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Arginine regulation by myeloid derived suppressor cells and tolerance in cancer: Mechanisms and therapeutic perspectives
Abstract
Patients with cancer have an impaired T-cell response that can decrease the potential therapeutic benefit of cancer vaccines and other forms of immunotherapy. L-arginine (L-Arg) is a conditionally essential amino acid that is fundamental for the function of T lymphocytes. Recent findings in tumor-bearing mice and cancer patients indicate that increased metabolism of L-Arg by myeloid derived suppressor cells (MDSCs) producing arginase I inhibits T-lymphocyte responses. Here we discuss some of the most recent concepts how MDSC expressing arginase I may regulate T-cell function in cancer and other chronic inflammatory diseases and suggest possible therapeutic interventions to overcome this inhibitory effect.
... As a result of this intense traffic, any modification in the TME can hypothetically affect the efficacy of ICIs. Among the immune checkpoint molecules are some metabolic enzymes like the indoleamine 2,3-dioxygenase (IDO), an effector expressed by tumour cells and myeloid cells of the tumour niche, and arginase, an amino acid produced by immune-suppressor cells by the myeloid line [43,44]. These enzymes are delivered to the TME and can inhibit immune responses through the local degradation of amino acids used for T-lymphocyte biosynthesis, like tryptophan, or through the action of specific natural ligands, thus altering lymphocyte functions in both COPD and NSCLC [44]. ...
... Among the immune checkpoint molecules are some metabolic enzymes like the indoleamine 2,3-dioxygenase (IDO), an effector expressed by tumour cells and myeloid cells of the tumour niche, and arginase, an amino acid produced by immune-suppressor cells by the myeloid line [43,44]. These enzymes are delivered to the TME and can inhibit immune responses through the local degradation of amino acids used for T-lymphocyte biosynthesis, like tryptophan, or through the action of specific natural ligands, thus altering lymphocyte functions in both COPD and NSCLC [44]. The IDO expression is upregulated in both these pathologies, leading to T-cell inhibition and immune escape [43,44]. ...
... These enzymes are delivered to the TME and can inhibit immune responses through the local degradation of amino acids used for T-lymphocyte biosynthesis, like tryptophan, or through the action of specific natural ligands, thus altering lymphocyte functions in both COPD and NSCLC [44]. The IDO expression is upregulated in both these pathologies, leading to T-cell inhibition and immune escape [43,44]. Table 1 reports the immune cells predominantly infiltrating the lung TME in NSCLC, COPD, and both (Table 1). ...
Simple Summary
The interaction between the immune system, chronic obstructive pulmonary disease (COPD), and non-small cell lung cancer (NSCLC) is complex and multifaceted and involves all cellular elements of the tumour microenvironment, together with the molecules expressed and secreted in the inflamed milieu. In patients with both diseases, considering that COPD is thought to impair the immune response against tumour cells, immune checkpoint inhibitors (ICIs) combined with chemotherapy appear to improve the pathological responses of NSCLC patients, showing promising improvements in survival. In the present review, we sought to understand the interaction between the two pathways and how the efficacy of immunotherapy in patients with NSCLC and COPD is affected in these patients.
Abstract
The interplay between the immune system and chronic obstructive pulmonary disease (COPD) and non-small cell lung cancer (NSCLC) is complex and multifaceted. In COPD, chronic inflammation and oxidative stress can lead to immune dysfunction that can exacerbate lung damage, further worsening the respiratory symptoms. In NSCLC, immune cells can recognise and attack the cancer cells, which, however, can evade or suppress the immune response by various mechanisms, such as expressing immune checkpoint proteins or secreting immunosuppressive cytokines, thus creating an immunosuppressive tumour microenvironment that promotes cancer progression and metastasis. The interaction between COPD and NSCLC further complicates the immune response. In patients with both diseases, COPD can impair the immune response against cancer cells by reducing or suppressing the activity of immune cells, or altering their cytokine profile. Moreover, anti-cancer treatments can also affect the immune system and worsen COPD symptoms by causing lung inflammation and fibrosis. Immunotherapy itself can also cause immune-related adverse events that could worsen the respiratory symptoms in patients with COPD-compromised lungs. In the present review, we tried to understand the interplay between the two pathologies and how the efficacy of immunotherapy in NSCLC patients with COPD is affected in these patients.
... Some IDO1 inhibitors also counteractively bind to and activate AHR or may not sufficiently penetrate inside the cells within the TME [149,152]. Arginase 1. Arginase 1 catabolizes L-arginine into L-ornithine, resulting in arginine depletion that limits T-cell activation and promotes immunosuppression [153]. While arginase 1 is expressed on immunosuppressive murine macrophages [153,154], its expression on human macrophages varies based on macrophage source (monocyte-derived vs. tissue-resident) and inflammatory environment [154]. ...
... Arginase 1. Arginase 1 catabolizes L-arginine into L-ornithine, resulting in arginine depletion that limits T-cell activation and promotes immunosuppression [153]. While arginase 1 is expressed on immunosuppressive murine macrophages [153,154], its expression on human macrophages varies based on macrophage source (monocyte-derived vs. tissue-resident) and inflammatory environment [154]. As arginase 1 is expressed on neutrophils and MDSCs rather than TAMs in human malignancies [155][156][157][158], small molecule arginase inhibitors (INCB001158, OATD-02) were excluded from our clinical landscape analysis. ...
Tumour-associated macrophages (TAMs) sustain a tumour-supporting and immunosuppressive milieu and therefore aggravate cancer prognosis. To modify TAM behaviour and unlock their anti-tumoural potential, novel TAM-reprogramming immunotherapies are being developed at an accelerating rate. At the same time, scientific discoveries have highlighted more sophisticated TAM phenotypes with complex biological functions and contradictory prognostic associations. To understand the evolving clinical landscape, we reviewed current and past clinically evaluated TAM-reprogramming cancer therapeutics and summarised almost 200 TAM-reprogramming agents investigated in more than 700 clinical trials. Observable overall trends include a high frequency of overlapping strategies against the same therapeutic targets, development of more complex strategies to improve previously ineffective approaches and reliance on combinatory strategies for efficacy. However, strong anti-tumour efficacy is uncommon, which encourages re-directing efforts on identifying biomarkers for eligible patient populations and comparing similar treatments earlier. Future endeavours will benefit from considering the shortcomings of past treatment strategies and accommodating the emerging complexity of TAM biology.
... We also found that RSV reversed the induction of several other inflammatory markers such as Myd88, CXCL1, and XBP1. MDSCs are well characterized for producing Arginase-1, which suppresses the T cell-mediated immune response [27]. This is one of the primary mechanisms through which MDSCs suppress anti-cancer immune response [27]. ...
... MDSCs are well characterized for producing Arginase-1, which suppresses the T cell-mediated immune response [27]. This is one of the primary mechanisms through which MDSCs suppress anti-cancer immune response [27]. It is noteworthy that RES decreased the TCDD-mediated upregulation of Arginase-1, thereby suggesting that this may be the mechanism through which RSV reduces the immunosuppressive properties of TCDD-induced MDSCs, as seen in the current study. ...
Citation: Neamah, W.H.; Rutkovsky, A.; Abdullah, O.; Wilson, K.; Bloomquist, R.; Nagarkatti, P.; Nagarkatti, M. Resveratrol Attenuates 2,3,7,8-Tetrachlorodibenzo-p-dioxin-Mediated Induction of Myeloid-Derived Suppressor Cells (MDSC) and Their Functions. Nutrients 2023, 15, 4667. https:// Abstract: Previously, we showed that 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor (AhR) ligand and a potent and persistent toxicant and carcinogenic agent, induces high levels of murine myeloid-derived suppressor cell (MDSC) when injected into mice. In the current study, we demonstrate that Resveratrol (3,4,5-trihydroxy-trans-stilbene; RSV), an AhR antagonist, reduces TCDD-mediated MDSC induction. RSV decreased the number of MDSCs induced by TCDD in mice but also mitigated the immunosuppressive function of TCDD-induced MDSCs. TCDD caused a decrease in F4/80+ macrophages and an increase in CD11C+ dendritic cells, while RSV reversed these effects. TCDD caused upregulation in CXCR2, a critical molecule involved in TCDD-mediated induction of MDSCs, and Arginase-1 (ARG-1), involved in the immunosuppressive functions of MD-SCs, while RSV reversed this effect. Transcriptome analysis of Gr1 + MDSCs showed an increased gene expression profile involved in the metabolic pathways in mice exposed to TCDD while RSV-treated mice showed a decrease in such pathways. The bio-energetic profile of these cells showed that RSV treatment decreased the energetic demands induced by TCDD. Overall, the data demonstrated that RSV decreased TCDD-induced MDSC induction and function by altering the dynamics of various myeloid cell populations involving their numbers, phenotype, and immunosuppressive potency. Because MDSCs play a critical role in tumor growth and metastasis, our studies also support the potential use of RSV to attenuate the immunosuppressive properties of MDSC.
... We also found that RSV reversed the induction of several other inflammatory markers such as Myd88, CXCL1, and XBP1. MDSCs are well characterized for producing Arginase-1, which suppresses the T cell-mediated immune response [27]. This is one of the primary mechanisms through which MDSCs suppress anti-cancer immune response [27]. ...
... MDSCs are well characterized for producing Arginase-1, which suppresses the T cell-mediated immune response [27]. This is one of the primary mechanisms through which MDSCs suppress anti-cancer immune response [27]. It is noteworthy that RES decreased the TCDD-mediated upregulation of Arginase-1, thereby suggesting that this may be the mechanism through which RSV reduces the immunosuppressive properties of TCDD-induced MDSCs, as seen in the current study. ...
Previously, we showed that 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor (AhR) ligand and a potent and persistent toxicant and carcinogenic agent, induces high levels of murine myeloid-derived suppressor cell (MDSC) when injected into mice. In the current study, we demonstrate that Resveratrol (3,4,5-trihydroxy-trans-stilbene; RSV), an AhR antagonist, reduces TCDD-mediated MDSC induction. RSV decreased the number of MDSCs induced by TCDD in mice but also mitigated the immunosuppressive function of TCDD-induced MDSCs. TCDD caused a decrease in F4/80+ macrophages and an increase in CD11C+ dendritic cells, while RSV reversed these effects. TCDD caused upregulation in CXCR2, a critical molecule involved in TCDD-mediated induction of MDSCs, and Arginase-1 (ARG-1), involved in the immunosuppressive functions of MDSCs, while RSV reversed this effect. Transcriptome analysis of Gr1+ MDSCs showed an increased gene expression profile involved in the metabolic pathways in mice exposed to TCDD while RSV-treated mice showed a decrease in such pathways. The bio-energetic profile of these cells showed that RSV treatment decreased the energetic demands induced by TCDD. Overall, the data demonstrated that RSV decreased TCDD-induced MDSC induction and function by altering the dynamics of various myeloid cell populations involving their numbers, phenotype, and immunosuppressive potency. Because MDSCs play a critical role in tumor growth and metastasis, our studies also support the potential use of RSV to attenuate the immunosuppressive properties of MDSC.
... In humans, MDSCs are broadly defined as CD14 − CD11b + cells or cells that express CD33 but lack mature myeloid and lymphoid cells markers and the MHC class II molecule HLA-DR [7,8]. The suppressive activity of MDSCs has been associated with arginase I, inducible nitric oxide synthase (iNOS) [9,10], reactive oxygen species [11,12], anti-inflammatory cytokines [5], regulatory T cells [13,14], and tumor-associated macrophages [15,16]. ...
... These immature myeloid cells quickly expand to control host immunity during infection, inflammation, trauma, and cancer [4,5]. The anti-inflammatory and immunoregulatory properties of MDSCs include increasing the expression of reactive oxygen species [11,12], arginase 1, iNOS [9,10], anti-inflammatory cytokines [5], regulatory T cells [13,14], macrophages associated with tumors [15,16], proangiogenic factors [20], and the impairment of natural killer cell cytotoxicity [21]. In a prior study, we demonstrated that MDSCs induced by hepatic stellate cells (HSCs) exhibited high immunoregulatory properties and prolonged the survival of mice with cotransplanted islet allografts through the induction of effector T-cell apoptosis and the generation of regulatory T cells [22]. ...
Type 1 diabetes is an inflammatory state. Myeloid-derived suppressive cells (MDSCs) originate from immature myeloid cells and quickly expand to control host immunity during infection, inflammation, trauma, and cancer. This study presents an ex vivo procedure to develop MDSCs from bone marrow cells propagated from granulocyte-macrophage-colony-stimulating factor (GM-CSF), interleukin (IL)-6, and IL-1β cytokines expressing immature morphology and high immunosuppression of T-cell proliferation. The adoptive transfer of cytokine-induced MDSCs (cMDSCs) improved the hyperglycemic state and prolonged the diabetes-free survival of nonobese diabetic (NOD) mice with severe combined immune deficiency (SCID) induced by reactive splenic T cells harvested from NOD mice. In addition, the application of cMDSCs reduced fibronectin production in the renal glomeruli and improved renal function and proteinuria in diabetic mice. Moreover, cMDSCs use mitigated pancreatic insulitis to restore insulin production and reduce the levels of HbA1c. In conclusion, administering cMDSCs propagated from GM-CSF, IL-6, and IL-1β cytokines provides an alternative immunotherapy protocol for treating diabetic pancreatic insulitis and renal nephropathy.
... Myeloid-derived suppressor cells (MDSCs) are also present in tumour tissues. MDSCs inhibit the anticancer activity of effector T (Teff) cells and natural killer (NK) cells via impeding arginine metabolism (Rodriguez and Ochoa, 2008). Tregs and MDSCs within the tumour microenvironment thus block the effector function of immune cells and consequently may impair anticancer immunotherapy, including the action of checkpoint inhibitor drugs. ...
The interplay of regulatory T cells (Tregs) within the tumour microenvironment presents a significant challenge in anticancer immunotherapy. This study investigates the potential of Treg blockade to enhance the efficiency of effector T cells. Two distinct treatment cocktails were examined: 3p-hpRNA (5′ triphosphate hairpin RNA) combined with unmethylated CpG oligonucleotide (CpG); CpG in combination with OX40 receptor-specific monoclonal antibody (anti-OX40). Treatment efficacy was assessed using a murine model of kidney adenocarcinoma.
Renca cells (renal cortical cells with adenocarcinoma) were subcutaneously engrafted in 30 BALB/c mice, then animals were allocated into three treatment groups: Group 1: CpG+anti-OX40, Group 2: CpG+3p-hpRNA, Group 3: untreated control. Treatment efficacy was evaluated based on tumour growth, the occurrence of metastases and overall survival.
On day 28 post-implantation, experiments had to be terminated due to tumour progression. Although comparisons of survival times and primary tumour sizes thus became inconsequential, histological examinations provided valuable insights. We observed distinct variations in primary tumour characteristics among the different groups: Groups 1 and 2 displayed demarcations, while Group 3 exhibited diffuse tumours with necrosis. Lung metastases were evident in 70% of untreated mice, whereas none were observed in either of the treated groups.
Our findings instil confidence in the potential efficacy of the treatments, thereby laying a solid foundation for future investigations.
... Tumor-infiltrating MDSCs suppress cytotoxic T cell activity by inducing oxidative stress and secrete reactive oxygen species (ROS) [65,66]. Indoleamine 2,3-dioxygenase 1 (IDO), Arginase (ARG1), and inducible nitric oxide synthase (NOS2) are all utilized by MDSCs to alter the TME [67][68][69] (Figure 1B). IDO depletes tryptophan, ARG1 depletes arginine, and all three enzymes enrich reactive nitrogen species, which inhibits CD3ζ chain expression and induces T cell apoptosis [70][71][72]. ...
Glioblastoma (GBM) is the most common primary malignant brain tumor, with a median overall survival of less than 2 years and a nearly 100% mortality rate under standard therapy that consists of surgery followed by combined radiochemotherapy. Therefore, new therapeutic strategies are urgently needed. The success of chimeric antigen receptor (CAR) T cells in hematological cancers has prompted preclinical and clinical investigations into CAR-T-cell treatment for GBM. However, recent trials have not demonstrated any major success. Here, we delineate existing challenges impeding the effectiveness of CAR-T-cell therapy for GBM, encompassing the cold (immunosuppressive) microenvironment, tumor heterogeneity, T-cell exhaustion, local and systemic immunosuppression, and the immune privilege inherent to the central nervous system (CNS) parenchyma. Additionally, we deliberate on the progress made in developing next-generation CAR-T cells and novel innovative approaches, such as low-intensity pulsed focused ultrasound, aimed at surmounting current roadblocks in GBM CAR-T-cell therapy.
... This approach has the potential to be adopted for theranostic monitoring of the PMN. Recent evidence has shown that MDSC depletion with anti-Gr-1 antibodies or gemcitabine may prevent metastasis formation and rescue the immunotherapy response of tumors [19,48,[55][56][57]. The coupling of therapies that eliminate MDSCs with Gr-ReANCs will permit a targeted approach to monitoring disease progression through SWIR imaging with simultaneous treatment of potential metastatic sites. ...
Metastatic breast cancer remains a significant source of mortality amongst breast cancer patients and is generally considered incurable in part due to the difficulty in detection of early micro-metastases. The pre-metastatic niche (PMN) is a tissue microenvironment that has undergone changes to support the colonization and growth of circulating tumor cells, a key component of which is the myeloid-derived suppressor cell (MDSC). Therefore, the MDSC has been identified as a potential biomarker for PMN formation, the detection of which would enable clinicians to proactively treat metastases. However, there is currently no technology capable of the in situ detection of MDSCs available in the clinic. Here, we propose the use of shortwave infrared-emitting nanoprobes for the tracking of MDSCs and identification of the PMN. Our rare-earth albumin nanocomposites (ReANCs) are engineered to bind the Gr-1 surface marker of murine MDSCs. When delivered intravenously in murine models of breast cancer with high rates of metastasis, the targeted ReANCs demonstrated an increase in localization to the lungs in comparison to control ReANCs. However, no difference was seen in the model with slower rates of metastasis. This highlights the potential utility of MDSC-targeted nanoprobes to assess PMN development and prognosticate disease progression.
... MDSCs can impair T-cell function by reducing metabolites and factors critical to the immune system, such as L-arginine, cysteine and tryptophan (Trp) [39]. A variety of tumor microenvironment (TME)-derived factors induce the upregulation of cationic amino acid transporter protein (CAT-2B) and ARG1 expression in MDSCs. ...
Paradoxically, tumor development and progression can be inhibited and promoted by the immune system. After three stages of immune editing, namely, elimination, homeostasis and escape, tumor cells are no longer restricted by immune surveillance and thus develop into clinical tumors. The mechanisms of immune escape include abnormalities in antitumor-associated immune cells, selection for immune resistance to tumor cells, impaired transport of T cells, and the formation of an immunosuppressive tumor microenvironment. A population of distinct immature myeloid cells, myeloid-derived suppressor cells (MDSCs), mediate immune escape primarily by exerting immunosuppressive effects and participating in the constitution of an immunosuppressive microtumor environment. Clinical trials have found that the levels of MDSCs in the peripheral blood of cancer patients are strongly correlated with tumor stage, metastasis and prognosis. Moreover, animal experiments have confirmed that elimination of MDSCs inhibits tumor growth and metastasis to some extent. Therefore, MDSCs may become the target of immunotherapy for many cancers, and eliminating MDSCs can help improve the response rate to cancer treatment and patient survival. However, a clear definition of MDSCs and the specific mechanism involved in immune escape are lacking. In this paper, we review the role of the MDSCs population in tumor development and the mechanisms involved in immune escape in different tumor contexts. In addition, we discuss the use of these cells as targets for tumor immunotherapy. This review not only contributes to a systematic and comprehensive understanding of the essential role of MDSCs in immune system reactions against tumors but also provides information to guide the development of cancer therapies targeting MDSCs.
... L-arginine in the surrounding environment is depleted by the secretion of ARG-1, which not only limits the formation of cD3ξ chains on the TCR, but also inhibits the expression of cyclin D3 (CCND3) and cyclin-dependent kinase 4 (CDK4), thus, T-cell arrest in the G0-G1 phase of the cell cycle, ultimately inhibits proliferation of T cells (24) . Certainly, both MDSCs can also suppress T cell immune responses by secreting ROS (25) . The LXR agonists can inhibite the immunosuppressive function of MDSCs by activating LXR transcriptional targets (13). ...
Objective
To investigate the effect and mechanism of saikosaponin A (SSA) on mouse myeloid-derived suppressor cells (MDSCs).
Methods
In vitro: Bone marrow cells (BMC) isolated from normal mouse were treated with Granulocyte-macrophage colony-stimulating factor (GM-CSF) and SSA for 96 h, flow cytometer (FCM) detected the effect of SSA on differentiation of mouse MDSCs. MDSCs were treated with SSA, FCM detected the effect of SSA on apoptosis, LXRα expression, ROS, ARG-1, p-STAT1 and p-NF-κB p65 expression levels. RT-qPCR detected the LXRα and ARG-1 mRNA expression. In vivo: After SSA gavage (ig) and intraperitoneal injection (ip) treatment, FCM detected the proportion of immune cells (T cells, B cells, NK cells, monocytes/macrophages and MDSCs) in the spleen of mice.
Results
In vitro, SSA could up-regulate the LXRα expression of MDSCs, reduce differentiation of M-MDSCs, induce early apoptosis and decrease the ROS and ARG-1 expression of MDSCs, SSA inhibits STAT1 and NF-κB signaling pathways. In vivo, compared with the control group, SSA up-regulated the proportion of splenic T cells, CD8⁺T cells and mononuclear/macrophage cells, and decreased the proportion of MDSCs in SSA ip group; SSA up-regulated the proportion of splenic CD8⁺T cells, B cells and mononuclear/macrophage cells, while decreased the proportion of splenic CD4⁺T cells and MDSCs in the SSA ig group.
Conclusion
SSA could regulate differentiation, induce apoptosis of MDSCs, and inhibit their immunosuppressive function, which may be associated with the up-regulation of LXRα expression in MDSCs by SSA. These results may provide a new theoretical basis for the clinical application of SSA.
... Tumor cells often express or secrete soluble mediators such as IL-10, TGF-b, and prostaglandin E2 that dampen the anti-tumor response or polarize immune populations toward anti-inflammatory phenotypes, yielding T regulatory cells, M2 macrophages, and myeloid-derived suppressor cells [64,65]. These cell types, in turn, produce IL-10 and TGF-b to further inhibit the anti-tumor response while supporting angiogenesis and tumorigenesis [66][67][68]. Additionally, MDSCs deplete L-arginine, a necessary metabolite for T-cell proliferation, from the tumor microenvironment via the expression and secretion of arginase-1 and nitric oxide synthase 2. Solid tumors provide the greatest challenge to CAR-T cell therapy as it also requires CAR-T cell infiltration of the tumor and survival in hypoxic and metabolically hostile conditions. ...
This review focuses on the use of chimeric antigen receptor (CAR)-T cell therapy to treat non-Hodgkin’s lymphoma (NHL), a classification of heterogeneous malignant neoplasms of the lymphoid tissue. Despite various conventional and multidrug chemotherapies, the poor prognosis for NHL patients remains and has prompted the utilization of groundbreaking personalized therapies such as CAR-T cells. CAR-T cells are T cells engineered to express a CAR that enables T cells to specifically lyse tumor cells with extracellular expression of a tumor antigen of choice. A CAR is composed of an extracellular antibody fragment or target protein binding domain that is conjugated to activating intracellular signaling motifs common to T cells. In general, CAR-T cell therapies for NHL are designed to recognize cellular markers ubiquitously expressed on B cells such as CD19+, CD20+, and CD22+. Clinical trials using CAR-T cells such as ZUMA-7 and TRANSFORM demonstrated promising results compared to standard of care and ultimately led to FDA approval for the treatment of relapsed/refractory NHL. Despite the success of CAR-T therapy for NHL, challenges include adverse side effects as well as extrinsic and intrinsic mechanisms of tumor resistance that lead to suboptimal outcomes. Overall, CAR-T cell therapies have improved clinical outcomes in NHL patients and generated optimism around their future applications.
... Metabolic reprogramming is a hallmark of the TME and contributes to tumor control or progression; thus, modifying bacteria to metabolize substances that are beneficial to the antitumor immune response is necessary for cancer treatment [35]. Larginine is crucial for the antitumor properties of T cells [36]. ...
As the understanding of the tumor microenvironment has deepened, immunotherapy has become a promising strategy for cancer treatment. In contrast to traditional therapies, immunotherapy is more precise and induces fewer adverse effects. In this field, some bacteria have attracted increased attention because of their natural ability to preferentially colonize and proliferate inside tumor sites and exert antitumor effects. Moreover, bacterial components may activate innate and adaptive immunity to resist tumor progression. However, the application of bacteria‐based cancer immunotherapy is hampered by potential infection‐associated toxicity and unpredictable behavior in vivo. Owing to modern developments in genetic engineering, bacteria can be modified to weaken their toxicity and enhance their ability to eliminate tumor cells or activate the antitumor immune response. This review summarizes the roles of bacteria in the tumor microenvironment, current strategies for bacterial engineering, and the synergistic efficiency of bacteria with other immunotherapies. In addition, the prospects and challenges of the clinical translation of engineered bacteria are summarized.
... M-MDSCs promote tumor development and metastasis by inhibiting T cells through the action of various molecules (2,3), such as IL-10, TGFβ and CD40, which induce the differentiation of CD4 T cells into Tregs (4,5). M-MDSCs also produce arginase 1, which decreases the levels of L-arginine, an amino acid essential for Tcell response (6). Additionally, they metabolize tryptophan into kynurenine through indoleamine 2, 3-dioxygenase, which inhibits T cell proliferation (7). ...
C-C chemokine receptor type 2 (CCR2) is the receptor for C-C motif chemokine 2 (CCL2) and is associated with various inflammatory diseases and cancer metastasis. Although many inhibitors for CCR2 have been developed, it remains unresolved which inhibitors are the most effective in the clinical setting. In the present study, we compared 10 existing human CCR2 antagonists in a calcium influx assay using human monocytic leukemia cells. Among them, MK0812 was found to be the most potent inhibitor of human CCR2. Furthermore, we generated a human CCR2B knock-in mouse model to test the efficacy of MK0812 against a lung metastasis model of breast cancer. Oral administration of MK0812 to humanized mice did indeed reduce the number of monocytic myeloid-derived suppressor cells and the rate of lung metastasis. These results suggest that MK0812 is the most promising candidate among the commercially available CCR2 inhibitors. We propose that combining these two screening methods may provide an excellent experimental method for identifying effective drugs that inhibit human CCR2.
... The proportion of Tregs has predictive and prognostic values [27][28][29] . In a study by Griffiths et al., a high frequency of Tregs in the peripheral blood of RCC patients was found to be associated with reduced survival [30] . ...
The introduction of immune checkpoint inhibitor (ICI) has revolutionized the treatment of metastatic renal cell carcinoma (mRCC) and has dramatically improved the outcomes of patients. The use of monotherapy or combinations of ICIs targeting PD-1/PD-L1 and CTLA-4, as well as the addition of ICIs with tyrosine kinase inhibitors, has significantly enhanced the overall survival of mRCC patients. Despite these promising results, there remains a subset of patients who either do not respond to treatment (primary resistance) or develop resistance to therapy over time (acquired resistance). Understanding the mechanisms underlying the development of resistance to ICI treatment is crucial in the management of mRCC, as they can be used to identify new targets for innovative therapeutic strategies. Currently, there is an unmet need to develop new predictive and prognostic biomarkers that can aid in the development of personalized treatment options for mRCC patients. In this review, we summarize several mechanisms of ICI resistance in RCC, including alterations in tumor microenvironment, upregulation of alternative immune checkpoint pathways, and genetic and epigenetic changes. Additionally, we highlight potential strategies that can be used to overcome resistance, such as combination therapy, targeted therapy, and immune modulation.
... FoxP3 + T regs not only inhibit the differentiation of naïve T cells to effector cells but also inhibit the function of CD4 + and CD8 + T cells as well as of NK cells, B cells and DCs [11,12]. MDSCs are able to suppress T cell activity with the production of ROS [10] and the expression of arginase and iNOS [13,14]. It was further shown that MDSCs promote the differentiation of FoxP3 + T regs in vivo [15,16]. ...
Finding a long-term cure for tumor patients still represents a major challenge. Immunotherapies offer promising therapy options, since they are designed to specifically prime the immune system against the tumor and modulate the immunosuppressive tumor microenvironment. Using nucleic-acid-based vaccines or cellular vaccines often does not achieve sufficient activation of the immune system in clinical trials. Additionally, the rapid degradation of drugs and their non-specific uptake into tissues and cells as well as their severe side effects pose a challenge. The encapsulation of immunomodulatory molecules into nanocarriers provides the opportunity of protected cargo transport and targeted uptake by antigen-presenting cells. In addition, different immunomodulatory cargos can be co-delivered, which enables versatile stimulation of the immune system, enhances anti-tumor immune responses and improves the toxicity profile of conventional chemotherapeutic agents.
... Moreover, Fig. 2F shows a potential subset of myeloid-derived suppressor cells (MDSCs) within the neutrophil gate defined by CD11b and Ly6G expression. MDSCs' immunomodulatory function, linked to increased Arg-1 and iNOS expression [51,52], may be involved in exacerbated lung inflammation post-anti-IL10 treatment in our model. However, additional research is required to confirm this relationship and its underlying mechanisms. ...
Inflammation resolution is critical for acute lung injury (ALI) recovery. Interleukin (IL)-10 is a potent anti-inflammatory factor. However, its role in ALI resolution remains unclear. We investigated the effects of IL-10 during the ALI resolution process in a murine lipopolysaccharide (LPS)-induced ALI model. Blockade of IL-10 signaling aggravates LPS-induced lung injury, as manifested by elevated pro-inflammatory factors production and increased neutrophils recruitment to the lung. Thereafter, we used IL-10 GFP reporter mice to discern the source cell of IL-10 during ALI. We found that IL-10 is predominantly generated by B cells during the ALI recovery process. Furthermore, we used IL-10-specific loss in B-cell mice to elucidate the effect of B-cell-derived IL-10 on the ALI resolution process. IL-10-specific loss in B cells leads to increased pro-inflammatory cytokine expression, persistent leukocyte infiltration, and prolonged alveolar barrier damage. Mechanistically, B cell-derived IL-10 inhibits the activation and recruitment of macrophages and downregulates the production of chemokine KC that recruits neutrophils to the lung. Moreover, we found that IL-10 deletion in B cells leads to alterations in the cGMP-PKG signaling pathway. In addition, an exogenous supply of IL-10 promotes recovery from LPS-induced ALI, and IL-10-secreting B cells are present in sepsis-related ARDS. This study highlights that B cell-derived IL-10 is critical for the resolution of LPS-induced ALI and may serve as a potential therapeutic target.
... Therefore, arginase is appreciated as an attractive target of cancer therapy. Arginase regulates the immune escape of cancer cells through several mechanisms: (i) high expression of Arg-1 and Arg-2 in cancer cells directly impairs the function of T cells by depleting L-arginine in the tumour microenvironment; (ii) secreted Arg-1 or extracellular vesicles containing Arg-1 from myeloid-derived suppressor cells (MDSCs) and TAMs deplete L-arginine levels in tumour microenvironment and suppress T-cell activation and proliferation; (iii) finally, the high expression of Arg-2 in Treg cells enhances the suppressive capacity and accumulation of Treg cells via the inhibition of the mTOR signalling pathway, which in turn enables the immune escape of tumour cells [46][47][48][49][50][51]. Our results showed significantly reduced activity of Arg-1 in groups treated with Cis + HT and Res + Cis + HT (p < 0.001) compared to the Control group ( Figure 8). ...
The aim of this study was to investigate the therapeutic potential of resveratrol in combination with cisplatin on the inhibition of tumour angiogenesis, growth, and macrophage polarization in mice bearing the solid form of an Ehrlich ascites tumour (EAT) that were exposed to whole-body hyperthermia treatment. In addition, we investigated whether a multimodal approach with hyperthermia and resveratrol could abolish cisplatin resistance in tumour cells through the modulation of histone deacetylase (HDAC) activity and levels of heat shock proteins (HSP70/HSP90) and contribute to the direct toxicity of cisplatin on tumour cells. The tumour was induced by injecting 1 × 106 EAT cells subcutaneously (sc) into the thighs of Balb/c mice. The mice were treated with resveratrol per os for five consecutive days beginning on day 2 after tumour injection and/or by injecting cisplatin intraperitoneally (ip) at a dose of 2.5 mg/kg on days 10 and 12 and at a dose of 5 mg/kg on day 15. Immediately thereafter, the mice were exposed to systemic hyperthermia for 15 min at a temperature of 41 °C. The obtained results showed that the administration of resveratrol did not significantly contribute to the antitumour effect of cisplatin and hyperthermia, but it partially contributed to the immunomodulatory effect and to the reduction of cisplatin toxicity and to a slight increase in animal survival. This treatment schedule did not affect microvessel density, but it inhibited tumour growth and modulated macrophage polarization to the M1 phenotype. Furthermore, it abolished the resistance of tumour cells to cisplatin by modulating HDAC activity and the concentration of HSP70 and HSP90 chaperones, contributing to the increased lifespan of mice. However, the precise mechanism of the interaction between resveratrol, cisplatin, and hyperthermia needs to be investigated further.
... Prior bulk RNA-Seq analysis of tdTomatolabeled Slfn4 + -MDSCs from infected mouse stomachs indicate that there is a >2000-fold increase in Nos2 expression (3), and increased expression of several IFNa-inducible GTPases, such as guanylate binding proteins (GBPs), IIGP1 and GVIN, which hydrolyze guanine triphosphate (GTP) to guanosine diphosphate (GDP) and provide energy for cellular activities (5). MDSCs use arginase-1 (ARG1) and inducible nitric oxide synthase (NOS2), key enzymes in L-arginine catabolism, which blunt T cell-mediated antitumor immunity either individually or together (6,7). The process of GTP metabolism is an important regulatory mechanism that controls the activity of NOS2 (8). ...
Introduction
MDSCs express SCHLAFEN 4 (SLFN4) in Helicobacter-infected stomachs coincident with spasmolytic polypeptide-expressing metaplasia (SPEM), a precursor of gastric cancer. We aimed to characterize SLFN4⁺ cell identity and the role of Slfn4 in these cells.
Methods
Single-cell RNA sequencing was performed on immune cells sorted from PBMCs and stomachs prepared from uninfected and 6-month H. felis-infected mice. Knockdown of Slfn4 by siRNA or PDE5/6 inhibition by sildenafil were performed in vitro. Intracellular ATP/GTP levels and GTPase activity of immunoprecipitated Slfn4 complexes were measured using the GTPase-Glo assay kit. The intracellular level of ROS was quantified by the DCF-DA fluorescent staining, and apoptosis was determined by cleaved Caspase-3 and Annexin V expression. Gli1CreERT2 x Slfn4 fl/fl mice were generated and infected with H. felis. Sildenafil was administered twice over 2 weeks by gavaging H. felis infected mice ~4 months after inoculation once SPEM had developed.
Results
Slfn4 was highly induced in both monocytic and granulocytic MDSCs from infected stomachs. Both Slfn4 ⁺-MDSC populations exhibited strong transcriptional signatures for type-I interferon responsive GTPases and exhibited T cell suppressor function. SLFN4-containing protein complexes immunoprecipitated from myeloid cell cultures treated with IFNa exhibited GTPase activity. Knocking down Slfn4 or PDE5/6 inhibition with sildenafil blocked IFNa induction of GTP, SLFN4 and NOS2. Moreover, IFNa induction of Slfn ⁺-MDSC function was inhibited by inducing their reactive oxygen species (ROS) production and apoptosis through protein kinase G activation. Accordingly, in vivo disruption of Slfn4 in Gli1CreERT2 x Slfn4 fl/fl mice or pharmacologic inhibition by sildenafil after Helicobacter infection also suppressed SLFN4 and NOS2, reversed T cell suppression and mitigated SPEM development.
Conclusion
Taken together, SLFN4 regulates the activity of the GTPase pathway in MDSCs and precludes these cells from succumbing to the massive ROS generation when they acquire MDSC function.
... Arginase overexpression in immune cells (T-cells) may contribute to disease pathogenesis because it reduces NO-mediated cytotoxicity by consuming L-arginine, boosts collagen production and fibrosis by creating proline, and promotes cellular proliferation by generating polyamines. Arginase is crucial to tumour immunology, according to years of research (Sica and Bronte, 2007); (Rodríguez and Ochoa, 2008). Earlier research have focused on arginase expression in primitive tumours' from mice or humans, carcinogenic tissue, and cell culture (Wu et al., 1996) and how it may promote tumour development, polyamine synthesis, or NO-mediated tumour cytotoxicity. ...
Rudolf Virchow was the first person to point out the important link between immune function and cancer. He did this by noticing that leukocytes were often found in tumors. Overexpression of arginase 1 (ARG1) and inducible nitric oxide synthase (iNOS) in myeloid-derived suppressor cells (MDSCs) and tumour-associated macrophages (TAMs) depletes both intracellular and extracellular arginine. TCR signalling is slowed as a result, and the same types of cells produce reactive oxygen and nitrogen species (ROS and RNS), which aggravates the situation. Human arginase I is a double-stranded manganese metalloenzyme that helps L-arginine break down into L-ornithine and urea. Thus, a quantitative structure-activity relationship (QSAR) analysis was performed to unearth the unrecognised structural aspects crucial for arginase-I inhibition. In this work, a balanced QSAR model with good prediction performance and clear mechanistic interpretation was developed using a dataset of 149 molecules encompassing a broad range of structural scaffolds and compositions. The model was made to meet OECD standards, and all of its validation parameters have values that are higher than the minimum requirements (R 2 tr = 0.89, Q 2 LMO = 0.86, and R 2 ex = 0.85). The present QSAR study linked structural factors to arginase-I inhibitory action, including the proximity of lipophilic atoms to the molecule's centre of mass (within 3A), the position of the donor to the ring nitrogen (exactly 3 bonds away), and the surface area ratio. As OAT-1746 and two others are the only arginase-I inhibitors in development at the time, we have performed a QSAR-based virtual screening with 1650 FDA compounds taken from the zinc database. In this screening, 112 potential hit compounds were found to have a PIC50 value of less than 10 nm against the arginase-I receptor. The created QSAR model's application domain was evaluated in relation to the most active hit molecules identified using QSAR-based virtual screening, utilising a training set of 149 compounds and a prediction set of 112 hit molecules. As shown in the Williams plot, the top hit molecule, ZINC000252286875, has a low leverage value of HAT i/i h* = 0.140, placing it towards the boundary of the usable range. Furthermore, one of 112 hit molecules with a docking score of −10.891 kcal/mol (P IC 50 = 10.023 M) was isolated from a study of arginase-I using molecular docking. Protonated ZINC000252286875
... Additionally, the HMGB1/RAGE pathway activation recruits a subpopulation of immature monocytes expressing CD11b + Gr-1 + on the cell membrane surface. The CD11b + Gr-1 + monocyte subpopulation induces apoptosis in activated lymphocytes (Rodríguez and Ochoa, 2008). Additionally, HMGB1/RAGE pathway activation causes expansion of the CD11b +Gr-1 + monocyte subpopulation, which exhibits a hyporesponsive state after stroke, as evidenced by the reduced expressions of MHC-II and costimulatory molecules and reduced secretion of the proinflammatory cytokines TNF-α and IL-12. ...
Introduction:
High-mobility group box 1 protein (HMGB1) is extensively involved in causing ischemic stroke, pathological damage of ischemic brain injury, and neural tissue repair after ischemic brain injury. However, the precise role of HMGB1 in ischemic stroke remains to be elucidated.
Methods:
Comprehensive literature search and narrative review to summarize the current field of HMGB1 in cerebral ischemic based on the basic structure, structural modification, and functional roles of HMGB1 described in the literature.
Results:
Studies have exhibited the crucial roles of HMGB1 in cell death, immunity and inflammation, thrombosis, and remodeling and repair. HMGB1 released after cerebral infarction is extensively involved in the pathological injury process in the early stage of cerebral infarction, whereas it is involved in the promotion of brain tissue repair and remodeling in the late stage of cerebral infarction. HMGB1 plays a neurotrophic role in acute white matter stroke, whereas it causes sustained activation of inflammation and plays a damaging role in chronic white matter ischemia.
Conclusions:
HMGB1 plays a complex role in cerebral infarction, which is related to not only the modification of HMGB1 and bound receptors but also different stages and subtypes of cerebral infarction. future studies on HMGB1 should investigate the spatial and temporal dynamics of HMGB1 after cerebral infarction. Moreover, future studies on HMGB1 should attempt to integrate different stages and infarct subtypes of cerebral infarction.
... MDSCs are mainly comprised of M-MDSCs and G-MDSCs. M-MDSCs exert their suppressive effects by inhibiting NK cell function, inducing Treg cell expansion, and activating STAT1, which upregulates inducible nitric oxide synthase (iNOS) expression to suppress T cell production (76,77). G-MDSCs are an important subpopulation of circulating neutrophils whose inhibitory mechanisms are primarily to suppress CD8 1 T cells through the production of reactive oxygen species. ...
Cystic echinococcosis (CE) is a common zoonotic parasitic disease that seriously impacts public health. However, the full spectrum of immune cell changes in Echinococcus granulosus infection, especially the negative immune regulation of subpopulations of regulatory T (Treg) cells, are not yet well understood. In this study, we used single-cell RNA sequencing and immunome repertoire (IR) sequencing to analyze 53,298 cells from the spleens and peripheral blood mononuclear cells (PBMCs) of healthy and E. granulosus-infected mice. We used immunofluorescence combined with RNA fluorescence in situ hybridization and quantitative real-time PCR to verify the sequencing results. Our results showed tissue-specific immune system alterations in mice infected with E. granulosus. E. granulosus-infected mice induced a subpopulation of CD4+ cells with type I interferon production potential. Furthermore, there were six different Treg cell subpopulations in vivo at three stages of differentiation, and Treg subpopulations of different classes and different stages of differentiation showed tissue specificity. After infection, the Lag3hi Treg and Gpr83+Igfbp4+ naive Treg subpopulations were specifically induced in PBMCs and the spleen, respectively. Furthermore, T follicular helper 2 (Tfh2) cells with high expression of Cxxc5 and Spock2 were found in E. granulosus-infected mice. Our data uncovered changes in the full spectrum of immune cells in mice following the late stages of E. granulosus infection, including subpopulations of cells that have not been emphasized in previous studies. These results further enrich the study of the bidirectional immunomodulatory mechanism and offer a different perspective for subsequent studies of infection in E. granulosus.
... They inhibit T cell growth, survival, and TCR signaling via their elevated ROS levels [342][343][344]. By arginase I overexpression, they deplete the TME of critical amino acids, which impairs T cell activation and proliferation [345,346]. Moreover, they inhibit T cells by downregulating the CD3 ζ-chain of the TCR complex [347]. ...
The immune system and autophagy share a functional relationship. Both innate and adaptive immune responses involve autophagy and, depending on the disease’s origin and pathophysiology, it may have a detrimental or positive role on autoimmune disorders. As a “double-edged sword” in tumors, autophagy can either facilitate or impede tumor growth. The autophagy regulatory network that influences tumor progression and treatment resistance is dependent on cell and tissue types and tumor stages. The connection between autoimmunity and carcinogenesis has not been sufficiently explored in past studies. As a crucial mechanism between the two phenomena, autophagy may play a substantial role, though the specifics remain unclear. Several autophagy modifiers have demonstrated beneficial effects in models of autoimmune disease, emphasizing their therapeutic potential as treatments for autoimmune disorders. The function of autophagy in the tumor microenvironment and immune cells is the subject of intensive study. The objective of this review is to investigate the role of autophagy in the simultaneous genesis of autoimmunity and malignancy, shedding light on both sides of the issue. We believe our work will assist in the organization of current understanding in the field and promote additional research on this urgent and crucial topic.
... Nevertheless, subsequent studies demonstrated that immunosuppressive and angiogenic molecules were generated by the both subcategories and especially by those MDSCs that infiltrate within the TME [41,42]. Among them, MDSCs are known to exert their immunosuppressive effects through multiple mechanisms, including the generation of arginase 1, TGFβ and IL-10, nitrosylation of the TCR, downregulation of CD62L, and cysteine sequestration [43][44][45][46][47][48][49]. Similarly, overexpression of POLD1 has a strong association with MDSCs. ...
DNA polymerase delta 1 catalytic subunit (POLD1) plays a vital role in genomic copy with high fidelity and DNA damage repair processes. However, the prognostic value of POLD1 and its relationship with tumor immunity in clear cell renal cell carcinoma (ccRCC) remains to be further explored. Transcriptional data sets and clinical information were obtained from the TCGA, ICGC, and GEO databases. Differentially expressed genes (DEGs) were derived from the comparison between the low and high POLD1 expression groups in the TCGA–KIRC cohort. KEGG and gene ontology (GO) analyses were performed for those DEGs to explore the potential influence of POLD1 on the biological behaviors of ccRCC. The prognostic clinical value and mutational characteristics of patients were described and analyzed according to the POLD1 expression levels. TIMER and TISIDB databases were utilized to comprehensively investigate the potential relevance between the POLD1 levels and the status of the immune cells, as well as the tumor infiltration of immune cells. In addition, RT-qPCR, Western blot, immunohistochemistry and several functional and animal experiments were performed for clinical, in vitro and in vivo validation. POLD1 was highly expressed in a variety of tumors including ccRCC, and further verified in a validation cohort of 60 ccRCC samples and in vitro cell line experiments. POLD1 expression levels in the ccRCC samples were associated with various clinical characteristics including pathologic tumor stage and histologic grade. ccRCC patients with high POLD1 expression have poor clinical outcomes and exhibit a higher rate of somatic mutations than those with low POLD1 expression. Cox regression analysis also showed that POLD1 could act as a potential independent prognostic biomarker. The DEGs associated with POLD1 were significantly enriched in the immunity-related pathways. Moreover, further immune infiltration analysis indicated that high POLD1 expression was associated with high NK CD56bright cells, Treg cells, and myeloid-derived suppressor cells’ (MDSCs) infiltration scores, as well as their marker gene sets of immune cell status. Meanwhile, POLD1 exhibited resistance to various drugs when highly expressed. Finally, the knockdown of POLD1 inhibited the proliferation and migration, and promoted the apoptosis of ccRCC cells in vitro and in vivo, as well as influenced the activation of oncogenic signaling. Our current study demonstrated that POLD1 is a potential prognostic biomarker for ccRCC patients. It might create a tumor immunosuppressive microenvironment and inhibit the susceptibility to ferroptosis leading to a poor prognosis.
... Tumor-derived granulocytecolony stimulating factor (G-CSF), IL-6, VEGF, and CCL2 cause MDSCs migration to HCC-TME (56). Two enzymes inducible nitric oxide synthase (iNOS) and arginase 1 (ARG1) are highly expressed in MDSCs and they cause the depletion of L-arginine, a conditionally essential amino acid related to T cells proliferation and differentiation (57,58). Mechanically, L-arginine deficiency decreases the levels of CD3 z-chain indispensable for the assemble and stabilization of the TCR-CD3 complex on T cells, which weakens the antigen-recognition capability of T cells, as well as TAA-specific immune responses (59). ...
Liver cancer is the third greatest cause of cancer-related mortality, which of the major pathological type is hepatocellular carcinoma (HCC) accounting for more than 90%. HCC is characterized by high mortality and is predisposed to metastasis and relapse, leading to a low five-year survival rate and poor clinical prognosis. Numerous crosstalk among tumor parenchymal cells, anti-tumor cells, stroma cells, and immunosuppressive cells contributes to the immunosuppressive tumor microenvironment (TME), in which the function and frequency of anti-tumor cells are reduced with that of associated pro-tumor cells increasing, accordingly resulting in tumor malignant progression. Indeed, sorting out and understanding the signaling pathways and molecular mechanisms of cellular crosstalk in TME is crucial to discover more key targets and specific biomarkers, so that develop more efficient methods for early diagnosis and individualized treatment of liver cancer. This piece of writing offers insight into the recent advances in HCC-TME and reviews various mechanisms that promote HCC malignant progression from the perspective of mutual crosstalk among different types of cells in TME, aiming to assist in identifying the possible research directions and methods in the future for discovering new targets that could prevent HCC malignant progression.
... Specifically, polymorphonuclear neutrophils (PMN) have been found to be increased in cancer patients both in tumor and in the periphery [20]. The immunosuppressive phenotype of neutrophils termed PMNmyeloid derived suppressor cells (MDSC) has been well studied by a number of groups [21][22][23][24]. PMN-MDSCs exert their immune suppressive function by producing and secreting high levels of ARG1 which depletes L-arginine [24][25][26]. ...
Anti-tumor immunity can be hampered by immunosuppressive mechanisms in the tumor microenvironment including recruitment of arginase (ARG) expressing myeloid cells which deplete L-arginine essential for optimal T cell and natural killer cell function. Hence, ARG inhibition can reverse immunosuppression enhancing anti-tumor immunity. We describe AZD0011, a novel peptidic boronic acid prodrug to deliver an orally available, highly potent, ARG inhibitor payload (AZD0011-PL). We demonstrate that AZD0011-PL is unable to permeate cells, suggesting this compound will only inhibit extracellular ARG. In vivo, AZD0011 monotherapy leads to arginine increases, immune cell activation, and tumor growth inhibition (TGI) in various syngeneic models. Anti-tumor responses increase when AZD0011 is combined with anti-PD-L1 treatment, correlating with increases in multiple tumor immune cell populations. We demonstrate a novel triple combination of AZD0011, anti-PD-L1 and anti-NKG2A, and combination benefits with type I interferon (IFN) inducers including polyI:C and radiation. Our pre-clinical data demonstrates AZD0011's ability to reverse tumor immunosuppression and enhance immune stimulation and anti-tumor responses with diverse combination partners providing potential strategies to increase immuno-oncology therapies clinically.
... 174,175 For instance, MDSCs can impair the antigen presentation of DCs and phagocytosis of NK cells to promote tumor immune escape. [176][177][178] In addition to suppressing immunity in the tumor microenvironment, MDSCs can also actively participate in the management of the immune microenvironment and tumor metastasis. 179 Interestingly, under the stimulation of the hypoxic tumor microenvironment, MDSCs usually produce high levels of basic FGF, VEGF, VEGF analog Bv8, and MMP-9 to promote angiogenesis and the creation of a premetastatic niche, indicating a close association with pulmonary metastasis of osteosarcoma. ...
Osteosarcoma, with poor survival after metastasis, is considered the most common primary bone cancer in adolescents. Notwithstanding the efforts of researchers, its five-year survival rate has only shown limited improvement, suggesting that existing therapeutic strategies are insufficient to meet clinical needs. Notably, immunotherapy has shown certain advantages over traditional tumor treatments in inhibiting metastasis. Therefore, managing the immune microenvironment in osteosarcoma can provide novel and valuable insight into the multifaceted mechanisms underlying the heterogeneity and progression of the disease. Additionally, given the advances in nanomedicine, there exist many advanced nanoplatforms for enhanced osteosarcoma immunotherapy with satisfactory physiochemical characteristics. Here, we review the classification, characteristics, and functions of the key components of the immune microenvironment in osteosarcoma. This review also emphasizes the application, progress, and prospects of osteosarcoma immunotherapy and discusses several nanomedicine-based options to enhance the efficiency of osteosarcoma treatment. Furthermore, we examine the disadvantages of standard treatments and present future perspectives for osteosarcoma immunotherapy.
... When repressed, Arg2 prevents the depletion of L-arginine, the obligate substrate of eNOS, leading to improved substrate availability and additional increases in NO-production and NO-bioavailability, further aiding the above-mentioned cardio-and renoprotective and antiviral actions ( L-arginine is crucial in promoting dendritic cell maturation and their ability to drive T cell proliferation further improving antiviral responses [78,79]. Low l-arginine levels impair T cell proliferation and IFN-γ production through reduced expression of the CD3ζ chain, a crucial part of the T-cell antigen receptor complex [121]. Moreover, Arg2 is essential for interleukin (IL)-10/miR-155 axis-induced metabolic reprogramming of inflammatory macrophages, including IL-1β secretion, deciding the fate of a cell's inflammatory status [80]. ...
Severe acute respiratory coronavirus 2 (SARS-CoV-2) infection in the young and healthy usually results in an asymptomatic or mild viral syndrome, possibly through an erythropoietin (EPO)-dependent, protective evolutionary landscape. In the old and in the presence of co-morbidities, however, a potentially lethal coronavirus disease 2019 (COVID-19) cytokine storm, through unrestrained renin-angiotensin aldosterone system (RAAS) hyperactivity, has been described. Multifunctional microRNA-155 (miR-155) elevation in malaria, dengue virus (DENV), the thalassemias, and SARS-CoV-1/2, plays critical antiviral and cardiovascular roles through its targeted translational repression of over 140 genes. In the present review, we propose a plausible miR-155-dependent mechanism whereby the translational repression of AGRT1, Arginase-2 and Ets-1, reshapes RAAS towards Angiotensin II (Ang II) type 2 (AT2R)-mediated balanced, tolerable, and SARS-CoV-2-protective cardiovascular phenotypes. In addition, it enhances EPO secretion and endothelial nitric oxide synthase activation and substrate availability, and negates proinflammatory Ang II effects. Disrupted miR-155 repression of AT1R + 1166C-allele, significantly associated with adverse cardiovascular and COVID-19 outcomes, manifests its decisive role in RAAS modulation. BACH1 and SOCS1 repression creates an anti-inflammatory and cytoprotective milieu, robustly inducing antiviral interferons. MiR-155 dysregulation in the elderly, and in comorbidities, allows unimpeded RAAS hyperactivity to progress towards a particularly aggressive COVID-19 course. Elevated miR-155 in thalassemia plausibly engenders a favorable cardiovascular profile and protection against malaria, DENV, and SARS-CoV-2. MiR-155 modulating pharmaceutical approaches could offer novel therapeutic options in COVID-19.
... Arginase overexpression in immune cells (T-cells) may contribute to disease pathogenesis because it reduces NO-mediated cytotoxicity by consuming L-arginine, boosts collagen production and fibrosis by creating proline, and promotes cellular proliferation by generating polyamines. Arginase is crucial to tumour immunology, according to years of research (Sica and Bronte, 2007); (Rodríguez and Ochoa, 2008). Earlier research have focused on arginase expression in primitive tumours' from mice or humans, carcinogenic tissue, and cell culture (Wu et al., 1996) and how it may promote tumour development, polyamine synthesis, or NO-mediated tumour cytotoxicity. ...
Rudolf Virchow was the first person to point out the important link between immune function and cancer. He did this by noticing that leukocytes were often found in tumors. Overexpression of arginase 1 (ARG1) and inducible nitric oxide synthase (iNOS) in myeloid-derived suppressor cells (MDSCs) and tumour-associated macrophages (TAMs) depletes both intracellular and extracellular arginine. TCR signalling is slowed as a result, and the same types of cells produce reactive oxygen and nitrogen species (ROS and RNS), which aggravates the situation. Human arginase I is a double-stranded manganese metalloenzyme that helps L-arginine break down into L-ornithine and urea. Thus, a quantitative structure-activity relationship (QSAR) analysis was performed to unearth the unrecognised structural aspects crucial for arginase-I inhibition. In this work, a balanced QSAR model with good prediction performance and clear mechanistic interpretation was developed using a dataset of 149 molecules encompassing a broad range of structural scaffolds and compositions. The model was made to meet OECD standards, and all of its validation parameters have values that are higher than the minimum requirements (R2tr = 0.89, Q2LMO = 0.86, and R2ex = 0.85). The present QSAR study linked structural factors to arginase-I inhibitory action, including the proximity of lipophilic atoms to the molecule’s centre of mass (within 3A), the position of the donor to the ring nitrogen (exactly 3 bonds away), and the surface area ratio. As OAT-1746 and two others are the only arginase-I inhibitors in development at the time, we have performed a QSAR-based virtual screening with 1650 FDA compounds taken from the zinc database. In this screening, 112 potential hit compounds were found to have a PIC50 value of less than 10 nm against the arginase-I receptor. The created QSAR model’s application domain was evaluated in relation to the most active hit molecules identified using QSAR-based virtual screening, utilising a training set of 149 compounds and a prediction set of 112 hit molecules. As shown in the Williams plot, the top hit molecule, ZINC000252286875, has a low leverage value of HAT i/i h* = 0.140, placing it towards the boundary of the usable range. Furthermore, one of 112 hit molecules with a docking score of −10.891 kcal/mol (PIC50 = 10.023 M) was isolated from a study of arginase-I using molecular docking. Protonated ZINC000252286875-linked arginase-1 showed 2.9 RMSD, whereas non-protonated had 1.8. RMSD plots illustrate protein stability in protonated and non-protonated ZINC000252286875-bound states. Protonated-ZINC000252286875-bound proteins contain 25 Rg. The non-protonated protein-ligand combination exhibits a 25.2-Rg, indicating compactness. Protonated and non-protonated ZINC000252286875 stabilised protein targets in binding cavities posthumously. Significant root mean square fluctuations (RMSF) were seen in the arginase-1 protein at a small number of residues for a time function of 500 ns in both the protonated and unprotonated states. Protonated and non-protonated ligands interacted with proteins throughout the simulation. ZINC000252286875 bound Lys64, Asp124, Ala171, Arg222, Asp232, and Gly250. Aspartic acid residue 232 exhibited 200% ionic contact. 500-ns simulations-maintained ions. Salt bridges for ZINC000252286875 aided docking. ZINC000252286875 created six ionic bonds with Lys68, Asp117, His126, Ala171, Lys224, and Asp232 residues. Asp117, His126, and Lys224 showed 200% ionic interactions. In protonated and deprotonated states, GbindvdW, GbindLipo, and GbindCoulomb energies played crucial role. Moreover, ZINC000252286875 meets all of the ADMET standards to serve as a drug. As a result, the current analyses were successful in locating a novel and potent hit molecule that inhibits arginase-I effectively at nanomolar concentrations. The results of this investigation can be used to develop brand-new arginase I inhibitors as an alternative immune-modulating cancer therapy.
... MDSCs can also induce Treg expansion and promote the negative regulatory effect of Treg on immunity (Serafini et al., 2008). In terms of adaptive immunity, MDSCs can inhibit T Cell immune response responses and proliferation through multiple pathways (Rodríguez and Ochoa, 2008). Studies have found that MDSCs are significantly expanded in arthritic mice and RA patients. ...
Background: Osteoarthritis is a common chronic degenerative disease, and recently, an increasing number of studies have shown that immunity plays an important role in the progression of osteoarthritis, which is exacerbated by local inflammation. The role of N6-methyladenine (m⁶A) modification in immunity is being explored. However, the role of m⁶A modification in regulating the immune microenvironment of osteoarthritis remains unknown. In this study, we sought to discuss the association between the N6-methyladenine (m⁶A) modification and the immune microenvironment of osteoarthritis.
Methods: First, the data and gene expression profiles of 139 samples, including 33 healthy samples and 106 osteoarthritis samples, were obtained from the Genetics osteoARthritis and Progression (GARP) study. Then the differences in m⁶A regulators between healthy individuals and osteoarthritis patients were analyzed. The correlation between m⁶A regulators and immune characteristics was also investigated by single-sample gene set enrichment analysis (ssGSEA). Principal component analysis (PCA), Gene Set Variation Analysis (GSVA) enrichment analysis, weighted gene coexpression network analysis (WGCNA), and Associated R packages were used to identify the m⁶A phenotype and its biological functions.
Results: A total of 23 m⁶A regulators were involved in this study. We found a close correlation between most m⁶A regulators in all samples as well as in osteoarthritis samples. VIRMA and LRPPRC were the most highly correlated m⁶A regulators and showed a positive correlation, whereas VIRMA and RBM15B were the most negatively correlated. M⁶A regulators are associated with osteoarthritis immune characteristics. For example, MDSC cell abundance was strongly correlated with RBM15B and HNRNPC. Meanwhile, RBM15B and HNRNPC were important effectors of natural killer cell immune responses. IGFBP3 is an important regulator of cytolytic activity immune function. We performed an unsupervised consensus cluster analysis of the osteoarthritis samples based on the expression of 23 m⁶A regulators. Three different m⁶A subtypes of osteoarthritis were identified, including 27 samples in subtype C1, 21 samples in subtype C2, and 58 samples in subtype C3. Different m⁶A subtypes have unique biological pathways and play different roles in the immune microenvironment of osteoarthritis.
Conclusion: The m⁶A modification plays a crucial role in the diversity and complexity of the immune microenvironment in osteoarthritis.
Cancer immunotherapy and vaccine development have significantly improved the fight against cancers. Despite these advancements, challenges remain, particularly in the clinical delivery of immunomodulatory compounds. The tumor microenvironment (TME), comprising macrophages, fibroblasts, and immune cells, plays a crucial role in immune response modulation. Nanoparticles, engineered to reshape the TME, have shown promising results in enhancing immunotherapy by facilitating targeted delivery and immune modulation. These nanoparticles can suppress fibroblast activation, promote M1 macrophage polarization, aid dendritic cell maturation, and encourage T cell infiltration. Biomimetic nanoparticles further enhance immunotherapy by increasing the internalization of immunomodulatory agents in immune cells such as dendritic cells. Moreover, exosomes, whether naturally secreted by cells in the body or bioengineered, have been explored to regulate the TME and immune-related cells to affect cancer immunotherapy. Stimuli-responsive nanocarriers, activated by pH, redox, and light conditions, exhibit the potential to accelerate immunotherapy. The co-application of nanoparticles with immune checkpoint inhibitors is an emerging strategy to boost anti-tumor immunity. With their ability to induce long-term immunity, nanoarchitectures are promising structures in vaccine development. This review underscores the critical role of nanoparticles in overcoming current challenges and driving the advancement of cancer immunotherapy and TME modification.
Osteosarcoma (OS) is a frequently occurring primary bone tumor, mostly affecting children, adolescents and young adults. Before 1970, surgical resection was the main treatment method for OS, but the clinical results were not promising. Subsequently, the advent of chemotherapy has improved the prognosis of patients with OS. However, there is still a high incidence of metastasis or recurrence, and chemotherapy has several side effects, thus making the 5-year survival rate markedly low. Recently, chimeric antigen receptor T (CAR-T) cell therapy represents an alternative immunotherapy approach with significant potential for hematologic malignancies. Nevertheless, the application of CAR-T cells in the treatment of OS faces numerous challenges. The present review focused on the advances in the development of CAR-T cells to improve their clinical efficacy, and discussed ways to overcome the difficulties faced by CAR T-cell therapy for OS.
The hypoxic microenvironment in solid tumors affects the metabolism of tumor cells and infiltrating immune cells, which aids in robust tumor growth and expansion. Myeloid-derived suppressor cells (MDSCs) are heterogenous immature myeloid cells in the TME, which play an essential role in immune evasion by subverting T/NK cell-mediated killing. The immunosuppressive function of MDSCs is tightly regulated to the metabolic pathways, in which hypoxia plays a critical role. In this chapter, we describe the isolation of murine MDSCs from bone marrows and the measurement of the transcriptomic changes of essential metabolic enzymes under hypoxic conditions. This method can be applied to study MDSCs function, mimicking the hypoxic environment in vitro. This method can be utilized to investigate the critical metabolic alterations under a given tumor context and help evaluate the efficacy of metabolic-targeted therapies in the long run.
Metabolic reprogramming of amino acids has been increasingly recognized to initiate and fuel tumorigenesis and survival. Therefore, there is emerging interest in the application of amino acid metabolic strategies in antitumor therapy. Tremendous efforts have been made to develop amino acid metabolic node interventions such as amino acid antagonists and targeting amino acid transporters, key enzymes of amino acid metabolism, and common downstream pathways of amino acid metabolism. In addition to playing an essential role in sustaining tumor growth, new technologies and studies has revealed amino acid metabolic reprograming to have wide implications in the regulation of antitumor immune responses. Specifically, extensive crosstalk between amino acid metabolism and T cell immunity has been reported. Tumor cells can inhibit T cell immunity by depleting amino acids in the microenvironment through nutrient competition, and toxic metabolites of amino acids can also inhibit T cell function. In addition, amino acids can interfere with T cells by regulating glucose and lipid metabolism. This crucial crosstalk inspires the exploitation of novel strategies of immunotherapy enhancement and combination, owing to the unprecedented benefits of immunotherapy and the limited population it can benefit. Herein, we review recent findings related to the crosstalk between amino acid metabolism and T cell immunity. We also describe possible approaches to intervene in amino acid metabolic pathways by targeting various signaling nodes. Novel efforts to combine with and unleash potential immunotherapy are also discussed. Hopefully, some strategies that take the lead in the pipeline may soon be used for the common good.
Sulforaphane (SFN) is a compound derived from cruciferous plants. It has received considerable attention in recent years due to its effectiveness in cancer prevention and anti-inflammatory properties. The purpose of this study was to evaluate the antitumor potential of sulforaphane on colitis-associated carcinogenesis (CAC) through the establishment of a mouse model with AOM/DSS. First, AOM/DSS and DSS-induced model were established and administered SFN for 10 wk, and then the severity of colitis-associated colon cancer was examined macroscopically and histologically. Subsequently, immune cells and cytokines in the tumor microenvironment (TME) were quantified. Finally, the influence of sulforaphane was also investigated using different colon cell lines. We found that sulforaphane treatment decreased tumor volume, myeloid-derived suppressor cells (MDSC) expansion, the expression of the proinflammatory cytokine IL-1β, and the level of IL-10 in serum. Also, it enhanced the antitumor activities of CD8+ T cells and significantly reduced tumorigenesis as induced by AOM/DSS. SFN also attenuated intestinal inflammation in DSS-induced chronic colitis by reshaping the inflammatory microenvironment. This work demonstrates that sulforaphane suppresses carcinogenesis-associated intestinal inflammation and prevents AOM/DSS-induced intestinal tumorigenesis and progression.
Lymphatic metastasis is the primary type of cervical cancer metastasis and is associated with an extremely poor prognosis in patients. The tumor microenvironment primarily includes cancer-associated fibroblasts, tumor-associated macrophages, myeloid-derived suppressor cells, immune and inflammatory cells, and blood and lymphatic vascular networks, which can promote the establishment of lymphatic metastatic sites within immunosuppressive microenvironments or promote lymphatic metastasis by stimulating lymphangiogenesis and epithelial-mesenchymal transformation. As the most important feature of the tumor microenvironment, hypoxia plays an essential role in lymph node metastasis. In this review, the known mechanisms of hypoxia, and the involvement of stromal components and immune inflammatory cells in the tumor microenvironment of lymphatic metastasis of cervical cancer are discussed. Additionally, a summary of the clinical trials targeting the tumor microenvironment for the treatment of cervical cancer is provided, emphasizing the potential and challenges of immunotherapy.
Myeloid-derived suppressor cells (MDSC) are a heterogeneous cell population of incompletely differentiated immune cells. They are known to suppress T cell activity and are implicated in multiple chronic diseases, which makes them an attractive cell population for drug discovery. Here, we characterized the baseline proteomes and phospho-proteomes of mouse MDSC differentiated from a progenitor cell line to a depth of 7,000 proteins and phosphorylation sites. We also validated the cellular system for drug discovery by recapitulating and identifying known and novel molecular responses to the well-studied MDSC drugs Entinostat and Mocetinostat. We established a high-throughput drug screening platform using a MDSC/T cell co-culture system and assessed the effects of ∼21,000 small molecule compounds on T cell proliferation and INF-γ secretion to identify novel MDSC modulator. The most promising candidates were validated in a human MDSC system and subsequent proteomic experiments showed significant upregulation of several proteins associated with the reduction of reactive oxygen species (ROS). Proteome-wide solvent-induced protein stability assays identified Acyp1 und Cd74 as potential targets and the ROS reducing drug phenotype was validated by measuring ROS levels in cells in response to compound, suggesting a potential mode of action. We anticipate that the data and chemical tools developed in this study will be valuable for further research on MDSC and related drug discovery.
Background:
While we strive to live with SARS-CoV-2, defining the immune response that leads to recovery rather than severe disease remains highly important. COVID-19 has been associated with inflammation and a profoundly suppressed immune response.
Objective:
To study myeloid-derived suppressor cells (MDSCs), which are potent immunosuppressive cells, in SARS-CoV-2 infection.
Results:
Patients with severe and critical COVID-19 showed higher frequencies of neutrophilic (PMN)-MDSCs than patients with moderate illness and control individuals (P = .005). Severe disease in individuals older and younger than 60 years was associated with distinct PMN-MDSC frequencies, being predominantly higher in patients of 60 years of age and younger (P = .004). However, both age groups showed comparable inflammatory markers. In our analysis for the prediction of poor outcome during hospitalization, MDSCs were not associated with increased risk of death. Still, patients older than 60 years of age (odds ratio [OR] = 5.625; P = .02) with preexisting medical conditions (OR = 2.818; P = .003) showed more severe disease and worse outcome. Among the immunological parameters, increased C-reactive protein (OR = 1.015; P = .04) and lymphopenia (OR = 5.958; P = .04) strongly identified patients with poor prognosis.
Conclusion:
PMN-MDSCs are associated with disease severity in COVID-19; however, MDSC levels do not predict increased risk of death during hospitalization.
Pulmonary hypertension (PH) is a chronic pulmonary vascular disorder characterized by an increase in pulmonary vascular resistance and pulmonary arterial pressure. The detailed molecular mechanisms remain unclear. In recent decades, increasing evidence shows that altered immune microenvironment, comprised of immune cells, mesenchymal cells, extra-cellular matrix and signaling molecules, might induce the development of PH. Myeloid-derived suppressor cells (MDSCs) have been proposed over 30 years, and the functional importance of MDSCs in the immune system is appreciated recently. MDSCs are a heterogeneous group of cells that expand during cancer, chronic inflammation and infection, which have a remarkable ability to suppress T-cell responses and may exacerbate the development of diseases. Thus, targeting MDSCs has become a novel strategy to overcome immune evasion, especially in tumor immunotherapy. Nowadays, severe PH is accepted as a cancer-like disease, and MDSCs are closely related to the development and prognosis of PH. Here, we review the relationship between MDSCs and PH with respect to immune cells, cytokines, chemokines and metabolism, hoping that the key therapeutic targets of MDSCs can be identified in the treatment of PH, especially in severe PH.
Tumor microenvironment (TME) is a heterogeneous system consisting of both cellular and acellular components. The growth and progression of tumors rely greatly on the nature of TME, marking it as an important target in cancer immunotherapy. Lewis Lung Carcinoma (LLC) is an established murine lung cancer model representing immunologically 'cold' tumors characterized by very few infiltrated cytotoxic T-cells, high levels of Myeloid-Derived Suppressor Cells (MDSCs) and Tumor-Associated Macrophages (TAMs). Here, we report various strategies we applied to reverse the non-immunogenic character of this cold tumor by imparting: a) immunogenic cell death using Hypericin nanoparticle-based photodynamic therapy (PDT), b) repolarising TAM using a TLR7/8 agonist, resiquimod, c) immune checkpoint inhibition using anti-PD-L1 and d) depleting MDSCs using low-dose 5-fluorouracil (5-FU) chemotherapy. Interestingly, the nano-PDT, resiquimod or anti-PD-L1 treatment had no major impact on tumor growth, whereas low-dose 5-FU-mediated depletion of MDSCs showed significant anti-tumor effect, primarily caused by the increased infiltration of CD8+ cytotoxic T-cells (∼96%). Though we have tested combining PDT with resiquimod or 5-FU for any synergistic effect, low-dose 5-FU alone showed better response than combinations. In effect, we show that depletion of MDSCs using low-dose 5-FU was one of the best methods to augment infiltration of CD8+ cytotoxic T-cells into a cold tumor, which is resistant to conventional therapies including immune checkpoint inhibitors.
Immunotherapy has revolutionized cancer treatment and revitalized efforts to harness the power of the immune system to combat a variety of cancer types more effectively. However, low clinical response rates and differences in outcomes due to variations in the immune landscape among patients with cancer continue to be major limitations to immunotherapy. Recent efforts to improve responses to immunotherapy have focused on targeting cellular metabolism, as the metabolic characteristics of cancer cells can directly influence the activity and metabolism of immune cells, particularly T cells. Although the metabolic pathways of various cancer cells and T cells have been extensively reviewed, the intersections among these pathways, and their potential use as targets for improving responses to immune-checkpoint blockade therapies, are not completely understood. This review focuses on the interplay between tumor metabolites and T-cell dysfunction as well as the relationship between several T-cell metabolic patterns and T-cell activity/function in tumor immunology. Understanding these relationships could offer new avenues for improving responses to immunotherapy on a metabolic basis.
Increased exposure to manmade chemicals may be linked to an increase in immune-related diseases in humans and immune system dysfunction in wildlife. Phthalates are a group of endocrine-disrupting chemicals (EDCs) suspected to influence the immune system. The aim of this study was to characterize the persistent effects on leukocytes in the blood and spleen, as well as plasma cytokine and growth factor levels, one week after the end of five weeks of oral treatment with dibutyl phthalate (DBP; 10 or 100 mg/kg/d) in adult male mice. Flow cytometry analysis of the blood revealed that DBP exposure decreased the total leukocyte count, classical monocyte and T helper populations, whereas it increased the non-classical monocyte population compared to the vehicle control (corn oil). Immunofluorescence analysis of the spleen showed increased CD11b+Ly6G+, a marker of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), and CD43+staining, a marker of non-classical monocytes, whereas CD3+ and CD4+ staining decreased. To investigate the mechanisms of action, levels of plasma cytokines and chemokines were measured using multiplexed immunoassays and key factors were analyzed using western blotting. The observed increase in M-CSF levels and the activation of STAT3 may promote PMN-MDSC expansion and activity. Increased ARG1, NOX2 (gp91phox), and protein nitrotyrosine levels, as well as GCN2 and phosphor-eIRFα, suggest that oxidative stress and lymphocyte arrest drive the lymphocyte suppression caused by PMN-MDSCs. The plasma levels of IL-21 (promotes the differentiation of T helper cells) and MCP-1 (regulates migration and infiltration of monocytes/macrophages) also decreased. These findings show that adult DBP exposure can cause persistent immunosuppressive effects, which may increase susceptibility to infections, cancers, and immune diseases, and decrease vaccine efficacy.
Purpose:
To assess whether MUC1 peptide vaccine produces an immune response and prevents subsequent colon adenoma formation.
Patients and methods:
Multicenter, double blind, placebo-controlled randomized trial in individuals age 40-70 with diagnosis of an advanced adenoma ≤1 year from randomization. Vaccine was administered at 0, 2, and 10 weeks with a booster injection at week 53. Adenoma recurrence was assessed ≥1 year from randomization. The primary endpoint was vaccine immunogenicity at 12 weeks defined by anti-MUC1 ratio ≥2.0.
Results:
53 participants received the MUC1 vaccine and 50 placebo. 13/52 (25%) of MUC1 vaccine recipients had a ≥2-fold increase in MUC1 IgG (range 2.9-17.3) at week 12 vs. 0/50 placebo recipients (1-sided Fisher's exact P<0.0001). Of 13 responders at week 12, 11 (84.6%) responded to a booster injection at week 52 with a ≥2-fold increase in MUC1 IgG measured at week 55. Recurrent adenoma was observed in 31 of 47 (66.0%) in the placebo group vs. 27 of 48 (56.3%) in the MUC1 group (adjusted relative risk (aRR) = 0.83 [95% CI, 0.60-1.14], P=0.25). Adenoma recurrence occurred in 3/11 (27.3%) immune responders at week 12 and week 55 (aRR = 0.41 [95% CI, 0.15-1.11], P=0.08 compared to placebo). There was no difference in serious adverse events.
Conclusion:
An immune response was observed only in vaccine recipients. Adenoma recurrence was not different than placebo, but a 38% absolute reduction in adenoma recurrence compared to placebo was observed in participants who had an immune response at week 12 and with the booster injection.
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.
Sites of inflammation with prominent macrophage infiltration, such as wounds and certain tumors, are uniquely deficient in free arginine. The effects of arginine availability on macrophage physiology were investigated. When cultured in media containing less than 0.1 mM L-arginine, rat resident peritoneal macrophages exhibited enhanced spreading, tumor cytotoxicity, superoxide production, phagocytosis, and protein synthesis. Thus, arginine concentrations similar to those found in sites of inflammation can augment macrophage functions, while those found in plasma (approximately 0.1 mM) and in commonly used culture media (0.4 to 1.2 mM) are inhibitory. Culture in homoarginine, but not D-arginine, ornithine, citrulline, urea, histidine, or lysine also inhibited macrophage tumor cytotoxicity, indicating the specificity of the effect. In contrast to resident macrophages, the tumor cytotoxicity of peritoneal macrophages obtained after C. parvum injection was suppressed by culture in arginine-deficient media. However, L-arginine-deficient media enhanced all other activation-associated functions in C. parvum-elicited macrophages as in resident cells. Arginine-free wound fluid promoted resident macrophage tumoricidal activity when compared with rat serum, and again, the addition of L-arginine was inhibitory. The marked effects of L-arginine availability on macrophage functions, together with the knowledge that these cells modify the extracellular arginine concentration in sites of inflammation through arginase, provide evidence for an autoregulatory mechanism of macrophage activation.
As observed for many types of cancers, heritable variants of ultraviolet light-induced tumors often grow more aggressively than the parental tumors. The aggressive growth of some variants is due to the loss of a T cell-recognized tumor-specific antigen; however, other variants retain such antigens. We have analyzed an antigen retention variant and found that the variant tumor cells grow at the same rate as the parental tumor cells in vitro, but grew more rapidly than the parental cells in the T cell-deficient host. The growth of the variant cells was stimulated in vitro by factors released from tumor-induced leukocytes and by several defined growth factors. In addition, the variant cancer cells actually attracted more leukocytes in vitro than the parental cells. Furthermore, elimination of granulocytes in vivo in nude mice by a specific antigranulocyte antibody inhibited the growth of the variant cancer, indicating that this tumor requires granulocytes for rapid growth.
Recent data suggest that the poor induction of a T-cell response to human renal cell carcinoma (RCC) may be related to alterations in signal transduction pathways. We report that T cells from RCC patients have two alterations in kappa B motif-specific DNA-binding activity. The first alteration involves the constitutive expression of substantial kappa B-binding activity in nuclear extracts, which was observed in the electrophoretic mobility shift assay. The magnitude of kappa B activity in unstimulated patient T cells was similar to that observed in T cells from normal individuals that had been activated in vitro. On the basis of Western blotting experiments using antibodies to kappa B/Rel family proteins, the kappa B-binding activity constitutively expressed in T cells from RCC patients is composed mostly of the NF-kappa B1 (p50) subunit. The second abnormality in kappa B-binding activity in T cells from these patients is that RelA, a member of the Rel homology family which is part of the normal NF-kappa B complex, was not induced in the nucleus following activation. Western blotting analysis did not detect any RelA in nuclear extracts either before or after stimulation of T cells. The altered kappa B-binding activity in T cells from RCC patients may impair their capacity to respond normally to various stimuli.
Cancer patients and mice bearing tumors develop a progressive immunosuppression manifested by a decreased delayed-type hypersensitivity, decreased T-cell lytic activity, diminished production of lymphokines, and a reduced T-cell proliferative response. The mechanisms underlying these changes are incompletely understood. We recently reported the presence of marked alterations in signal transduction in T-cells from mice bearing long-term (28-day) tumours. We hypothesized that a soluble product produced by the tumor or resulting from the immune response to tumor might be responsible for inducing the changes in T-cells. Tumor-infiltrating lymphocytes from patients with renal cell carcinoma tested here showed, in 10 of 11 cases, a marked decrease in the expression of the T-cell receptor zeta chain and in p56lck tyrosine kinase. The presence of major alterations in the tumor-infiltrating lymphocytes with only minor changes in the peripheral blood leukocyte T-cells supports the notion that the defects are induced by exposure to tumor. These results suggest that tumor-infiltrating lymphocytes may be compromised in their antitumor efficacy in patients with renal cell cancer.
Advanced stages of mycobacterial diseases such as leprosy and tuberculosis are characterized by a loss of T-cell function. The basis of this T-cell dysfunction is not well understood. The present report demonstrates major alterations in the expression of signal transduction molecules in T cells of leprosy patients. These alterations were most frequently observed in lepromatous leprosy (LL) patients. Of 29 LL patients, 69% had decreased T-cell receptor zeta-chain expression, 48% had decreased p56(lck) tyrosine kinase, and 63% had a loss of nuclear transcription factor NF-kappaB p65. An electrophoretic mobility shift assay with the gamma interferon core promoter region revealed a loss of the Th1 DNA-binding pattern in LL patients. In contrast, tuberculoid leprosy patients had only minor signal transduction alterations. These novel findings might improve our understanding of the T-cell dysfunction observed in leprosy and other infectious diseases and consequently might lead to better immunologic evaluation of patients.
We have recently reported that tumor-associated lymphocytes obtained from ascitic fluids of women with ovarian carcinoma (OvCA) demonstrate a marked decrease in expression of cytoplasmic CD3-zeta and surface CD3-epsilon chains, which is associated with altered function of T cell receptor (TcR). We now demonstrate that OvCAs in situ and in culture express functional Fas ligand (FasL), capable of triggering an intrinsic cell death program in Fas-expressing T cells. The possibility of a relationship between cell death and altered expression of TcR was examined. The data indicate that alterations in expression of CD3-zeta and CD3-epsilon chains in T cells coincubated with OvCA are related to tumor-induced apoptosis, as the addition of pan-caspase inhibitors, DEVD-cho or YVAD-cho, prevents both the in vitro induction of T cell death by OvCA cells and the changes in the level of expression of CD3-zeta and CD3-epsilon chains. In the presence of Fas-Fc fusion protein, but not Fc-control protein, the loss in expression of CD3-zeta and CD3-epsilon chains induced in T cells by FasL+ OvCA cells was prevented. These results suggest that the loss in expression of CD3-zeta and CD3-epsilon chains in T lymphocytes interacting with OvCA cells is associated with apoptosis mediated by FasL-expressing tumor cells.
The las quorum-sensing system of Pseudomonas aeruginosa controls the expression of elastase and rhamnolipid. We report that starvation can select a mutant producing these virulence factors in spite of a lasR deletion. Expression of the autoinducer synthase gene rhlI was increased in this suppressor mutant, suggesting compensation by the rhl system. These data show that P. aeruginosa can restore elastase and rhamnolipid production in the absence of a functional las quorum-sensing system.
An impaired immune response is frequently observed in patients and experimental animals with advanced cancer. We and others have shown alterations in CD3-associated signal-transducing zeta molecules in tumor-infiltrating T cells and peripheral blood lymphocytes (PBLs) of patients with advanced cancer. By using flow cytometric analysis of permeabilized cells with a monoclonal antibody (TIA-2) that reacts with the cytoplasmic domain of the zeta chain, here we demonstrate a marked decrease (P < 0.01) in the expression of the signal-transducing CD3 zeta chain of PBLs in patients with cervical cancer (n = 22) as compared to PBLs from healthy donors (n = 21). In addition, PBLs isolated from patients (n = 23) with cervical intraepithelial neoplasia (CIN), to a lesser but significant (P < 0. 01) extent, expressed reduced CD3 zeta levels as compared to those from healthy donors. This decreased expression of zeta chains was also observed on CD16(+) natural killer cells in PBLs from patients with cervical cancer. Surface expression of CD3 epsilon on PBLs was also decreased in cervical cancer patients as compared to healthy donors, but not on PBLs from patients with CIN. CD3 zeta chain expression significantly (r = 0.53, P < 0.01) correlated with the ability of the PBLs to produce tumor necrosis factor in response to anti-CD3 stimulation. These findings suggest that alterations of signal-transducing zeta molecules commonly occur in patients with cervical cancer and to a lesser extent with CIN, and that they are associated with reduced cellular functions such as production of tumor necrosis factor.
We have recently described molecular changes in T cells from tumor-bearing patients that are associated with depressed immune function. The present work investigates changes in T-cell signal transduction proteins including the T-cell receptor-zeta (TCR-zeta) chain and receptor-associated tyrosine kinases in patients with metastatic malignant melanoma. A marked decrease in the expression of the TCR-zeta chain was observed in the peripheral blood T cells of 19 (43%) of 44 patients. Decreases in several tyrosine kinases were found in 12 (57%) of 21 patients tested. T cells from patients with diminished TCR-zeta chain expression also showed statistically significant differences in cytokine production pattern, with lower interleukin 2 and IFN-zeta production compared with normal subjects and melanoma patients with normal TCR-zeta chain status. The overall survival of melanoma patients with low TCR-zeta chain expression was significantly shorter than that of patients with normal TCR-zeta chain expression (P = 0.0013). TCR-zeta-deficient patients showed a trend toward having faster growing tumors. There was no correlation between the pretreatment TCR-zeta chain status and albumin or performance status. These findings suggest that alterations in T-cell function occur commonly in melanoma patients and may be independent predictors of clinical outcome.
Apoptotic death of CD8+ T cells can be induced by a population of inhibitory myeloid cells that are double positive for the CD11b and Gr-1 markers. These cells are responsible for the immunosuppression observed in pathologies as dissimilar as tumor growth and overwhelming infections, or after immunization with viruses. The appearance of a CD11b+/Gr-1+ population of inhibitory macrophages (iMacs) could be attributed to high levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) in vivo. Deletion of iMacs in vitro or in vivo reversed the depression of CD8+ T-cell function. We isolated iMacs from the spleens of immunocompromised mice and found that these cells were positive for CD31, ER-MP20 (Ly-6C), and ER-MP58, markers characteristic of granulocyte/monocyte precursors. Importantly, although iMacs retained their inhibitory properties when cultured in vitro in standard medium, suppressive functions could be modulated by cytokine exposure. Whereas culture with the cytokine interleukin 4 (IL-4) increasediMac inhibitory activity, these cells could be differentiated into a nonadherent population of fully mature and highly activated dendritic cells when cultured in the presence of IL-4and GM-CSF. A common CD31+/CD11b+/Gr-1+ progenitor can thus give rise to cells capable of either activating or inhibiting the function of CD8+ T lymphocytes, depending on the cytokinemilieu that prevails during antigen-presenting cell maturation.
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.
Progression through the first gap phase (Gi) of the mammalian cell cycle is regulated by growth factors, but once cells commit to replicate their cellular DNA, they can undergo mitosis even if deprived of growth factors during ensuing cell cycle inter-vals.1 Recently isolated mammalian cyclins, including cyclins D1, D2, D3, and E, 2–6 appear likely to play central roles in integrating growth factor-induced signals with the cell cycle clock, thereby driving cells into S phase. To date, the hypothesis that D-type cyclins and cyclin E function to govern G1 transitions has rested largely on circumstantial evidence, but recent data now indicate that their activities are rate limiting for G1 progression and required for the entry of cells into the DNA synthetic (S) phase of the cell cycle.
The cytokines IL-4 and IL-13 inhibit the production of NO from activated macrophages through an unresolved molecular mechanism. We show here that IL-4 and IL-13 regulate NO production through depletion of arginine, the substrate of inducible NO synthase (iNOS). Inhibition of NO production from murine macrophages stimulated with LPS and IFN-gamma by IL-4 or IL-13 was dependent on Stat6, cell density in the cultures, and pretreatment for at least 6 h. IL-4/IL-13 did not interfere with the expression or activity of iNOS but up-regulated arginase I (the liver isoform of arginase) in a Stat6-dependent manner. Addition of exogenous arginine completely restored NO production in IL-4-treated macrophages. Furthermore, impaired killing of the intracellular pathogen Toxoplasma gondii in IL-4-treated macrophages was overcome by supplementing L-arginine. The simple system of regulated substrate competition between arginase and iNOS has implications for understanding the physiological regulation of NO production.
Sites of inflammation with prominent macrophage infiltration, such as wounds and certain tumors, are uniquely deficient in free arginine. The effects of arginine availability on macrophage physiology were investigated. When cultured in media containing less than 0.1 mM L-arginine, rat resident peritoneal macrophages exhibited enhanced spreading, tumor cytotoxicity, superoxide production, phagocytosis, and protein synthesis. Thus, arginine concentrations similar to those found in sites of inflammation can augment macrophage functions, while those found in plasma (approximately 0.1 mM) and in commonly used culture media (0.4 to 1.2 mM) are inhibitory. Culture in homoarginine, but not D-arginine, ornithine, citrulline, urea, histidine, or lysine also inhibited macrophage tumor cytotoxicity, indicating the specificity of the effect. In contrast to resident macrophages, the tumor cytotoxicity of peritoneal macrophages obtained after C. parvum injection was suppressed by culture in arginine-deficient media. However, L-arginine-deficient media enhanced all other activation-associated functions in C. parvum-elicited macrophages as in resident cells. Arginine-free wound fluid promoted resident macrophage tumoricidal activity when compared with rat serum, and again, the addition of L-arginine was inhibitory. The marked effects of L-arginine availability on macrophage functions, together with the knowledge that these cells modify the extracellular arginine concentration in sites of inflammation through arginase, provide evidence for an autoregulatory mechanism of macrophage activation.
As observed for many types of cancers, heritable variants of ultraviolet light-induced tumors often grow more aggressively than the parental tumors. The aggressive growth of some variants is due to the loss of a T cell-recognized tumor-specific antigen; however, other variants retain such antigens. We have analyzed an antigen retention variant and found that the variant tumor cells grow at the same rate as the parental tumor cells in vitro, but grew more rapidly than the parental cells in the T cell-deficient host. The growth of the variant cells was stimulated in vitro by factors released from tumor-induced leukocytes and by several defined growth factors. In addition, the variant cancer cells actually attracted more leukocytes in vitro than the parental cells. Furthermore, elimination of granulocytes in vivo in nude mice by a specific antigranulocyte antibody inhibited the growth of the variant cancer, indicating that this tumor requires granulocytes for rapid growth.
Agmatine, an amine formed by decarboxylation of L-arginine by arginine decarboxylase (ADC), has been recently discovered in mammalian brain and other tissues. While the cloning and sequencing of ADC from plant and bacteria have been reported extensively, the structure of mammalian enzyme is not known. Using homology screening approach, we have identified a human cDNA clone that exhibits ADC activity when expressed in COS-7 cells. The cDNA and deduced amino acid sequence of this human ADC clone is distinct from ADC of other forms. Human ADC is a 460-amino acid protein that shows about 48% identity to mammalian ornithine decarboxylase (ODC) but has no ODC activity. While naive COS-7 cells do not make agmatine, these cells are able to produce agmatine, as measured by HPLC, when transfected with ADC cDNA. Northern blot analysis using the cDNA probe indicated the expression of ADC message in selective human brain regions and other human tissues.
The development of mouse models of human organ-specific autoimmune diseases has been hampered by the need to immunize mice with autoantigens in potent adjuvants. Even autoantigen-specific T cell receptor transgenic models of autoimmunity have proven to be complex as the transgenic mice frequently fail to develop disease spontaneously. We have isolated a CD4+ T cell clone (TxA23)that recognizes the gastric parietal cell antigen, H/K ATPase α-chain630–641, from a mouse with autoimmune gastritis that developed after thymectomy on day 3 of life. The T cell receptor α and β genes from this clone were used to generate A23 transgenic mice. All A23 transgenic animals spontaneously developed severe autoimmune gastritis, and evidence of disease was detected as early as day 10 of life. Gastritis could be transferred to immunocompromised mice with a limited number of transgenic thymocytes (103), but as many as 107 induced only mild disease in wild-type animals. Due to the complete penetrance of spontaneous disease, identity of the auto-antigen, susceptibility to immunoregulation, and close relation to autoimmune gastritis in man, A23 transgenic mice represent a unique CD4+ T cell-mediated disease model for understanding the multiple factors regulating organ-specific autoimmunity.
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.
Background:
The carefully orchestrated events that result in a protective immune response are coordinated to a large extent by cytokines produced by T helper 1 (Th1) and T helper 2 (Th2) T-cell subsets, which are two arms of the immune system. Th1 cells preferentially produce interleukin 2 (IL-2), interferon gamma (IFN gamma), and tumor necrosis factor (TNF), resulting in a cellular response that helps to eliminate infected cells. In contrast, Th2 cells produce IL-4, IL-5, IL-6, and IL-10 and stimulate an antibody response that helps to prevent the cells from becoming infected. The clinical progression of several infectious diseases, including human immunodeficiency virus, some types of parasitoses, and tuberculosis, is thought to be associated with the predominance of a Th2-type T-cell response. Recent reports have demonstrated the presence of T cells producing Th2 lymphokines (IL-4, IL-6, and IL-10) in tumor-infiltrating lymphocytes of renal cell carcinoma.
Purpose:
The purpose of this study was to investigate at the molecular level whether there was any change in the splenic T cells of mice with progressively growing tumors from a Th1 to a Th2 DNA-binding pattern or phenotype.
Methods:
Splenic T cells from mice bearing renal cell carcinoma or MCA-38 colon carcinoma were tested for cytokine production after in vitro activation. Nuclear extracts of splenic T cells were used for the DNA-binding assay using IFN-gamma core promoter region, the kappa B (kappa B) site from immunoglobulin gene, and the nuclear factor of activated T-cell (NFAT) site from IL-2 gene.
Results:
Splenic T cells from mice bearing renal cell carcinoma or MCA-38 colon carcinoma preferentially produced Th2 cytokines (i.e., IL-4) upon activation and showed a marked decrease in Th1 cytokine (particularly IFN gamma) production compared with the production observed in normal splenic T cells. The DNA-binding assay with the IFN-gamma core promoter region confirmed the gradual decline in the nuclear transcription factors associated with the Th1 phenotype during tumor progression in both tumor models. Renal cell carcinoma-bearing mice, successfully treated with flavone-8-acetic acid and recombinant human IL-2, showed a reversion to a Th1-like pattern. In addition, nuclear extracts of T cells from tumor-bearing animals showed a Th2-type kappa B-binding pattern. Moreover, the NFAT complex present in the normal splenic T cells was lost at the later stages of tumor progression; instead, a new complex was present in mice bearing long-term tumors.
Conclusion:
T cells from tumor-bearing mice lose the Th1 phenotype with progressive tumor growth.
In the present paper we studied the immunological hyporesponsiveness and the suppressor activity in mice bearing a transplantable adenocarcinoma, ADK-1t, that spontaneously arose in BALB/c mice. Phytohemagglutinin (PHA) and lipopolysaccharide from Escherichia coli 0111:BH-induced T- and B-cell proliferation and PHA-stimulated migration inhibitory factor (MF) production were monitored. Mixing experiments were performed to detect the suppressor activity. The progressive growth of ADK-1t was accompanied by an increasing hyporesponsiveness of spleen cells to PHA-induced proliferation. The hyporesponsiveness was associated with concomitant suppressor activity by the spleen cells. Both hyporesponsiveness and suppression were abrogated by the following treatments of the spleen cells: passage over a nylon column: and pretreatment with carrageenan or carbonyl iron and magnet. The suppressor cells, moreover, were resistant to anti-Thy 1.2 plus complement treatment, and were adherent to plastic and nylon. Washing of the cultures before the addition of the tritiated thymidine or enrichment of the culture medium with glucose, arginine, or lysine did not affect the suppressor activity. We therefore concluded that macrophages or macrophage-like cells exerted an inhibitory effect on the PHA-induced proliferation. B-lymphocyte proliferation and MIF production were also inhibited by macrophages from the spleens of tumor-bearing mice. Macrophages from normal spleens demonstrated a significant but always smaller suppressive effect. The demonstration that macrophages suppress MIF production as well as proliferative responses provides further insight into the mechanism of the progressive depression of cell-mediated immunity that has been associated with tumor growth.
Supplemental L-arginine has been shown to enhance thymic and T-cell responses in rodents. We examined the ability of supplemental dietary L-arginine to induce T-cell function in athymic nude mice that lack a normally developed T-cell system. Groups of male nude (nu/nu) mice (Balb/c background) 7 to 8 weeks old were given for 2 weeks 1.2% arginine hydrochloride solution for drinking, whereas controls received acidified tap water. All mice ingested a standard laboratory chow. In the first experiment, the arginine-supplemented animals had significantly greater number of T cells in the spleen (assessed by the number of Thy 1.2-positive lymphocytes) and these cells had enhanced mitogenic responses to mitogenic stimulation (phytohemagglutinin and concanavalin A). In vivo delayed-type hypersensitivity responses to 2,4-dinitro-1-difluorobenzene were also significantly increased after the 2 weeks of arginine supplementation. In a second experiment, mice maintained under the same conditions were skin grafted with rat tail skin. Animals were observed for 100 days for rejection but no significant difference was noted in skin graft survival. We conclude that dietary arginine can increase extrathymic T-cell maturation and function, but cannot induce in vivo allogeneic graft recognition in athymic nude mice.
Impaired immune responses occur frequently in cancer patients or in tumor-bearing mice, but the mechanisms of the tumor-induced
immune defects remain poorly understood. In an in vivo murine colon carcinoma model (MCA-38), animals bearing a tumor longer
than 26 days develop CD8+ T cells with impaired cytotoxic function, decreased expression of the tumor necrosis factor-alpha
and granzyme B genes, and decreased ability to mediate an antitumor response in vivo. T lymphocytes from tumor-bearing mice
expressed T cell antigen receptors that contained low amounts of CD3 gamma and completely lacked CD3 zeta, which was replaced
by the Fc epsilon gamma-chain. Expression of the tyrosine kinases p56lck and p59fyn was also reduced. These changes could
be the basis of immune defects in tumor-bearing hosts.
Conditioned medium (CM) from cultures of cytotoxic activated macrophages causes inhibition of mitochondrial respiration, DNA synthesis, and aconitase activity in murine EMT-6 mammary adenocarcinoma cells by an L-arginine dependent effector mechanism. CM induces cytotoxicity and nitrite synthesis in EMT-6 cells in a dose dependent manner. We have identified the soluble factors in CM that induce cytotoxicity and synthesis of inorganic nitrogen oxides from L-arginine by EMT-6 cells. Using functional inhibition experiments, the activity of lipopolysaccharide (LPS), tumor necrosis factor alpha (TNF alpha), and interferon gamma (IFN gamma) in CM was investigated. The LPS inhibitor polymyxin B and TNF alpha antibody produced a modest decrease in nitrite production, while IFN gamma antibody markedly inhibited both nitrite production and cytostasis. Simultaneous treatment with polymyxin B, TNF alpha antibody, and IFN gamma antibody reduced EMT-6 cell nitrite production by 81%, and cytostasis by 74%. By Western blot, IFN gamma and TNF alpha were shown to be present in CM. When CM was subjected to hydrophobic interaction chromatography, a single peak of activity was eluted, and Western blot showed that the active fractions contained IFN gamma. Furthermore, IFN gamma antibody neutralized the activity in these chromatographic fractions. We conclude that induction of inorganic nitrogen oxide synthesis from L-arginine by the synergistic combination of IFN gamma, TNF alpha, and LPS accounts for most of the biologic activity of CM, and that IFN gamma is the major priming factor.
Previous studies have shown that cytotoxic activated macrophages cause inhibition of DNA synthesis, of mitochondrial respiration, and of aconitase activity in tumor target cells. An L-arginine-dependent biochemical pathway synthesizing L-citrulline and nitrite, coupled to an effector mechanism, is now shown to cause this pattern of metabolic inhibition. Murine cytotoxic activated macrophages synthesize L-citrulline and nitrite in the presence of L-arginine but not D-arginine. L-Citrulline and nitrite biosynthesis by cytotoxic activated macrophages is inhibited by NG-monomethyl-L-arginine, which also inhibits this cytotoxic effector mechanism. This activated macrophage cytotoxic effector system is associated with L-arginine deiminase activity, and the imino nitrogen removed from the guanido group of L-arginine by the deiminase reaction subsequently undergoes oxidation to nitrite. L-Homoarginine, an alternative substrate for this deiminase, is converted to L-homocitrulline with concurrent nitrite synthesis and similar biologic effects.
Tumor-infiltrating lymphocytes (TIL) were obtained from 22 humans with solid tumors. In three cases only, one colon and two lung carcinomas, TIL which contained from 3 to 10% of T cells expressing the interleukin 2 receptor (IL 2R) were obtained, and these proliferated in the presence of exogenous IL 2. In most TIL preparations, however, the T lymphocytes did not express the IL 2R and failed to proliferate in response to IL 2. In contrast, TIL were able to proliferate in response to irradiated allogeneic spleen cells in mixed lymphocyte culture. Proliferative responses of autologous PBL were not inhibited by the addition of TIL. In most tumors, the TIL showed no response or had significantly lower (p less than 0.01) responses to PHA, Con A, and the phorbol ester TPA than did autologous peripheral blood lymphocytes (PBL). A limiting-dilution microculture system which allows clonal growth of every T cell was used to demonstrate decreased responses of the TIL to PHA at a single-cell level. In contrast to normal PBL-T with proliferating frequencies from 0.46 to 1.0, those for T cells in three TIL preparations were zero, 0.005, and 0.01. Normal PBL exposed in vitro to tumor cells or their supernatants lost the ability to respond to mitogens and to clone normally (e.g., proliferating frequency of 0.147 vs 0.863 in control). The TIL isolated from solid tumors resemble normal PBL exposed in vitro to tumor cells or their supernatants in terms of decreased responses to mitogens and poor clonogenicity in the PHA-dependent microculture system. It is possible that tumor cells may inhibit certain functions of the TIL in human solid tumors.
Mice bearing a metastatic variant of Lewis lung carcinoma (LLC-C3) were studied to determine if there might be a relationship between tumor induced hematopoiesis and immune suppression. Growth of LLC-C3 in C57BL/6 mice corresponded with increased hematopoiesis and an increase in the proportion of monocytes in the peripheral blood, spleen, and bone marrow. The LLC-C3 cells secreted colony stimulating factor activity and, thus, could have directly stimulated the hematopoiesis in the hosts. As tumor growth progressed, the bone marrow of the tumor bearing mice became suppressive to T-cell blastogenesis. The bone marrow suppressor cells obtained from mice bearing large (greater than 3 g) LLC-C3 tumors were nonadherent to nylon wool, sensitive to treatment with L-leucine methyl ester, insensitive to treatment with anti-Thy-1.2 and complement, and mediated their suppression through an indomethacin sensitive mechanism. Secretion of colony stimulating factor activity by the LLC-C3 cells could have induced the appearance of the bone marrow suppressor cells since normal bone marrow cells which were cultured in the presence of LLC-C3 culture supernatants had an increased proportion of monocytes and were suppressive to T-lymphocyte blastogenesis. Our results suggest that the colony stimulating factor activity produced by LLC-C3 cells stimulates hematopoiesis which, in turn, could result in the appearance of bone marrow suppressor cells.
The vast majority of tumor infiltrating lymphocytes (TIL) are either CD4+ or CD8+ T-lymphocytes. In order to examine directly the functional capabilities of the individual CD4+ and CD8+ TIL subsets we performed cell sorting of double immunofluorescence-labeled TIL recovered from 15 biopsies by enzyme digestion. These CD4+ and CD8+ TIL subsets were compared with similar subsets of T-lymphocytes from peripheral blood of normal subjects. Both CD4+ and CD8+ TIL showed a reduced clonogenicity as assessed quantitatively by limiting dilution analysis in a microculture system which allows every normal T-lymphocyte to undergo clonal expansion. The reduced clonogenic potential was unequally distributed among the CD4+ and CD8+ subsets with the CD8+ TIL showing a significant reduction of the frequency of proliferating T-lymphocyte precursors compared to the CD4+ TIL (with a median of 1/50 proliferating T-lymphocytes in CD8+ TIL versus a median of 1/11 in CD4+ TIL). The reduced response of CD8+ TIL was not caused by suppressor cells, lack of surface expression of CD2 and CD3 antigens nor of the alpha, beta T-cell receptor, nor by an accumulation of CD8+ cells of large granular lymphocyte morphology. Using low density cultures, the highly purified CD4+ and CD8+ TIL were stimulated either via the T-cell receptor or the CD2-mediated antigen-independent pathway of activation. Whereas CD8+ TIL did not respond to either stimulus the CD4+ TIL showed evidence of responder and nonresponder groups. In addition, we show that the deficient response obtained by triggering CD4+ TIL via the TCR can be restored by activation of the antigen-independent pathway. Finally, a total of 94 clones from four different TIL samples were obtained by limiting dilution and examined for their respective helper and cytolytic capabilities: 57% of the CD4+ TIL clones were able to produce interleukin 2 and 93% of the CD8+ TIL clones demonstrated cytolytic activity mediated by the T-cell receptor complex, indicating that the functional potential of proliferating TIL is intact.
Blood lymphocytes from tumor patients can specifically destroy cultivated neoplastic cells of the same histological origin as the tumors of the lymphocyte donors, irrespective of whether or not the donors have symptoms of growing tumor.
The purpose of the present study was to investigate whether sera from tumor patients could block the cytotoxic effect of lymphocytes immune to the specific antigens of the respective neoplasms. A wide variety of tumors were included in the tests, namely malignant melanomas, carcinomas of the colon, breast, ovary, endometrium, kidney, cervix uteri, lung, larynx, bladder, Fallopian tube, lip, seminomas and sarcomas.
Sera from 67 out of 81 patients with growing neoplasms were found to block the cytotoxic effect of specifically immune lymphocytes. A blocking effect was seen both when the tumor cells, lymphocytes and sera were derived from the same patients and when the lymphocytes and sera were taken from different donors who had the same types of tumor as the target cells. No blocking was seen when the same sera were tested on tumors of histological types other than those of the respective serum donors.
A blocking serum activity was seen in only three of 19 patients who were symptomfree after tumor therapy. The findings thus suggest that there is a correlation between tumor growth in vivo and the presence of a blocking serum activity in vitro .
During tumor progression, variants may arise that grow more vigorously. The fate of such variants depends upon the balance between aggressiveness of the variant and the strength of the host immunity. Although enhancing host immunity to cancer is a logical objective, eliminating host factors necessary for aggressive growth of the variant should also be considered. The present study illustrates this concept in the model of a spontaneously occurring, progressively growing variant of an ultraviolet light-induced tumor. The variant produces chemotactic factors that attract host leukocytes and is stimulated in vitro by defined growth factors that can be produced or induced by leukocytes. This study also shows that CD8+ T-cell immunity reduces the rate of tumor growth; however, the variant continues to grow and kills the host. Treatment with a monoclonal anti-granulocyte antibody that counteracts the infiltration of the tumor cell inoculum by non-T-cell leukocytes did not interfere with the CD8+ T-cell-mediated immune response but resulted in rejection of the tumor challenge, indicating a synergy between CD8+ T-cell-mediated immunity and the inhibition of paracrine stimulation.
Macrophage arginine metabolism via nitric oxide (NO) synthase and arginase pathways reduces and enhances tumor cell proliferation, respectively. Transforming growth factor-beta (TGF-beta) has been shown to down-regulate the NO synthase pathway. The present study describes the effect of TGF-beta on the arginase pathway. TGF-beta up-regulated arginase activity in rat peritoneal macrophages as assessed by measuring the generation of [14C]urea from [14C]-L-arginine in the presence of NG-monomethyl-L-arginine (L-NMMA). The stimulation, which reached fivefold after a 48-h exposure of macrophages to 10 ng/ml TGF-beta, was due to reduction in Km value of arginase. TGF-beta-induced up-regulation of arginase activity led to the release of more polyamines, mainly putrescine. The role of this up-regulation on macrophage cytotoxicity toward L-929 tumor cells was analyzed in coculture experiments. Macrophages blunted DNA synthesis by L-929 cells as assessed by measuring the incorporation of [3H]TdR into the cells and the proportion of cells in the G2 phase. Addition of TGF-beta in the presence of L-NMMA permitted L-929 cells cocultured with macrophages to resume DNA synthesis. The mechanism responsible for this restoration was the up-regulation of arginase activity rather than the down-regulation of NO synthase activity since TGF-beta in the presence of L-NMMA failed to further reduce NO synthase activity whereas it still enhanced arginase activity; synthetic putrescine (1-10 microM) also blunted macrophage cytotoxicity toward L-929 cells. This is the first evidence that TGF-beta up-regulates arginase activity in macrophages and, hence, limits macrophage-dependent cytostasis.
We have studied the properties of eosinophils from 26 patients with malignant melanoma and 16 patients with renal cell carcinoma (RCC) who were entered into a phase II clinical trial using various schedules of low‐dose rhIL‐2 immunotherapy. Eosinophilia was observed in 65% of melanoma patients and 100% of renal patients when receiving rhIL‐2 therapy.
The eosinophil count increased up to 20‐fold approximately 5 d after the appearance of lymphocyte activation markers. This would be consistent with eosinophil kinetics and the release of soluble mediators, for example IL‐5, from lymphocytes. Eosinophils from eosinophilic patients became hypodense compared to their pre‐treatment levels as demonstrated by sedimentation through a discontinuous metrizamide density gradient; they also showed an increased expression of CD4, CD25 and CD11b cell surface activation markers. Eosinophil count could not be correlated to either patient survival or response to therapy in melanoma patients: however, patients with renal cell carcinoma demonstrated a significant correlation ( P 0·05) between eosinophil count and survival but not with clinical response. Therefore the maximum eosinophil count achieved during rhIL‐2 therapy is of prognostic significance in patients with renal cell carcinoma.
An impaired immune response is frequently observed in cancer patients and tumor-bearing mice. T-cells from mice with an experimental colon carcinoma were recently shown to express T-cell receptors that completely lacked the signal-transducing molecule CD3 zeta. Here, we have investigated the expression of the signal-transducing molecule zeta on lymphocytes from 14 patients with colorectal carcinomas using flow cytometric analysis of permeabilized cells with a monoclonal antibody (TIA-2; IgG1) specific for the cytoplasmic domain of the zeta chain as well as with immunoprecipitation and analysis on diagonal gel electrophoresis. We demonstrate that T-cells isolated from the tumors of the patients express significantly less CD3 zeta than T-cells in the peripheral blood of the same patients and that the peripheral blood of the patients express decreased levels of zeta chains, as compared to the levels found in lymphocytes from healthy controls. This decreased expression was also observed on zeta chains associated with the low affinity Fc receptor for IgG found in tumor-infiltrating NK cells (Fc gamma RIIIA alpha; CD16).
Although alterations in CD3-associated signal-transducing molecules in tumor-infiltrating T cells of patients with advanced cancer have been previously described, the mechanism behind these changes is not known. We demonstrate that macrophages isolated from metastatic lymph nodes of patients with malignant melanoma down-regulate levels of CD3 zeta in autologous peripheral blood T cells. Lipopolysaccharide (LPS)- or phorbol 12-myristate 13-acetate (PMA)-stimulated monocytes derived from peripheral blood of healthy donors also induced decreased expression of CD3 and CD16-associated zeta chains similar to that observed in T cells and natural killer (NK) cells of patients with advanced cancer. Co-culture with activated monocytes impaired Ca2+ mobilization in peripheral blood derived-T cells when stimulated with monoclonal antibodies to CD3 and also strongly inhibited melanoma-specific cytotoxic T lymphocyte (CTL) activity and NK activity. The presence of catalase, a scavenger of H2O2, during co-culture almost totally abrogated the inhibitory effect of activated monocytes on melanoma-specific CTL lines and on NK cells. Pre-treatment of CTL or NK cells with nontoxic concentrations (1 x 10(-5) M) of H2O2 also severely reduced their cytotoxic activity which could be prevented by catalase. The decrease in CD3 zeta and in CD16 zeta expression, induced by macrophages isolated from metastatic lymph nodes or by LPS-stimulated monocytes, was also prevented by catalase when maintained throughout the co-culture period. The possibility that monocyte/macrophage-derived reactive oxygen metabolites contribute directly to alterations in signal transducing molecules of T cells and NK cells and to the mechanism of immunosuppression in individuals with cancer should be considered.
Anti-melanoma cytolytic T-lymphocyte (CTL) clones were derived from peripheral blood lymphocytes of HLA-A2 melanoma patient LB265 after stimulation with the autologous tumor cell line LB265-MEL, which showed high expression of melanocyte-lineage specific genes. Of 55 CTL clones, 46 recognized HLA-A2-restricted antigens. These 46 CTL clones were studied for their ability to specifically release tumor necrosis factor in the presence of COS cells cotransfected with the HLA-A2 gene and the cDNA of either tyrosinase, Melan-A/MART1, Pmel17/gpl00, gp75/TRP1, or MSH receptor. Six CTL clones recognized the Melan-A/MART1 antigen, whereas the remaining 40 CTL clones recognized a Pmel17/gp100 antigen. These 40 anti-PmelI7/gpl00 CTL clones were all able to lyse T2 cells pulsed with the antigenic peptide YLEPGPVTA, as previously reported. The T-cell receptor beta chain hypervariable region was sequenced and found to be identical in the 15 CTL clones analyzed. Taken together, these data show a high frequency of Pmell7/gp100-specific T cells in autologous antitumor CTL clones derived from peripheral blood of a melanoma patient.
One of the important mechanisms of immunosuppression in the tumor-bearing status has been attributed to the down-modulation of the CD3 zeta chain and its associated signaling molecules in T cells. Thus, the mechanism of the disappearance of CD3 zeta was investigated in tumor-bearing mice (TBM). The decrease of CD3 zeta was observed both in the cell lysate and intact cells. Direct interaction of T cells with macrophages from TBM (TBM-macrophages) induced the decrease of CD3 zeta, and depletion of macrophages rapidly restored the CD3 zeta expression. We found that treatment of such macrophages with N-acetylcysteine, known as antioxidant compound, prevented the decrease of CD3 zeta. Consistent with this result, the addition of oxidative reagents such as hydrogen peroxide and diamide induced the decrease of CD3 zeta expression in T cells. Consequently, the loss of CD3 zeta resulted in suppression of the antigen-specific T-cell response. These results demonstrate that oxidative stress by macrophages in tumor-bearing status induces abnormality of the T-cell receptor complex by cell interactions with T cells. Therefore, our findings suggest that oxidative stress contributes to the regulation of the expression and function of the T-cell receptor complex.
Mammalian D-type cyclins are differentially expressed during the first gap phase (G1) of the cell cycle in various cell types, and function as regulatory subunits of cyclin-dependent kinases (cdks), cdk4 and cdk6, to form holoenzymes whose activities are both necessary and rate limiting for G1 progression. Mitogenic signals induce the expression of cyclin D and cdk4 proteins, and facilitate their assembly into holoenzymes and their post-translational modification, while anti-proliferative stimuli extinguish the activity of cyclin D-dependent kinases by inducing cdk inhibitors which directly interfere with their catalytic functions and/or inhibit the post-translational activation of cyclin-bound cdks. Therefore, a variety of extracellular signals target and regulate the cyclin D/cdk4 serine/threonine kinases, which execute their critical functions during middle to late G1 phase by phosphorylating key substrates, including the retinoblastoma tumor suppressor gene products (pRb). Although overexpression of cyclin D, or inactivation of Rb or cdk inhibitor gene alone is not sufficient for cell transformation, high frequency of alterations of these genes in cancers suggests that inactivation of this particular pathway is involved in tumor development.
Activated murine macrophages metabolize L-arginine via two main pathways that are catalyzed by the inducible enzymes nitric oxide synthase (iNOS) and arginase. We have previously shown that CD4+ T cell-derived cytokines regulate a competitive balance in the expression of both enzymes in macrophages; Thl-type cytokines induce iNOS while they inhibit arginase, whereas the reverse is the case for Th2-type cytokines. Here we addressed the regulation of both metabolic pathways by CD4+ T cells directly. Macrophages were used as APCs for established Th1 and Th2 T cell clones as well as for in vitro polarized Th1 or Th2 T cells of transgenic mice bearing an MHC class II-restricted TCR. Both systems revealed a similar dichotomy in the macrophages; Th1 T cells led to an exclusive induction of iNOS, whereas Th2 T cells up-regulated arginase without inducing iNOS. Arginase levels induced by Th2 T cells far exceeded those inducible by individual Th2 cytokines. Similarly, high arginase levels could be induced by supernatants of Th2 cells stimulated in various ways. Ab blocking experiments revealed the critical importance of IL-4 and IL-10 for arginase up-regulation. Finally, strong synergistic effects between IL-4/IL-13 and IL-10 were observed, sufficient to account for the extraordinarily high arginase activity induced by Th2 cells. Our results suggest that the iNOS/arginase balance in macrophages is competitively regulated in the context of Th1- vs Th2-driven immune reactions, most likely by cytokines without the requirement for direct cell interaction.
The primary metabolic fates of L-arginine are conversion to L-citrulline by nitric oxide synthase (NOS) and to L-ornithine by arginase. In the lung, arginine utilization is increased after the inducible form of NOS (iNOS) is expressed during inflammation. The expression of arginase in normal lung and after sepsis, and its potential relationships with iNOS, however, are not known. Since arginase and iNOS share the substrate L-arginine, we tested the hypothesis that lung arginase would be co-induced with iNOS in sepsis and its cellular distribution would be related to that of iNOS in the lung. Lungs from cecal ligation and puncture (CLP) and sham-operated (S) rats were harvested 6 or 16 hours after the procedures. Lung wet-to-dry weight ratio, myeloperoxidase content, and lipid peroxidation products were measured as indices of lung injury. Western blot analyses were performed with polyclonal antibodies against two isoforms of rat arginase (I and II) and iNOS. Additional lungs from CLP and S animals were inflation-fixed for immunohistochemistry using the same antibodies. We found by Western blot that arginase II at 39 kDa was the main isoform present in normal rat lung. The enzyme was distributed diffusely in alveolar and bronchial epithelial cells, endothelial cells, and alveolar macrophages. After CLP, arginase II was almost undetectable in rat lungs at 16 hours. In contrast, in normal lung, the iNOS was not detectable by Western blot or immunohistochemistry. After CLP, strong expression of iNOS was found in similar cell types to arginase II. These data demonstrate loss of constitutive expression of arginase II in rat lung as iNOS is upregulated by the response to sepsis.
We investigated whether L-2-oxothiazolidine-4-carboxylic acid (OTC) [in the form of Procysteine, kindly donated by Transcend Therapeutics] could protect peripheral blood lymphocytes (PBL) and lymphokine-activated killer (LAK) cells from CD3zeta and CD16zeta chain down-regulation induced by H2O2 produced by lipopolysaccharide (LPS)-activated autologous monocytes. OTC is known to enhance glutathione production in cells in which glutathione was depleted by reactive oxygen species. Our data showed that OTC induced a significant increase in CD3zeta and CD16zeta chain expression in peripheral blood lymphocytes and LAK cells, respectively, pretreated for 12 hr at 37 degrees. Moreover, OTC significantly protected peripheral blood lymphocytes and LAK against decreased zeta chain expression induced by lipopolysaccharide-activated monocytes or the addition of H2O2 to the culture medium. Our experiments thus suggested that alterations in signal-transducing molecules, such as decreased CD3zeta and CD16zeta expression observed in cytotoxic T lymphocytes and LAK cells in response to oxidative stress, could be prevented by the use of OTC.
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.
Patients with squamous cell carcinoma of the head and neck (SCCHN) frequently have impaired immune responses. Alterations in T-cell receptor-associated signaling molecules in tumor-infiltrating as well as circulating lymphocytes have been reported in these patients. Using quantitative flow cytometry analysis, we have demonstrated that expression of the zeta chain is significantly decreased relative to normal controls in both CD8+ and CD4+ T cells as well as CD3- CD56+ CD16+ natural killer cells in the peripheral blood of patients with SCCHN who, as a result of previous therapies, have no evident disease. Patients with a more aggressive type of SCCHN and those who experienced a recurrence or had a second primary cancer within the last 2 years of the study had the lowest zeta chain expression. In addition, SCCHN patients showed a significantly greater spontaneous ex vivo apoptosis, as measured by a terminal deoxynucleotide transferase-mediated dUTP nick end labeling assay, in PBMCs, compared to normal controls. The observed decreased expression of zeta in T and natural killer cells coincided but did not directly correlate with significantly increased spontaneous apoptosis of lymphocytes obtained from treated patients with no evident disease. The results suggest that in patients with SCCHN, zeta chain defects and lymphocyte apoptosis are manifestations of long-lasting negative effects of tumor on the immune system.