(24)(25). When looking at TAMs, known as prominent players of the cell repertoire that populates tumors, we face again with a chemoattractant role of VEGF. ...
Several studies report the key role of the vascular endothelial growth factor (VEGF) signaling on angiogenesis and on tumor growth. This has led to the development of a number of VEGF-targeted agents to treat cancer patients by disrupting the tumor blood vessel supply. Of them, bevacizumab, an FDA-approved humanized monoclonal antibody against VEGF, is the most promising. Although the use of antibodies targeting the VEGF pathway has shown clinical benefits associated with a reduction in the tumor blood vessel density, the inhibition of VEGF-driven vascular effects is only part of the functional mechanism of these therapeutic agents in the tumor ecosystem. Compelling reports have demonstrated that VEGF confers, in addition to the activation of angiogenesis-related processes, immunosuppressive properties in tumors. It is also known that structural remodeling of the tumor blood vessel bed by anti-VEGF approaches affect the influx and activation of immune cells into tumors, which might influence the therapeutic results. Besides that, part of the therapeutic effects of antiangiogenic antibodies, including their role in the tumor vascular network, might be triggered by Fc receptors in an antigen-independent manner. In this mini-review, we explore the role of VEGF inhibitors in the tumor microenvironment with focus on the immune system, discussing around the functional contribution of both bevacizumab's Fab and Fc domains to the therapeutic results and the combination of bevacizumab therapy with other immune-stimulatory settings, including adjuvant-based vaccine approaches.
... Although DC maturation is activated by the NF-κB pathway, the increase in VEGF due to the hypoxic environment of the tumor reduces the number of mDCs by inhibiting DC maturation through inhibition of the NF-κB pathway and suppresses immunity [103][104][105]. Furthermore, VEGF binds to VEGFR2, inhibits the T cell activation function of mDCs, up-regulates the expression of programmed cell death ligand 1 (PD-L1) (B7-H1/CD274), and suppresses the function of DCs [106]. The migration and adhesion of vascular adhesion molecules to vascular endothelial cells plays an important role in the activation of immunity by causing the accumulation of immune cells, such as macrophages, NK cells, granulocytes, B cells, and T cells [107]. ...
Tumors undergo fast neovascularization to support the rapid proliferation of cancer cells. Vasculature in tumors, unlike that in wound healing, is immature and affects the tumor microenvironment, resulting in hypoxia, acidosis, glucose starvation, immune cell infiltration, and decreased activity, all of which promote cancer progression, metastasis, and drug resistance. This innate defect of tumor vasculature can however represent a useful therapeutic target. Angiogenesis inhibitors targeting tumor vascular endothelial cells important for angiogenesis have attracted attention as cancer therapy agents that utilize features of the tumor microenvironment. While angiogenesis inhibitors have the advantage of targeting neovascularization factors common to all cancer types, some limitations to their deployment have emerged. Further understanding of the mechanism of tumor angiogenesis may contribute to the development of new antiangiogenic therapeutic approaches to control tumor invasion and metastasis. This review discusses the mechanism of tumor angiogenesis as well as angiogenesis inhibition therapy with antiangiogenic agents.
... Since the earlier studies, a crucial role has been attributed to soluble factors released by tumor cells, particularly to VEGF [92]. This signalling molecule is in fact not only essential to ensure neo-angiogenesis and subsequent tumor growth and progression [93], but it has also important, proven immunoregulatory effects, such as: i) hampering DC development from CD34 + cell precursors [94], ii) impairment of DC maturation [95], and iii) induction of reduced in vitro T cell stimulation capability by DCs [96]. Interestingly, in line with these data, it has been shown that VEGF serum levels in CRC patients inversely correlates with PB-DC circulating levels [87], hence reinforcing the view that VEGF plays a dual role in tumor progression, contributing to both tumor angiogenesis and immune escape. ...
Although different types of therapeutic vaccines against established cancerous lesions in various indications have been developed since the 1990s, their clinical benefit is still very limited. This observed lack of effectiveness in cancer eradication may be partially due to the often deficient immunocompetent status of cancer patients, which may facilitate tumor development by different mechanisms, including immune evasion. The most frequently used cellular vehicle in clinical trials are dendritic cells (DCs), thanks to their crucial role in initiating and directing immune responses. Viable vaccination options using DCs are available, with a positive toxicity profile. For these reasons, despite their limited therapeutic outcomes, DC vaccination is currently considered an additional immunotherapeutic option that still needs to be further explored. In this review, we propose potential actions aimed at improving DC vaccine efficacy by counteracting the detrimental mechanisms recognized to date and implicated in establishing a poor immunocompetent status in cancer patients.
... VEGF binds its corresponding Flt-1 (VEGFR1) and VEGFR2 receptors expressed on DCs and can negatively affect maturation via inhibition of the Nf-κB pathway (109). While VEGFR1 can be found both on immature and mature DCs, the expression of VEGFR2 was reported only on mature DCs (110). Although the effect of VEGF on DC co-stimulatory molecules is less pronounced, it extensively suppresses the T cell-stimulatory capacity of DCs (111). ...
The importance of microenvironment on dendritic cell (DC) function and development has been strongly established during the last two decades. Although DCs with general tolerogenic characteristics have been isolated and defined as a particular sub-population, it is predominantly their unequivocal biological plasticity, which allows for unparalleled responsiveness to environmental ques and shaping of their tolerogenic characteristics when interacting with tolerance-inducing biomolecules. Dendritic cells carry receptors for a great number of endogenous factors, which, after ligation, can importantly influence the development of their activation state. For this there is ample evidence merely by observation of DC characteristics isolated from various anatomical niches, e.g., the greater immunosuppressive potential of DCs isolated from intestine compared to conventional blood DCs. Endogenous biomolecules present in these environments most likely play a major role as a determinant of their phenotype and function. In this review, we will concisely summarize in what way various, tolerance-inducing endogenous factors influence DC biology, the development of their particular tolerogenic state and their subsequent actions in context of immune response inhibition and induction of regulatory T cells.
... Indeed, the TME actively suppresses the activation of the immune system. Tumor cells secrete immunosuppressive cytokines, as vascular endothelial growth factor (165,166), macrophage colony-stimulating factor (167), transforming growth factor β (TGF-β) (168), and IL-10 (169,170). Even though some of these cytokine display controversial roles, depending on the pathological context, they generally promote DCs tolerogenicity, by limiting their activation and increasing their expression of pro-tumor molecules, such as programmed cell death 1 (PD-1) and indoleamine 2,3-dioxygenase (IDO). ...
Vaccines represent the discovery of utmost importance for global health, due to both prophylactic action to prevent infections and therapeutic intervention in neoplastic diseases. Despite this, current vaccination strategies need to be refined to successfully generate robust protective antigen-specific memory immune responses. To address this issue, one possibility is to exploit the high efficiency of dendritic cells (DCs) as antigen-presenting cells for T cell priming. DCs functional plasticity allows shaping the outcome of immune responses to achieve the required type of immunity. Therefore, the choice of adjuvants to guide and sustain DCs maturation, the design of multifaceted vehicles, and the choice of surface molecules to specifically target DCs represent the key issues currently explored in both preclinical and clinical settings. Here, we review advances in DCs-based vaccination approaches, which exploit direct in vivo DCs targeting and activation options. We also discuss the recent findings for efficient antitumor DCs-based vaccinations and combination strategies to reduce the immune tolerance promoted by the tumor microenvironment.
... • Proteins with major roles in angiogenesis can also have direct or indirect effects on components of the immune system, most often resulting in immunosuppressive outcomes • The tumour vasculature can upregulate or downregulate proteins that control the homing and trafficking of immune cells, creating a selective immune-cell barrier on endothelium • The use of anti-angiogenic drugs and other vascular-targeting agents can normalize and remodel the tortuous tumour vasculature, enabling alleviation of hypoxia and efficient tumour infiltration by effector immune cells • Combinations of anti-angiogenic agents with various immunotherapies, including immune-checkpoint inhibitors, have been shown preclinically to generate more-potent antitumour effects and might have clinical potential • Anti-angiogenic agents can alleviate immunosuppression, and conversely, immunotherapies can induce changes in the vasculature or bring about antivascular effects; thus, immunotherapy and/or anti-angiogenic therapies have the potential to create a cycle of immunostimulation and vascular remodelling within tumours One of the first described immunosuppressive functions of VEGF was the inhibition of dendritic cell maturation, which results in reduced tumour-antigen presentation and thus in potential immune evasion by tumours 30 . The mechanism underlying this effect was later shown to involve the inhibition of nuclear factor-κB (NF-κB) signalling, a direct consequence of VEGF binding to VEGFR2 on dendritic cells 31,32 . Neuropilin 1 has also been implicated in VEGF-mediated inhibition of dendritic cell maturation 33 . ...
Immunotherapies have revolutionized medical oncology following the remarkable and, in some cases, unprecedented outcomes observed in certain groups of patients with cancer. Combination with other therapeutic modalities, including anti-angiogenic agents, is one of the many strategies currently under investigation to improve the response rates and duration of immunotherapies. Such a strategy might seem counterintuitive given that anti-angiogenic agents can increase tumour hypoxia and reduce the number of blood vessels within tumours. Herein, we review the additional effects mediated by drugs targeting VEGF-dependent signalling and other pathways, such as those mediated by angiopoietin 2 or HGF, which might increase the efficacy of immunotherapies. In addition, we discuss the seldom considered possibility that immunotherapies, and immune-checkpoint inhibitors in particular, might increase the efficacy of anti-angiogenic or other types of antivascular therapies and/or promote changes in the tumour vasculature. In short, we propose that interactions between both therapeutic modalities could be considered a 'two-way street'.
... This factor has also been introduced as vascular permeability factor (VPF) which released by tumor cells. (Gerhardt et al., 2003;Mimura et al., 2007;Smith et al., 2010). VEGF consider as a critical (Spilsbury et al., 2000;Xu et al., 2003). ...
Acute myeloid leukemias (AMLs) are blood disorders that exhibit uncontrolled growth and reduction of apoptosis rates. As with other malignancies, progression may be result of induction and formation of new blood vessels influenced by disease conditions. Cancer cells produce a variety of factors which play important roles in angiogenesis. Vascular endothelial growth factor (VEGF) is critical for many malignancies, including AMLs. Curcumin, as a natural compound, is able to enhance apoptosis via a mechanism affecting regulatory genes. As a new strategy we here evaluated anti- VEGF properties of curcumin, alone and in combination with thalidomide, in leukemic cell lines. Growth inhibitory effects were assessed by MTT assay and apoptosis was detected by annexin/PI staining in U937 and KG-1 cell lines. mRNA expression levels of VEGF isoforms were evaluated by qRT-PCR. Curcumin inhibited proliferation and induced apoptosis in both KG-1 and U937 cells and this effect was stronger in combination with thalidomide. In KG-1 cells, the level of VEGF (A, B, C and D) mRNA was decreased in curcumin-treated as compared to untreated cells. Maximum effects were obtained at the concentration of 40 μM curcumin in U937 cells. Taken together, the results indicate that the VEGF autocrine loop may have an impact on AML development and progression and could be considered as a therapeutic target. Thalidomide as a VEGF inhibitor in combination with curcumin appears to have a synergistic impact on inhibition of cell proliferation and promotion of apoptosis.
... However, DCs have the ability to cross-present extracellular antigens to CD8 + T cells, which is important for tumor-suppressive immunity. The mechanism by which the TME inhibits the ability of DCs to present antigens effectively is to retain DCs in an immature state, which blocks expression of co-stimulatory molecules, resulting in tolerance through T cell deletion [25]. Additionally, TAM-derived IL10 inhibits the production of IL12 by dendritic cells, ultimately leading to suppressed CD8 + T cell responses and DC tumor-suppressive functions ( Figure 1) [26]. ...
Cancer research in recent decades has highlighted the potential influence of the tumor microenvironment on the progression and metastasis of most known cancer types. Within the established microenvironment, tumor-associated macrophages (TAMs) are one of the most abundant and crucial non-neoplastic cell types. The polarization of macrophages into tumor-suppressive M1 or tumor-promoting M2 types is a fundamental event in the establishment of the tumor microenvironment. Although ample evidence indicates that TAMs are primarily M2 polarized, the mechanisms responsible for the regulation and maintenance of M1 and M2 polarization imbalance remain unclear. The manipulation of this critical axis through three main approaches may provide new strategies for cancer therapy - (I) specific interference with M2-like TAM survival or inhibiting their signaling cascades, (II) repression of macrophage recruitment to tumors, and (III) repolarization of tumor-promoting M2-like TAMs to a tumoricidal M1-like phenotype. This review summarizes current strategies for cancer intervention via manipulation of macrophage polarization, with particular focus on composition of the tumor microenvironment and its influence on cancer progression and metastasis. It is clear that additional fundamental and preclinical research is required to confirm the efficacy and practicality of this novel and promising strategy for treating cancer.
Angiogenic growth factors (AGFs) are a class of secreted cytokines related to angiogenesis that mainly include vascular endothelial growth factors (VEGFs), stromal-derived factor-1 (SDF-1), platelet-derived growth factors (PDGFs), fibroblast growth factors (FGFs), transforming growth factor-beta (TGF-β) and angiopoietins (ANGs). Accumulating evidence indicates that the role of AGFs is not only limited to tumor angiogenesis but also participating in tumor progression by other mechanisms that go beyond their angiogenic role. AGFs were shown to be upregulated in the glioma microenvironment characterized by extensive angiogenesis and high immunosuppression. AGFs produced by tumor and stromal cells can exert an immunomodulatory role in the glioma microenvironment by interacting with immune cells. This review aims to sum up the interactions among AGFs, immune cells and cancer cells with a particular emphasis on glioma and tries to provide new perspectives for understanding the glioma immune microenvironment and in-depth explorations for anti-glioma therapy.
There is an increasing interest in combining immune checkpoint inhibitors (ICIs) with anti-angiogenic drugs to enhance their anti-tumor effects. In this study, three anti-angiogenic agents, DC101 (acting on VEGFR2), SAR131675 (acting on VEGFR3), and fruquintinib (a small-molecule inhibitor acting on multiple targets) were administered to B16F1-OVA-loaded C57BL/6 mice. Immune cells infiltration in the tumor tissues, vascular normalization, and high-endothelial venule (HEV) formation were assessed to provide evidence for drug combination. Both DC101 and fruquintinib significantly slowed the melanoma growth and increased the proportion of CD3+ and CD8+ T cells infiltration compared with SAR131675, of note, the effect of DC101 was more pronounced. Moreover, DC101 and fruquintinib increased the interferon-γ and perforin levels, meanwhile, DC101 increased the granzyme B levels, whereas fruquintinib and SAR131675 did not. Only the fruquintinib-treated group showed decreased regulatory T cells infiltration. We found upregulation of PD-L1 expression in tumor cells and CD45+ immune cells in DC101-treated group as well as upregulation of PD-1 expression on CD3+ T cells. However, fruquintinib only increased PD-L1 expression in tumors. Both DC101 and fruquintinib reduced the proportion of CD31+ vessels, while DC101 increased the ratio of α-SMA +/CD31+ cells and reduced the expression of HIF-1α more than fruquintinib. Moreover, DC101 enhanced the infiltration of dendritic cells and B cells, and local HEV formation. In conclusion, our data indicate that DC101 may be a better choice for the combined clinical application of ICIs and anti-angiogenic agents.
Angiogenesis is a double-edged sword; it is a mechanism that defines the boundary between health and disease. In spite of its central role in physiological homeostasis, it provides the oxygen and nutrition needed by tumor cells to proceed from dormancy if pro-angiogenic factors tip the balance in favor of tumor angiogenesis. Among pro-angiogenic factors, vascular endothelial growth factor (VEGF) is a prominent target in therapeutic methods due to its strategic involvement in the formation of anomalous tumor vasculature. In addition, VEGF exhibits immune-regulatory properties which suppress immune cell antitumor activity. VEGF signaling through its receptors is an integral part of tumoral angiogenic approaches. A wide variety of medicines have been designed to target the ligands and receptors of this pro-angiogenic superfamily. Herein, we summarize the direct and indirect molecular mechanisms of VEGF to demonstrate its versatile role in the context of cancer angiogenesis and current transformative VEGF-targeted strategies interfering with tumor growth.
Implantable tissue-engineered vascular grafts (TEVGs) usually trigger the host reaction which is inextricably linked with the immune system, including blood–material interaction, protein absorption, inflammation, foreign body reaction, and so on. With remarkable progress, the immune response is no longer considered to be entirely harmful to TEVGs, but its therapeutic and impaired effects on angiogenesis and tissue regeneration are parallel. Although the implicated immune mechanisms remain elusive, it is certainly worthwhile to gain detailed knowledge about the function of the individual immune components during angiogenesis and vascular remodeling. This review provides a general overview of immune cells with an emphasis on macrophages in light of the current literature. To the extent possible, we summarize state-of-the-art approaches to immune cell regulation of the vasculature and suggest that future studies are needed to better define the timing of the activity of each cell subpopulation and to further reveal key regulatory switches.
Immunotherapy has achieved revolutionary success in clinics, but it remains challenging for treating hepatocellular carcinoma (HCC) characterized by high vascularization. Here, we reported that metal‐organic framework‐801 (MOF‐801) could be employed as stimulator of interferon genes (STING) through Toll‐like receptor 4 (TLR4) not just a drug delivery carrier. Notably, cytosine‐phosphate‐guanine oligodeoxynucleotides (CpG ODNs) and 5, 6‐dimethylxanthenone‐4‐acetic acid (DMXAA) STING agonist with vascular disrupting function could coordinate with MOF‐801 to self‐assemble into a nanoparticle (MOF‐CpG‐DMXAA) that effectively delivered CpG ODNs and DMXAA to cells for synergistically improving the tumour microenvironment by reprogramming tumor‐associated macrophages (TAMs), promoting dendritic cells (DCs) maturation as well as destroying tumour blood vessels. In HCC‐bearing mouse models, we demonstrated that MOF‐CpG‐DMXAA triggered systemic immune activation and stimulated robust tumoricidal immunity, resulting in a superior immunotherapeutic efficiency in orthotopic and recurrent HCC. This article is protected by copyright. All rights reserved
Marching into the second decade after the approval of ipilimumab, it is clear that immune checkpoint inhibitors (ICIs) have dramatically improved the prognosis of melanoma. Although the current edge is already high, with a 4-year OS% of 77.9% for adjuvant nivolumab and a 6.5-year OS% of 49% for nivolumab/ipilimumab combination in the metastatic setting, a high proportion of patients with advanced melanoma have no benefit from immunotherapy, or experience an early disease relapse/progression in the first few months of treatment, surviving much less. Reasonably, the primary and acquired resistance to ICIs has entered into the focus of clinical research with positive (e.g., nivolumab and relatlimab combination) and negative feedbacks (e.g., nivolumab with pegylated-IL2, pembrolizumab with T-VEC, nivolumab with epacadostat, and combinatorial triplets of BRAF/MEK inhibitors with immunotherapy). Many intrinsic (intracellular or intra-tumoral) but also extrinsic (systematic) events are considered to be involved in the development of this resistance to ICIs: i) melanoma cell immunogenicity (e.g., tumor mutational burden, antigen-processing machinery and immunogenic cell death, neoantigen affinity and heterogeneity, genomic instability, melanoma dedifferentiation and phenotypic plasticity), ii) immune cell trafficking, T-cell priming, and cell death evasion, iii) melanoma neovascularization, cellular TME components(e.g., Tregs, CAFs) and extracellular matrix modulation, iv) metabolic antagonism in the TME(highly glycolytic status, upregulated CD39/CD73/adenosine pathway, iDO-dependent tryptophan catabolism), v) T-cell exhaustion and negative immune checkpoints, and vi) gut microbiota. In the present overview, we discuss how these parameters compromise the efficacy of ICIs, with an emphasis on the lessons learned by the latest melanoma studies; and in parallel, we describe the main ongoing approaches to overcome the resistance to immunotherapy. Summarizing this information will improve the understanding of how these complicated dynamics contribute to immune escape and will help to develop more effective strategies on how anti-tumor immunity can surpass existing barriers of ICI-refractory melanoma.
Purpose
Endometrial cancer (EC) is one of the most common gynaecologic malignancies. Tumor infiltrating regulatory T-cells (Treg) have been reported to have a prognostic impact in many malignancies. Immunotherapeutic strategies are gaining interest for advanced and recurrent EC cases, where treatment options are rare. Our study was aimed at determining the value of Treg in EC progression.
Methods
EC specimens from 275 patients and 28 controls were screened immunohistochemically for the presence of Treg represented by FoxP3. Correlations with clinicopathological and survival parameters were performed. Functional assays were performed using EC cell lines Ishikawa + and RL95-2 after co-culturing with isolated CD4 + CD25 + CD127dim Treg. To assess the influence of EC on the composition of peripheral blood mononuclear cells (PBMC), flow cytometric analyses were performed.
Results
We found that an increased infiltration of Treg was associated with high grades and a reduced overall survival. Treg were almost absent in endometrium tissues from healthy control patients. Co-culture of tumor cells with CD4 + CD25 + CD127dim Treg led to functional changes: enhanced invasion, migration and viability indicated that increased levels of Treg in the tumor microenvironment may promote tumor growth. Furthermore, we found that the presence of EC cells led to phenotypic changes in PBMC, showing significantly increased levels of CD25 and FoxP3.
Conclusion
Our results indicate that the presence of Treg in the EC tumor environment is associated with a poorer outcome. A remarkable impact of Treg on tumor cell behaviour and vice versa of tumor cells on PBMC subpopulations support this notion mechanistically. Our findings provide a basis for focusing on Treg as potential future therapeutic targets in EC.
Triple‐negative breast cancer (TNBC) as “cold” tumor is characterized by severe immunosuppression of the tumor microenvironment (TME). To effectively activate the immune response of TNBC, a new kind of therapy strategy called cancer catalytic immunotherapy is proposed based on magnetic nanoparticles (NPs) as immune activators. Utilizing the weak acidity and excessive hydrogen peroxide of TME, these magnetic NPs can release ferrous ions to promote Fenton reaction, leading to abundant ·OH and reactive oxygen species (ROS) for ultimately killing cancer cells. Mechanistically, these magnetic NPs activate the ROS‐related signaling pathway to generate more ROS. Meanwhile, these magnetic NPs with unique immunological properties can promote the maturation of dendritic cells and the polarization of macrophages from M2 to M1, resulting in the infiltration of more T cells to reprogram the immunoecology of TNBC from “cold” to “hot” state. Besides directly affecting immune cells, these magnetic NPs can also affect the secretion of some immune‐related cytokines by cancer cells, to further indirectly activate the immune response. In conclusion, these catalytic immune activators are designed to achieve the synergistic treatment of chemodynamic therapy‐enhanced immunotherapy guided by computed tomography (CT)/near‐infrared region‐II (NIR‐II) dual‐mode imaging, providing a new strategy for TNBC treatment.
Immune checkpoint blockade (ICB) has become well-known in cancer therapy, strengthening the body’s anti-tumor immune response rather than directly targeting cancer cells. Therapies targeting immune inhibitory checkpoints, such as PD-1, PD-L1, and CTLA-4, have resulted in impressive clinical responses across different types of solid tumors. However, as with other types of cancer treatments, ICB-based immunotherapy is hampered by both innate and acquired drug resistance. We previously reported the enrichment of gene signatures associated with the wound healing, epithelial-to-mesenchymal, and angiogenesis processes in the tumors of patients with innate resistance to PD-1 checkpoint antibody therapy; we termed these the Innate Anti-PD-1 Resistance (IPRES) signatures. Based on gene signatures, the TGF-β and VEGFA pathways emerge as the dominant drivers of IPRES-associated processes. Here, we review these pathways’ functions, their roles in immunosuppression, and the currently available therapies that target them. We also discuss recent developments in the targeting of TGF-β using a specific antibody class called the trap antibody. The application of trap antibodies opens the promise of localized targeting of the TGF-β and VEGFA pathways within the tumor microenvironment. Such specificity may offer an enhanced therapeutic window that allows suppression of the IPRES processes in the tumor while sparing the normal homeostatic functions of the TGF-β and VEGFA in normal tissues.
Vascular endothelial growth factor‐A (VEGF) is the predominant angiogenic factor that is expressed in solid tumors. Besides its critical function in mediating tumor angiogenesis, multiple studies have demonstrated that VEGF also contributes to tumor immunosuppression. VEGF interferes with immune cell trafficking indirectly by promoting a vascular immune barrier through VEGF receptor (VEGFR) activity on endothelial cells. However, VEGFRs are also expressed on multiple immune cell types, including T cells (effector T cells, Tregs) and myeloid cells (DCs, TAMs, MDSCs), where VEGF can have direct effects on immune cell phenotype and function. Thus, it is not surprising that strategies targeting VEGF/VEGFRs have shown efficacy in alleviating tumor‐associated immunosuppression and have been combined with immunotherapies, especially immune checkpoint blockade. In this review, we discuss the direct and indirect effects of VEGF on the immunosuppressive tumor microenvironment with particular focus on the direct regulation of immune cells through VEGFR2 activity. We also summarize preclinical and clinical observations of combining antiangiogenesis agents with immunotherapies for the treatment of solid tumors. Review on the function of vascular endothelial growth factor‐A (VEGF) in regulating immune cells in the tumor microenvironment and theuse of anti‐VEGF as cancer immunotherapy.
As a new concept of glioma therapy, immunotherapy combined with standard therapies is a promising modality to improve glioma patient survival. VEGF and its signaling pathway molecules not only inhibit angiogenesis but also may reinforce the immunosuppressive tumor microenvironment, including promotion of the accumulation of immunosuppressive tumor-associated macrophages (TAMs). In this review, we discuss VEGF-targeted therapy as a new treatment option of the TAM-targeted therapy for high-grade gliomas, as well as other TAM-targeted therapies. The authors also discuss the potential of these therapies combined with conventional immunotherapies.
Introduction: Glioblastoma is invariably deadly and is characterized by extensive vascularization and macrophage-dominant immunosuppression; nevertheless, anti-angiogenesis has so far failed to prolong overall survival of patients. Regardless of the problems in clinical development, the rationale for the application of anti-angiogenics in glioblastoma remains.
Areas covered: Mechanisms of glioblastoma resistance to anti-angiogenic agents are discussed, including vessel co-option and amplification of hypoxic signaling in response to vessel destruction. The modulation of GSC and tumor-associated macrophages by dysfunctional tumor vessels and by hypoxia are outlined. Pharmacologic approaches to sensitizing glioblastomas to anti-angiogenics and evidence for the cooperation of anti-angiogenics with immunotherapy approaches are summarized. Database search: https://pubmed.ncbi.nlm.nih.gov prior to December 12, 2020.
Expert opinion: Despite drawbacks in the clinical development of vascular endothelial growth factor A (VEGF)-targeted agents, there is still rationale for the use of anti-angiogenics. The better understanding of vascular co-option and adverse effects of blood vessel destruction guides to improve strategies for vascular targeting. The pivotal role of the vasculature and of angiogenic factors such as VEGF for the induction and maintenance of immunosuppression in glioblastoma supports the use of anti-angiogenics in combination with immunotherapy. Proinflammatory repolarization of perivascular and perinecrotic tumor-associated macrophages is probably paramount for overcoming treatment resistance to virtually any treatment.
A great deal of evidence has shown that anti-angiogenic molecules and antibodies targeting the VEGF-A/VEGFRs signal pathway can also reverse tumor-induced immunosuppression to an extent. VEGF165b, an anti-angiogenic VEGF-A isoform, has demonstrated capacity as an efficacious anti-tumor therapy in mice as an anti-angiogenic agent. However, whether VEGF165b also plays an immunomodulatory role in anti-tumor field remains unclear. mVEGF165b effect on regulatory T cells (Tregs) in vitro were evaluated using flow cytometry and Cell Counting Kit-8 (CCK-8) methods. Its effects on Tregs (or Foxp3 expressing cells) and myeloid-derived suppressor cells (MDSCs) were analyzed in vivo using flow cytometry and immunostaining techniques. In this study, we found VEGF165b and its mutant (its half-life in plasma was extended 10 times while retaining its bioactivity; the VEGF165b mutant is called mVEGF165b for short) inhibited the proliferation of Tregs in vitro. In addition, mVEGF165b dramatically inhibited the accumulation of MDSCs and Tregs (or Foxp3 expressing cells) in the spleen and tumor in tumor-bearing mice. In conclusion, our findings demonstrated for the first time that VEGF165b and its mutant has immunoregulatory functions. It may be used as a potential immunomodulatory agent, beyond its anti-angiogenic capacities, in cancer therapies.
Anti-angiogenic therapies that target the vascular endothelial growth factor (VEGF) pathway have been used clinically to combat cancer for over a decade. Beyond having a direct impact on blood vessel development and tumor perfusion, accumulating evidence indicates that these agents also affect antitumor immune responses. Numerous clinical trials combining anti-angiogenic drugs with immunotherapies for the treatment of cancer are ongoing, but a mechanistic understanding of how disruption of tumor angiogenesis may impact immunity is not fully discerned. Here we reveal that blockade of VEGF-A with a monoclonal antibody to VEGF augments activation of CD8+ T cells within tumors and potentiates their capacity to produce cytokines. We demonstrate that this phenomenon relies on the disruption of VEGFR2 signaling in the tumor microenvironment, but does not affect CD8+ T cells directly. Instead, the augmented functional capacity of CD8+ T cells stems from increased tumor hypoxia that initiates a hypoxia-inducible factor-1α (HIF-1α) program within CD8+ T cells that directly enhances cytokine production. Lastly, combinatorial administration of anti-VEGF with an immunotherapeutic antibody, anti-OX40, improved antitumor activity over single-agent treatments. Our findings illustrate that anti-VEGF treatment enhances CD8+ T-cell effector function and provides a mechanistic rationale for combining anti-angiogenic and immunotherapeutic drugs for cancer treatment.
Cancer immunotherapy (CIT) has transformed cancer treatment. In particular, immunotherapies targeting the programmed death ligand 1 (PD-L1)/programmed death 1 pathway have demonstrated durable clinical benefit in some patients. However, CIT combinations may create a more favorable environment in which to maximize the potential of the immune system to eliminate cancer. Here we describe 3 key mechanisms related to vascular endothelial growth factor (VEGF)-mediated immunosuppression: inhibition of dendritic cell maturation, reduction of T-cell tumor infiltration, and promotion of inhibitory cells in the tumor microenvironment; supporting data are also described. In addition, we discuss immunomodulatory properties observed within tumors following bevacizumab treatment. Combining anti-PD-L1 and anti-VEGF therapies has shown synergy and positive outcomes in phases I to III studies, particularly in settings where high VEGF levels are known to play an important role in tumor growth. We also review data from key studies supporting combination of bevacizumab and CIT, with a focus on PD-L1/programmed death 1 inhibitors.
Sentinel lymph node metastasis is a prognostic indicator for systemic tumor spread in many types of cancers, and tumor lymphangiogenesis correlates with reduced survival. Consequently, lymphatic vessels have been suggested to promote tumor progression in multiple ways. Tumor lymphangiogenesis occurs both in primary tumors and at distant (pre-) metastatic sites, and facilitates lymphatic invasion and tumor cell dissemination. Lymphatic vessels have also emerged as regulators of tumor immunity, transporting tumor antigens to lymph nodes and directly interacting with immune cells. Furthermore, lymphatic vessels might provide a 'lymphovascular' niche contributing to the maintenance of stem-like tumor cells that are tightly related to tumor recurrence. Thus, targeting tumor lymphangiogenesis or specific lymphatic-associated functions might represent a promising approach to inhibit tumor progression.
Neutrophils represent the most abundant leukocyte subpopulation in human peripheral blood and play an important role in host defence against pathogens during the earliest phases of inflammatory processes. Neutrophils are considered as macrophages, i.e. capable to phagocyte small particles such as bacteria, viruses, and small pieces of cell debris. Similarly to TAMs, tumor associated neutrophils (TANs) can exert both anti-tumoral and pro-tumoral functions (Fig. 7.1) (Fridlender et al. 2009).
Two distinct receptors for vascular endothelial growth factor (VEGF), the tyrosine kinase receptors Flt-1 and Flk-1/KDR, have been described. In this study we show that monocytes, in contrast to endothelium, express only the VEGF receptor Flt-1, and that this receptor specifically binds also the VEGF homolog placenta growth factor (PlGF). Both VEGF and PlGF stimulate tissue factor production and chemotaxis in monocytes at equivalent doses. In contrast, endothelial cells expressing both the Flt-1 and the Flk-1/KDR receptors produce more tissue factor upon stimulation with VEGF than after stimulation with PlGF. Neutralizing antibodies to the KDR receptor reduce the VEGF- stimulated tissue factor induction in endothelial cells to levels obtained by stimulation with PlGF alone, but do not affect PlGF-induced tissue factor induction in endothelial cells nor the VEGF-dependent tissue factor production in monocytes. These findings strongly suggest Flt-1 as a functional receptor for VEGF and PlGF in monocytes and endothelial cells and identify this receptor as a mediator of monocyte recruitment and procoagulant activity.
Vascular endothelial growth factor (VEGF), produced by almost all tumor cells, affects the ability of hemopoietic progenitor cells (HPC) to differentiate into functional dendritic cells (DC) during the early stages of their maturation. In this study we demonstrate specific binding of VEGF to HPC. This binding was efficiently competed by placenta growth factor (PlGF), a ligand reportedly specific for the Flt-1 receptor. The number of binding sites for VEGF decreased during DC maturation in vitro associated with decreased levels of mRNA for Flt-1. VEGF significantly inhibited nuclear factor-kB (NF-kB)-dependent activation of reporter gene transcription during the first 24 h in culture. The presence of VEGF significantly decreased the specific DNA binding of NF-kB as early as 30 min after induction with TNF-a. This was followed on days 7 to 10 by decreases in the mRNA for RelB and c-Rel, two subunits of NF-kB. Blockade of NF-kB activity in HPC at early stages of differentiation with an adenovirus expressing a dominant IkB inhibitor of NF-kB reproduced the pattern of effects observed with VEGF. Thus, NF-kB plays an important role in maturation of HPCs to DC, and VEGF activation of the Flt-1 receptor is able to block the activation of NF-kB in this system. Blockade of NF-kB activation in HPCs by tumor-derived factors may therefore be a mechanism by which tumor cells can directly down-modulate the ability of the immune system to generate effective antitumor immune responses. The Journal of Immunology, 1998, 160: 1224 -1232.
Vascular permeability factor (VPF) is an Mr 40-kD protein that has been purified from the conditioned medium of guinea pig line 10 tumor cells grown in vitro, and increases fluid permeability from blood vessels when injected intradermally. Addition of VPF to cultures of vascular endothelial cells in vitro unexpectedly stimulated cellular proliferation. VPF promoted the growth of new blood vessels when administered into healing rabbit bone grafts or rat corneas. The identity of the growth factor activity with VPF was established in four ways: (a) the molecular weight of the activity in preparative SDS-PAGE was the same as VPF (Mr approximately 40 kD); (b) multiple isoforms (pI greater than or equal to 8) for both VPF and the growth-promoting activity were observed; (c) a single, unique NH2-terminal amino acid sequence was obtained; (d) both growth factor and permeability-enhancing activities were immunoadsorbed using antipeptide IgG that recognized the amino terminus of VPF. Furthermore, 125I-VPF was shown to bind specifically and with high affinity to endothelial cells in vitro and could be chemically cross-linked to a high-molecular weight cell surface receptor, thus demonstrating a mechanism whereby VPF can interact directly with endothelial cells. Unlike other endothelial cell growth factors, VPF did not stimulate [3H]thymidine incorporation or promote growth of other cell types including mouse 3T3 fibroblasts or bovine smooth muscle cells. VPF, therefore, appears to be unique in its ability to specifically promote increased vascular permeability, endothelial cell growth, and angio-genesis.
Langerhans cells (LC), the APCs in the skin, serve as a model for investigation of dendritic cell (DC) function in tissues. DC play a crucial role in the generation of antitumor immune responses. In this study, we investigated the effect of the presence of tumor in vivo on the ability of LC to take up Ag, migrate to draining lymph nodes, and stimulate primary T cell responses. In two animal models, these functions were substantially inhibited. This effect was not restricted to LC located in the skin near a tumor but was also seen at sites distant from the tumor. The duration of tumor exposure, and not its ultimate size, were found to be important, suggesting that tumors could be inhibiting the maturation of LC rather than directly inhibiting their function. Model experiments with radiation chimeras supported this hypothesis. To investigate the potential role of vascular endothelial growth factor (VEGF) in these effects we used anti-VEGF-neutralizing Ab to treat animals bearing tumors. Treatment with the Ab at a dose of 10 microg i.p. per mouse, twice a week for 4 wk, significantly improved the number and function of LC as measured by their ability to migrate to lymph nodes and stimulate primary T cell responses, even at doses that do not affect the growth of these established poorly immunogenic tumors. Thus, inhibition of VEGF signaling may improve DC function in tumor-bearing hosts and possibly serve to improve the efficacy of cancer immunotherapy.
It has been reported that decreased numbers of dendritic cells (DCs) are correlated with poor prognosis in some types of malignancy, such as gastric cancer. However, factors that determine the density of DCs have not been characterized. It was recently reported that vascular endothelial growth factor (VEGF) inhibits the functional maturation of DCs from CD34+ precursors. In this study, we analysed the relationship between the expression of VEGF and the density of DCs in gastric carcinoma tissues by immunohistochemical staining. The extent of infiltration by DCs was graded from marked to slight on the basis of the mean densities of DCs. The prognosis of patients with marked infiltration was significantly better than that of patients with slight infiltration among patients who had undergone curative resection. Multivariate analysis showed that infiltration by DCs was an independent prognostic indicator. Furthermore, there was an inverse correlation between the density of DCs and the expression of VEGF Our results suggest that expression of VEGF might be associated with tumour progression and poor prognosis not only because VEGF stimulates angiogenesis, but also because it allows tumours to escape from attack by the immune system in patients with gastric carcinoma.
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To investigate the clinical significance of vascular endothelial growth factor (VEGF) in osteosarcoma, we immunohistochemically stained biopsy specimens of 27 primary osteosarcomas using an antibody against VEGF and evaluated the correlation between the expression of VEGF and local density of CD34-positive microvessels, clinicopathological variables, and survival of patients. VEGF staining was positive in 17 tumors (63.0%) in which the density of CD34-positive microvessels was significantly higher than that in VEGF-negative 10 tumors (P < 0.05). In terms of clinicopathological variables, there was no correlation between the expression of VEGF and histological subtype, stage, or response to neoadjuvant chemotherapy, or, strikingly, to the development of pulmonary metastasis (89% of VEGF-positive tumors versus 10% of VEGF-negative tumors; P < 0.0003). Moreover, patients with a VEGF-positive tumor were poorer in both disease-free survival (P < 0.001) and overall survival (P < 0.03) compared to those with a VEGF-negative tumor. These findings strongly suggest that VEGF expression in untreated osteosarcoma is predictive of pulmonary metastasis and poor prognosis in patients who underwent aggressive therapy and also provide the basis for a therapeutic strategy targeting angiogeneic property of osteosarcoma.
Flt-1, also known as vascular endothelial growth factor receptor 1 (VEGFR-1), is a high-affinity tyrosine kinase receptor for VEGF and is expressed almost exclusively on vascular endothelial cells. As an exception, Flt-1 transcript was recently found to be expressed in human peripheral blood monocytes. However, the protein of the Flt-1 receptor on the cell surface of monocytes is yet to be identified, and whether the Flt-1 protein is expressed during the differentiation of monocyte-macrophage lineage cells has not been examined. Using monoclonal antibodies against 2 different antigenic epitopes on the Flt-1 extracellular domain, this study found that the major population of the monocyte-marker CD97+ cells in human peripheral blood express Flt-1 as a cell surface molecule. VEGFR-2 (KDR/Flk-1) was not expressed at detectable levels in these cells. An Flt-1 neutralizing monoclonal antibody significantly suppressed VEGF-induced migration of the monocytes, suggesting an important role for Flt-1 in the biologic function of monocytes. Furthermore, CD34+ cells in human cord blood, originally negative for the Flt-1 expression, differentiated into Flt-1+ cells in association with the appearance of monocyte-macrophage markers after a 2-week culture in the presence of hematopoietic cytokines. In addition, the Flt-1+ CD11b+ cell fraction from CD34+ cells was found to efficiently differentiate into multinuclear osteoclasts in the presence of macrophage colony-stimulating factor and osteoclast differentiation factor. These results strongly suggest that Flt-1 is a novel cell surface marker as well as a biologically functional molecule for monocyte-macrophage lineages in humans.
The mechanism of tumor-associated T cell dysfunction remains an unresolved problem of tumor immunology. Development of T cell defects in tumor-bearing hosts are often associated with increased production of immature myeloid cells. In tumor-bearing mice, these immature myeloid cells are represented by a population of Gr-1(+) cells. In this study we investigated an effect of these cells on T cell function. Gr-1(+) cells were isolated from MethA sarcoma or C3 tumor-bearing mice using cell sorting. These Gr-1(+) cells expressed myeloid cell marker CD11b and MHC class I molecules, but they lacked expression of MHC class II molecules. Tumor-induced Gr-1(+) cells did not affect T cell responses to Con A and to a peptide presented by MHC class II. In sharp contrast, Gr-1(+) cells completely blocked T cell response to a peptide presented by MHC class I in vitro and in vivo. Block of the specific MHC class I molecules on the surface of Gr-1(+) cells completely abrogated the observed effects of these cells. Thus, immature myeloid cells specifically inhibited CD8-mediated Ag-specific T cell response, but not CD4-mediated T cell response. Differentiation of Gr-1(+) cells in the presence of growth factors and all-trans retinoic acid completely eliminated inhibitory potential of these cells. This may suggest a new approach to cancer treatment.
The mechanism of antitumor effect of monoclonal antibodies (mAbs) is not fully understood. Here we show that coating myeloma cells with anti-syndecan-1 antibody promotes cross-presentation of cellular antigens by dendritic cells (DCs) to autologous T cells from healthy donors. The tumor cells treated with anti-syndecan-1 or isotype-matched control antibody were fed to HLA-mismatched monocyte-derived immature DCs. Tumor cell-loaded mature DCs induced a strong CD8(+) T cell response that was specific for the cancer-testis (C-T) antigens expressed in the tumor. The CD8(+) T cells killed peptide-pulsed targets, as well as myeloma tumor cells. Importantly, mAbs-coated tumor-loaded DCs were consistently superior to DCs loaded with peptides or dying cells for eliciting tumor-specific killer T cells. This enhanced cross-presentation was not due to enhanced tumor cell uptake or to DC maturation. When mixtures of NY-Eso-1-positive and -negative myeloma cells were captured by DCs, the anti-syndecan-1 antibody had to be on the NY-Eso-1-positive cells to elicit NY-Eso-1-specific response. Cross-presentation was inhibited by pretreatment of DCs with Fc gamma receptor blocking antibodies. Targeting of mAb-coated tumors to DCs may contribute to the efficacy of tumor-reactive mAb and offers a new strategy for immunotherapy.
T-cell defects and premature thymic atrophy occur in cancer patients and tumor-bearing animals. We demonstrate that exposure of mice to recombinant vascular endothelial growth factor (VEGF) at concentrations similar to those observed in advanced stage cancer patients reproduces this profound thymic atrophy and is highlighted by a dramatic reduction in CD4+/CD8+ thymocytes. We find that VEGF does not induce thymocyte apoptosis, but instead rapidly decreases the number of the earliest observable progenitors in the thymus. VEGF does not inhibit thymocyte development in fetal thymic organ culture, further suggesting a prethymic effect. We also demonstrate that bone marrow progenitors from animals infused with recombinant VEGF and transferred to irradiated untreated animals recolonize the thymus more efficiently than progenitors from control animals. This suggests that VEGF exposure is associated with an increased population of thymus-committed progenitors in the bone marrow. We hypothesize that pathophysiologically relevant concentrations of VEGF may block the differentiation and/or emigration of these progenitors resulting in the observed thymic atrophy. Removal of VEGF via cessation of infusion or adoptive transfer of progenitors to a congenic host induces a preferential commitment of lymphoid progenitors to the T lineage and results in a restoration of the normal composition and cellularity of the thymus. These data demonstrate that at pathophysiologic concentrations, VEGF interferes with the development of T cells from early hematopoetic progenitor cells and this may contribute to tumor-associated immune deficiencies.
Dendritic cells (DC) are increasingly explored as cellular vaccines for tumor immunotherapy. In most reported DC-based cancer vaccine trials, DC have been pulsed with soluble tumor antigen-derived peptide ligands of MHC molecules. Considering that the half-life of peptide/MHC complexes on the cell surface is relatively short and that soluble exogenous protein antigens cannot be efficiently processed via the MHC class I-processing pathway, the current vaccination procedure is not optimal for the induction of strong T cell responses aiming at tumor rejection. Recently, we have shown that antigen presentation can be prolonged when synthetic peptides were encapsulated in biodegradable poly(D,L-lactide-co-glycolide) (PLGA) microspheres (MS) for uptake by DC. In the present study, we investigated the phenotypic and functional consequences of MS uptake by human monocyte-derived dendritic cells (MoDC) in vitro. We found that immature MoDC that were prepared in serum free media suitable for clinical application were able to phagocytose high numbers of MS, while matured MoDC showed a reduced capacity for phagocytosis of MS. The ingestion of MS did not change the cell surface expression of CD80, CD83, CD86 and HLA-DR of immature and mature DC, suggesting that MS uptake did not induce DC maturation but that maturation by cytokines or LPS was unaltered in the presence of MS. Furthermore, MS-loaded mature MoDC expressed normal levels of the chemokine receptor CCR7 and migrated as efficiently towards CCL19 or CCL21 as unloaded MoDC. DC viability and the secretion of TNF-alpha and IL-12 was not significantly changed by MS loading. Taken together, our data indicate that PLGA-MS loading has no negative effects on the pivotal properties of MoDC in vitro. It should therefore be feasible to further develop this antigen loading strategy for clinical use in immunotherapy against viral infections and tumors.
Impaired Ag-presenting function in dendritic cells (DCs) due to abnormal differentiation is an important mechanism of tumor escape from immune control. A major role for vascular endothelial growth factor (VEGF) and its receptors, VEGFR1/Flt-1 and VEGFR2/KDR/Flk-1, has been documented in hemopoietic development. To study the roles of each of these receptors in DC differentiation, we used an in vitro system of myeloid DC differentiation from murine embryonic stem cells. Exposure of wild-type, VEGFR1(-/-), or VEGFR2(-/-) embryonic stem cells to exogenous VEGF or the VEGFR1-specific ligand, placental growth factor, revealed distinct roles of VEGF receptors. VEGFR1 is the primary mediator of the VEGF inhibition of DC maturation, whereas VEGFR2 tyrosine kinase signaling is essential for early hemopoietic differentiation, but only marginally affects final DC maturation. SU5416, a VEGF receptor tyrosine kinase inhibitor, only partially rescued the mature DC phenotype in the presence of VEGF, suggesting the involvement of both tyrosine kinase-dependent and independent inhibitory mechanisms. VEGFR1 signaling was sufficient for blocking NF-kappaB activation in bone marrow hemopoietic progenitor cells. VEGF and placental growth factor affect the early stages of myeloid/DC differentiation. The data suggest that therapeutic strategies attempting to reverse the immunosuppressive effects of VEGF in cancer patients might be more effective if they specifically targeted VEGFR1.
Defective function of dendritic cells (DC) in cancer has been recently described and may represent one of the mechanisms of tumor evasion from immune system control. We have previously shown in vitro that vascular endothelial growth factor (VEGF), produced by almost all tumors, is one of the tumor-derived factors responsible for the defective function of these cells. In this study, we investigated whether in vivo infusion of recombinant VEGF could reproduce the observed DC dysfunction. Continuous VEGF infusion, at rates as low as 50 ng/h (resulting in serum VEGF concentrations of 120 to 160 pg/mL), resulted in a dramatic inhibition of dendritic cell development, associated with an increase in the production of B cells and immature Gr-1+ myeloid cells. Infusion of VEGF was associated with inhibition of the activity of the transcription factor NF-κB in bone marrow progenitor cells. Experiments in vitro showed that VEGF itself, and not factors released by VEGF-activated endothelial cells, affected polypotent stem cells resulting in the observed abnormal hematopoiesis. These data suggest that VEGF, at pathologically relevant concentrations in vivo, may exert effects on pluripotent stem cells that result in blocked DC development as well as affect many other hematopoietic lineages.
Dendritic cells (DC) in 121 colorectal adenocarcinomas were investigated immunohistochemically, using anti-S-100 protein antibody. S-100(+) DC were recognized among the malignant cells and/or around the tumor and differed in distribution either from lysozyme-positive macrophages or from neuron-specific enolase-positive neural tissue. Patients with many S-100(+) DC (more than 30 cells per 10 high-power fields) in the tumor survived longer than did those with few such cells (less than 30 cells), most often with no metastases (P < 0.001). The grade of S-100(+) DC infiltration was related to both density of lymphocytic infiltration in the primary tumor and the degree of paracortical hyperplasia in the regional lymph nodes (P < 0.05). Dendritic cells, therefore, as antigen-presenting cells, conceivably mediate cell immunity in a tumor with lymphoid infiltration and in the regional lymph nodes. The number of S-100(+) DC in the primary colorectal carcinomas represents one aspect of such a series of antitumor immunoreaction, in vivo.
Flt-1, also known as vascular endothelial growth factor receptor 1 (VEGFR-1), is a high-affinity tyrosine kinase receptor for VEGF and is expressed almost exclusively on vascular endothelial cells. As an exception, Flt-1 transcript was recently found to be expressed in human peripheral blood monocytes. However, the protein of the Flt-1 receptor on the cell surface of monocytes is yet to be identified, and whether the Flt-1 protein is expressed during the differentiation of monocyte-macrophage lineage cells has not been examined. Using monoclonal antibodies against 2 different antigenic epitopes on the Flt-1 extracellular domain, this study found that the major population of the monocyte-marker CD97⁺ cells in human peripheral blood express Flt-1 as a cell surface molecule. VEGFR-2 (KDR/Flk-1) was not expressed at detectable levels in these cells. An Flt-1 neutralizing monoclonal antibody significantly suppressed VEGF-induced migration of the monocytes, suggesting an important role for Flt-1 in the biologic function of monocytes. Furthermore, CD34⁺cells in human cord blood, originally negative for the Flt-1 expression, differentiated into Flt-1⁺ cells in association with the appearance of monocyte-macrophage markers after a 2-week culture in the presence of hematopoietic cytokines. In addition, the Flt-1⁺CD11b⁺ cell fraction from CD34⁺ cells was found to efficiently differentiate into multinuclear osteoclasts in the presence of macrophage colony-stimulating factor and osteoclast differentiation factor. These results strongly suggest that Flt-1 is a novel cell surface marker as well as a biologically functional molecule for monocyte-macrophage lineages in humans.
Decreased immune function in cancer patients is well-characterized (I), and tumor cells have developed a variety of mechanisms, to avoid anti-tumor immune responses (2–8). One mechanism for inhibition of immune cell function by tumors in the production of soluble factors, such as IL-10, TNF,
TGF-β, and Vascular Endothelial Growth Factor (VEGF). The effects of these factors appear, to be twofold: To inhibit effect
or function and to impair the development of immune cells by acting on earlier stages of immunopoiesis. Immune suppression
by tumors is accomplished by a variety of cellular and molecular mechanisms, and virtually all branches of the immune system
can be affected. VEGF and its receptors have profound effects on the early development and differentiation of both vascular
endothelial and hematopoetic progenitors (9). It induces proliferation of mature endothelial cells and is an important component in the formation of tumor neovasculature
(10). VEGF is abundantly expressed by a large percentage of solid tumors and this over-expression is closely associated with
a poor prognosis (11, 12). Some of the earliest hematopoetic progenitors express receptors for VEGF (13), and we have demonstrated that VEGF causes a defect in the functional maturation of dendritic cells (DC) from progenitors.
This developmental defect is associated with impaired activation of NF-κB (14–17). This review describes research demonstrating that VEGF is not only important for tumor vascularization, but is also a key
factor produced by solid tumors to inhibit recognition and destruction of tumor cells by the immune system.
Induction of specific antitumor cytotoxic T cell responses was studied in BALB/c mice bearing tumors transfected with a mutant human p53 minigene. We observed that mice were resistant to the induction of peptide-specific CTL as early as 5 days after challenge with a minimal lethal dose of tumor cells, and the cell types responsible for this effect were further characterized. The contribution of CD4+and CD8+T cells in this response was studied after peptide-pulsed dendritic cell (DC) immunization.In vitrodepletion of CD4+cells during peptide restimulation reduced the level of specific lysis in control mice, and depletion of CD8+T cells completely abrogated it. Substitution of CD8+cells from immunized control mice during restimulation of cells from immunized tumor-bearing mice did not change the level of specific lysis. Substitution of the CD4+from tumor-bearing mice by CD4+cells from control mice improved CTL response, although this response did not reach control values. Peptide-pulsed dendritic cells isolated from tumor-bearing mice showed a significantly reduced ability to induce specific CTL in control animals and reduced ability to restimulate immune T cells from control micein vitro.DC from tumor-bearing mice also had a reduced ability to stimulate control allogeneic T cells. Restimulation of T cells from immunized tumor-bearing mice with DC from control animals, but not from tumor-bearing mice, dramatically increased specific CTL responses to control levels. Macrophages at the same concentration were not able to improve CTL function. Thus, defective antigen presentation by DC appears to be a major determinant for CTL nonresponsiveness to peptide antigens in tumor-bearing mice, and addition of control DC can restore specific lysis. These data provide a basis for new approaches to peptide-based cancer immunotherapy.
Antitumor CTL responses were studied in a model tumor bearing a mutant human p53 gene. We found ineffective induction of antitumor CTL in mice bearing these tumors associated with measurable defects in the function of dendritic cells (DC) from these animals. In this study we investigate the mechanism of this defect in mature DC and find that functional DC can be generated by growth from the bone marrow of tumor-bearing animals. Tumor cell supernatants did not affect the function of mature DC obtained from the spleen of tumor-bearing animals, but significantly suppressed the ability to generate functional DC from the bone marrow of control micein vitro.This suggests that tumor cells may release factors which block early stages of DC maturation from precursors. DC generated from the bone marrow of tumor-bearing mice showed normal potential to stimulate allogeneic T cells, to stimulate anti-mutant p53 peptide-specific cytotoxic T cells, and to induce anti-p53 CTL responsesin vivoin control mice. Repeated immunization with peptide-pulsed DC generated from the bone marrow of control mice (every 4–5 days) blocked progression of established tumors. Immunization of mice with peptide-pulsed DC obtained from the spleen of tumor-bearing mice (4 weeks after tumor injection) did not affect the tumor growth, whereas immunization with peptide-pulsed DC generated from bone marrow of tumor-bearing mice resulted in significantly prolonged survival and delayed tumor growth. Tumor progression was associated with change of the balance Th1/Th2 cells in favor of the Th2-like cytokine profile, while effective immunization was associated with a shift to the Th1 phenotype. Thus, frequent immunization of mice with mutant p53 peptide-pulsed DC generated from stem cells of tumor-bearing hosts can induce effective antitumor CTL responses associated with production of Th1 cells and lead to significant antitumor effects.
The level of expression of H/Le(y)/Le(b) antigens is high in various histologic types of lung cancer, a feature that may be related to deletion of A and B blood-group antigens. We evaluated the possibility that expression of this antigen, which can be defined by the monoclonal antibody MIA-15-5, might be of prognostic value, as suggested by our previous observation that MIA-15-5 inhibits tumor-cell motility and metastasis.
We used MIA-15-5 to stain tissue sections from 149 patients with primary lung cancer whose clinico-pathological histories were well documented. The survival curves for patients whose tumors stained positively were compared with the curves for those whose tumors stained negatively. Multivariate analyses were performed with a Cox proportional-hazards regression model.
Among the 149 patients studied, five-year survival in the 91 patients with MIA-positive tumors was significantly lower than survival in the 58 with MIA-negative tumors (20.9 percent vs. 58.6 percent, P less than 0.001). Among the 67 patients with squamous-cell carcinoma, the rates also differed significantly (10.5 percent vs. 62.1 percent, P less than 0.001). The difference in survival between patients with MIA-positive tumors and those with MIA-negative tumors was significant among patients with blood groups A and AB (P less than 0.001), but not among those with blood group B or O (P = 0.071 and 0.068, respectively). Multivariate analysis with the Cox regression model indicated that positivity best correlated with five-year mortality, followed by lymph-node status (N stage) and tumor size status (T stage), whereas sex, age, and blood group did not correlate with mortality.
Positivity for MIA (i.e., immunohistologic staining by MIA-15-5, which defines H/Le(y)/Le(b) antigens) is inversely correlated with survival among patients with primary lung cancer and may be of prognostic value.
Localization and intensity of squamous cell carcinoma-related antigen (SCC-Ag) and infiltration of Langerhans' cells (LC) were investigated immunohistochemically, using anti-SCC-Ag and anti-S-100 protein antisera, respectively, in 36 cases of squamous cell carcinoma of the human esophagus. The SCC-Ag was an indicator of histologic differentiation of squamous cell carcinoma but not of malignant potential. The population density of LC correlated well with the histologic stage, vessel invasion, and postoperative survival time. In patients with a marked infiltration of LC, survival time was longer than for those in whom the infiltration was slight (P less than 0.05). The density of the LC can serve an indicator of defense of the host against the carcinoma. There was no correlation between SCC-Ag and S-100 protein-positive cells.
Dendritic cells (DC) in 121 colorectal adenocarcinomas were investigated immunohistochemically, using anti-S-100 protein antibody. S-100(+)DC were recognized among the malignant cells and/or around the tumor and differed in distribution either from lysozyme-positive macrophages or from neuron-specific enolase-positive neural tissue. Patients with many S-100(+)DC (more than 30 cells per 10 high-power fields) in the tumor survived longer than did those with few such cells (less than 30 cells), most often with no metastases (P less than 0.001). The grade of S-100(+)DC infiltration was related to both density of lymphocytic infiltration in the primary tumor and the degree of paracortical hyperplasia in the regional lymph nodes (P less than 0.05). Dendritic cells, therefore, as antigen-presenting cells, conceivably mediate cell immunity in a tumor with lymphoid infiltration and in the regional lymph nodes. The number of S-100(+) DC in the primary colorectal carcinomas represents one aspect of such a series of antitumor immunoreaction, in vivo.
Infiltration of T-zone histiocytes (Langerhans' cells and their precursors) and macrophages was investigated by immunohistochemical methods with the use of anti-S100 protein and anti-lysozyme antibodies in 40 Stage Ia cases of adenocarcinoma of the lung. Varying population densities of S100+ T-zone histiocytes were demonstrated in 31 (77.5%) of 40 adenocarcinomas; however, lysozyme+ macrophages were found in almost equal quantities in all cases of adenocarcinoma. The distribution of T-zone histiocytes was clearly different from that of macrophages. Namely, the former was mainly interspersed among the tumor cells, whereas macrophages were found in the stroma and around necrotic foci. The prognosis of Stage Ia adenocarcinoma cases was related to the density of T-zone histiocytes in tumor tissues. Patients with marked infiltration of T-zone histiocytes survived longer than those without or with only slight infiltration (P less than 0.05). Such relationship was not observed with regard to macrophages. This indicates that T-zone histiocytes infiltrating within the tumor and regional lymph nodes may play a role in host defense mechanisms against tumor in the early stage of adenocarcinoma of the lung.
Dendritic cells are potent antigen-presenting cells that initiate primary immune responses. Although dendritic cells derive from bone marrow stem cells, the intermediate stages in their development remain unknown. In this study, plastic-adherent blood monocytes (CD14+, CD1a-) cultured for 7 days with granulocyte-monocyte colony-stimulating factor, interleukin 4, and tumor necrosis factor alpha were shown to differentiate into CD1a+ CD83+ dendritic cells. These cells displayed all phenotypic and morphologic characteristics of mature dendritic cells and were the most potent stimulatory cells in allogeneic mixed leukocyte reactions. The identification of specific culture conditions that generate large numbers of dendritic cells from purified monocytes uncovers an important step in dendritic cell maturation that will allow the further characterization of their role in autoimmune diseases, graft rejection, and human immunodeficiency virus infection.
Colon cancer cells express potentially immunogenic proteins but are not rejected by the immune system. To induce an effective immune response, antigenic peptides have to be presented to T lymphocytes by professional antigen-presenting cells in association with HLA class II molecules. Antigen-presenting cells also have to express B7 family molecules, B7-1 and B7-2, which deliver the costimulatory signals that are required to prevent T cell anergy. We studied B7-1 and B7-2 expression by the antigen-presenting cells that infiltrate colorectal cancer stroma. In 25 samples of colorectal carcinomas, a panel of monoclonal antibodies was used to label macrophages, dendritic cells, and T lymphocytes that infiltrate the tumor stroma and the morphologically normal distant mucosa. The expression of HLA class II and B7 molecules involved in T-cell activation was studied using specific monoclonal antibodies. Biopsy pieces from two patients with active Crohn's disease were used as controls. All of the samples were heavily infiltrated by macrophages and/or dendritic cells that strongly expressed HLA class II molecules. In contrast, antibodies to B7-1 and/or B7-2 stained no cells in 16 of the 25 samples of colorectal tumors and less than 1% of the inflammatory cells that infiltrated tumor stroma of the other nine tumor samples. B7 molecules were also poorly expressed by rare cells in the lamina propria of the morphologically normal colorectal mucosa. In contrast, many inflammatory cells that infiltrated the two Crohn's disease samples strongly expressed B7-1 and B7-2, especially in the granulomas. We conclude that most HLA class II+ inflammatory cells that infiltrate colorectal cancers do not express the B7-1 and B7-2 costimulatory molecules. This defect may contribute to the failure of the immune system to recognize tumor cells as antigenic.
Inadequate presentation of tumor antigens by host professional antigen-presenting cells (APCs), including dendritic cells (DCs), is one potential mechanism for the escape of tumors from the host immune system. Here, we show that human cancer cell lines release a soluble factor or factors that dramatically affect DC maturation from precursors without affecting the function of relatively mature DCs. One factor responsible for these effects was identified as vascular endothelial growth factor (VEGF). Thus, VEGF may play a broader role in the pathogenesis of cancer than was previously thought, and therapeutic blockade of VEGF action may improve prospects for immunotherapy as well as inhibit tumor neovasculature.
Streptococcal preparation OK-432 is a bacterial immunopotentiator extensively used in Japan for adjuvant cancer therapy. Using a C57BL/6 mouse model, OK-432 was found to induce multiple cytokines including the Th1 polarizing cytokine IL-12. Expression of IL-12 protein by murine splenocytes was restricted to macrophages and B cells and led to high levels of IFN-gamma production from both CD4+ and CD8+ T cells. Of the Th2 cytokines IL-4 and IL-10, only IL-10 protein was detected and originated primarily from the adherent cell population. Its expression was delayed relative to IL-12. A similar pattern of cytokine induction was observed from human PBMCs. OK-432-driven IFN-gamma production was inhibited by anti-IL-12 Ab, anti-IL-2 Ab, anti-TNF-alpha Ab, and anti-IL-2R alpha Ab, suggesting that IFN-gamma production from Th1 cells is induced by the cooperation action of these cytokines through the IL-2R alpha pathway. When compared with another widely used immunopotentiator bacillus Calmette-Guérin (BCG), OK-432 was a stronger IL-12 and IFN-gamma inducer. Furthermore, the mechanism of IFN-gamma induction by OK-432 differed from BCG in that coincident granulocyte-macrophage CSF and IL-1 expression played little to no role. These results suggest that OK-432 is a potent multicytokine inducer, specifically a strong inducer of IL-12, and that OK-432 may exert its antitumor effect by promoting a Th1-dominant state.
Tumors are tolerated by the immune system notwithstanding the expression of tumor-associated antigens. PROb tumor cells, derived from a rat colon carcinoma, are rejected by tumor-immune hosts but give rise to progressive tumors in naive hosts. Paradoxically, these tumors are heavily infiltrated by dendritic cells that express MHC class II and ICAM-1. These tumor-infiltrating dendritic cells (TiDCs) could be expected to process and present to T cells the antigens released by the adjacent tumor cells. Indeed, we report here that TiDCs, compared with splenic dendritic cells, are poor stimulators of primary allogeneic T-cell proliferation and cytokine [interleukin-2 (IL-2) and interferon-gamma] production. Most of them (89-97%) do not express B7, an essential co-stimulatory signal for T cells, even after a culture period allowing B7 up-regulation on epidermal Langerhans cells. GM-CSF in association with tumor necrosis factor-alpha or IL-4, or cell-associated CD40-ligand, all known to be potent stimulators of B7 expression on other dendritic cells, did not restore B7 expression by TiDCs. After a first exposure to TiDCs, allogeneic T-cell response to a second challenge to splenic dendritic cells was decreased. The failure of most dendritic cells infiltrating PROb tumors to express B7, even after stimulation, may contribute to their poor capacity to stimulate T cells and could play a role in the immune tolerance allowing tumor growth.
We evaluated T-cell responses to mitogens and to defined antigens in breast cancer patients. Significant defects in responses to tetanus toxoid and influenza virus were observed in patients with advanced-stage breast cancer. To define whether these defects were associated with a defect in antigen presentation [dendritic cells (DCs)] or effector function (T cells), these cells were studied separately. Purified DCs from 32 patients with breast cancer demonstrated a significantly decreased ability to stimulate control allogeneic T cells, but stimulation of patient T cells with either control allogeneic DCs or immobilized anti-CD3 antibody resulted in normal T-cell responses, even in patients with stage IV tumors. These data suggest that reduced DC function could be one of the major causes of the observed defect in cellular immunity in patients with advanced breast cancer. We then tested whether stem cells from these patients could give rise to functional DCs after in vitro growth with granulocyte/macrophage colony-stimulating factor and interleukin 4. Normal levels of control allogeneic and tetanus toxoid-dependent T-cell proliferation were observed when DCs obtained from precursors were used as stimulators. Those cells also induced substantially higher levels of influenza virus-specific CTL responses than mature DCs from the peripheral blood of these patients, although responses did not quite reach control values. Thus, defective T-cell function in patients with advanced breast cancer can be overcome by stimulation with DCs generated from precursors, suggesting that these cells may better serve as autologous antigen carriers for cancer immunotherapy than mature peripheral blood DCs.
Defective function of dendritic cells (DC) in cancer has been recently described and may represent one of the mechanisms of tumor evasion from immune system control. We have previously shown in vitro that vascular endothelial growth factor (VEGF), produced by almost all tumors, is one of the tumor-derived factors responsible for the defective function of these cells. In this study, we investigated whether in vivo infusion of recombinant VEGF could reproduce the observed DC dysfunction. Continuous VEGF infusion, at rates as low as 50 ng/h (resulting in serum VEGF concentrations of 120 to 160 pg/mL), resulted in a dramatic inhibition of dendritic cell development, associated with an increase in the production of B cells and immature Gr-1(+) myeloid cells. Infusion of VEGF was associated with inhibition of the activity of the transcription factor NF-kappaB in bone marrow progenitor cells. Experiments in vitro showed that VEGF itself, and not factors released by VEGF-activated endothelial cells, affected polypotent stem cells resulting in the observed abnormal hematopoiesis. These data suggest that VEGF, at pathologically relevant concentrations in vivo, may exert effects on pluripotent stem cells that result in blocked DC development as well as affect many other hematopoietic lineages.
Tumors produce a number of immunosuppressive factors that block the maturation of CD34+ stem cells into dendritic cells (DC). We hypothesized that tumors might also interfere with the maturation and/or function of human monocyte-derived DC. In contrast to stem cells, we found that CD14+ cells responded to tumor culture supernatant (TSN) by increasing expression of APC surface markers, up-regulating nuclear translocation of RelB, and developing allostimulatory activity. Although displaying these characteristics of mature DC, TSN-exposed DC lacked the capacity to produce IL-12, did not acquire full allostimulatory activity, and rapidly underwent apoptosis. The effects of TSN appeared to be specific for maturing DC, and were not reversed by Abs against known DC regulatory factors including IL-10, vascular endothelial growth factor, TGF-beta, or PGE2. Supernatants collected from nonmalignant cell sources had no effect on DC maturation. The altered maturation and early apoptosis of monocyte-derived DC may represent another mechanism by which tumors evade immune detection.
Defective dendritic cell (DC) function has been described previously in cancer patients and tumor-bearing mice. It can be an important factor in the escape of tumors from immune system control. However, the mechanism and clinical significance of this phenomenon remain unclear. Here, 93 patients with breast, head and neck, and lung cancer were investigated. The function of peripheral blood and tumor draining lymph node DCs was equally impaired in cancer patients, consistent with a systemic rather than a local effect of tumor on DCs. The number of DCs was dramatically reduced in the peripheral blood of cancer patients. This decrease was associated with the accumulation of cells lacking markers of mature hematopoietic cells. The presence of these immature cells was closely associated with the stage and duration of the disease. Surgical removal of tumor resulted in partial reversal of the observed effects. The presence of immature cells in the peripheral blood of cancer patients was closely associated with an increased plasma level of vascular endothelial growth factor but not interleukin 6, granulocyte macrophage colony-stimulating factor, macrophage colony-stimulating factor, interleukin 10, or transforming growth factor-beta and was decreased in lung cancer patients receiving therapy with antivascular endothelial growth factor antibodies. These data indicate that defective DC function in cancer patients is the result of decreased numbers of competent DCs and the accumulation of immature cells. This effect may have significant clinical implications.
Defective dendritic cell (DC) function caused by abnormal differentiation of these cells is an important mechanism of tumor escape from immune system control. Previously, we have demonstrated that the number and function of DC were dramatically reduced in cancer patients. This effect was closely associated with accumulation of immature cells (ImC) in peripheral blood. In this study, we investigated the nature and functional role of those ImC. Using flow cytometry, electron microscopy, colony formation assays, and cell differentiation in the presence of different cell growth factors, we have determined that the population of ImC is composed of a small percentage (<2%) of hemopoietic progenitor cells, with all other cells being represented by MHC class I-positive myeloid cells. About one-third of ImC were immature macrophages and DC, and the remaining cells were immature myeloid cells at earlier stages of differentiation. These cells were differentiated into mature DC in the presence of 1 microM all-trans-retinoic acid. Removal of ImC from DC fractions completely restored the ability of the DC to stimulate allogeneic T cells. In two different experimental systems ImC inhibited Ag-specific T cell responses. Thus, immature myeloid cells generated in large numbers in cancer patients are able to directly inhibit Ag-specific T cell responses. This may represent a new mechanism of immune suppression in cancer and may suggest a new approach to cancer treatment.
CD14-positive monocytes obtained from human peripheral blood were cultured with GM-CSF and IL-4. During the early culture phase immature dendritic cells (DCs) developed which not only expressed CD1a, HLA-DR and CD86, but also expressed the endothelial cell markers von Willebrand factor (vWF), VE-cadherin and VEGF receptors Flt-1 and Flt-4. Further maturation of DCs was achieved by prolonged cultivation with TNFalpha. These cells showed typical DC morphology and like professional antigen-presenting cells (APCs) expressed CD83 and high levels of HLA-DR and CD86. However, if immature DCs were grown with VEGF, bFGF and IGF-1 on fibronectin/vitronectin-coated culture dishes, a marked change in morphology into caudated or oval cells occurred. In the presence of these angiogenic growth factors the cultured cells developed into endothelial-like cells (ELCs), characterized by increased expression of vWF, KDR and Flt-4 and a disappearance of CD1a and CD83. Addition of IL-4 and Oncostatin M also increased VE-cadherin expression, and the loosely adherent cells formed clusters, cobblestones and network-like structures. vWF- expressing ELCs mainly originated from CD1a-positive cells, and VEGF was responsible for the decrease in the expression of the DC markers CD1a and CD83. In mixed leukocyte cultures, mature DCs were more potent APCs than ELCs. Moreover, Ac-LDL uptake, and the formation of tubular structures on a plasma matrix was restricted to ELCs. These results suggest that in the presence of specific cytokines immature DCs have the potential to differentiate along different lineages, i.e. into a cell type resembling ELCs.
Human monocyte-derived dendritic cells (DC) can ingest apoptotic tumor cells (ATC) and present tumor-associated antigens (TAA) to T cells, leading to the generation of tumor-specific cytotoxic effector cells (Cancer Res 2000;60:3542-9). To further augment antitumor effector cell responses, attempts were made to modify antigen presentation and cross-priming of T cells by DC fed with ATC. Proinflammatory cytokines (PC), CD40 ligand (CD40L) and/or interferon-gamma (IFN-gamma) were found to markedly enhance the immunogenicity of TAA presented by DC. While PC upregulated expression of major histocompatibility complex class I/II and costimulatory molecules on the surface of DC, CD40L +/- IFN-gamma increased interleukin (IL)- 12 and to a lesser extent, IL-15 production by DC. Additionally, lactacystin, a specific proteasome inhibitor, significantly abrogated the effects of IFN-gamma and, in part, also those of CD40L or PC. The ability of DC + ATC to cross-prime TAA-inexperienced ("naive") T cells was significantly enhanced by PC and CD40L or CD40L + IFN-gamma, but not by IFN-gamma alone. These results indicate that future vaccines for patients with cancer incorporating DC fed with ATC could be made more effective by the addition of proinflammatory cytokines or CD40L +/- IFN-gamma to improve the DC function.
Vascular endothelial growth factor receptor-1 (VEGFR-1/Flt-1) is structurally a typical tyrosine kinase receptor of about 180 kDa, and carries seven Ig-like domains in the extracellular region and a tyrosine kinase domain with a long kinase insert. Recent studies have revealed that the VEGFR-1 gene and its gene product have several unique characteristics structurally and functionally. In addition to the full length receptor, VEGFR-1 gene encodes for a soluble form carrying only six Ig domains via an alternative splicing. Both the full length and soluble form of VEGFR-1 show strong binding affinity for VEGF, but the kinase activity of the full length receptor is one order of magnitude lower than that of VEGFR-2 (KDR/Flk-1). Early in embryogenesis, null mutation of VEGFR-1 gene results in lethality due to a disorganization of blood vessels and an overgrowth of endothelial-like cells, suggesting a regulatory role in vivo. Mice carrying the extracellular domain of VEGFR-1 gene without the tyrosine kinase domain develop an almost normal circular system and survive. Thus, the extracellular region of VEGFR-1 is necessary and sufficient for physiological angiogenesis at the early stage of embryogenesis, possibly acting to trap VEGF and suppress VEGF levels to an appropriate range. The tyrosine kinase domain of VEGFR-1, although much weaker than that of VEGFR-2, transduces signals for endothelial cells. Furthermore, VEGFR-1 is involved in the VEGF-dependent migration and gene expression of monocyte/macrophages. Therefore, VEGFR-1 functions both in a positive and negative manner in different cellular systems and biological conditions.
Dendritic cells (DC) are highly specialized antigen-presenting cells that on activation by inflammatory stimuli (eg, tumor necrosis factor alpha [TNF-alpha] and interleukin-1beta [IL-1beta]) or infectious agents (eg, lipopolysaccharide [LPS]), mature and migrate into lymphoid organs. During maturation, DC acquire the capacity to prime and polarize resting naive T lymphocytes. Maturation of monocyte-derived DC (MDDC) is inhibited by the p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580. This study found that in the presence of the mitogen-activated protein kinase kinase 1-extracellular signal-regulated kinase (ERK) inhibitors PD98059 or U0126, TNF-alpha- and LPS-induced phenotypic and functional maturation is enhanced. ERK pathway inhibitors increased expression of major histocompatibility complex and costimulatory molecules; loss of mannose-receptor-mediated endocytic activity; nuclear factor-kappaB DNA-binding activity; release of IL-12 p40; and allogeneic T-cell proliferation induced by LPS or TNF-alpha. Moreover, PD98059 and U0126 enhanced LPS-triggered production of IL-12 p70. In agreement with the effect of ERK inhibitors, maturation of MDDC was delayed in the presence of serum, an effect that was reversed by U0126. These results indicate that the ERK and p38 MAPK signaling pathways differentially regulate maturation of MDDC and suggest that their relative levels of activation might modulate the initial commitment of naive T-helper (Th) cells toward Th1 or Th2 subsets. The findings also suggest that maturation of MDDC might be pharmacologically modified by altering the relative levels of activation of both intracellular signaling routes.
Extracellular signals transduced via receptor tyrosine kinases, G-protein-coupled receptors or integrins activate Ras, a key switch in cellular signalling. Although Ras can activate multiple downstream effectors (PI3K, Ral …) one of the major activated pathway is a conserved sequential protein kinase cascade referred to as the mitogen activated protein (MAP) kinase module: Raf>MEK>ERK. The fidelity of signalling among protein kinases and the spatio-temporal activation are certainly key determinants for generating precise biological responses. The fidelity is ensured by scaffold proteins, a sort of protein kinase “insulators” and/or specific docking sites among the members of the signalling cascade. These docking sites are found in upstream and downstream regulators and MAPK substrates [Nat Cell Biol 2 2000 110]. The duration and the intensity of the response are in part controlled by the compartmentalisation of the signalling molecules. Growth factors promote nuclear accumulation and persistent activation of ERK (p42/p44 MAP kinases) during the entire G1 period with an extinction during S-phase. These features are exquisitely well controlled by (i) the temporal induction of the MAP kinase phosphatases, MKP1-3, and (ii) the compartmentalisation of the signalling molecules. We have shown that MKP1-2 induction is strictly controlled by the activation of the MAP kinase module providing evidence for an autoregulatory mechanism. This negative regulatory loop was further enhanced by the capacity of ERK to phosphorylate MKP1 and 2. This action reduced the degradation rate of these MKPs through the ubiquitin–proteasomal system [Science 286 1999 2514].
Dendritic cells (DCs) are potent antigen-presenting cells, which have recently been applied for cancer immunotherapy using epitope peptides. Accumulating results of the clinical trials of such a strategy suggest that maturity of the applied DCs has a significant impact on the outcome of the vaccination. Here we examined the effects of penicillin-killed Streptococcus pyogenes (OK-432) on DC maturation and functions including induction of CTLs. DCs generated from peripheral blood using granulocyte macrophage colony-stimulating factor and interleukin (IL)-4 showed immunophenotypes consistent with immature DCs (iDCs). These iDCs were further incubated with medium alone, tumor necrosis factor alpha, lipopolysaccharide, or OK-432. The immunophenotypical analysis showed DCs stimulated with OK-432 (OK-DCs) possessed significantly higher expression of CD83 compared with unstimulated DCs. Furthermore, OK-DCs showed significantly higher production of IL-12 and IFN-gamma compared with DCs with other stimulations. These results indicate that OK-432 stimulates iDCs to have a mature phenotype and to produce a significant amount of T-helper 1-type cytokines. To examine the potency of OK-DCs on the induction of specific CTLs, the tumor rejection peptide derived from carcinoembryonic antigen was used as a model antigen. The HLA-tetramer assay showed that potent CTL was induced with OK-DCs at high frequency. These results indicate that OK-432 efficiently stimulates DCs without interfering with the presentation of pulsed peptide. Furthermore, OK-432 does not activate nuclear factor kappaB through Toll-like receptor 2 or Toll-like receptor 4 in the indicator cell system; however, it induces IL-12 production through the beta(2) integrin system on DCs. These results strongly suggest that OK-432 could be applied to develop an efficient cancer vaccine using DCs pulsed with tumor rejection peptides.
Dendritic cells (DCs) play an important role in the host's immunosurveillance against cancer. It has been shown that the function of DCs is impaired and their population decreased in a cancer-bearing host. In the present study, we investigated the mechanism of down-regulation of DCs in a cancer-bearing host.
We evaluated the relationship between DC infiltration and production of vascular endothelial growth factor (VEGF) in carcinoma tissue by immunohistochemistry. Furthermore, functional and phenotypical alterations of DCs were evaluated when monocyte-derived, mature DCs were treated with VEGF in vitro. Monocyte-derived DCs were generated in a culture of monocyte with interleukin 4 (IL-4) and granulocyte-macrophage colony-stimulating factor, and the maturation of DCs was induced by either lipopolysaccharide (LPS) or a proinflammatory cytokine cocktail: tumor-necrosis factor alpha, prostaglandin E2, IL-6, and IL-1beta.
A significant inverse correlation was found between the density of DCs and the quantity of VEGF production in gastric carcinoma tissue (r=-0.39, p<0.05). In LPS-induced maturation, the ability of mature DCs to stimulate allogenic T cells and produce IL-12 (p70 heterodimer) was suppressed by the addition of VEGF in a dose-dependent manner. A lesser expression of costimulatory molecules (CD80 and CD86) was seen in DCs treated with exogenous VEGF than in DCs not treated with VEGF. The population of dead DCs (early and late apoptosis) treated with VEGF increased more than that without VEGF treatment, using the annexin V and propidium iodide evaluation in DCs matured by LPS. In contrast, in DCs matured by the proinflammatory cytokine cocktail, the down-regulation of costimulatory molecules and induction of DC apoptosis was not seen.
These findings show that the inhibition of DC maturation by VEGF differs depending on the maturation status of the DCs.
Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen in vitro and an angiogenic inducer in a variety of in vivo models. Hypoxia has been shown to be a major inducer of VEGF gene transcription. The tyrosine kinases Flt-1 (VEGFR-1) and Flk-1/KDR (VEGFR-2) are high-affinity VEGF receptors. The role of VEGF in developmental angiogenesis is emphasized by the finding that loss of a single VEGF allele results in defective vascularization and early embryonic lethality. VEGF is critical also for reproductive and bone angiogenesis. Substantial evidence also implicates VEGF as a mediator of pathological angiogenesis. In situ hybridization studies demonstrate expression of VEGF mRNA in the majority of human tumors. Anti-VEGF monoclonal antibodies and other VEGF inhibitors block the growth of several tumor cell lines in nude mice. Clinical trials with various VEGF inhibitors in a variety of malignancies are ongoing. Very recently, an anti-VEGF monoclonal antibody (bevacizumab; Avastin) has been approved by the Food and Drug Administration as a first-line treatment for metastatic colorectal cancer in combination with chemotherapy. Furthermore, VEGF is implicated in intraocular neovascularization associated with diabetic retinopathy and age-related macular degeneration.
Angiogenesis is a hallmark of wound healing, the menstrual cycle, cancer, and various ischemic and inflammatory diseases. A rich variety of pro- and antiangiogenic molecules have already been discovered. Vascular endothelial growth factor (VEGF) is an interesting inducer of angiogenesis and lymphangiogenesis, because it is a highly specific mitogen for endothelial cells. Signal transduction involves binding to tyrosine kinase receptors and results in endothelial cell proliferation, migration, and new vessel formation. In this article, the role of VEGF in physiological and pathological processes is reviewed. We also discuss how modulation of VEGF expression creates new therapeutic possibilities and describe recent developments in this field.
We have previously demonstrated that iC3b is deposited at the dermal-epidermal junction of the skin following ultraviolet (UV) exposure and that it plays a role in UV-induced immunosuppression and antigenic tolerance. In vitro, iC3b differentially regulates monocyte production of interleukin-10 (IL-10) and IL-12. Additionally, iC3b arrests monocytic cell differentiation into CD1c-expressing dendritic cell (DC) precursors. The present study addresses mitogen-activated protein kinase (MAPK) signalling following the cross-linking of CR3 by its ligand iC3b with regard to monocyte differentiation and cytokine regulation. Sheep erythrocytes were coated with IgM alone (EA) or iC3b (EAiC3b) to allow for CR3 cross-linking onto monocytes. EAiC3b increased the phosphorylation (p) of extracellular signal-regulated kinase (ERK) MAPK in fresh human monocyte, particularly in monocyte-derived DC (MDDC) that were differentiated by means of GM-CSF (1000 U/ml) and IL-4 (200 U/ml) for 2 days before iC3b exposure for an additional 24 h (P=0.034, n=3). CD1a expression, induced by GM-CSF and IL-4, was inhibited by iC3b (EAiC3b vs. EA, P=0.012, n=4). Conversely, the inhibition of ERK by the specific inhibitor (PD98059), but not the p-38 inhibitor SB203580, restored CD1a expression (P=0.011, n=4) in iC3b-stimulated MDDC. Concordantly, the inhibition of ERK during iC3b exposure fully reversed the inhibition of IL-12p70 induction in MDDC by 95% (P<0.01, n=4) and decreased IL-10 production. Taken together, our data demonstrate that iC3b interferes with MDDC differentiation and IL-12 and IL-10 production is mediated via an ERK MAPK-dependent mechanism. Thus, ERK MAPK inhibition may represent a therapeutic strategy for preventing monocytic precursor diversion away from DC differentiation when monocytes enter injured tissues in which iC3b is generated, such as UV-exposed skin.
Vascular endothelial growth factor (VEGF) is a major inducer of angiogenesis and vasculogenesis. Two distinct receptors for VEGF, the tyrosine kinase receptors VEGFR-1 (Flt-1) and VEGFR-2 (Flk-1/KDR), have been identified. Transfection studies could demonstrate biological activities for the Flk-1/KDR-, but not for the Flt-1-receptor, which led to the hypothesis that Flt-1 is a decoy receptor for VEGF. However, Flt-1 is biologically active in non-endothelial cells, namely monocytes, which exclusively express this receptor. In addition, the Flt-1 ligand placenta growth factor (PlGF), which is unable to bind and activate Flk-1/KDR, elicits activities in both monocytes and endothelial cells. The implications of Flt-1 mediated monocyte transmigration through endothelial monolayers and induction of the procoagulant tissue factor on monocytes for the field of vascular medicine are discussed.