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Antitumor effect of HCC-specific oncolytic Ad in orthotopic HCC model. (A,B) Luciferase-expressing Hep3B cells were injected directly into the left lobe of the liver in mice. Once the expression of AFP reached 300 ng/mL, PBS or 2.5 × 10¹⁰ VP of d19, a2bm-d19, or Ha2bm-d19 was intravenously injected every 2 days for a total of three times. Tumor growth was analyzed every week by optical imaging. *P < 0.05. (C) The percentage of surviving mice was determined by monitoring tumor growth-related events (ROI (p/s) > 2 × 10⁹ for orthotopic tumor) over the given time periods. ***P < 0.001. ***P < 0.001. (D) Fold changes in the serum levels of AFP in each treatment group, starting from week 0 (before treatment) to week 4 of treatment were assessed by ELISA. ***P < 0.001. (E) PBS, a2bm-d19, or Ha2bm-d19 was systemically injected total of 3 times every other day into the tail vein of the mice (n = 3 per group). The blood, muscle, lung, heart, kidney, spleen, liver, and tumor tissues were harvested at 72 h after the third injection. Real-time quantitative PCR was performed to detect Ad genomes. Data was normalized by subtracting values from PBS-treated group and presented as mean ± SD. **P < 0.01. (F) Serum ALT and AST levels were measured on day 3 after the systemic administration of PBS, d19, a2bm-d19, or Ha2bm-d19. Data represent mean ± SD. ***P < 0.001. (G) PBS, d19, a2bm-d19, or Ha2bm-d19 was systemically injected into mice. At 6 h post injection, serum was collected, and IL-6 levels were quantified by ELISA. Bars represent mean ± SD. ***P < 0.001.
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Cancer-specific promoter driven replication of oncolytic adenovirus (Ad) is cancer-specific, but shows low transcriptional activity. Thus, we generated several chimeric α-fetoprotein (AFP) promoter variants, containing reconstituted enhancer and silencer regions, to preferentially drive Ad replication in hepatocellular carcinoma (HCC). Modified AFP...
Citations
... The dual safety valves constituted by OVs and tumorspecific promoters can preferably avoid the occurrence of "offtarget" events, further improving the targeting and safety of OVTs. For some cancers, promoters that regulate the expression of tumor-specific antigens (TSAs) are optimal candidates for OVTs; for example, the alpha-fetoprotein (AFP) promoter for hepatocellular carcinoma ( Figure 5A) and the prostate-specific antigen (PSA) promoter for prostate cancer ( Figure 5B) (134,135). ...
Gastric cancer (GC) is a leading contributor to global cancer incidence and mortality. According to the GLOBOCAN 2020 estimates of incidence and mortality for 36 cancers in 185 countries produced by the International Agency for Research on Cancer (IARC), GC ranks fifth and fourth, respectively, and seriously threatens the survival and health of people all over the world. Therefore, how to effectively treat GC has become an urgent problem for medical personnel and scientific workers at this stage. Due to the unobvious early symptoms and the influence of some adverse factors such as tumor heterogeneity and low immunogenicity, patients with advanced gastric cancer (AGC) cannot benefit significantly from treatments such as radical surgical resection, radiotherapy, chemotherapy, and targeted therapy. As an emerging cancer immunotherapy, oncolytic virotherapies (OVTs) can not only selectively lyse cancer cells, but also induce a systemic antitumor immune response. This unique ability to turn unresponsive ‘cold’ tumors into responsive ‘hot’ tumors gives them great potential in GC therapy. This review integrates most experimental studies and clinical trials of various oncolytic viruses (OVs) in the diagnosis and treatment of GC. It also exhaustively introduces the concrete mechanism of invading GC cells and the viral genome composition of adenovirus and herpes simplex virus type 1 (HSV-1). At the end of the article, some prospects are put forward to determine the developmental directions of OVTs for GC in the future.
... In initial stages of gene therapy, transgenes were under the control of viral promoters such as cytomegalovirus (CMV) or simian virus 40 (SV40), which have demonstrated capacity to promote gene expression (Boshart et al., 1985;Schmidt et al., 1990;Makrides, 2003). However, in recent years, mammalian promoters have emerged, especially in cancer gene therapy, to direct therapeutic genes towards target cells (Yoon et al., 2018;Rama Ballesteros et al., 2020;Yan et al., 2020). In the ophthalmic field, some groups have reported promising results using mammalian promoters to increase cell-specific gene expression, as summarized in Table 1. ...
Retinal diseases lead to severe vision loss and are currently a major cause of vision impairment in industrialized countries. The significant number of genetic defects of the retina underlying these disorders, coupled to the absence of effective treatments, require new therapeutic solutions. Recent gene therapy developments in the field of ophthalmic research reveal the great potential of this approach. In recent years, non-viral vectors have been extensively studied due to their properties such as large gene packaging capacity and low immunogenicity. Hitherto, their development and optimisation for retinal gene therapy have been hindered by their inability to directly target retinal cells. The goal of this review is to summarize the most promising strategies to direct non-viral vectors for retinal cells to avoid off-target effects and promote their specific uptake, gene expression and overall efficiency.
... 63 Alpha-fetoprotein expression is highly associated with clinical stage, early recurrence, and poor prognosis in HCC patients. 64 For the fluorescence labeling of AFP-positive HCC cells, Yoon et al. 65 developed an AFP promoter-specific nonreplicative adenovirus carrying the GFP gene (Ad/Ha2bm-GFP) ( Table 1) ...
Conventional imaging techniques are available for clinical identification of tumor sites. However, detecting metastatic tumor cells that are spreading from primary tumor sites using conventional imaging techniques remains difficult. In contrast, fluorescence-based labeling systems are useful tools for detecting tumor cells at the single-cell level in cancer research. The ability to detect fluorescent-labeled tumor cells enables investigations of the biodistribution of tumor cells for the diagnosis and treatment of cancer. For example, the presence of fluorescent tumor cells in the peripheral blood of cancer patients is a predictive biomarker for early diagnosis of distant metastasis. The elimination of fluorescent tumor cells without damaging normal tissues is ideal for minimally invasive treatment of cancer. To capture fluorescent tumor cells within normal tissues, however, tumor-specific activated target molecules are needed. This review focuses on recent advances in tumor-targeted fluorescence labeling systems, in which indirect reporter labeling using tumor-specific promoters is applied to fluorescence labeling of tumor cells for the diagnosis and treatment of cancer. Telomerase promoter-dependent fluorescence labeling using replication-competent viral vectors produces fluorescent proteins that can be used to detect and eliminate telomerase-positive tumor cells. Tissue-specific promoter-dependent fluorescence labeling enables identification of specific tumor cells. Vimentin promoter-dependent fluorescence labeling is a useful tool for identifying tumor cells that undergo epithelial-mesenchymal transition (EMT). The evaluation of tumor cells undergoing EMT is important for accurately assessing metastatic potential. Thus, tumor-targeted fluorescence labeling systems represent novel platforms that enable the capture of tumor cells for the diagnosis and treatment of cancer.
... 148 Also, the addition of hypoxia-responsive elements to the OVs can help overcome the hypoxia-mediated downregulation of viral replication experienced at the tumor site. 162 Finally, targeting of dysregulated signaling pathways involved in cancer growth and spread can enhance the cancer cell-killing effects of the OVs employed. 15 ...
Oncolytic viruses (OV) have emerged as a very promising anti-cancer therapeutic strategy in the past decades. However, despite their preclinical promise, many OV clinical evaluations for cancer therapy have highlighted the continued need for their improved delivery and targeting. Mesenchymal stromal cells (MSC) have emerged as excellent candidate vehicles for the delivery of OV due to their tumor-homing properties and low immunogenicity. MSC can enhance OV delivery by protecting viruses from rapid clearance following administration and also by more efficiently targeting tumor sites, consequently augmenting the therapeutic potential of OV. MSC can function as ‘biological factories’, enabling OV amplification within these cells to promote tumor lysis following MSC-OV arrival at the tumor site. MSC-OV can promote enhanced safety profiles and therapeutic effects relative to OV alone. In this review we explore the general characteristics of MSC as delivery tools for cancer therapeutic agents. Furthermore, we discuss the potential of OV as immune therapeutics and highlight some of the promising applications stemming from combining MSC to achieve enhanced delivery and antitumor effectiveness of OV at different pre-clinical and clinical stages. We further provide potential pitfalls of the MSC-OV platform, and the strategies under development for enhancing the efficacy of these emerging therapeutics.
... For instance, Zou et al. recently reported that OVs associated with quercetin have a synergistic effect on the reduction of HCC growth and tumor volume in mice injected with HuH-7 hepatocyte-derived carcinoma cells [24]. Yoon et al. described the engineering of an OV to preferentially drive OV replication and cell killing in hepatocellular carcinoma (HCC) [25]. OVs have also been used for gene-targeted oncolytic viral therapy in HCC, a novel strategy based on the generation of viral vectors engineered with anticancer genes that selectively infect and kill cancer cells while having no toxic effect on the healthy ones [23]. ...
Despite significant advances in chemotherapy, the overall prognosis of hepatocellular carcinoma (HCC) remains extremely poor. HCC targeting strategies were combined with the tumor cell cytotoxicity of oncolytic viruses (OVs) to develop a more efficient and selective therapeutic system. OVs were coated with a polygalactosyl-b-agmatyl diblock copolymer (Gal32-b-Agm29), with high affinity for the asialoglycoprotein receptor (ASGPR) expressed on the liver cell surface, exploiting the electrostatic interaction of the positively charged agmatine block with the negatively charged adenoviral capsid surface. The polymer coating altered the viral particle diameter (from 192 to 287 nm) and zeta-potential (from –24.7 to 23.3 mV) while hiding the peculiar icosahedral symmetrical OV structure, as observed by TEM. Coated OVs showed high potential therapeutic value on the human hepatoma cell line HepG2 (cytotoxicity of 72.4% ± 4.96), expressing a high level of ASGPRs, while a lower effect was attained with ASPGR-negative A549 cell line (cytotoxicity of 54.4% ± 1.59). Conversely, naked OVs showed very similar effects in both tested cell lines. Gal32-b-Agm29 OV coating enhanced the infectivity and immunogenic cell death program in HepG2 cells as compared to the naked OV. This strategy provides a rationale for future studies utilizing oncolytic viruses complexed with polymers toward effective treatment of hepatocellular carcinoma.
... Cancer/tumor-specific promoters have been used to perform gene therapy in many types of neoplasia; within the most studied ones we have hepatocellular carcinoma, breast, lung, colorectal, pancreas and prostate cancer (8,(10)(11)(12)(13). Gene therapy success in cancer treatment relies not only on a good molecular strategy, which consists of the design of specific genetic material being exclusively expressed within tumor cells, but also on the need of a safe, efficient and specific gene delivery system. ...
... AFP promoter is usually active in the fetal stage and then suffers inactivation 6 months after birth. Notwithstanding, it can be reactivated in abnormal conditions like cirrhosis and certain types of cancer such as HCC or, less importantly, pancreatic cancer and lung cancer (11,87,103,104,172). For that reason, it has been widely used in gene therapy for HCC in order to direct the expression of genes such as sodium/iodide symporter (NIS) with the purpose of improving radiotherapy efficiency (105,106) and HSV1-tk gene to increase tumor-sensitivity facing chemotherapy (103,107). ...
... Later, AFP-a2bm was further modified using hypoxia-response elements (HRE), increasing transcriptional activity under hypoxic conditions. This allowed to overcome the hypoxic tumor environment and to target HCC with high specificity, proving it as a promising candidate for HCC treatment based on gene therapy (11). ...
Cancer is the second cause of death worldwide, surpassed only by cardiovascular diseases, due to the lack of early diagnosis, and high relapse rate after conventional therapies. Chemotherapy inhibits the rapid growth of cancer cells, but it also affects normal cells with fast proliferation rate. Therefore, it is imperative to develop other safe and more effective treatment strategies, such as gene therapy, in order to significantly improve the survival rate and life expectancy of patients with cancer. The aim of gene therapy is to transfect a therapeutic gene into the host cells to express itself and cause a beneficial biological effect. However, the efficacy of the proposed strategies has been insufficient for delivering the full potential of gene therapy in the clinic. The type of delivery vehicle (viral or non viral) chosen depends on the desired specificity of the gene therapy. The first gene therapy trials were performed with therapeutic genes driven by viral promoters such as the CMV promoter, which induces non-specific toxicity in normal cells and tissues, in addition to cancer cells. The use of tumor-specific promoters over-expressed in the tumor, induces specific expression of therapeutic genes in a given tumor, increasing their localized activity. Several cancer- and/or tumor-specific promoters systems have been developed to target cancer cells. This review aims to provide up-to-date information concerning targeting gene therapy with cancer- and/or tumor-specific promoters including cancer suppressor genes, suicide genes, anti-tumor angiogenesis, gene silencing, and gene-editing technology, as well as the type of delivery vehicle employed. Gene therapy can be used to complement traditional therapies to provide more effective treatments.
... Viruses can cause cell death not only due to the genes they express, but also as a consequence of viral replication and spread itself [69]. To utilize this mechanism of cell death while creating a therapeutic window that allows for healthy cells to go unharmed, conditionally replicative adenoviruses (CRADs) have been used to treat a variety of cancers, including HCC [15,[69][70][71]. Unlike the nonreplicative Ads that totally lack the E1A gene, CRADs contain either partial deletions of early replication genes or the entire intact E1A and E1B genes under a cancer specific promoter [69]. ...
... The first conditionally replicative virus to receive FDA approval occurred in 2015 for the modified herpes virus T-VEC in melanoma [78]. More recently, a CRAD specific to HCC was designed by modifying the AFP promoter to create several chimeras with modified enhancer and silencer regions [15]. No clinical trials for this agent (Ha2bm-d19) have been initiated at the time of this review. ...
Hepatocellular carcinoma (HCC) is the third most common cause of cancer death globally, mainly due to lack of effective treatments – a problem that gene therapy is poised to solve. Successful gene therapy requires safe and efficient delivery vectors, and recent advances in both viral and nonviral vectors have made an important impact on HCC gene therapy delivery. This review explores how adenoviral, retroviral and adeno-associated viral vectors have been modified to increase safety and delivery capacity, highlighting studies and clinical trials using these vectors for HCC gene therapy. Nanoparticles, liposomes, exosomes and virosomes are also featured in their roles as HCC gene delivery vectors. Finally, new discoveries in gene editing technology and their impacts on HCC gene therapy are discussed.
... An activated Wnt signaling pathway promotes the epithelial-tomesenchymal transition (EMT), which contributes to the metastatic and drug-resistant phenotypes of cancer (21). Thus, to enhance the therapeutic efficacy of oAd against HCC, we inserted a sequence encoding a Wnt-inhibiting decoy receptor (WNTi) into the previously reported oAd that targets alpha-fetoprotein (AFP)positive HCCs (22), generating a WNTi-expressing and HCCtargeting oAd (HCC-oAd-WNTi). ...
... 23,24). These E3 shuttle vectors went through homologous recombination with linearized HCC-oAd (Ha2bm-d19-k35; ref. 22) to generate Ha2bm-d19-k35/Luc (HCC-oAd-Luc) or Ha2bm-d19-k35/WNTi (HCC-oAd-WNTi), respectively. Upon generation of viral particles (VP) in HEK293 cells by transfection, HCC-oAd-Luc and HCC-oAd-WNTi were propagated in A549 cells and purified by CsCl gradient centrifugation. ...
... Therefore, we previously developed an oAd that expresses WNTi and demonstrated that WNTi expression can effectively inhibit the overactive Wnt signaling pathway in cancer (31). To continue this line of work, in our current study we designed and generated a HCC-specific oAd that expresses WNTi by utilizing a enhancer region-modified AFP promoter (Ha2bm; ref. 22) to restrict oAd replication to AFPpositive HCCs, ultimately generating HCC-oAd-WNTi (Fig. 3A). ...
Oncolytic virotherapy is a promising alternative to conventional treatment, yet systemic delivery of these viruses to tumors remains a major challenge. In this regard, mesenchymal stem cells (MSC) with well-established tumor-homing property could serve as a promising systemic delivery tool. We showed that MSCs could be effectively infected by hepatocellular carcinoma (HCC)-targeted oncolytic adenovirus (HCC-oAd) through modification of the virus' fiber domain and that the virus replicated efficiently in the cell carrier. HCC-targeting oAd loaded in MSCs (HCC-oAd/MSC) effectively lysed HCC cells in vitro under both normoxic and hypoxic conditions as a result of the hypoxia responsiveness of HCC-oAd. Importantly, systemically administered HCC-oAd/MSC, which were initially infected with a low viral dose, homed to HCC tumors and resulted in a high level of virion accumulation in the tumors, ultimately leading to potent tumor growth inhibition. Furthermore, viral dose reduction and tumor localization of HCC-oAd/MSC prevented the induction of hepatotoxicity by attenuating HCC-oAd hepatic accumulation. Taken together, these results demonstrate that MSC-mediated systemic delivery of oAd is a promising strategy for achieving synergistic antitumor efficacy with improved safety profiles.
Significance
Mesenchymal stem cells enable delivery of an oncolytic adenovirus specifically to the tumor without posing any risk associated with systemic administration of naked virions to the host.
... Notably, oAd, which is currently being marketed as Oncorine, was the first oncolytic virus to be approved for clinical use [6]. In support, numerous reports have demonstrated that locally administered oAds can induce potent antitumor effect in preclinical and clinical studies [7][8][9][10][11][12][13]. However, there are several notable limitations in clinical trials that restrict the therapeutic efficacy of oAds. ...
Adenovirus (Ad) has been most extensively evaluated gene transfer vector in clinical trials due to facile production in high viral titer, highly efficient transduction, and proven safety record. Similarly, an oncolytic Ad, which replicates selectively in cancer cells through genetic modifications, is actively being evaluated in various phases of clinical trials as a promising next generation therapeutic against cancer. Most of these trials with oncolytic Ads to date have employed intratumoral injection as the standard administration route. Although these locally administered oncolytic Ads have shown promising outcomes, the therapeutic efficacy is not yet optimal due to poor intratumoral virion retention, nonspecific shedding of virion to normal organs, variable infection efficacy due to heterogeneity of tumor cells, adverse antiviral immune response, and short biological activity of oncolytic viruses in situ. These inherent problems associated with locally administered Ad also holds true for other oncolytic viral vectors. Thus, this review will aim to discuss various nanomaterial-based delivery strategies to improve the intratumoral administration efficacy of oncolytic Ad as well as other types of oncolytic viruses.
Researchers have tried to find novel strategies for cancer treatment in the past decades. Among the utilized methods, administering oncolytic viruses (OVs) alone or combined with other anticancer therapeutic approaches has had promising outcomes, especially in solid tumors. Infecting the tumor cells by these viruses can lead to direct lysis or induction of immune responses. However, the immunosuppressive tumor microenvironment (TME) is considered a significant challenge for oncolytic virotherapy in treating cancer. Based on OV type, hypoxic conditions in the TME can accelerate or repress virus replication. Therefore, genetic manipulation of OVs or other molecular modifications to reduce hypoxia can induce antitumor responses. Moreover, using OVs with tumor lysis capability in the hypoxic TME may be an attractive strategy to overcome the limitations of the therapy. This review summarizes the latest information available in the field of cancer virotherapy and discusses the dual effect of hypoxia on different types of OVs to optimize available related therapeutic methods.
