TRAIL gene-armed oncolytic poxvirus and oxaliplatin can work synergistically against colorectal cancer

Comprehensive assessment on the applications of oncolytic viruses for cancer immunotherapy

The worldwide burden of cancers is increasing at a very high rate, including the aggressive and resistant forms of cancers. Certain levels of breakthrough have been achieved with the conventional treatment methods being used to treat different forms of cancers, but with some limitations. These limitations include hazardous side effects, destruction of non-tumor healthy cells that are rapidly dividing and developing, tumor resistance to anti-cancer drugs, damage to tissues and organs, and so on. However, oncolytic viruses have emerged as a worthwhile immunotherapeutic option for the treatment of different types of cancers. In this treatment approach, oncolytic viruses are being modeled to target cancer cells with optimum cytotoxicity and spare normal cells with optimal safety, without the oncolytic viruses themselves being killed by the host immune defense system. Oncolytic viral infection of the cancer cells are also being genetically manipulated (either by removal or addition of certain genes into the oncolytic virus genome) to make the tumor more visible and available for attack by the host immune cells. Hence, different variants of these viruses are being developed to optimize their antitumor effects. In this review, we examined how grave the burden of cancer is on a global level, particularly in sub-Saharan Africa, major conventional therapeutic approaches to the treatment of cancer and their individual drawbacks. We discussed the mechanisms of action employed by these oncolytic viruses and different viruses that have found their relevance in the fight against various forms of cancers. Some pre-clinical and clinical trials that involve oncolytic viruses in cancer management were reported. This review also examined the toxicity and safety concerns surrounding the adoption of oncolytic viro-immunotherapy for the treatment of cancers and the likely future directions for researchers and general audience who wants updated information.

The employment of vaccinia virus for colorectal cancer treatment: A review of preclinical and clinical studies

Colorectal cancer (CRC) is one of the leading malignancies that causes death worldwide. Cancer vaccines and oncolytic immunotherapy bring new hope for patients with advanced CRC. The capability of vaccinia virus (VV) in carrying foreign genes as antigens or immunostimulatory factors has been demonstrated in animal models. VV of Wyeth, Western Reserve, Lister, Tian Tan, and Copenhagen strains have been engineered for the induction of antitumor response in multiple cancers. This paper summarized the preclinical and clinical application and development of VV serving as cancer vaccines and oncolytic vectors in CRC treatment. Additionally, the remaining challenges and future direction are also discussed.

Expression profiling of anticancer genes in colorectal cancer patients and their in vitro induction by riproximin, a ribosomal inactivating plant protein

BACKGROUND

Ectopic expression of anticancer genes (ACGs) imposes antineoplastic effects on transformed cells. Clinically, reduced expression of these genes has been linked with poor prognosis, metastasis and chemo/radiotherapy resistance in cancers. Identifying expression pattern of ACGs is crucial to establish their prognostic and therapeutic relevance in colorectal cancer (CRC). In addition to the clinical perspective, naturally occurring compounds can be explored in parallel for inducing ACGs to achieve cancer cell-specific death.

METHODOLOGY

Expression profiles of three ACGs (NOXA, PAR-4, TRAIL) were identified via real-time PCR in CRC clinical isolates. Time lapse-based expression modifications in ACGs were studied in a CRC liver metastasis animal model using microarray methodology. Effects of a purified plant protein (riproximin) on selected ACGs were identified in three primary and metastatic CRC cell lines by real-time PCR. Lastly, importance of the ACGs in a cellular environment was highlighted via bioinformatic analysis.

RESULTS

ACGs (except NOXA) were persistently downregulated in clinical isolates when comparing the overall mean expression values with normal mucosa levels. In vivo studies showed a prominent inhibition of NOXA and PAR-4 genes in implanted CRC cells during rat liver colonization. TRAIL showed deviation from this theme while showing marked induction during the early period of liver colonization (days 3 and 6 after CRC cell implantation). Riproximin exhibited substantial potential of inducing ACGs at transcriptome levels in selected CRC cell lines. Bioinformatic analysis showed that vital molecular/functional aspects of a cell are associated with the presence of ACGs.

CONCLUSION

ACGs are downregulated in primary and metastatic phase of CRC. Riproximin effectively induces ACGs in CRC cells and can be exploited for clinical investigations over time.

Oncolytic adenovirus-mediated intratumoral expression of TRAIL and CD40L enhances immunotherapy by modulating the tumor microenvironment in immunocompetent mouse models

The immune status of the tumor microenvironment is a key indicator determining the antitumor effect of immunotherapy. Oncolytic viruses directly target tumor cells or indirectly modulate the tumor microenvironment (TME) especially when properly armed. It was previously demonstrated that conditionally replicating adenovirus serotype 5 (CRAd5) encoding tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) had outstanding antitumor effects in different human cancer cells xenograft models; however, its antitumor immune mechanism has not been evaluated in immunocompetent preclinical mouse models. We first explored the antitumor activity of CRAd5-TRAIL in several murine tumor models and found that the expression of TRAIL induced increases or activation in tumor-infiltrating T cells. To further improve the antitumor effects, mouse CD40 ligand (mCD40L) as an immune activator expressed by recombinant Ad5 vector was firstly used in combination with CRAd5-TRAIL for tumor immunotherapy. Both in vitro and in vivo studies demonstrated that mCD40L effectively activated dendritic cells (DCs), B cells, and tumor-infiltrating T cells, and also promoted tumor cell apoptosis by increasing the expression of TRAIL receptors, thereby significantly enhancing the antitumor activity of oncolytic adenoviruses in CT26 and B16 tumor-bearing models. Although affected by the restriction of oncolytic adenovirus replication in mouse cells, the combination treatment failed to completely eliminate tumor cells, our research still provided a promising strategy for oncolytic adenovirus-mediated solid tumor immunotherapy.

Combining Oncolytic Viruses and Small Molecule Therapeutics: Mutual Benefits

The focus of treating cancer with oncolytic viruses (OVs) has increasingly shifted towards achieving efficacy through the induction and augmentation of an antitumor immune response. However, innate antiviral responses can limit the activity of many OVs within the tumor and several immunosuppressive factors can hamper any subsequent antitumor immune responses. In recent decades, numerous small molecule compounds that either inhibit the immunosuppressive features of tumor cells or antagonize antiviral immunity have been developed and tested for. Here we comprehensively review small molecule compounds that can achieve therapeutic synergy with OVs. We also elaborate on the mechanisms by which these treatments elicit anti-tumor effects as monotherapies and how these complement OV treatment.

Bi- and Tri-Specific T Cell Engager-Armed Oncolytic Viruses: Next-Generation Cancer Immunotherapy

Oncolytic viruses (OVs) are potent anti-cancer biologics with a bright future, having substantial evidence of efficacy in patients with cancer. Bi- and tri-specific antibodies targeting tumor antigens and capable of activating T cell receptor signaling have also shown great promise in cancer immunotherapy. In a cutting-edge strategy, investigators have incorporated the two independent anti-cancer modalities, transforming them into bi- or tri-specific T cell engager (BiTE or TriTE)-armed OVs for targeted immunotherapy. Since 2014, multiple research teams have studied this combinatorial strategy, and it showed substantial efficacy in various tumor models. Here, we first provide a brief overview of the current status of oncolytic virotherapy and the use of multi-specific antibodies for cancer immunotherapy. We then summarize progress on BiTE and TriTE antibodies as a novel class of cancer therapeutics in preclinical and clinical studies, followed by a discussion of BiTE- or TriTE-armed OVs for cancer therapy in translational models. In addition, T cell receptor mimics (TCRm) have been developed into BiTEs and are expected to greatly expand the application of BiTEs and BiTE-armed OVs for the effective targeting of intracellular tumor antigens. Future applications of such innovative combination strategies are emerging as precision cancer immunotherapies.

IL-24-Armed Oncolytic Vaccinia Virus Exerts Potent Antitumor Effects via Multiple Pathways in Colorectal Cancer

Colorectal cancer is an aggressive malignancy for which there are limited treatment options. Oncolytic vaccinia virus is being developed as a novel strategy for cancer therapy. Arming vaccinia virus with immunostimulatory cytokines can enhance the tumor cell-specific replication and antitumor efficacy. Interleukin-24 (IL-24) is an important immune mediator, as well as a broad-spectrum tumor suppressor. We constructed a targeted vaccinia virus of Guang9 strain harboring IL-24 (VG9-IL-24) to evaluate its antitumor effects. In vitro, VG9-IL-24 induced an increased number of apoptotic cells and blocked colorectal cancer cells in the G₂/M phase of the cell cycle. VG9-IL-24 induced apoptosis in colorectal cancer cells via multiple apoptotic signaling pathways. In vivo, VG9-IL-24 significantly inhibited the tumor growth and prolonged the survival both in human and murine colorectal cancer models. In addition, VG9-IL-24 stimulated multiple antitumor immune responses and direct bystander antitumor activity. Our results indicate that VG9-IL-24 can inhibit the growth of colorectal cancer tumor by inducing oncolysis and apoptosis as well as stimulating the antitumor immune effects. These findings indicate that VG9-IL-24 may exert a potential therapeutic strategy for combating colorectal cancer.

Engineering vaccinia virus as an immunotherapeutic battleship to overcome tumor heterogeneity

INTRODUCTION

Immunotherapy is a rapidly evolving area of cancer therapeutics aimed at driving a systemic immune response to fight cancer. Oncolytic viruses (OVs) are at the cutting-edge of innovation in the immunotherapy field. Successful OV platforms must be effective in reshaping the tumor microenvironment and controlling tumor burden, but also be highly specific to avoid off-target side effects. Large DNA viruses, like vaccinia virus (VACV), have a large coding capacity, enabling the encoding of multiple immunostimulatory transgenes to reshape the tumor immune microenvironment. VACV-based OVs have shown promising results in both pre-clinical and clinical studies, including safe and efficient intravenous delivery to metastatic tumors.

AREA COVERED

This review summarizes attenuation strategies to generate a recombinant VACV with optimal tumor selectivity and immunogenicity. In addition, we discuss immunomodulatory transgenes that have been introduced into VACV and summarize their effectiveness in controlling tumor burden.

EXPERT OPINION

VACV encodes several immunomodulatory genes which aid the virus in overcoming innate and adaptive immune responses. Strategic deletion of these virulence factors will enable an optimal balance between viral persistence and immunogenicity, robust tumor-specific expression of payloads and promotion of a systemic anti-cancer immune response. Rational selection of therapeutic transgenes will maximize the efficacy of OVs and their synergy in combinatorial immunotherapy schemes.

Co-treatment With BGP-15 Exacerbates 5-Fluorouracil-Induced Gastrointestinal Dysfunction

Gastrointestinal (GI) side-effects of chemotherapy present a constant impediment to efficient and tolerable treatment of cancer. GI symptoms often lead to dose reduction, delays and cessation of treatment. Chemotherapy-induced nausea, bloating, vomiting, constipation, and/or diarrhea can persist up to 10 years post-treatment. We have previously reported that long-term 5-fluorouracil (5-FU) administration results in enteric neuronal loss, acute inflammation and intestinal dysfunction. In this study, we investigated whether the cytoprotectant, BGP-15, has a neuroprotective effect during 5-FU treatment. Balb/c mice received tri-weekly intraperitoneal 5-FU (23 mg/kg/d) administration with and without BGP-15 (15 mg/kg/d) for up to 14 days. GI transit was analyzed via in vivo serial X-ray imaging prior to and following 3, 7, and 14 days of treatment. On day 14, colons were collected for assessment of ex vivo colonic motility, neuronal mitochondrial superoxide, and cytochrome c levels as well as immunohistochemical analysis of myenteric neurons. BGP-15 did not inhibit 5-FU-induced neuronal loss, but significantly increased the number and proportion of choline acetyltransferase (ChAT)-immunoreactive (IR) and neuronal nitric oxide synthase (nNOS)-IR neurons in the myenteric plexus. BGP-15 co-administration significantly increased mitochondrial superoxide production, mitochondrial depolarization and cytochrome c release in myenteric plexus and exacerbated 5-FU-induced colonic inflammation. BGP-15 exacerbated 5-FU-induced colonic dysmotility by reducing the number and proportion of colonic migrating motor complexes and increasing the number and proportion of fragmented contractions and increased fecal water content indicative of diarrhea. Taken together, BGP-15 co-treatment aggravates 5-FU-induced GI side-effects, in contrast with our previous findings that BGP-15 alleviates GI side-effects of oxaliplatin.

Trail armed oncolytic poxvirus suppresses lung cancer cell by inducing apoptosis

Lung cancer has a high morbidity rate worldwide and is often resistant to therapy. Oncolytic virus therapy is a developing trend for cancer treatment. Thus, we constructed an oncolytic poxvirus carrying human trail gene that expresses a membrane-binding tumor necrosis factor and associated apoptosis-inducing ligand (TRAIL, Oncopox-trail). We hypothesized that the expression of trail would increase the efficacy of the oncolytic poxvirus. The effect of the TRAIL protein depends on the death receptors on the surface of different cancer cells. The expression of death receptors in lung cancer cell lines was analyzed by western blot analysis. In vitro, the oncolytic poxvirus carrying the trail gene displayed a better cytotoxicity at the cell level in the lung cancer cell line than that carrying the Oncopox-empty. TRAIL protein mainly induced apoptosis and inhibited necrosis. In vivo, two transplanted tumor models of human A549 lung cancer cells and mouse Lewis lung cancer cells were used to verify the anti-cancer effect of the oncolytic poxvirus carrying the trail gene. TUNEL staining results of the tumor histological sections also verified the anti-cancer effect. Similarly, through systemic administration of Oncopox-trail, the oncolytic poxvirus also exhibited anti-cancer effect.

PARK7 modulates autophagic proteolysis through binding to the N-terminally arginylated form of the molecular chaperone HSPA5

Macroautophagy is induced under various stresses to remove cytotoxic materials, including misfolded proteins and their aggregates. These protein cargoes are collected by specific autophagic receptors such as SQSTM1/p62 (sequestosome 1) and delivered to phagophores for lysosomal degradation. To date, little is known about how cells sense and react to diverse stresses by inducing the activity of SQSTM1. Here, we show that the peroxiredoxin-like redox sensor PARK7/DJ-1 modulates the activity of SQSTM1 and the targeting of ubiquitin (Ub)-conjugated proteins to macroautophagy under oxidative stress caused by TNFSF10/TRAIL (tumor necrosis factor [ligand] superfamily, member 10). In this mechanism, TNFSF10 induces the N-terminal arginylation (Nt-arginylation) of the endoplasmic reticulum (ER)-residing molecular chaperone HSPA5/BiP/GRP78, leading to cytosolic accumulation of Nt-arginylated HSPA5 (R-HSPA5). In parallel, TNFSF10 induces the oxidation of PARK7. Oxidized PARK7 acts as a co-chaperone-like protein that binds the ER-derived chaperone R-HSPA5, a member of the HSPA/HSP70 family. By forming a complex with PARK7 (and possibly misfolded protein cargoes), R-HSPA5 binds SQSTM1 through its Nt-Arg, facilitating self-polymerization of SQSTM1 and the targeting of SQSTM1-cargo complexes to phagophores. The 3-way interaction among PARK7, R-HSPA5, and SQSTM1 is stabilized by the Nt-Arg residue of R-HSPA5. PARK7-deficient cells are impaired in the targeting of R-HSPA5 and SQSTM1 to phagophores and the removal of Ub-conjugated cargoes. Our results suggest that PARK7 functions as a co-chaperone for R-HSPA5 to modulate autophagic removal of misfolded protein cargoes generated by oxidative stress.

Oxaliplatin-induced enteric neuronal loss and intestinal dysfunction is prevented by co-treatment with BGP-15

BACKGROUND AND PURPOSE

Gastrointestinal side effects of chemotherapy are an under-recognized clinical problem, leading to dose reduction, delays and cessation of treatment, presenting a constant challenge for efficient and tolerated anti-cancer treatment. We have found that oxaliplatin treatment results in intestinal dysfunction, oxidative stress and loss of enteric neurons. BGP-15 is a novel cytoprotective compound with potential HSP72 co-inducing and PARP inhibiting properties. In this study, we investigated the potential of BGP-15 to alleviate oxaliplatin-induced enteric neuropathy and intestinal dysfunction.

EXPERIMENTAL APPROACH

Balb/c mice received oxaliplatin (3 mg·kg^-1 ·day^-1 ) with and without BGP-15 (15 mg·kg^-1 ·day^-1 : i.p.) tri-weekly for 14 days. Gastrointestinal transit was analysed via in vivo X-ray imaging, before and after treatment. Colons were collected to assess ex vivo motility, neuronal mitochondrial superoxide and cytochrome c levels and for immunohistochemical analysis of myenteric neurons.

KEY RESULTS

Oxaliplatin-induced neuronal loss increased the proportion of neuronal NO synthase-immunoreactive neurons and increased levels of mitochondrial superoxide and cytochrome c in the myenteric plexus. These changes were correlated with an increase in PARP-2 immunoreactivity in the colonic mucosa and were attenuated by BGP-15 co-treatment. Significant delays in gastrointestinal transit, intestinal emptying and pellet formation, impaired colonic motor activity, reduced faecal water content and lack of weight gain associated with oxaliplatin treatment were restored to sham levels in mice co-treated with BGP-15.

CONCLUSION AND IMPLICATIONS

Our results showed that BGP-15 ameliorated oxidative stress, increased enteric neuronal survival and alleviated oxaliplatin-induced intestinal dysfunction, suggesting that BGP-15 may relieve the gastrointestinal side effects of chemotherapy.

Genetically Engineered Vaccinia Viruses As Agents for Cancer Treatment, Imaging, and Transgene Delivery

Despite advances in technology, the formidable challenge of treating cancer, especially if advanced, still remains with no significant improvement in survival rates, even with the most common forms of cancer. Oncolytic viral therapies have shown great promise for the treatment of various cancers, with the possible advantages of stronger treatment efficacy compared to conventional therapy due to higher tumor selectivity, and less toxicity. They are able to preferentially and selectively propagate in cancer cells, consequently destroying tumor tissue mainly via cell lysis, while leaving non-cancerous tissues unharmed. Several wild-type and genetically engineered vaccinia virus (VACV) strains have been tested in both preclinical and clinical trials with promising results. Greater understanding and advancements in molecular biology have enabled the generation of genetically engineered oncolytic viruses for safer and more efficacious treatment, including arming VACVs with cytokines and immunostimulatory molecules, anti-angiogenic agents, and enzyme prodrug therapy, in addition to combining VACVs with conventional external and systemic radiotherapy, chemotherapy, immunotherapy, and other virus strains. Furthermore, novel oncolytic vaccinia virus strains have been generated that express reporter genes for the tracking and imaging of viral therapy and monitoring of therapeutic response. Further study is needed to unlock VACVs’ full potential as part of the future of cancer therapy.

Oncolytic Immunotherapy: Conceptual Evolution, Current Strategies, and Future Perspectives

The concept of oncolytic virus (OV)-mediated cancer therapy has been shifted from an operational virotherapy paradigm to an immunotherapy. OVs often induce immunogenic cell death (ICD) of cancer cells, and they may interact directly with immune cells as well to prime antitumor immunity. We and others have developed a number of strategies to further stimulate antitumor immunity and to productively modulate the tumor microenvironment (TME) for potent and sustained antitumor immune cell activity. First, OVs have been engineered or combined with other ICD inducers to promote more effective T cell cross-priming, and in many cases, the breaking of functional immune tolerance. Second, OVs may be armed to express Th1-stimulatory cytokines/chemokines or costimulators to recruit and sustain the potent antitumor immunity into the TME to focus their therapeutic activity within the sites of disease. Third, combinations of OV with immunomodulatory drugs or antibodies that recondition the TME have proven to be highly promising in early studies. Fourth, combinations of OVs with other immunotherapeutic regimens (such as prime-boost cancer vaccines, CAR T cells; armed with bispecific T-cell engagers) have also yielded promising preliminary findings. Finally, OVs have been combined with immune checkpoint blockade, with robust antitumor efficacy being observed in pilot evaluations. Despite some expected hurdles for the rapid translation of OV-based state-of-the-art protocols, we believe that a cohort of these novel approaches will join the repertoire of standard cancer treatment options in the near future.

Animal models of colorectal peritoneal metastasis

Colorectal cancer remains an important cause of mortality worldwide. The presence of peritoneal carcinomatosis (PC) causes significant symptoms and is notoriously difficult to treat. Therefore, informative preclinical research into the mechanisms and possible novel treatment options of colorectal PC is essential in order to improve the prognostic outlook in these patients. Several syngeneic and xenograft animal models of colorectal PC were established, studying a wide range of experimental procedures and substances. Regrettably, more sophisticated models such as those giving rise to spontaneous PC or involving genetically engineered mice are lacking. Here, we provide an overview of all reported colorectal PC animal models and briefly discuss their use, strengths, and limitations.

Oncolytic vaccinia virus synergizes with irinotecan in colorectal cancer

Metastatic colorectal cancer (CRC) is complex clinical challenge for which there are limited treatment options. Chemotherapy with or without surgery provides moderate improvements in overall survival and quality of life; nevertheless the 5-year survival remains below 30%. Oncolytic vaccinia virus (VV) shows strong anti-tumour activity in models of CRC, however transient delays in disease progression are insufficient to lead to long-term survival. Here we examined the efficacy of VV with oxaliplatin or SN-38 (active metabolite of irinotecan) in CRC cell lines in vitro and VV with irinotecan in an orthotopic model of metastatic CRC. Synergistic improvements in in vitro cell killing were observed in multiple cell lines. Combination therapy was well tolerated in tumour-bearing mice and the median survival was significantly increased relative to monotherapy despite a drug-dependent decrease in the mean tumour titer. Increased apoptosis following in vitro and in vivo combination therapy was observed. In vitro cell cycle analysis showed increases in S-phase cells following infection occurred in both infected and uninfected cell populations. This corresponded to a 4-fold greater increase in apoptosis in the uninfected compared to infected cells following combination therapy. Combination treatment strategies are among the best options for patients with advanced cancers. VV is currently under clinical investigation in patients with CRC and the data presented here suggest that its combination with irinotecan may provide benefit to a subset of CRC patients. Further, investigation of this combination is necessary to determine the tumour characteristics responsible for mediating synergy.

Tumor vascularization is critical for oncolytic vaccinia virus treatment of peritoneal carcinomatosis

Peritoneal carcinomatosis (PC) represents a significant clinical challenge for which there are few treatment options. Oncolytic viruses are ideal candidates for PC treatment because of their high tumor specificity, excellent safety profile and suitability for peritoneal delivery. Here, we described the use of vvDD-SR-RFP, a recombinant vaccinia virus, in xenograft and syngeneic models of colorectal PC. Colorectal cancer cell lines were highly susceptible to vvDD-SR-RFP replication and cytotoxicity. Intraperitoneal delivery of vvDD-SR-RFP on Day 12 to mice with colorectal carcinomatosis significantly improved survival whereas survival was not improved following virus treatment on Day 8, when tumors were smaller. Immunohistochemistry revealed early tumors had a poorly distributed network of blood vessels and lower proliferation index compared to later tumors. Virus infection was also restricted to tumor rims following Day 8 treatment, whereas it was disseminated in tumors treated on Day 12. Additionally, direct infection of tumor endothelium was observed and virus infection correlated with a loss of endothelial staining and induction of cell death. Our results demonstrate that tumor vasculature has a critical role in virus delivery and tumor response. This will have significant implications in the clinical setting, both in understanding timing of therapies and in designing combination treatment strategies.

Optimization and preclinical design of genetically engineered viruses for human oncolytic therapy

INTRODUCTION

Oncolytic viruses (OVs) occupy a strategic niche in the dynamic era of biological and gene therapy of human cancers. However, the use of OVs is the subject of close scrutiny due to impediments such as the insufficiency of patient generalizations posed by heterogeneous tumor responses to treatment, inherent or potentially lethal viral pathogenicities, unanticipated host- or immune-related adverse effects, and the emergence of virus-resistant cancer cells. These challenges can be overcome by the design and development of more definitive (optimized, targeted, and individualized) cancer virotherapeutics.

AREAS COVERED

The translation of current knowledge and recent innovations into rational treatment prospects hinges on an iterative loop of variables pertaining to genetically engineered viral oncolytic efficacy and safety profiles, mechanism-of-action data, potencies of synergistic oncolytic viral combinations with conventional tumor, immuno-, chemo-, and radiation treatment modalities, optimization of the probabilities of treatment successes in heterogeneous (virus-sensitive and -resistant) tumor cell populations by mathematical modeling, and lessons learned from preclinical studies and human clinical trials.

EXPERT OPINION

In recent years, it has become increasingly clear that proof-of-principle is critical for the preclinical optimization of oncolytic viruses to target heterogeneous forms of cancer and to prioritize current concerns related to the efficacy and safety of oncolytic virotherapy.

Functional hyper-IL-6 from vaccinia virus-colonized tumors triggers platelet formation and helps to alleviate toxicity of mitomycin C enhanced virus therapy

Background

Combination of oncolytic vaccinia virus therapy with conventional chemotherapy has shown promise for tumor therapy. However, side effects of chemotherapy including thrombocytopenia, still remain problematic.

Methods

Here, we describe a novel approach to optimize combination therapy of oncolytic virus and chemotherapy utilizing virus-encoding hyper-IL-6, GLV-1h90, to reduce chemotherapy-associated side effects.

Results

We showed that the hyper-IL-6 cytokine was successfully produced by GLV-1h90 and was functional both in cell culture as well as in tumor-bearing animals, in which the cytokine-producing vaccinia virus strain was well tolerated. When combined with the chemotherapeutic mitomycin C, the anti-tumor effect of the oncolytic virotherapy was significantly enhanced. Moreover, hyper-IL-6 expression greatly reduced the time interval during which the mice suffered from chemotherapy-induced thrombocytopenia.

Conclusion

Therefore, future clinical application would benefit from careful investigation of additional cytokine treatment to reduce chemotherapy-induced side effects.

Oncolytic poxvirus armed with Fas ligand leads to induction of cellular Fas receptor and selective viral replication in FasR-negative cancer

The TNF superfamily members including Fas ligand and TRAIL have been studied extensively for cancer therapy, including as components of gene therapy. We examined the use of FasL expression to achieve tumor selective replication of an oncolytic poxvirus (vFasL) and explored its biology and therapeutic efficacy for FasR− and FasR+ cancers. Infection of FasR+ normal and MC38 cancer cells by vFasL led to abortive viral replication due to acute apoptosis and subsequently displayed both reduced pathogenicity in non-tumor bearing mice and reduced efficacy in FasR+ tumor-bearing mice. Infection of FasR− B16 cancer cells by vFasL led to efficient viral replication, followed by late induction of FasR and subsequent apoptosis. Treatment with vFasL compared to its parental virus (vJS6) led to increased tumor regression and prolonged survival of mice with FasR− cancer (B16), but not with FasR+ cancer (MC38). The delayed induction of FasR by viral infection in FasR− cells provides for potential increased efficacy beyond the limit of the direct oncolytic effect. FasR induction provides one mechanism for tumor selective replication of oncolytic poxviruses in FasR− cancers with enhanced safety. The overall result is both a safer and more effective oncolytic virus for FasR− cancer.

Recent advances in oncolytic virus design

The cytolytic properties of viruses can be used to treat cancer. Replication of certain viruses is favoured in cancer cells, whereas others can be modified to obtain tumour specificity. This approach has evolved to become a new discipline called virotherapy. In addition, these replication-competent (oncolytic) viruses can be adapted as vectors for cancer gene therapy. The "armed" viruses show a double mechanism of action: direct destruction of cancer cells as a consequence of the lytic viral cycle, in combination with the effect of the therapeutic gene incorporated in the viral genome. Current trends in the field include strategies to increase the oncolytic potency of existing viruses; the evaluation of new candidates; the search for synergistic effects between different viruses and conventional therapies; and a rational approach to take advantage of the interplay between the viruses and the host immune system. This review summarises the most relevant achievements in recent years.

Current good manufacturing practice production of an oncolytic recombinant vesicular stomatitis viral vector for cancer treatment

Vesicular stomatitis virus (VSV) is an oncolytic virus currently being investigated as a promising tool to treat cancer because of its ability to selectively replicate in cancer cells. To enhance the oncolytic property of the nonpathologic laboratory strain of VSV, we generated a recombinant vector [rVSV(MΔ51)-M3] expressing murine gammaherpesvirus M3, a secreted viral chemokine-binding protein that binds to a broad range of mammalian chemokines with high affinity. As previously reported, when rVSV(MΔ51)-M3 was used in an orthotopic model of hepatocellular carcinoma (HCC) in rats, it suppressed inflammatory cell migration to the virus-infected tumor site, which allowed for enhanced intratumoral virus replication leading to increased tumor necrosis and substantially prolonged survival. These encouraging results led to the development of this vector for clinical translation in patients with HCC. However, a scalable current Good Manufacturing Practice (cGMP)-compliant manufacturing process has not been described for this vector. To produce the quantities of high-titer virus required for clinical trials, a process that is amenable to GMP manufacturing and scale-up was developed. We describe here a large-scale (50-liter) vector production process capable of achieving crude titers on the order of 10(9) plaque-forming units (PFU)/ml under cGMP. This process was used to generate a master virus seed stock and a clinical lot of the clinical trial agent under cGMP with an infectious viral titer of approximately 2 × 10(10) PFU/ml (total yield, 1 × 10(13) PFU). The lot has passed all U.S. Food and Drug Administration-mandated release testing and will be used in a phase 1 clinical translational trial in patients with advanced HCC.

Oncolytic vaccinia virus: a theranostic agent for cancer

Vaccinia virus (VACV) is arguably the most successful live biotherapeutic agent because of its critical role in the eradication of smallpox, one of the most deadly diseases in human history. VACV has been exploited as an oncolytic therapeutic agent for cancer since 1922. This virus selectively infects and destroys tumor cells, while sparing normal cells, both in cell cultures and in animal models. A certain degree of therapeutic efficacy also has been demonstrated in patients with different types of cancer. In recent years, several strategies have been successfully developed to further improve its tumor selectivity and antitumor efficacy. Oncolytic VACVs carrying imaging genes represent a new treatment strategy that combines tumor site-specific therapeutics with diagnostics (theranostics).