Effect Of Oncolytic Virus Research Articles

ONCOLYTIC ACTIVITY OF HUMAN RESPIRATORY SYNCYTIAL VIRUS.

Oncolytic viruses (OVs) are emerging as novel tools in cancer therapy. Oncolytic virotherapy offers an attractive therapeutic combination of tumor-specific killing and immune co-stimulation, therefore amplifying the host immune response against tumors. Moreover, OVs can be engineered for the expression of different immunostimulatory molecules to optimize and enhance the efficacy of oncolytic virotherapy. The effectiveness of OVs has been demonstrated in many preclinical studies for different types of cancers to achieve the aim of personalized cancer therapy. Human respiratory syncytial virus (RSV), an RNA virus of the Pneumoviridae family causes severe lower respiratory tract infections in infants and immunocompromised individuals. Interestingly, the oncolytic activity of RSV demonstrated in human prostate, hepatocellular, and dermal cancer cells is mostly mediated via apoptotic cell death associated with the impaired NF-κB activation or with the defect of the IFNα/β-induced STAT-1 activation. At the same time, the studies on cervical cancer revealed that RSV infection resulted in autophagy activation and apoptosis through the ROS-BAX and TNF- α-mediated pathways. The rational combinations of OVs, including RSV, with other approaches may benefit patients whose response to conventional therapies is limited. Here, we discuss the oncolytic activity of RSV and its potential use against different types of cancer.

Oncolytic viruses alter the biogenesis of tumor extracellular vesicles and influence their immunogenicity

Extracellular vesicles (EVs) are mediators of intercellular communication in the tumor microenvironment. Tumor EVs are commonly associated with metastasis, immunosuppression or drug resistance. Viral infections usually increase EV secretion, but little is known about the effect of oncolytic viruses (OVs) on tumor EVs. Here, we investigated the impact of oncolytic vesicular stomatitis virus (VSV) and vaccinia virus (VACV) on EVs secreted by human melanoma and thoracic cancer cells. We found that OV infection increases the production of EVs by tumor cells. These EVs contain proteins of viral origin, such as VSV-G, thus creating a continuum of particles sharing markers of both canonical EVs and viruses. As such, the presence of VSV-G on EVs improves the transfer of their protein content to cell types commonly found in the tumor microenvironment. A proteomic analysis also revealed that EVs-OV secreted during VSV infection are enriched in immunity-related proteins. Finally, CD8+ T cells incubated with EVs-OV from infected cells display slightly enhanced cytotoxic functions. Taken together, these data suggest that OVs enhance the communication mediated by tumor EVs, which could participate to the therapeutic efficacy of OVs. These results also provide rationale for engineering OVs to exploit EVs and disseminate therapeutic proteins within the tumor microenvironment.

An optimal promoter regulating cytokine transgene expression is crucial for safe and effective oncolytic virus immunotherapy

In general, ensuring safety is the top priority of a new modality. Although oncolytic virus armed with an immune stimulatory transgene (OVI) showed some promise, the strategic concept of simultaneously achieving maximum effectiveness and minimizing side effects has not been fully explored. We generated a variety of survivin-responsive “conditionally replicating adenoviruses that can target and treat cancer cells with multiple factors (m-CRAs)” (Surv.m-CRAs) armed with the granulocyte-macrophage colony-stimulating factor (GM-CSF) transgene downstream of various promoters using our m-CRA platform technology. We carefully analyzed both therapeutic and adverse effects of them in the in vivo syngeneic Syrian hamster cancer models. Surprisingly, an intratumor injection of a conventional OVI, which expresses the GM-CSF gene under the constitutively and strongly active “cytomegalovirus enhancer and β-actin promoter”, provoked systemic and lethal GM-CSF circulation and shortened overall survival (OS). In contrast, a new conceptual type of OVI, which expressed GM-CSF under the cancer-predominant and mildly active E2F promoter or the moderately active “Rous sarcoma virus long terminal repeat”, not only abolished lethal adverse events but also prolonged OS and systemic anti-cancer immunity. Our study revealed a novel concept that optimal expression levels of an immune stimulatory transgene regulated by a suitable upstream promoter is crucial for achieving high safety and maximal therapeutic effects simultaneously in OVI therapy. These results pave the way for successful development of the next-generation OVI and alert researchers about possible problems with ongoing clinical trials.

Oncolytic Activity of Sindbis Virus with the Help of GM-CSF in Hepatocellular Carcinoma.

Hepatocellular carcinoma is a refractory tumor with poor prognosis and high mortality. Many oncolytic viruses are currently being investigated for the treatment of hepatocellular carcinoma. Based on previous studies, we constructed a recombinant GM-CSF-carrying Sindbis virus, named SINV-GM-CSF, which contains a mutation (G to S) at amino acid 285 in the nsp1 protein of the viral vector. The potential of this mutated vector for liver cancer therapy was verified at the cellular level and in vivo, respectively, and the changes in the tumor microenvironment after treatment were also described. The results showed that the Sindbis virus could effectively infect hepatocellular carcinoma cell lines and induce cell death. Furthermore, the addition of GM-CSF enhanced the tumor-killing effect of the Sindbis virus and increased the number of immune cells in the intra-tumor microenvironment during the treatment. In particular, SINV-GM-CSF was able to efficiently kill tumors in a mouse tumor model of hepatocellular carcinoma by regulating the elevation of M1-type macrophages (which have a tumor-resistant ability) and the decrease in M2-type macrophages (which have a tumor-promoting capacity). Overall, SINV-GM-CSF is an attractive vector platform with clinical potential for use as a safe and effective oncolytic virus.

OV Modulators of the Paediatric Brain TIME: Current Status, Combination Strategies, Limitations and Future Directions.

Oncolytic viruses (OVs) are characterised by their preference for infecting and replicating in tumour cells either naturally or after genetic modification, resulting in oncolysis. Furthermore, OVs can elicit both local and systemic anticancer immune responses while specifically infecting and lysing tumour cells. These characteristics render them a promising therapeutic approach for paediatric brain tumours (PBTs). PBTs are frequently marked by a cold tumour immune microenvironment (TIME), which suppresses immunotherapies. Recent preclinical and clinical studies have demonstrated the capability of OVs to induce a proinflammatory immune response, thereby modifying the TIME. In-depth insights into the effect of OVs on different cell types in the TIME may therefore provide a compelling basis for using OVs in combination with other immunotherapy modalities. However, certain limitations persist in our understanding of oncolytic viruses' ability to regulate the TIME to enhance anti-tumour activity. These limitations primarily stem from the translational limitations of model systems, the difficulties associated with tracking reliable markers of efficacy throughout the course of treatment and the role of pre-existing viral immunity. In this review, we describe the different alterations observed in the TIME in PBTs due to OV treatment, combination therapies of OVs with different immunotherapies and the hurdles limiting the development of effective OV therapies while suggesting future directions based on existing evidence.

Swine pseudorabies virus attenuated vaccine reprograms the kidney cancer tumor microenvironment and synergizes with PD-1 blockade.

The global incidence rate of kidney cancer (KC) has been steadily increasing over the past 30 years. With the aging global population, kidney cancer has become an escalating concern that necessitates vigilant surveillance. Nowadays, surgical intervention remains the optimal therapeutic approach for kidney cancer, while the availability of efficacious treatments for advanced tumors remains limited. Oncolytic viruses, an emerging form of immunotherapy, have demonstrated encouraging anti-neoplastic properties and are progressively garnering public acceptance. However, research on oncolytic viruses in kidney cancer is relatively limited. Furthermore, given the high complexity and heterogeneity of kidney cancer, it is crucial to identify an optimal oncolytic virus agent that is better suited for its treatment. The present study investigates the oncolytic activity of the Pseudorabies virus live attenuated vaccine (PRV-LAV) against KC. The findings clearly demonstrate that PRV-LAV exhibits robust oncolytic activity targeting KC cell lines. Furthermore, the therapeutic efficacy of PRV-LAV was confirmed in both a subcutaneous tumor-bearing nude mouse model and a syngeneic mouse model of KC. Combined RNA-seq analysis and flow cytometry revealed that PRV-LAV treatment substantially enhances the infiltration of a diverse range of lymphocytes, including T cells, B cells, macrophages, and NK cells. Additionally, PRV-LAV treatment enhances T cell activation and exerts antitumor effects. Importantly, the combination of PRV-LAV with anti-PD-1 antibodies, an approved drug for KC treatment, synergistically enhances the efficacy against KC. Overall, the discovery of PRV-LAV as an effective oncolytic virus holds significant importance for improving the treatment efficacy and survival rates of KC patients.

The artificial amino acid change in the sialic acid-binding domain of the hemagglutinin neuraminidase of newcastle disease virus increases its specificity to HCT 116 colorectal cancer cells and tumor suppression effect

BackgroundOncolytic viruses are being studied and developed as novel cancer treatments. Using directed evolution technology, structural modification of the viral surface protein increases the specificity of the oncolytic virus for a particular cancer cell. Newcastle disease virus (NDV) does not show specificity for certain types of cancer cells during infection; therefore, it has low cancer cell specificity. Hemagglutinin is an NDV receptor-binding protein on the cell surface that determines host cell tropism. NDV selectivity for specific cancer cells can be increased by artificial amino acid changes in hemagglutinin neuraminidase HN proteins via directed evolution, leading to improved therapeutic effects.MethodsSialic acid-binding sites (H domains) of the HN protein mutant library were generated using error-prone PCR. Variants of the H domain protein were screened by enzyme-linked immunosorbent assay using HCT 116 cancer cell surface molecules. The mutant S519G H domain protein showed the highest affinity for the surface protein of HCT 116 cells compared to that of different types of cancer cells. This showed that the S519G mutant H domain protein gene replaced the same part of the original HN protein gene, and S519G mutant recombinant NDV (rNDV) was constructed and recovered. S519G rNDV cancer cell killing effects were tested using the MTT assay with various cancer cell types, and the tumor suppression effect of the S519G mutant rNDV was tested in a xenograft mouse model implanted with cancer cells, including HCT 116 cells.ResultsS519G rNDV showed increased specificity and enhanced killing ability of HCT 116 cells among various cancer cells and a stronger suppressive effect on tumor growth than the original recombinant NDV. Directed evolution using an artificial amino acid change in the NDV HN (S519G mutant) protein increased its specificity and oncolytic effect in colorectal cancer without changing its virulence.ConclusionThese results provide a new methodology for the use of directed evolution technology for more effective oncolytic virus development.

Oncolytic viruses in lung cancer treatment: a review article.

Lung cancer has a high morbidity rate worldwide due to its resistance to therapy. So new treatment options are needed to improve the outcomes of lung cancer treatment. This study aimed to evaluate the effectiveness of oncolytic viruses (OVs) as a new type of cancer treatment. In this study, 158 articles from PubMed and Scopus from 1994 to 2022 were reviewed on the effectiveness of OVs in the treatment of lung cancer. The oncolytic properties of eight categories of OVs and their interactions with treatment options were investigated. OVs can be applied as a promising immunotherapy option, as they are reproduced selectively in different types of cancer cells, cause tumor cell lysis and trigger efficient immune responses.

Stability and Hopf Bifurcation Analysis of an Oncolytic Virus Infection Model with Two Time Delays and Saturation Incidence

In this paper, we study a model of oncolytic virus infection with two time delays, one of which is the time from the entry of viruses into tumor cells to start gene replication, and the other is the time from the entry of viruses into tumor cells to release new virus particles by infected tumor cells. In previous studies on oncolytic virus infection models, the infection rate was linear. Combined with the virus infection models, the saturated infection rate, β T V / 1 + q V is further considered to describe the dynamic evolution between viruses and tumor cells more objectively so as to further study the therapeutic effect of oncolytic viruses. This paper discusses the dynamics of the system under three conditions: (1) τ 1 = τ 2 = 0 , (2) τ 1 = 0 and τ 2 > 0 , and (3) τ 1 > 0 and τ 2 > 0 , and proves the global stability and local stability of the virusfree equilibrium, the stability of the infection equilibrium, and the existence of Hopf bifurcation. Finally, the conclusions of the paper are verified by MATLAB numerical simulations.

Abstract 3565: Viroimmunotherapy for solid tumors results in local and abscopal anti-cancer effects and the remodeling of tumor microenvironment

Abstract Oncolytic viruses are a promising experimental treatment for solid tumors. Recently, several phase 1 clinical trials have reported encouraging therapeutic effects of oncolytic viruses in adult and pediatric patients with malignant gliomas. To further improve the therapeutic outcome of viroimmunotherapy, we have developed Delta-24-RGDOX (DNX-2440), a replication competent adenovirus encompassing the T-cell activator OX40L in the genetic backbone of Delta-24-RGD. We have previously reported the effect of Delta-24-RGDOX in murine brain tumors supporting the translation of this new agent to treat patients with recurrent malignant gliomas (NCT03714334). In the work presented here, we have tested the therapeutic effect of Delta-24-RGDOX in murine syngeneic models of breast (4T1), gastric (M12) and lung cancer (LLC and CMT 167). We found that Delta-24-RGDOX infected all cancer cell lines efficiently. In addition, infection of cells was followed by the expression of the ectopic ligand in vitro and in vivo. Because the elicitation of an anti-tumor immunity is part of the mechanisms underlying the therapeutic effect of oncolytic viruses, we examined whether infection of tumors led to the reshaping of the tumor microenvironment. We observed that Delta-24-RGDOX infection was followed by increased frequencies of tumor infiltrating lymphocytes, particularly CD8+ T cells and NK cells. In addition, the CD8+/CD4+ ratio was increased in Delta-24-RGDOX-treated tumor versus PBS-treated tumors. Interestingly, abscopal modifications were observed in breast cancer brain metastases with increased frequency of CD8+ T cells at the distal, untreated site. Delta-24-RGDOX treatment induced an anti-cancer effect in orthotopically implanted breast cancer and subcutaneously implanted lung and gastric tumors, as well as in metastatic niches. In summary, our data showed that treatment of solid tumors with Delta-24-RGDOX induces robust remodeling of the tumor microenvironment and produces anti-tumor effects leading to decrease in tumor volume, along with a delay in the development and in the reduction of the number of metastases. These data suggest that Delta-24-RGDOX should be tested in the clinical setting in patients with metastatic breast, gastric and lung cancers. Citation Format: Arie C. Van Wieren, Sagar Sahoni, Teresa Nguyen, Ashley Ossimetha, Yisel Rivera-Molina, Hong Jiang, Dong Ho Shin, Debora Kim, Xuejun Fan, Yanhua Yi, Natalie M. Melendez-Vazquez, Filipa Godoy-Vitorino, Joy Gumin, Frederick F. Lang, Marta M. Alonso, Juan Fueyo, Candelaria Gomez-Manzano. Viroimmunotherapy for solid tumors results in local and abscopal anti-cancer effects and the remodeling of tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3565.

Preclinical studies of the anti-tumor effects of novel Avian paramyxovirus 4 (APMV-4) oncolytic viral therapy combined with vascular endothelial growth factor-C (VEGF-C) in melanoma.

e15050 Background: Avian paramyxoviruses (APMVs) are negative-sense, single-stranded RNA viruses, of which best known is APMV-1, commonly referred to as Newcastle disease virus (NDV). NDV has been extensively studied as an oncolytic virus (OV) and has been shown to be a promising viral agent for human cancer therapy. We identified APMV-4 as a novel OV from the APMV family, with several advantages over NDV and other classes of OVs. APMV-4 is selective for cancer cells, it is not a human pathogen, there is no pre-existing immunity to this virus in humans, and it can be engineered to deliver various therapeutics. Here, we investigated anti-tumor properties of APMV-4 in mouse tumor models, and the role of Vascular Endothelial Growth Factor-C (VEGF-C), a key lymphangiogenesis factor, on therapeutic effects of AMPV-4. Methods: Anti-tumor effects of OVs were assessed using B16F10 melanoma and CT26.WT colon carcinoma in syngeneic mouse models. Tumor cells were injected intradermally into the flank, and treatment commenced when tumors reached ̃50mm3. Viruses were injected intratumorally (107 PFU) every two days, for a total of four treatments. For studies of VEGF-C, B16F10 cells were transfected with VEGF-C or with an empty vector. Tumor regression and long-term survival were assessed. Mice in complete remission were re-challenged with tumor cells on the opposite side. High-dimensional immunophenotyping using Aurora Spectral flow cytometry was performed on tumor samples collected 12 hr after the 2nd treatment with OVs. Results: Intratumoral administration of APMV-4 extended survival, promoted tumor elimination and conferred protection against re-challenge in murine colon carcinoma and melanoma tumor models, and was more effective than NDV strain LaSota. Expression of VEGF-C in B16F10 melanoma enhanced anti-tumor effects of APMV-4 or NDV, resulting in complete remission in 100% and 86% of mice, respectively (n = 7). Mice remained tumor-free during the 90-day observation period, and following re-challenge remained tumor-free for more than a year. Protection from tumor development upon re-challenge was observed in 71% and 83% of mice treated with APMV-4 or NDV, respectively. Results are representative of two experiments. VEGF-C expression in tumors induced lymphangiogenesis, which correlated with high T-cell densities. Analysis of tumor immune cell composition by flow cytometry revealed multiple unique T-cell and NK-cell subsets associated with complete remission. Conclusions: These studies identify APMV-4 as a novel oncolytic agent with great therapeutic potential and VEGF-C as potent enhancer of anti-tumor immunity. High anti-tumor efficacy of APMV-4/VEGF-C monotherapy, that in preclinical models leads to tumor eradication, indicates great therapeutic and vaccine potential of APMV-4 when combined with VEGF-C.

Identification of the receptor of oncolytic virus M1 as a therapeutic predictor for multiple solid tumors

Over the last decade, oncolytic virus (OV) therapy has shown its promising potential in tumor treatment. The fact that not every patient can benefit from it highlights the importance for defining biomarkers that help predict patients’ responses. As particular self-amplifying biotherapeutics, the anti-tumor effects of OVs are highly dependent on the host factors for viral infection and replication. By using weighted gene co-expression network analysis (WGCNA), we found matrix remodeling associated 8 (MXRA8) is positively correlated with the oncolysis induced by oncolytic virus M1 (OVM). Consistently, MXRA8 promotes the oncolytic efficacy of OVM in vitro and in vivo. Moreover, the interaction of MXRA8 and OVM studied by single-particle cryo-electron microscopy (cryo-EM) showed that MXRA8 directly binds to this virus. Therefore, MXRA8 acts as the entry receptor of OVM. Pan-cancer analysis showed that MXRA8 is abundant in most solid tumors and is highly expressed in tumor tissues compared with adjacent normal ones. Further study in cancer cell lines and patient-derived tumor tissues revealed that the tumor selectivity of OVM is predominantly determined by a combinational effect of the cell membrane receptor MXRA8 and the intracellular factor, zinc-finger antiviral protein (ZAP). Taken together, our study may provide a novel dual-biomarker for precision medicine in OVM therapy.

EXTH-56. ZIKA VIRUS TREATMENT SIGNIFICANTLY PROLONGS SURVIVAL IN A GLIOBLASTOMA PATIENT DERIVED XENOGRAFT MODEL

Abstract The poor median survival for patients with glioblastoma (GBM) of 15 months has not budged for the past 15 years, when the current standard treatment was first approved. There is no standard of care chemotherapy for recurrent GBM. We previously showed that Zika virus (ZIKV) tropism for GBM cells is mediated through the receptor tyrosine kinase, AXL. This infection is cytotoxic. In this study we show that ZIKV is an effective oncolytic virus in a patient derived xenograft model. Fox N1 Nude homozygous female mice 6-8-weeks-old were grouped into 4 experimental arms: two patient derived cell lines, each with a ZIKV treated and a control group. There were 12 mice in each arm. Animals received subcutaneous flank injections of GBM 8049 or its AXL CRISPR knockout 8049 AXLKO (2x106 cells). When tumors reached 200 mm3, mice received intra-tumoral injection of 2.5x106 ZIKV particles or saline. ZIKV induced complete tumor remission in 22 of 24 animals (8049: 11/12; 8049 AXLKO: 11/12). There was no tumor remission in the saline treated animals. Median survival of 8049 and 8049 AXLKO ZIKV treated mice was 124 days and 125 days, respectively. This is compared to median survival of control animals 8049: 42 days; 8049 AXLKO: 46 days (P= 0.001). Among ZIKV treated mice, there were two recurrences: one in the 8049 tumor (24 days after significant tumor remission) and one 8049 AXLKO tumor (7 days after significant tumor remission). We conclude that ZIKV should be considered a candidate oncolytic virus for GBM.

S-1 facilitates canerpaturev (C-REV)-induced antitumor efficacy in a triple-negative breast cancer model.

ABSTRACTCanerpaturev (C-REV) is a highly attenuated, replication-competent, mutant strain of oncolytic herpes simplex virus type 1 that may be an effective new cancer treatment option. S-1, an oral formulation containing the 5-fluorouracil (5-FU) prodrug tegafur and the two enzyme modulators gimeracil and oteracil, is used as a key chemotherapeutic agent for metastatic recurrent breast cancer. Although the antitumor effects of oncolytic viruses combined with 5-FU in vivo have been reported, the detailed mechanisms are unknown. Here, we investigated the antitumor mechanism of the combination of C-REV and S-1 in triple-negative breast cancer (TNBC) in the context of tumor immunity. The combined effect of C-REV and S-1 was evaluated in a bilateral tumor model of murine TNBC 4T1 in vivo. S-1 enhanced the TNBC growth inhibitory effects of C-REV, and decreased the number of tumor-infiltrating, myeloid-derived suppressor cells (MDSCs), which suppress both innate and adaptive immune responses. Moreover, C-REV alone and in combination with S-1 significantly increased the number of CD8+ T cells in the tumor and the production of interferon γ (IFNγ) from these cells. Our findings indicate that C-REV suppresses TNBC tumor growth by inducing the expansion of effector CD8+ T cell subsets in tumors in which S-1 can inhibit MDSC function. Our study suggests that MDSCs may be an important cellular target for breast cancer treatment. The combination of C-REV and S-1 is a new approach that might be directly translated into future clinical trials against TNBC.

CAR T Cell-Packaged Oncolytic Vaccinia Virus Displays Enhanced Antitumor Efficacy

Background: Oncolytic vaccinia virus is a promising cancer therapeutic modality. However, the effectiveness of oncolytic viruses is limited by several factors. Systemic or intratumoral delivery of vaccinia viruses with the subsequent quick clearance of the viruses from the tumor site and the body by the strong immune responses induced by the virus are among the key challenges. In this study, we explored CAR T cell-packaged oncolytic vaccinia virus as a combinational therapy strategy in order to overcome current limitations for oncolytic virotherapy. Materials and Methods: We generated human HER2-CAR T cells and infected the HER2-CAR T cells with a EphA2-CD3 T cell engager-armed oncolytic vaccinia virus and evaluated the virus infectivity and replication within the T cells by flow analysis and virus tittering. T cell activation and cytotoxicity were determined by ELISA and 51Cr release assay. Results: We demonstrated that oncolytic vaccinia virus infected human HER2-CAR T cells effectively and virus particle in the activated human T cells increased >1000 fold in 3 days. In addition, EphA2-CD3 T cell engager effectively activated HER2-CAR T cells in the presence of HER2dimEphA2high NSCLC A549 cell lines, indicated by the elevated expression level of IFNγ and IL2. Importantly, in vitro studies showed that HER2-CAR T cell-packaged EphA2-TEA-VV displayed enhanced cytotoxicity against HER2dimEphA2high NSCLC A549 cell lines compared to HER2-CAR T cells or EphA2-TEA-VV alone. Conclusion: HER2-CAR T cell-packaged EphA2-TEA-VV is a promising therapeutic candidate with the ability to overcome the virus’s high immunogenicity and tumor heterogeneity, resulting in enhanced antitumor effects.

Abstract 1785: Inhibition of the IDO-Kyn-AhR cascade optimizes virotherapy in glioblastoma and depends on CD4 T-cell activation

Abstract Immune enhancement of virotherapy by reshaping the tumor immune landscape may improve its success rates. IDO, an IFNγ inducible tryptophan catabolizing enzyme, is upregulated in glioblastoma, correlating with poor prognoses. IDO-mediated tryptophan depletion in the tumor-microenvironment decreases viral replication and diminishes cell proliferation and induces apoptosis of surrounding effector T-cells. Furthermore, kynurenine (kyn), a metabolite of tryptophan, induces T-cell differentiation into Tregs. Excess kynurenine also elicits AhR-mediated lymphocyte dysfunction and immunosuppression. The immune stimulating effect of oncolytic-virus, D24-RGDOX, clinically known as DNX-2440, triggers IFNγ production contributing to a positive IDO-Kyn-AhR feedback loop. Thus, we hypothesized that combining D24-RGDOX with IDO inhibitors will synergize to treat glioblastoma. We studied the IDO-Kyn-AhR cascade in response to D24-RGDOX infection in human and murine glioblastoma cells. Orthotopic syngeneic glioblastoma mouse models were used to determine efficacy and tumor immune effects of D24-RGDOX and IDO inhibitors as single agents or as a combination treatment. We characterized IDO and AhR in D24-RGDOX infected cancers using immunofluorescence, qRT-PCR, and flow cytometry and found increased expression of both proteins in vitro and in vivo compared to mock infected controls. D24-RGDOX also increased activity of AhR in cancer cells as indicated by an AhR responsive elements transcription assay. Furthermore, we showed that viral protein expression and viral activity was enhanced in D24-RGDOX infected cultures under IDO inhibition. To test the therapeutic efficacy of combining D24-RGDOX with IDO inhibitors, we used a murine immunocompetent glioblastoma model; the combination produced 30% more long-term survivors compared D24-RGDOX alone (P=0.03, log-rank test). Next, lymphocytic depletion studies illustrated that this anticancer effect was dependent on CD4+ T-cell activation. We observed 100% survival in the re-challenged long-term glioblastoma survivors, indicating the establishment of immune memory by the combination. Functional studies showed significant increases in anti-tumor activity of splenocytes from combination-treated mice compared to D24-RGDOX-treated mice (P=0.009, student t-test). Flow cytometry studies revealed that combination-treated mice yielded the highest levels of chronically activated T-cells and lowest levels of Tregs and MDSCs compared to D24-RGDOX alone (P≤0.05 in all populations, student t-test). This microenvironment remodeling correlated with complete tumor elimination. Altogether, D24-RGDOX activates the IDO-Kyn-AhR cascade in gliomas, identifying new targets, which when inhibited have the potential to enhance the anti-glioma effect of oncolytic-viruses by reversing tumor immunosuppression. Citation Format: Teresa T. Nguyen, Dong Ho Shin, Hong Jiang, Derek A. Wainwright, Sagar Sohoni, Sumit Gupta, Ashley Ossimetha, Frederick Lang, Marta Alonso, Candelaria Gomez-Manzano, Juan Fueyo. Inhibition of the IDO-Kyn-AhR cascade optimizes virotherapy in glioblastoma and depends on CD4 T-cell activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1785.

Expanding the Spectrum of Pancreatic Cancers Responsive to Vesicular Stomatitis Virus-Based Oncolytic Virotherapy: Challenges and Solutions.

Simple SummaryPancreatic ductal adenocarcinoma (PDAC) is a devastating malignancy with a poor prognosis and a dismal survival rate. Oncolytic virus (OV) is an anticancer approach that utilizes replication-competent viruses to preferentially infect and kill tumor cells. Vesicular stomatitis virus (VSV), one such OV, is already in several phase I clinical trials against different malignancies. VSV-based recombinant viruses are effective OVs against a majority of tested PDAC cell lines. However, some PDAC cell lines are resistant to VSV. This review discusses multiple mechanisms responsible for the resistance of some PDACs to VSV-based OV therapy, as well multiple rational approaches to enhance permissiveness of PDACs to VSV and expand the spectrum of PDACs responsive to VSV-based oncolytic virotherapy.Pancreatic ductal adenocarcinoma (PDAC) is a devastating malignancy with poor prognosis and a dismal survival rate, expected to become the second leading cause of cancer-related deaths in the United States. Oncolytic virus (OV) is an anticancer approach that utilizes replication-competent viruses to preferentially infect and kill tumor cells. Vesicular stomatitis virus (VSV), one such OV, is already in several phase I clinical trials against different malignancies. VSV-based recombinant viruses are effective OVs against a majority of tested PDAC cell lines. However, some PDAC cell lines are resistant to VSV. Upregulated type I IFN signaling and constitutive expression of a subset of interferon-simulated genes (ISGs) play a major role in such resistance, while other mechanisms, such as inefficient viral attachment and resistance to VSV-mediated apoptosis, also play a role in some PDACs. Several alternative approaches have been shown to break the resistance of PDACs to VSV without compromising VSV oncoselectivity, including (i) combinations of VSV with JAK1/2 inhibitors (such as ruxolitinib); (ii) triple combinations of VSV with ruxolitinib and polycations improving both VSV replication and attachment; (iii) combinations of VSV with chemotherapeutic drugs (such as paclitaxel) arresting cells in the G2/M phase; (iv) arming VSV with p53 transgenes; (v) directed evolution approach producing more effective OVs. The latter study demonstrated impressive long-term genomic stability of complex VSV recombinants encoding large transgenes, supporting further clinical development of VSV as safe therapeutics for PDAC.

Oncolytic Virotherapy in Solid Tumors: The Challenges and Achievements.

Simple SummaryOncolytic 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. 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.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.

Effects of oncolytic viruses and viral vectors on immunity in glioblastoma.

Glioblastoma (GBM) is regarded as an incurable disease due to its poor prognosis and limited treatment options. Virotherapies were once utilized on cancers for their oncolytic effects. And they are being revived on GBM treatment, as accumulating evidence presents the immunogenic effects of virotherapies in remodeling immunosuppressive GBM microenvironment. In this review, we focus on the immune responses induced by oncolytic virotherapies and viral vectors in GBM. The current developments of GBM virotherapies are briefly summarized, followed by a detailed depiction of their immune response. Limitations and lessons inferred from earlier experiments and trials are discussed. Moreover, we highlight the importance of engaging the immune responses induced by virotherapies into the multidisciplinary management of GBM.

Retargeted and Multi-cytokine-Armed Herpes Virus Is a Potent Cancer Endovaccine for Local and Systemic Anti-tumor Treatment

Oncolytic viruses (OVs) are novel anti-tumor agents with the ability to selectively infect and kill tumor cells while sparing normal tissue. Beyond tumor cytolysis, OVs are capable of priming an anti-tumor immune response via lysis and cross-presentation of locally expressed endogenous tumor antigens, acting as an “endovaccine.” The effectiveness of OVs, similar to other immunotherapies, can be hampered by an immunosuppressive tumor microenvironment. In this study, we modified a previously generated oncolytic herpes simplex virus (oHSV) retargeted to the human HER2 (hHER2) tumor molecule and encoding murine interleukin-12 (mIL-12), by insertion of a second immunomodulatory molecule, murine granulocyte-macrophage colony-stimulating factor (mGM-CSF), to maximize therapeutic efficacy. We assessed the efficacy of this double-armed virus (R-123) compared to singly expressing GM-CSF and IL-12 oHSVs in tumor-bearing mice. While monotherapies were poorly effective, combination with α-PD1 enhanced the anti-tumor response, with the highest efficacy of 100% response rate achieved by the combination of R-123 and α-PD1. Efficacy was T cell-dependent, and the induced immunity was long lasting and able to reject a second contralateral tumor. Importantly, systemic delivery of R-123 combined with α-PD1 was effective in inhibiting the development of tumor metastasis. As such, this approach could have a significant therapeutic impact paving the way for further development of this platform in cancer immunotherapy.