Harnessing oncolytic virus-mediated antitumor immunity in an infected cell vaccine

Tuning cellular metabolism for cancer virotherapy

Oncolytic viruses (OVs) represent an emerging immunotherapeutic strategy owing to their capacity for direct tumor lysis and induction of antitumor immunity. However, hurdles like transient persistence and moderate efficacy necessitate innovative approaches. Metabolic remodeling has recently gained prominence as a strategic intervention, wherein OVs or combination regimens could reprogram tumor and immune cell metabolism to enhance viral replication and oncolysis. In this review, we summarize recent advances in strategic reprogramming of tumor and immune cell metabolism to enhance OV-based immunotherapies. Specific tactics include engineering viruses to target glycolytic, glutaminolytic, and nucleotide synthesis pathways in cancer cells, boosting viral replication and tumor cell death. Additionally, rewiring T cell and NK cell metabolism of lipids, amino acids, and carbohydrates shows promise to enhance antitumor effects. Further insights are discussed to pave the way for the clinical implementation of metabolically enhanced oncolytic platforms, including balancing metabolic modulation to limit antiviral responses while promoting viral persistence and tumor clearance.

Genetic Alchemy unveiled: MicroRNA-mediated gene therapy as the Artisan craft in the battlefront against hepatocellular carcinoma-a comprehensive chronicle of strategies and innovations

Investigating therapeutic miRNAs is a rewarding endeavour for pharmaceutical companies. Since its discovery in 1993, our understanding of miRNA biology has advanced significantly. Numerous studies have emphasised the disruption of miRNA expression in various diseases, making them appealing candidates for innovative therapeutic approaches. Hepatocellular carcinoma (HCC) is a significant malignancy that poses a severe threat to human health, accounting for approximately 70%-85% of all malignant tumours. Currently, the efficacy of several HCC therapies is limited. Alterations in various biomacromolecules during HCC progression and their underlying mechanisms provide a basis for the investigation of novel and effective therapeutic approaches. MicroRNAs, also known as miRNAs, have been identified in the last 20 years and significantly impact gene expression and protein translation. This atypical expression pattern is strongly associated with the onset and progression of various malignancies. Gene therapy, a novel form of biological therapy, is a prominent research area. Therefore, miRNAs have been used in the investigation of tumour gene therapy. This review examines the mechanisms of action of miRNAs, explores the correlation between miRNAs and HCC, and investigates the use of miRNAs in HCC gene therapy.

Advances in cell-based delivery of oncolytic viruses as therapy for lung cancer

Lung cancer's intractability is enhanced by its frequent resistance to (chemo)therapy and often high relapse rates that make it the leading cause of cancer death worldwide. Improvement of therapy efficacy is a crucial issue that might lead to a significant advance in the treatment of lung cancer. Oncolytic viruses are desirable combination partners in the developing field of cancer immunotherapy due to their direct cytotoxic effects and ability to elicit an immune response. Systemic oncolytic virus administration through intravenous injection should ideally lead to the highest efficacy in oncolytic activity. However, this is often hampered by the prevalence of host-specific, anti-viral immune responses. One way to achieve more efficient systemic oncolytic virus delivery is through better protection against neutralization by several components of the host immune system. Carrier cells, which can even have innate tumor tropism, have shown their appropriateness as effective vehicles for systemic oncolytic virus infection through circumventing restrictive features of the immune system and can warrant oncolytic virus delivery to tumors. In this overview, we summarize promising results from studies in which carrier cells have shown their usefulness for improved systemic oncolytic virus delivery and better oncolytic virus therapy against lung cancer.

NLRC5 overexpression in ovarian tumors remodels the tumor microenvironment and increases T-cell reactivity toward autologous tumor-associated antigens

Introduction

Epithelial ovarian cancer (OC) stands as one of the deadliest gynecologic malignancies, urgently necessitating novel therapeutic strategies. Approximately 60% of ovarian tumors exhibit reduced expression of major histocompatibility complex class I (MHC I), intensifying immune evasion mechanisms and rendering immunotherapies ineffective. NOD-like receptor CARD domain containing 5 (NLRC5) transcriptionally regulates MHC I genes and many antigen presentation machinery components. We therefore explored the therapeutic potential of NLRC5 in OC.

Methods

We generated OC cells overexpressing NLRC5 to rescue MHC I expression and antigen presentation and then assessed their capability to respond to PD-L1 blockade and an infected cell vaccine.

Results

Analysis of microarray datasets revealed a correlation between elevated NLRC5 expression and extended survival in OC patients; however, NLRC5 was scarcely detected in the OC tumor microenvironment. OC cells overexpressing NLRC5 exhibited slower tumor growth and resulted in higher recruitment of leukocytes in the TME with lower CD4/CD8 T-cell ratios and increased activation of T cells. Immune cells from peripheral blood, spleen, and ascites from these mice displayed heightened activation and interferon-gamma production when exposed to autologous tumor-associated antigens. Finally, as a proof of concept, NLRC5 overexpression within an infected cell vaccine platform enhanced responses and prolonged survival in comparison with control groups when challenged with parental tumors.

Discussion

These findings provide a compelling rationale for utilizing NLRC5 overexpression in "cold" tumor models to enhance tumor susceptibility to T-cell recognition and elimination by boosting the presentation of endogenous tumor antigens. This approach holds promise for improving antitumoral immune responses in OC.

Construction of VSVΔ51M oncolytic virus expressing human interleukin-12

The use of oncolytic viruses (OVs) in combination with cytokines, such as IL-12, is a promising approach for cancer treatment that addresses the limitations of current standard treatments and traditional cancer immunotherapies. IL-12, a proinflammatory cytokine, triggers intracellular signaling pathways that lead to increased apoptosis of tumor cells and enhanced antitumor activity of immune cells via IFN-γ induction, making this cytokine a promising candidate for cancer therapy. Targeted expression of IL-12 within tumors has been shown to play a crucial role in tumor eradication. The recent development of oncolytic viruses enables targeted delivery and expression of IL-12 at the tumor site, thereby addressing the systemic toxicities associated with traditional cancer therapy. In this study, we constructed an oncolytic virus, VSVΔ51M, based on the commercially available VSV wild-type backbone and further modified it to express human IL-12. Our preclinical data confirmed the safety and limited toxicity of the modified virus, VSV-Δ51M-hIL-12, supporting its potential use for clinical development.

SARS-CoV-2 RBD protein enhances the oncolytic activity of the vesicular stomatitis virus

Despite recent advances in the research on oncolytic viruses (OVs), a better understanding of how to enhance their replication is key to improving their therapeutic index. Understanding viral replication is important to improve treatment outcomes based on enhanced viral spreading within the tumor milieu. The VSV-Δ51 oncolytic virus has been widely used as an anticancer agent with a high selectivity profile. In this study, we examined the role of the SARS-CoV-2 spike protein receptor-binding domain (RBD) in enhancing VSV-Δ51 viral production and oncolytic activity. To test this hypothesis, we first generated a novel VSV-Δ51 mutant that encoded the SARS-COV-2 RBD and compared viral spreading and viral yield between VSV-Δ51-RBD and VSV-Δ51 in vitro. Using the viral plaque assay, we demonstrated that the presence of the SARS-CoV-2 RBD in the VSV-Δ51 genome is associated with a significantly larger viral plaque surface area and significantly higher virus titers. Subsequently, using an ATP release-based assay, we demonstrated that the SARS-CoV-2 RBD could enhance VSV-Δ51 oncolytic activity in vitro. This observation was further supported using the B16F10 tumor model. These findings highlighted a novel use of the SARS-CoV-2 RBD as an anticancer agent.

Heterologous prime-boost cellular vaccination induces potent antitumor immunity against triple negative breast cancer

Introduction

Triple negative breast cancer (TNBC) is the most aggressive and hard-to-treat subtype of breast cancer, affecting 10-20% of all women diagnosed with breast cancer. Surgery, chemotherapy and hormone/Her2 targeted therapies are the cornerstones of treatment for breast cancer, but women with TNBC do not benefit from these treatments. Although the prognosis is dismal, immunotherapies hold significant promise in TNBC, even in wide spread disease because TNBC is infiltrated with more immune cells. This preclinical study is proposing to optimize an oncolytic virus-infected cell vaccine (ICV) based on a prime-boost vaccination strategy to address this unmet clinical need.

Methods

We used various classes of immunomodulators to improve the immunogenicity of whole tumor cells in the prime vaccine, followed by their infection with oncolytic Vesicular Stomatitis Virus (VSVd51) to deliver the boost vaccine. For in vivo studies, we compared the efficacy of a homologous prime-boost vaccination regimen to a heterologous strategy by treating 4T1 tumor bearing BALB/c mice and further by conducting re-challenge studies to evaluate immune memory responses in surviving mice. Due to the aggressive nature of 4T1 tumor spread (akin to stage IV TNBC in human patients), we also compared early surgical resection of primary tumors versus later surgical resection combined with vaccination.

Results

In vitro results demonstrated that immunogenic cell death (ICD) markers and pro-inflammatory cytokines were released at the highest levels following treatment of mouse 4T1 TNBC cells with oxaliplatin chemotherapy and influenza vaccine. These ICD inducers also contributed towards higher dendritic cell recruitment and activation. With the top ICD inducers at hand, we observed that treatment of TNBC-bearing mice with the influenza virus-modified prime vaccine followed by VSVd51 infected boost vaccine resulted in the best survival. Furthermore, higher frequencies of both effector and central memory T cells along with a complete absence of recurrent tumors were observed in re-challenged mice. Importantly, early surgical resection combined with prime-boost vaccination led to improved overall survival in mice.

Conclusion

Taken together, this novel cancer vaccination strategy following early surgical resection could be a promising therapeutic avenue for TNBC patients.

Oncolytic Adenovirus, a New Treatment Strategy for Prostate Cancer

Prostate cancer is the most common cancer and one of the leading causes of cancer mortality in males. Androgen-deprivation therapy (ADT) is an effective strategy to inhibit tumour growth at early stages. However, 10~50% of cases are estimated to progress to metastatic castration-resistant prostate cancer (mCRPC) which currently lacks effective treatments. Clinically, salvage treatment measures, such as endocrine therapy and chemotherapy, are mostly used for advanced prostate cancer, but their clinical outcomes are not ideal. When the existing clinical therapeutic methods can no longer inhibit the development of advanced prostate cancer, human adenovirus (HAdV)-based gene therapy and viral therapy present promising effects. Pre-clinical studies have shown its powerful oncolytic effect, and clinical studies are ongoing to further verify its effect and safety in prostate cancer treatment. Targeting the prostate by HAdV alone or in combination with radiotherapy and chemotherapy sheds light on patients with castration-resistant and advanced prostate cancer. This review summarizes the advantages of oncolytic virus-mediated cancer therapy, strategies of HAdV modification, and existing preclinical and clinical investigations of HAdV-mediated gene therapy to further evaluate the potential of oncolytic adenovirus in prostate cancer treatment.

Vanadyl sulfate-enhanced oncolytic virus immunotherapy mediates the antitumor immune response by upregulating the secretion of pro-inflammatory cytokines and chemokines

Oncolytic viruses (OVs) are promising anticancer treatments that specifically replicate in and kill cancer cells and have profound immunostimulatory effects. We previously reported the potential of vanadium-based compounds such as vanadyl sulfate (VS) as immunostimulatory enhancers of OV immunotherapy. These compounds, in conjunction with RNA-based OVs such as oncolytic vesicular stomatitis virus (VSVΔ51), improve viral spread and oncolysis, leading to long-term antitumor immunity and prolonged survival in resistant tumor models. This effect is associated with a virus-induced antiviral type I IFN response shifting towards a type II IFN response in the presence of vanadium. Here, we investigated the systemic impact of VS+VSVΔ51 combination therapy to understand the immunological mechanism of action leading to improved antitumor responses. VS+VSVΔ51 combination therapy significantly increased the levels of IFN-γ and IL-6, and improved tumor antigen-specific T-cell responses. Supported by immunological profiling and as a proof of concept for the design of more effective therapeutic regimens, we found that local delivery of IL-12 using VSVΔ51 in combination with VS further improved therapeutic outcomes in a syngeneic CT26WT colon cancer model.

Immunovirotherapy Based on Recombinant Vesicular Stomatitis Virus: Where Are We?

Vesicular stomatitis virus (VSV), a negative-strand RNA virus of the Vesiculovirus genus, has demonstrated encouraging anti-neoplastic activity across multiple human cancer types. VSV is particularly attractive as an oncolytic agent because of its broad tropism, fast replication kinetics, and amenability to genetic manipulations. Furthermore, VSV-induced oncolysis can elicit a potent antitumor cytotoxic T-cell response to viral proteins and tumor-associated antigens, resulting in a long-lasting antitumor effect. Because of this multifaceted immunomodulatory property, VSV was investigated extensively as an immunovirotherapy alone or combined with other anticancer modalities, such as immune checkpoint blockade. Despite these recent opportunities to delineate synergistic and additive antitumor effects with existing anticancer therapies, FDA approval for the use of oncolytic VSV in humans has not yet been granted. This mini-review discusses factors that have prompted the use of VSV as an immunovirotherapy in human cancers and provides insights into future perspectives and research areas to improve VSV-based oncotherapy.

Current challenges in the manufacture of clinical-grade autologous whole cell vaccines for hematological malignancies

Autologous whole cell vaccines use a patient's own tumor cells as a source of antigen to elicit an anti-tumor immune response in vivo. Recently, the authors conducted a systematic review of clinical trials employing these products in hematological cancers that showed a favorable safety profile and trend toward efficacy. However, it was noted that manufacturing challenges limit both the efficacy and clinical implementation of these vaccine products. In the current literature review, the authors sought to define the issues surrounding the manufacture of autologous whole cell products for hematological cancers. The authors describe key factors, including the acquisition, culture, cryopreservation and transduction of malignant cells, that require optimization for further advancement of the field. Furthermore, the authors provide a summary of pre-clinical work that informs how the identified challenges may be overcome. The authors also highlight areas in which future basic research would be of benefit to the field. The goal of this review is to provide a roadmap for investigators seeking to advance the field of autologous cell vaccines as it applies to hematological malignancies.

IL-27 Improves Prophylactic Protection Provided by a Dead Tumor Cell Vaccine in a Mouse Melanoma Model

The protocol used to induce cell death for generating vaccines from whole tumor cells is a critical consideration that impacts vaccine efficacy. Here we compared how different protocols used to induce cell death impacted protection provided by a prophylactic whole tumor cell vaccine in a mouse melanoma model. We found that melanoma cells exposed to γ-irradiation or lysis combined with UV-irradiation (LyUV) provided better protection against tumor challenge than lysis only or cells exposed to UV-irradiation. Furthermore, we found that the immunoregulatory cytokine, IL-27 enhanced protection against tumor growth in a dose-dependent manner when combined with either LyUV or γ-irradiated whole tumor cell vaccine preparations. Taken together, this data supports the use of LyUV as a potential protocol for developing whole tumor cell prophylactic cancer vaccines. We also showed that IL-27 can be used at low doses as a potent adjuvant in combination with LyUV or γ-irradiation treated cancer cells to improve the protection provided by a prophylactic cancer vaccine in a mouse melanoma model.

Engineering strategies to enhance oncolytic viruses in cancer immunotherapy

Oncolytic viruses (OVs) are emerging as potentially useful platforms in treatment methods for patients with tumors. They preferentially target and kill tumor cells, leaving healthy cells unharmed. In addition to direct oncolysis, the essential and attractive aspect of oncolytic virotherapy is based on the intrinsic induction of both innate and adaptive immune responses. To further augment this efficacious response, OVs have been genetically engineered to express immune regulators that enhance or restore antitumor immunity. Recently, combinations of OVs with other immunotherapies, such as immune checkpoint inhibitors (ICIs), chimeric antigen receptors (CARs), antigen-specific T-cell receptors (TCRs) and autologous tumor-infiltrating lymphocytes (TILs), have led to promising progress in cancer treatment. This review summarizes the intrinsic mechanisms of OVs, describes the optimization strategies for using armed OVs to enhance the effects of antitumor immunity and highlights rational combinations of OVs with other immunotherapies in recent preclinical and clinical studies.

Intravesical immunotherapy with a GM-CSF armed oncolytic vesicular stomatitis virus improves outcome in bladder cancer

A significant proportion of non-muscle invasive bladder cancer cases will progress to muscle invasive disease. Transurethral resection followed by Bacillus Calmette Guerin immunotherapy can reduce this risk, while cystectomy prior to muscle invasion provides the best option for survival. Currently, there are no effective treatments for Bacillus Calmette Guerin refractory disease. A novel oncolytic vesicular stomatitis virus containing the human GM-CSF transgene (VSVd51-hGM-CSF) was rescued and tested as a potential bladder-sparing therapy for aggressive bladder cancer. The existing variant expressing mouse GM-CSF was also used. Measurement of gene expression and protein level alterations of canonical immunogenic cell death associated events on mouse and human bladder cancer cell lines and spheroids showed enhanced release of danger signals and immunogenic factors following infection with VSVd51-m/hGM-CSF. Intravesical instillation of VSVd51-mGM-CSF into MB49 bladder cancer bearing C57Bl/6 mice demonstrated enhanced activation of peripheral and bladder infiltrating effector immune cells, along with improved survival and reduced tumor volume. Importantly, virus-mediated anti-tumor immunity was recapitulated in bladder cancer patient-derived organoids. These results suggest that VSVd51-hGM-CSF is a promising viro/immunotherapy that could benefit bladder cancer patients.

Oncolytic Vaccinia Virus in Lung Cancer Vaccines

Therapeutic cancer vaccines represent a promising therapeutic modality via the induction of long-term immune response and reduction in adverse effects by specifically targeting tumor-associated antigens. Oncolytic virus, especially vaccinia virus (VV) is a promising cancer treatment option for effective cancer immunotherapy and thus can also be utilized in cancer vaccines. Non-small cell lung cancer (NSCLC) is likely to respond to immunotherapy, such as immune checkpoint inhibitors or cancer vaccines, since it has a high tumor mutational burden. In this review, we will summarize recent applications of VV in lung cancer treatment and discuss the potential and direction of VV-based therapeutic vaccines.

The phosphoinositide 3-kinase inhibitor ZSTK474 increases the susceptibility of osteosarcoma cells to oncolytic vesicular stomatitis virus VSVΔ51 via aggravating endoplasmic reticulum stress

Blockage of phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signal pathway is effective to increase the cytotoxic effects of oncolytic virus on cancer cells, but the detailed mechanisms are still largely unknown. Based on this, the present study managed to investigate the anti-tumor effects of PI3K inhibitor ZSTK474 and oncolytic vesicular stomatitis virus VSVΔ51 combination treatments on osteosarcoma (OS) in vitro and in vivo. Specifically, ZSTK474 aggravated the inhibiting effects of VSVΔ51 on osteosarcoma development by triggering endoplasmic reticulum (ER)-stress mediated apoptotic cell death. Mechanistically, either ZSTK474 or VSVΔ51 alone had limited effects on cell viability in osteosarcoma cells, while ZSTK474 and VSVΔ51 combination treatments significantly induced osteosarcoma cell apoptosis. Interestingly, VSVΔ51 increased the expression levels of IRE1α and p-PERK to initiate ER stress in osteosarcoma cells, which were aggravated by co-treating cells with ZSTK474. Next, the promoting effects of ZSTK474-VSVΔ51 combined treatment on osteosarcoma cell death were abrogated by the ER-stress inhibitor 4-phenyl butyric acid (4-PBA), indicating that ZSTK474 enhanced the cytotoxic effects of VSVΔ51 on osteosarcoma cells in an ER-stress dependent manner. Finally, the xenograft tumor-bearing mice models were established, and the results showed that ZSTK474-VSVΔ51 combined treatment synergistically hindered tumorigenesis of osteosarcoma cells in vivo. Taken together, our data suggested that ZSTK474 was a novel agent to enhance the cytotoxic effects of VSVΔ51 on osteosarcoma by aggravating ER-stress, and the present study might provide alternative therapy treatments for osteosarcoma in clinic.

Natural Killer Cells Recruitment in Oncolytic Virotherapy: A Mathematical Model

In this paper, we investigate how natural killer (NK) cell recruitment to the tumor microenvironment (TME) affects oncolytic virotherapy. NK cells play a major role against viral infections. They are, however, known to induce early viral clearance of oncolytic viruses, which hinders the overall efficacy of oncolytic virotherapy. Here, we formulate and analyze a simple mathematical model of the dynamics of the tumor, OV and NK cells using currently available preclinical information. The aim of this study is to characterize conditions under which the synergistic balance between OV-induced NK responses and required viral cytopathicity may or may not result in a successful treatment. In this study, we found that NK cell recruitment to the TME must take place neither too early nor too late in the course of OV infection so that treatment will be successful. NK cell responses are most influential at either early (partly because of rapid response of NK cells to viral infections or antigens) or later (partly because of antitumoral ability of NK cells) stages of oncolytic virotherapy. The model also predicts that: (a) an NK cell response augments oncolytic virotherapy only if viral cytopathicity is weak; (b) the recruitment of NK cells modulates tumor growth; and (c) the depletion of activated NK cells within the TME enhances the probability of tumor escape in oncolytic virotherapy. Taken together, our model results demonstrate that OV infection is crucial, not just to cytoreduce tumor burden, but also to induce the stronger NK cell response necessary to achieve complete or at least partial tumor remission. Furthermore, our modeling framework supports combination therapies involving NK cells and OV which are currently used in oncolytic immunovirotherapy to treat several cancer types.

Adjuvant oncolytic virotherapy for personalized anti-cancer vaccination

By conferring systemic protection and durable benefits, cancer immunotherapies are emerging as long-term solutions for cancer treatment. One such approach that is currently undergoing clinical testing is a therapeutic anti-cancer vaccine that uses two different viruses expressing the same tumor antigen to prime and boost anti-tumor immunity. By providing the additional advantage of directly killing cancer cells, oncolytic viruses (OVs) constitute ideal platforms for such treatment strategy. However, given that the targeted tumor antigen is encoded into the viral genomes, its production requires robust infection and therefore, the vaccination efficiency partially depends on the unpredictable and highly variable intrinsic sensitivity of each tumor to OV infection. In this study, we demonstrate that anti-cancer vaccination using OVs (Adenovirus (Ad), Maraba virus (MRB), Vesicular stomatitis virus (VSV) and Vaccinia virus (VV)) co-administered with antigenic peptides is as efficient as antigen-engineered OVs and does not depend on viral replication. Our strategy is particularly attractive for personalized anti-cancer vaccines targeting patient-specific mutations. We suggest that the use of OVs as adjuvant platforms for therapeutic anti-cancer vaccination warrants testing for cancer treatment.

Viruses expressing tumour antigens can prime and boost anti-tumour immunity but the efficiency of this approach depends on the capacity of the virus to infect the host. Here, the authors show that vaccination with oncolytic viruses co-administered with tumour antigenic peptides is as efficient as antigen-engineered oncolytic viruses.

Oncolytic Virotherapy in Solid Tumors: The Challenges and Achievements

Oncolytic virotherapy (OVT) is a promising approach in cancer immunotherapy. Oncolytic viruses (OVs) could be applied in cancer immunotherapy without in-depth knowledge of tumor antigens. The capability of genetic modification makes OVs exciting therapeutic tools with a high potential for manipulation. Improving efficacy, employing immunostimulatory elements, changing the immunosuppressive tumor microenvironment (TME) to inflammatory TME, optimizing their delivery system, and increasing the safety are the main areas of OVs manipulations. Recently, the reciprocal interaction of OVs and TME has become a hot topic for investigators to enhance the efficacy of OVT with less off-target adverse events. Current investigations suggest that the main application of OVT is to provoke the antitumor immune response in the TME, which synergize the effects of other immunotherapies such as immune-checkpoint blockers and adoptive cell therapy. In this review, we focused on the effects of OVs on the TME and antitumor immune responses. Furthermore, OVT challenges, including its moderate efficiency, safety concerns, and delivery strategies, along with recent achievements to overcome challenges, are thoroughly discussed.

De novo necroptosis creates an inflammatory environment mediating tumor susceptibility to immune checkpoint inhibitors

Cancer immunotherapies using monoclonal antibodies to block inhibitory checkpoints are showing durable remissions in many types of cancer patients, although the majority of breast cancer patients acquire little benefit. Human melanoma and lung cancer patient studies suggest that immune checkpoint inhibitors are often potent in patients that already have intratumoral T cell infiltrate; although it remains unknown what types of interventions can result in an intratumoral T cell infiltrate in breast cancer. Using non-T cell-inflamed mammary tumors, we assessed what biological processes and downstream inflammation can overcome the barriers to spontaneous T cell priming. Here we show a specific type of combination therapy, consisting of oncolytic virus and chemotherapy, activates necroptosis and limits tumor growth in autochthonous tumors. Combination therapy activates proinflammatory cytokines; intratumoral influx of myeloid cells and cytotoxic T cell infiltrate in locally treated and distant autochthonous tumors to render them susceptible to immune checkpoint inhibitors.

Cytokines in oncolytic virotherapy

Tumors represent a hostile environment for the effector cells of cancer immunosurveillance. Immunosuppressive receptors and soluble or membrane-bound ligands are abundantly exposed and released by malignant entities and their stromal accomplices. As a consequence, executioners of antitumor immunity inefficiently navigate across cancer tissues and fail to eliminate malignant targets. By inducing immunogenic cancer cell death, oncolytic viruses profoundly reshape the tumor microenvironment. They trigger the local spread of danger signals and tumor-associated (as well as viral) antigens, thus attracting antigen-presenting cells, promoting the activation and expansion of lymphocytic populations, facilitating their infiltration in the tumor bed, and reinvigorating cytotoxic immune activity. The present review recapitulates key chemokines, growth factors and other cytokines that orchestrate this ballet of antitumoral leukocytes upon oncolytic virotherapy.

Treatment and Prevention of Lung Cancer Using a Virus-Infected Reprogrammed Somatic Cell-Derived Tumor Cell Vaccination (VIReST) Regime

Lung cancer is one of the most commonly diagnosed cancer and despite therapeutic advances, mortality remains high. The long period of clinical latency associated with lung cancer provides an ideal window of opportunity to administer vaccines to at-risk individuals that can prevent tumor progression and initiate long-term anti-tumor immune surveillance. Here we describe a personalized vaccination regime that could be applied for both therapeutic and prophylactic prevention of lung cancer, based on the derivation of lung cancer cells from induced pluripotent stem cells. Stem cells from healthy mice were modified to express Cre-dependent KRASG12D and Trp53R172H prior to differentiation to lung progenitor cells. Subsequent viral delivery of Cre caused activation of exogenous driver mutations, resulting in transformation and development of lung cancer cells. iPSC-derived lung cancer cells were highly antigenically related to lung cancer cells induced in LSL-KRASG12D/+; Trp53R172H/+ transgenic mice and were antigenically unrelated to original pluripotent stem cells or pancreatic cancer cells derived using the same technological platform. For vaccination, induced lung cancer cells were infected with oncolytic Adenovirus or Vaccinia virus, to act as vaccine adjuvants, prior to delivery of vaccines sequentially to a murine inducible transgenic model of lung cancer. Application of this Virus-Infected, Reprogrammed Somatic cell-derived Tumor cell (VIReST) regime primed tumor-specific T cell responses that significantly prolonged survival in both subcutaneous post-vaccine challenge models and induced transgenic models of lung cancer, demonstrating that stem cell-derived prophylactic vaccines may be a feasible intervention for treatment or prevention of lung cancer development in at-risk individuals.

Killers 2.0: NK cell therapies at the forefront of cancer control

Natural killer (NK) cells are innate cytotoxic lymphocytes involved in the surveillance and elimination of cancer. As we have learned more and more about the mechanisms NK cells employ to recognize and eliminate tumor cells, and how, in turn, cancer evades NK cell responses, we have gained a clear appreciation that NK cells can be harnessed in cancer immunotherapy. Here, we review the evidence for NK cells' critical role in combating transformed and malignant cells, and how cancer immunotherapies potentiate NK cell responses for therapeutic purposes. We highlight cutting-edge immunotherapeutic strategies in preclinical and clinical development such as adoptive NK cell transfer, chimeric antigen receptor-expressing NK cells (CAR-NKs), bispecific and trispecific killer cell engagers (BiKEs and TriKEs), checkpoint blockade, and oncolytic virotherapy. Further, we describe the challenges that NK cells face (e.g., postsurgical dysfunction) that must be overcome by these therapeutic modalities to achieve cancer clearance.

Combining Oncolytic Viruses With Cancer Immunotherapy: Establishing a New Generation of Cancer Treatment

The recent successes of tumor immunotherapy approaches, such as immune checkpoint blockade (ICB) and chimeric antigen receptor T cell (CAR-T) therapy, have revolutionized cancer treatment, improving efficacy and extending treatment to a larger proportion of cancer patients. However, due to high heterogeneity of cancer, poor tumor cell targeting, and the immunosuppressive status of the tumor microenvironment (TME), combinatorial agents are required to obtain more effective and consistent therapeutic responses in a wide range of cancers. Oncolytic viruses (OVs) are able to selectively replicate in and destroy tumor cells and subsequently induce systematic anti-tumor immune responses. Thus, they are ideal for combining with cancer immunotherapy. In this review, we discuss the current understanding of OVs, as well as the latest preclinical and clinical progress of combining OVs with cancer immunotherapies, including ICB, CAR-T therapy, bispecific T cell engagers (BiTEs), and cancer vaccines. Moreover, we consider future directions for applying OVs to personalized cancer immunotherapies, which could potentially launch a new generation of cancer treatments.

A Virus-Infected, Reprogrammed Somatic Cell-Derived Tumor Cell (VIReST) Vaccination Regime Can Prevent Initiation and Progression of Pancreatic Cancer

PURPOSE

Pancreatic cancer remains one of the most lethal cancers, and late detection renders most tumors refractory to conventional therapies. Development of cancer prophylaxis may be the most realistic option for improving mortality associated with this disease. Here, we develop a novel individualized prophylactic and therapeutic vaccination regimen using induced pluripotent stem cells (iPSC), gene editing, and tumor-targeted replicating oncolytic viruses.

EXPERIMENTAL DESIGN

We created a Virus-Infected, Reprogrammed Somatic cell-derived Tumor cell (VIReST) regime. iPSCs from healthy cells were induced to pancreatic tumor cells using in situ gene editing via stable provision of KRas ^G12D and p53 ^R172H tumor driver mutations. These cells were preinfected with oncolytic Adenovirus (AdV) as prime or Vaccinia virus (VV) as boost, to improve vaccine immunogenicity, prior to delivery of vaccines in a sequential regime to young KPC transgenic mice, genetically programmed to develop pancreatic cancer, to prevent and delay disease development.

RESULTS

Tumor cells preinfected with oncolytic AdV as prime or VV as boost were the best regime to induce tumor-specific immunity. iPSC-derived tumor cells were highly related in antigen repertoire to pancreatic cancer cells of KPC transgenic mice, suggesting that an individual's stem cells can provide an antigenically matched whole tumor cell vaccine. The VIReST vaccination primed tumor-specific T-cell responses, resulting in delayed disease emergence and progression and significantly prolonged survival of KPC transgenic mice. Importantly, this regime was well-tolerated and nontoxic.

CONCLUSIONS

These results provide both proof of concept and a robust technology platform for the development of personalized prophylactic cancer vaccines to prevent pancreatic malignancies in at-risk individuals.

The lytic activity of VSV-GP treatment dominates the therapeutic effects in a syngeneic model of lung cancer

Background

Oncolytic virotherapy is thought to result in direct virus-induced lytic tumour killing and simultaneous activation of innate and tumour-specific adaptive immune responses. Using a chimeric vesicular stomatitis virus variant VSV-GP, we addressed the direct oncolytic effects and the role of anti-tumour immune induction in the syngeneic mouse lung cancer model LLC1.

Methods

To study a tumour system with limited antiviral effects, we generated interferon receptor-deficient cells (LLC1-IFNAR1^−/−). Therapeutic efficacy of VSV-GP was assessed in vivo in syngeneic C57BL/6 and athymic nude mice bearing subcutaneous tumours. VSV-GP treatment effects were analysed using bioluminescent imaging (BLI), immunohistochemistry, ELISpot, flow cytometry, multiplex ELISA and Nanostring® assays.

Results

Interferon insensitivity correlated with VSV-GP replication and therapeutic outcome. BLI revealed tumour-to-tumour spread of viral progeny in bilateral tumours. Histological and gene expression analysis confirmed widespread and rapid infection and cell killing within the tumour with activation of innate and adaptive immune-response markers. However, treatment outcome was increased in the absence of CD8⁺ T cells and surviving mice showed little protection from tumour re-challenge, indicating limited therapeutic contribution by the activated immune system.

Conclusion

These studies present a case for a predominantly lytic treatment effect of VSV-GP in a syngeneic mouse lung cancer model.

Dimethyl fumarate potentiates oncolytic virotherapy through NF-κB inhibition

Resistance to oncolytic virotherapy is frequently associated with failure of tumor cells to get infected by the virus. Dimethyl fumarate (DMF), a common treatment for psoriasis and multiple sclerosis, also has anticancer properties. We show that DMF and various fumaric and maleic acid esters (FMAEs) enhance viral infection of cancer cell lines as well as human tumor biopsies with several oncolytic viruses (OVs), improving therapeutic outcomes in resistant syngeneic and xenograft tumor models. This results in durable responses, even in models otherwise refractory to OV and drug monotherapies. The ability of DMF to enhance viral spread results from its ability to inhibit type I interferon (IFN) production and response, which is associated with its blockade of nuclear translocation of the transcription factor nuclear factor κB (NF-κB). This study demonstrates that unconventional application of U.S. Food and Drug Administration-approved drugs and biological agents can result in improved anticancer therapeutic outcomes.

Treatment of Metastatic Disease through Natural Killer Cell Modulation by Infected Cell Vaccines

Oncolytic viruses (OVs) are a form of immunotherapy that release tumor antigens in the context of highly immunogenic viral signals following tumor-targeted infection and destruction. Emerging preclinical and clinical evidence suggests that this in situ vaccine effect is critical for successful viro-immunotherapy. In this review, we discuss the application of OV as an infected cell vaccine (ICV) as one method of enhancing the potency and breadth of anti-tumoral immunity. We focus on understanding and manipulating the critical role of natural killer (NK) cells and their interactions with other immune cells to promote a clinical outcome. With a synergistic tumor killing and immune activating mechanism, ICVs represent a valuable new addition to the cancer fighting toolbox with the potential to treat malignant disease.

Virus oncolíticos: un arma contra el cáncer

Introducción. Los virus oncolíticos son virus atenuados, mutados o que por naturaleza se dirigen y matan específicamente células tumorales, sin afectar a las células normales. La administración intratumoral del virus ofrece la oportunidad de tratar el tumor primario pero no focos metastásicos, los cuales pueden ser alcanzados mediante la administración intravenosa. Sin embargo, su eficiencia puede disminuir por la presencia de una respuesta inmunológica preexistente en los sujetos tratados.Objetivo. Exponer las técnicas utilizadas para envolver y transportar los virus con el fin de eludir el sistema inmunológico antes de que el virus llegue al tumor.Materiales y métodos. Se realizó una búsqueda narrativa de la literatura original y de revisión en las bases de datos PubMed, JSTOR y EBSCO sobre métodos o técnicas utilizadas para el tratamiento del cáncer mediante el uso de virus oncolíticos.Resultados. La formación de nanocomplejos entre los virus oncolíticos y biopolímeros —ya sea mediante la unión química o mediante la unión a través de interacciones electrostáticas o el uso de micropartículas, células transportadoras, liposomas, ultrasonido o terapias combinadas– es eficaz para evitar la respuesta inmunológica del huésped contra el virus.Conclusión. Para evitar la respuesta inmunológica del huésped contra los virus oncolíticos se han desarrollo diversos métodos que permiten la liberación controlada y especifica de los mismos. Sin embargo, debido a la diversidad de los virus, se debe tener en cuenta que la eficacia de los métodos de protección y transporte depende de las características bioquímicas tanto del biomaterial como del virus.

Ovarian Cancer Immunotherapy: Preclinical Models and Emerging Therapeutics

Immunotherapy has emerged as one of the most promising approaches for ovarian cancer treatment. The tumor microenvironment (TME) is a key factor to consider when stimulating antitumoral responses as it consists largely of tumor promoting immunosuppressive cell types that attenuate antitumor immunity. As our understanding of the determinants of the TME composition grows, we have begun to appreciate the need to address both inter- and intra-tumor heterogeneity, mutation/neoantigen burden, immune landscape, and stromal cell contributions. The majority of immunotherapy studies in ovarian cancer have been performed using the well-characterized murine ID8 ovarian carcinoma model. Numerous other animal models of ovarian cancer exist, but have been underutilized because of their narrow initial characterizations in this context. Here, we describe animal models that may be untapped resources for the immunotherapy field because of their shared genomic alterations and histopathology with human ovarian cancer. We also shed light on the strengths and limitations of these models, and the knowledge gaps that need to be addressed to enhance the utility of preclinical models for testing novel immunotherapeutic approaches.

Combination of IAP Antagonists and TNF-α-Armed Oncolytic Viruses Induce Tumor Vascular Shutdown and Tumor Regression

Smac mimetic compounds (SMCs) are anti-cancer drugs that antagonize Inhibitor of Apoptosis proteins, which consequently sensitize cancer cells to death in the presence of proinflammatory ligands such as tumor necrosis factor alpha (TNF-α). SMCs synergize with the attenuated oncolytic vesicular stomatitis virus (VSVΔ51) by eliciting an innate immune response, which is dependent on the endogenous production of TNF-α and type I interferon. To improve on this SMC-mediated synergistic response, we generated TNF-α-armed VSVΔ51 to produce elevated levels of this death ligand. Due to ectopic expression of TNF-α from infected cells, a lower viral dose of TNF-α-armed VSVΔ51 combined with treatment of the SMC LCL161 was sufficient to improve the survival rate compared to LCL161 and unarmed VSVΔ51 co-therapy. This improved response is attributed to a bystander effect whereby the spread of TNF-α from infected cells leads to the death of uninfected cells in the presence of LCL161. In addition, the treatments induced vascular collapse in solid tumors with a concomitant increase of tumor cell death, revealing another mechanism by which cytokine-armed VSVΔ51 in combination with LCL161 can kill tumor cells. Our studies demonstrate the potential for cytokine-engineered oncolytic virus and SMCs as a new combination immunotherapy for cancer treatment.

Oncolytic Virus Combination Therapy: Killing One Bird with Two Stones

Over the last 60 years an eclectic collection of microbes has been tested in a variety of pre-clinical models as anti-cancer agents. At the forefront of this research are a number of virus-based platforms that have shown exciting activity in a variety of pre-clinical models and are collectively referred to as oncolytic viruses. Our true understanding of the potential and limitations of this therapeutic modality has been substantially advanced through clinical studies carried out over the last 25 years. Perhaps not surprising, as with all other cancer therapeutics, it has become clear that current oncolytic virus therapeutics on their own are unlikely to be effective in the majority of patients. The greatest therapeutic gains will therefore be made through thoughtful combination strategies built upon an understanding of cancer biology.

Armed oncolytic viruses: A kick-start for anti-tumor immunity

Oncolytic viruses (OVs), viruses that specifically result in killing tumor cells, represent a promising class of cancer therapy. Recently, the focus in the OV therapy field has shifted from their direct oncolytic effect to their immune stimulatory effect. OV therapy can function as a "kick start" for the antitumor immune response by releasing tumor associated antigens and release of inflammatory signals. Combining OVs with immune modulators could enhance the efficacy of both immune and OV therapies. Additionally, genetic engineering of OVs allows local expression of immune therapeutics, thereby reducing related toxicities. Different options to modify the tumor microenvironment in combination with OV therapy have been explored. The possibilities and obstacles of these combinations will be discussed in this review.

Trial watch: DNA-based vaccines for oncological indications

DNA-based vaccination is a promising approach to cancer immunotherapy. DNA-based vaccines specific for tumor-associated antigens (TAAs) are indeed relatively simple to produce, cost-efficient and well tolerated. However, the clinical efficacy of DNA-based vaccines for cancer therapy is considerably limited by central and peripheral tolerance. During the past decade, considerable efforts have been devoted to the development and characterization of novel DNA-based vaccines that would circumvent this obstacle. In this setting, particular attention has been dedicated to the route of administration, expression of modified TAAs, co-expression of immunostimulatory molecules, and co-delivery of immune checkpoint blockers. Here, we review preclinical and clinical progress on DNA-based vaccines for cancer therapy.

Oncolytic potency and reduced virus tumor-specificity in oncolytic virotherapy. A mathematical modelling approach

In the present paper, we address by means of mathematical modeling the following main question: How can oncolytic virus infection of some normal cells in the vicinity of tumor cells enhance oncolytic virotherapy? We formulate a mathematical model describing the interactions between the oncolytic virus, the tumor cells, the normal cells, and the antitumoral and antiviral immune responses. The model consists of a system of delay differential equations with one (discrete) delay. We derive the model's basic reproductive number within tumor and normal cell populations and use their ratio as a metric for virus tumor-specificity. Numerical simulations are performed for different values of the basic reproduction numbers and their ratios to investigate potential trade-offs between tumor reduction and normal cells losses. A fundamental feature unravelled by the model simulations is its great sensitivity to parameters that account for most variation in the early or late stages of oncolytic virotherapy. From a clinical point of view, our findings indicate that designing an oncolytic virus that is not 100% tumor-specific can increase virus particles, which in turn, can further infect tumor cells. Moreover, our findings indicate that when infected tissues can be regenerated, oncolytic viral infection of normal cells could improve cancer treatment.

Oncolytic Vesicular Stomatitis Virus as a Viro-Immunotherapy: Defeating Cancer with a "Hammer" and "Anvil"

Oncolytic viruses have gained much attention in recent years, due, not only to their ability to selectively replicate in and lyse tumor cells, but to their potential to stimulate antitumor immune responses directed against the tumor. Vesicular stomatitis virus (VSV), a negative-strand RNA virus, is under intense development as an oncolytic virus due to a variety of favorable properties, including its rapid replication kinetics, inherent tumor specificity, and its potential to elicit a broad range of immunomodulatory responses to break immune tolerance in the tumor microenvironment. Based on this powerful platform, a multitude of strategies have been applied to further improve the immune-stimulating potential of VSV and synergize these responses with the direct oncolytic effect. These strategies include: 1. modification of endogenous virus genes to stimulate interferon induction; 2. virus-mediated expression of cytokines or immune-stimulatory molecules to enhance anti-tumor immune responses; 3. vaccination approaches to stimulate adaptive immune responses against a tumor antigen; 4. combination with adoptive immune cell therapy for potentially synergistic therapeutic responses. A summary of these approaches will be presented in this review.

NK-Cell Recruitment Is Necessary for Eradication of Peritoneal Carcinomatosis with an IL12-Expressing Maraba Virus Cellular Vaccine

Despite improvements in chemotherapy and radical surgical debulking, peritoneal carcinomatosis (PC) remains among the most common causes of death from abdominal cancers. Immunotherapies have been effective for selected solid malignancies, but their potential in PC has been little explored. Here, we report that intraperitoneal injection of an infected cell vaccine (ICV), consisting of autologous tumor cells infected ex vivo with an oncolytic Maraba MG1 virus expressing IL12, promotes the migration of activated natural killer (NK) cells to the peritoneal cavity in response to the secretion of IFNγ-induced protein-10 (IP-10) from dendritic cells. The recruitment of cytotoxic, IFNγ-secreting NK cells was associated with reduced tumor burden and improved survival in a colon cancer model of PC. Even in mice with bulky PC (tumors > 8 mm), a complete radiologic response was demonstrated within 8 to14 weeks, associated with 100% long-term survival. The impact of MG1-IL12-ICV upon NK-cell recruitment and function observed in the murine system was recapitulated in human lymphocytes exposed to human tumor cell lines infected with MG1-IL12. These findings suggest that an MG1-IL12-ICV is a promising therapy that could provide benefit to the thousands of patients diagnosed with PC each year. Cancer Immunol Res; 5(3); 211-21. ©2017 AACR.

Murine Tumor Models for Oncolytic Rhabdo-Virotherapy

The preclinical optimization and validation of novel treatments for cancer therapy requires the use of laboratory animals. Although in vitro experiments using tumor cell lines and ex vivo treatment of patient tumor samples provide a remarkable first-line tool for the initial study of tumoricidal potential, tumor-bearing animals remain the primary option to study delivery, efficacy, and safety of therapies in the context of a complete tumor microenvironment and functional immune system. In this review, we will describe the use of murine tumor models for oncolytic virotherapy using vesicular stomatitis virus. We will discuss studies using immunocompetent and immunodeficient models with respect to toxicity and therapeutic treatments, as well as the various techniques and tools available to study cancer therapy with Rhabdoviruses.

Taking a Stab at Cancer; Oncolytic Virus-Mediated Anti-Cancer Vaccination Strategies

Vaccines have classically been used for disease prevention. Modern clinical vaccines are continuously being developed for both traditional use as well as for new applications. Typically thought of in terms of infectious disease control, vaccination approaches can alternatively be adapted as a cancer therapy. Vaccines targeting cancer antigens can be used to induce anti-tumour immunity and have demonstrated therapeutic efficacy both pre-clinically and clinically. Various approaches now exist and further establish the tremendous potential and adaptability of anti-cancer vaccination. Classical strategies include ex vivo-loaded immune cells, RNA- or DNA-based vaccines and tumour cell lysates. Recent oncolytic virus development has resulted in a surge of novel viruses engineered to induce powerful tumour-specific immune responses. In addition to their use as cancer vaccines, oncolytic viruses have the added benefit of being directly cytolytic to cancer cells and thus promote antigen recognition within a highly immune-stimulating tumour microenvironment. While oncolytic viruses are perfectly equipped for efficient immunization, this complicates their use upon previous exposure. Indeed, the host's anti-viral counter-attacks often impair multiple-dosing regimens. In this review we will focus on the use of oncolytic viruses for anti-tumour vaccination. We will explore different strategies as well as ways to circumvent some of their limitations.

Whole cell vaccination using immunogenic cell death by an oncolytic adenovirus is effective against a colorectal cancer model

Cancer vaccine application is limited to specific cancer types because few cancer-associated antigens are known to induce tumor rejection. Accordingly, we assessed the utility of Ad881, an oncolytic adenovirus in which viral replication was strictly regulated by the cancer-specific midkine promoter, as a cancer vaccine in a murine colorectal cancer model lacking specific cancer-associated antigens. In CT26 and CMT93 cells, Ad881 (multiplicity of infection: 100 or 1,000) showed stronger cytotoxicity and oncolysis in vitro than its equivalent replication-defective adenovirus, Ad884. CT26 cells (1 × 10⁴) infected with Ad881 (multiplicity of infection: 1,000) for 24 hours were suitable as vaccine antigens without tumor formation in our model. Repeated vaccinations, but not single vaccination, induced a greater prophylactic immune response. The percentage of mice that rejected the tumor challenge was 0, 4, and 38% after no vaccination, single vaccination, and repeated vaccinations, respectively. Immunogenic cell death marker high-mobility group box 1 protein (HMGB1) and adenosine triphosphate in culture medium were higher after Ad881 infection (24.3 ng/ml and 48.2 nmol/l, respectively) than after Ad884 infection (8.6 ng/ml and 15.4 nmol/l, respectively) or oxaliplatin treatment (3.7 ng/ml and 1.8 nmol/l, respectively). These results indicate that repeated whole cell vaccination using an oncolytic adenovirus may be a potent approach to evoke immunogenic cell death.

Viruses as nanomedicine for cancer

Oncolytic virotherapy, a type of nanomedicine in which oncolytic viruses (OVs) are used to selectively infect and lyse cancer cells, is an emerging field in cancer therapy. Some OVs exhibit a specific tropism for cancer cells, whereas others require genetic modification to enhance their binding with and entry into cancer cells. OVs both kill tumor cells and induce the host’s immune response against tumor cells. Armed with antitumor cellular molecules, antibodies, and/or in combination with anticancer drugs, OVs can accelerate the lysis of cancer cells. Among the OVs, vaccinia virus has been the focus of preclinical and clinical research because of its many favorable properties. In this review, the basic mechanisms of action of OVs are presented, including their entry, survival, tumor lysis, and immune activation, and the latest research in vaccinia virus-based virotherapy and its status as an anticancer nanomedicine in prospective clinical trials are discussed.

Capitalizing on Cancer Specific Replication: Oncolytic Viruses as a Versatile Platform for the Enhancement of Cancer Immunotherapy Strategies

The past decade has seen considerable excitement in the use of biological therapies in treating neoplastic disease. In particular, cancer immunotherapy and oncolytic virotherapy have emerged as two frontrunners in this regard with the first FDA approvals for agents in both categories being obtained in the last 5 years. It is becoming increasingly apparent that these two approaches are not mutually exclusive and that much of the therapeutic benefit obtained from the use of oncolytic viruses (OVs) is in fact the result of their immunotherapeutic function. Indeed, OVs have been shown to recruit and activate an antitumor immune response and much of the current work in this field centers around increasing this activity through strategies such as engineering genes for immunomodulators into OV backbones. Because of their broad immunostimulatory functions, OVs can also be rationally combined with a variety of other immunotherapeutic approaches including cancer vaccination strategies, adoptive cell transfer and checkpoint blockade. Therefore, while they are important therapeutics in their own right, the true power of OVs may lie in their ability to enhance the effectiveness of a wide range of immunotherapies.

Oncolysis by paramyxoviruses: preclinical and clinical studies

Preclinical studies demonstrate that a broad spectrum of human malignant cells can be killed by oncolytic paramyxoviruses, which include cells of ecto-, endo-, and mesodermal origin. In clinical trials, significant reduction in size or even complete elimination of primary tumors and established metastases are reported. Different routes of viral administration (intratumoral, intravenous, intradermal, intraperitoneal, or intrapleural), and single- versus multiple-dose administration schemes have been explored. The reported side effects are grade 1 and 2, with the most common among them being mild fever. Some advantages in using paramyxoviruses as oncolytic agents versus representatives of other viral families exist. The cytoplasmic replication results in a lack of host genome integration and recombination, which makes paramyxoviruses safer and more attractive candidates for widely used therapeutic oncolysis in comparison with retroviruses or some DNA viruses. The list of oncolytic paramyxovirus representatives includes attenuated measles virus (MV), mumps virus (MuV), low pathogenic Newcastle disease (NDV), and Sendai (SeV) viruses. Metastatic cancer cells frequently overexpress on their surface some molecules that can serve as receptors for MV, MuV, NDV, and SeV. This promotes specific viral attachment to the malignant cell, which is frequently followed by specific viral replication. The paramyxoviruses are capable of inducing efficient syncytium-mediated lyses of cancer cells and elicit strong immunomodulatory effects that dramatically enforce anticancer immune surveillance. In general, preclinical studies and phase 1–3 clinical trials yield very encouraging results and warrant continued research of oncolytic paramyxoviruses as a particularly valuable addition to the existing panel of cancer-fighting approaches.

Role of NK cells in immunotherapy and virotherapy of solid tumors

Although natural killer (NK) cells are endowed with powerful cytolytic activity against cancer cells, their role in different therapies against solid tumors has not yet been fully elucidated. Their interactions with various elements of the tumor microenvironment as well as their possible effects in contributing to and/or limiting oncolytic virotherapy render this potential immunotherapeutic tool still difficult to exploit at the bedside. Here, we will review the current literature with the aim of providing new hints to manage this powerful cell type in future innovative therapies, such as the use of NK cells in combination with new cytokines, specific mAbs (inducing ADCC), Tyr-Kinase inhibitors, immunomodulatory drugs and/or the design of oncolytic viruses aimed at optimizing the effect of NK cells in virotherapy.

Interleukin-4 Expressed By Neoplastic Cells Provokes an Anti-Metastatic Myeloid Immune Response

OBJECTIVE

Interleukin-4 (IL-4) can induce macrophages to undergo alternative activation and polarize toward an M2-like or wound healing phenotype. Tumor associated macrophages (TAMs) are thought to assume M2-like properties, and it has been suggested they promote tumor growth and metastasis through effects on the tumor stroma, including extracelluar matrix remodeling and angiogenesis. IL-4 also promotes macrophage survival and formation of multinucleated giant cells, which have enhanced phagocytic behavior. This study was designed to explore the effect of cancer cell derived IL-4 on the tumor immune stroma and metastasis.

METHODS

The metastatic mouse mammary carcinoma cell line AC2M2 was transduced with control or IL-4 encoding retroviruses and employed in orthotopic engraftment models. Tumor growth and metastasis were assessed. The cellular composition and biomarker expression of tumors were examined by immunohistochemical staining and flow cytometry; the transcriptome of the immune stroma was analyzed by nanoString based transcript quantitation; and in vivo and in vitro interactions between cancer cells and macrophages were assessed by flow cytometry and co-culture with video-time lapse microscopy, respectively.

RESULTS

Unexpectedly, tumors from IL-4 expressing AC2M2 engrafted cells grew at reduced rates, and most surprising, they lost all metastatic potential relative to tumors from control AC2M2 cells. Myeloid cell numbers were not increased in IL-4 expressing tumors, but their expression of the M2 marker arginase I was elevated. Transcriptome analysis revealed an immune signature consistent with IL-4 induced M2 polarization of the tumor microenvironment and a generalized increase in myeloid involvement in the tumor stroma. Flow cytometry analysis indicated enhanced cancer cell phagocytosis by TAMs from IL-4 expressing tumors, and co-culture studies showed that IL-4 expressing cancer cells supported the survival and promoted the in vitro phagocytic behavior of macrophages.

CONCLUSIONS

Although M2-like TAMs have been linked to enhanced tumorigenesis, this study shows that IL-4 production by cancer cells is associated with suppressed tumor growth and loss of metastatic potential as well as enhanced phagocytic behavior of TAMs.

Emerging role of Natural killer cells in oncolytic virotherapy

Natural killer (NK) cells constitute a subtype of lymphocytes that initiate innate immune responses against tumors and virus-infected cells. The ability of NK cells to kill target cells or to produce cytokines depends on the balance between signals from activating and inhibitory cell-surface receptors. Therapies with NK cells involve activation of endogenous NK cells and/or exogenous transfer by hematopoietic stem cell transplantation/adoptive cell therapy. To exploit the diverse functional abilities of NK cells for cancer immunotherapy, it is important to understand NK cell biology and the underlying regulatory mechanisms. The state of immune suppression prevalent in malignancies creates the need for innovative therapies. Oncolytic viruses are novel anticancer agents showing selective tropism for tumor cells and lacking pathogenicity in humans, but the use of oncolytic virotherapy (OVT) presents multiple challenges. An increasing body of evidence suggests that the host immune response may critically influence the outcome of OVT. Classically, the immune system is thought to limit the efficacy of therapy through virus clearance mediated by innate immune effectors or through adaptive antiviral immune responses eliminating infected cells. Effective strategies do need to be designed in OVT to circumvent the early antiviral activity of NK cells and to augment late NK-cell-mediated antitumor responses. The intrinsic immunostimulating capacity of oncolytic viruses and the possibility of engineering them to express heterologous immunostimulatory molecules (eg, cytokines) support the use of these agents to enhance antitumor immune responses besides inducing direct oncolytic effects. OVT has indeed shown promising therapeutic outcomes in various clinical trials. Here, we review the biology of NK cells, strategies involving NK cells for achieving cancer therapy, and, more particularly, the emerging role of NK cells in OVT.

Microtubule disruption synergizes with oncolytic virotherapy by inhibiting interferon translation and potentiating bystander killing

In this study, we show that several microtubule-destabilizing agents used for decades for treatment of cancer and other diseases also sensitize cancer cells to oncolytic rhabdoviruses and improve therapeutic outcomes in resistant murine cancer models. Drug-induced microtubule destabilization leads to superior viral spread in cancer cells by disrupting type I IFN mRNA translation, leading to decreased IFN protein expression and secretion. Furthermore, microtubule-destabilizing agents specifically promote cancer cell death following stimulation by a subset of infection-induced cytokines, thereby increasing viral bystander effects. This study reveals a previously unappreciated role for microtubule structures in the regulation of the innate cellular antiviral response and demonstrates that unexpected combinations of approved chemotherapeutics and biological agents can lead to improved therapeutic outcomes.

The ex vivo purge of cancer cells using oncolytic viruses: recent advances and clinical implications

Hematological malignancies are treated with intensive high-dose chemotherapy, with or without radiation. This is followed by hematopoietic stem cell (HSC) transplantation (HSCT) to rescue or reconstitute hematopoiesis damaged by the anticancer therapy. Autologous HSC grafts may contain cancer cells and purging could further improve treatment outcomes. Similarly, allogeneic HSCT may be improved by selectively purging alloreactive effector cells from the graft rather than wholesale immune cell depletion. Viral agents that selectively replicate in specific cell populations are being studied in experimental models of cancer and immunological diseases and have potential applications in the context of HSC graft engineering. This review describes preclinical studies involving oncolytic virus strains of adenovirus, herpes simplex virus type 1, myxoma virus, and reovirus as ex vivo purging agents for HSC grafts, as well as in vitro and in vivo experimental studies using oncolytic coxsackievirus, measles virus, parvovirus, vaccinia virus, and vesicular stomatitis virus to eradicate hematopoietic malignancies. Alternative ex vivo oncolytic virus strategies are also outlined that aim to reduce the risk of relapse following autologous HSCT and mitigate morbidity and mortality due to graft-versus-host disease in allogeneic HSCT.