Virus specific tolerance enhanced efficacy of cancer immuno-virotherapy

Oncolytic reovirus enhances the effect of CEA immunotherapy when combined with PD1-PDL1 inhibitor in a colorectal cancer model

AIM

The effectiveness of immunotherapy with tumor associated antigen vaccines can be enhanced by combining oncolytic viruses with immune checkpoint inhibitors. This study evaluates the efficacy of oncolytic reovirus in combination with an adenovector expressing carcinoembryonic antigen (Ad-CEA) and a programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) inhibitor in a mouse model.

METHODS

Mice bearing CEA-expressing CT26 tumor cells were immunized with Ad-CEA along with a PD-1/PD-L1 inhibitor. Subsequently, three doses of reovirus were injected into the tumors. Tumor size, histopathological examination, CD8 and FOXP3 expression, the cytotoxicity of spleen T cell lymphocytes, and the secretion of Interferon-γ (IFN-γ) and Tumor necrosis factor- α (TNF-α) were examined.

RESULTS

The triple therapy used in this study resulted in the lowest tumor growth and the highest level of cytotoxic immunity. The Foxp3 levels in the tumor microenvironment and TNF-α secretion decreased compared to other control groups. Additionally, this group exhibited the lowest number of mitotic figures and the highest amount of tumor-infiltrating lymphocytes.

CONCLUSION

The combination of tumor vaccines with oncolytic viruses significantly improves treatment efficacy. Furthermore, inhibiting the PD-1/PD-L1 interaction during vaccination and also with virotherapy enhances immunovirotherapy by reducing immunosuppressive effects and stimulating the immune system, leading to improved therapeutic outcomes.

Oncolytic avian reovirus-sensitized tumor infiltrating CD8+ T cells triggering immunogenic apoptosis in gastric cancer

BACKGROUND

Gastric cancer (GC) is a leading malignant disease in numerous countries, including Taiwan with limited therapeutic options. Animal viruses including oncolytic avian reovirus (ARV) have the possibility to avoid pre-existing immunity in humans, while being safe and immunostimulatory. Here, we provide a novel insight into oncolytic ARV and UV-ARV-sensitized patient's peripheral blood mononuclear cells (P-PBMCs) and tumor infiltrating lymphocytes (TILs) killing primary GC (PGC) cells through the surface TLR3 and TRAIL/DR4/DR5 immunogenic apoptosis pathway.

METHODS

We conducted a comprehensive study to reveal whether ARV- or UV-inactivated ARV (UV-ARV)-modulated P-PBMCs or TILs killing ARV- and UV-ARV-sensitized AGS cells and PGC cells derived from clinical patients and to investigate the regulation of surface TLR3 receptor and upstream signaling pathways. Apoptosis analysis by flow cytometry and Western blot, suppression of signal pathway by specific inhibitors, in situ proximity ligation assay (PLA), time-resolved flurometry and lactate dehydrogenase (LDH) cytotoxicity assays, and an in vitro co-culture model were established to study the interplay between ARV- and UV-ARV-sensitized P-PBMCs and TILs to kill PGC cells and their upstream pathways.

RESULTS

Our results reveal that increased levels of DR4 and DR5 were observed in ARV and UV-ARV sensitized PGC cells through the TLR3/p38/p53 signaling pathway. Importantly, we found that the σC protein of ARV or UV-ARV interacted with surface TLR3 of CD8+ TILs, thereby triggering the TLR3/NF-κB/IFN-γ/TRAIL signaling pathway which induces immunogenic apoptosis of PGC cells. This study sheds further light on the molecular basis behind ARV oncolysis and facilitates the ARV or UV-ARV as a cancer therapeutic.

CONCLUSIONS

The study provides novel insights into ARV- or UV-ARV-sensitized P-PBMCs and CD8+ TILs to kill PGC cells through the immunogenic apoptosis pathway. We conclude that P-PBMCs can easily be obtained from GC patients and provide a rich source as TILs to kill PGC cells.

Oncolytic viruses in hematological malignancies: hijacking disease biology and fostering new promises for immune and cell-based therapies

The increased tropism for malignant cells of some viruses has been highlighted in recent studies, prompting their use as a strategy to modify the transcriptional profile of those cells, while sparing the healthy ones. Likewise, they have been recognized as players modulating microenvironmental immunity, namely through an increase in antigen-presenting, natural-killer, and T CD8+ cytotoxic cells by a cross-priming mechanism elicited by tumor-associated antigens. The immunomodulatory role of the oncolytic virus seems relevant in hematological malignancies, which may relapse as a result of a proliferative burst elicited by an external stimulus in progenitor or neoplastic stem cells. By reprogramming the host cells and the surrounding environment, the potential of virotherapy ranges from the promise to eradicate the minimal measurable disease (in acute leukemia, for example), to the ex vivo purging of malignant progenitor cells in the setting of autologous bone marrow transplantation. In this review, we analyze the recent advances in virotherapy in hematological malignancies, either when administered alone or together with chemotherapeutic agents or other immunomodulators.

Oncolytic viruses-modulated immunogenic cell death, apoptosis and autophagy linking to virotherapy and cancer immune response

Recent reports have revealed that oncolytic viruses (OVs) play a significant role in cancer therapy. The infection of OVs such as oncolytic vaccinia virus (OVV), vesicular stomatitis virus (VSV), parvovirus, mammalian reovirus (MRV), human adenovirus, Newcastle disease virus (NDV), herpes simplex virus (HSV), avian reovirus (ARV), Orf virus (ORFV), inactivated Sendai virus (ISV), enterovirus, and coxsackievirus offer unique opportunities in immunotherapy through diverse and dynamic pathways. This mini-review focuses on the mechanisms of OVs-mediated virotherapy and their effects on immunogenic cell death (ICD), apoptosis, autophagy and regulation of the immune system.

Cellular resistance to an oncolytic virus is driven by chronic activation of innate immunity

The emergence of cellular resistances to oncolytic viruses is an underexplored process that could compromise the efficacy of cancer virotherapy. Here, we isolated and characterized B16 mouse melanoma cells that evolved resistance to an oncolytic vesicular stomatitis virus (VSV-D51). RNA-seq revealed that resistance was associated to broad changes in gene expression, which typically involved chronic upregulation of interferon-stimulated genes. Innate immunity activation was maintained in the absence of the virus or other infection signals, and conferred cross-resistance to wild-type VSV and the unrelated Sindbis virus. Furthermore, we identified differentially expressed genes with no obvious role in antiviral immunity, such as Mnda, Psmb8 and Btn2a2, suggesting novel functions for these genes. Transcriptomic changes associated to VSV resistance were similar among B16 clones and in some clones derived from the mouse colon carcinoma cell line CT26, suggesting that oncolytic virus resistance involves certain conserved mechanisms and is therefore a potentially predictable process.

The application of oncolytic viruses in cancer therapy

Oncolytic therapy is a treatment method used to directly combat tumor cells by modifying the genes of naturally occurring low pathogenic viruses to form "rhizobia" virus. By taking the advantage of abnormal signal pathways in cancer cells, it selectively replicates in tumor cells leading to tumor cell lysis and death. At present, clinical studies widely employ biomolecular technology to transform oncolytic viruses to exert stronger oncolytic effects and reduce their adverse reactions. This review summarizes the current progresses and the molecular mechanism of oncolytic viruses towards tumor treatment and management.

Current strategies to circumvent the antiviral immunity to optimize cancer virotherapy

Cancer virotherapy is a paradigm-shifting treatment modality based on virus-mediated oncolysis and subsequent antitumor immune responses. Clinical trials of currently available virotherapies showed that robust antitumor immunity characterizes the remarkable and long-term responses observed in a subset of patients. These data suggest that future therapies should incorporate strategies to maximize the immunotherapeutic potential of oncolytic viruses. In this review, we highlight the recent evidence that the antiviral immunity of the patients may limit the immunotherapeutic potential of oncolytic viruses and summarize the most relevant approaches to strategically redirect the immune response away from the viruses and toward tumors to heighten the clinical impact of viro-immunotherapy platforms.