Anti-tumor efficacy of oncolytic reovirus against gastrointestinal stromal tumor cells

Reovirus combined with a STING agonist enhances anti-tumor immunity in a mouse model of colorectal cancer

Reovirus, a naturally occurring oncolytic virus, initiates the lysis of tumor cells while simultaneously releasing tumor antigens or proapoptotic cytokines in the tumor microenvironment to augment anticancer immunity. However, reovirus has developed a strategy to evade antiviral immunity via its inhibitory effect on interferon production, which negatively affects the induction of antitumor immune responses. The mammalian adaptor protein Stimulator of Interferon Genes (STING) was identified as a key regulator that orchestrates immune responses by sensing cytosolic DNA derived from pathogens or tumors, resulting in the production of type I interferon. Recent studies reported the role of STING in innate immune responses to RNA viruses leading to the restriction of RNA virus replication. In the current study, we found that reovirus had a reciprocal reaction with a STING agonist regarding type I interferon responses in vitro; however, we found that the combination of reovirus and STING agonist enhanced anti-tumor immunity by enhancing cytotoxic T cell trafficking into tumors, leading to significant tumor regression and survival benefit in a syngeneic colorectal cancer model. Our data indicate the combination of reovirus and a STING agonist to enhance inflammation in the tumor microenvironment might be a strategy to improve oncolytic reovirus immunotherapy.

The oncolytic efficacy and safety of avian reovirus and its dynamic distribution in infected mice

Primary liver cancer is a major public health challenge that ranks as the third most common cause of cancer worldwide despite therapeutic improvement. Reovirus has been emerging as a potential anti-cancer agent and is undergoing multiple clinical trials, and it is reported that reovirus can preferentially cause the cell death of a variety of cancers in a manner of apoptosis. As few studies have reported the efficacy of oncolytic activity and safety profile of avian reovirus, in our study, LDH assay, MTT assay, DAPI staining, and flow cytometry assay were performed to demonstrate the oncolytic effects of avian reovirus against the HepG2 cells, and quantitative real-time PCR (qRT-PCR) and animal experiments were conducted to investigate the dynamic distribution of avian reovirus in infected mice and then illustrate the safety and tissue tropism of avian reovirus. LDH assay, DAPI staining, and flow cytometry assay confirmed the efficacy of the oncotherapeutic effects of avian reovirus, and MTT assay has indicated that avian reovirus suppressed the proliferation of HepG2 cells and decreased their viability significantly. qRT-PCR revealed the dynamic distribution of avian reovirus in infected mice that avian reovirus might replicate better and have more powerful oncolytic activity in liver, kidney, and spleen tissues. Furthermore, histopathological examination clearly supported that avian reovirus appeared non-pathogenic to the normal host, so our study may provide the new insights and rationale for the new strategy of removing liver cancer.

Impact statement

We demonstrated the efficacy of oncolytic activity of avian reovirus (ARV) by LDH assay, MTT assay, DAPI staining, and flow cytometry assay, and also investigated the dynamic distribution of ARV in infected mice and then illustrated the safety and tissue tropism of ARV by quantitative real-time PCR (qRT-PCR) and animal experiments. Collectively, our study may provide the new insights and rationale for the new strategy of removing liver cancer.