Korean researchers have found that an ingestible (oral) anticancer reovirus effectively induces an immune response against cancer by reconstituting the gut microbiome (microbial system).

Oncolytic viruses are anticancer therapeutics that selectively infect and destroy cancer cells to trigger an anticancer immune response.

One of them, reoviruses, has been administered via injection or intravenous infusion in preclinical and clinical trials for various cancers. However, satisfactory treatment effects in cancer patients have been difficult to achieve due to limitations such as challenges in administering viral drugs and their inactivation in the blood.

CHA University Bundang Medical Center said Wednesday that a research team led by Professors Kim Chan and Chon Hong-jae and Research Professor Lee Won-suk of the Department of Hematology-Oncology, in collaboration with a team from the University of Ottawa, Canada, found that an oral reovirus effectively induces an immune response against cancer.

They also confirmed that oral administration of the reovirus was over three times as effective as direct tumor administration.

Notably, the researchers found that orally administered oncolytic reovirus interacts with the immune system in the Peyer's patch at the end of the small intestine and increases the number of immunoglobulin A (IgA) antibody-secreting cells in the small intestinal mucosa through specialized intestinal blood vessels that express mucoprotein cell adhesion molecules. As a result, the IgA antibodies secreted into the intestine reconstitute the gut microbiome and enhance the antitumor immune response within the tumor.

Additionally, the number of CD8 T cells, killer cells that attack colorectal cancer, increased by more than two times compared to the control group after treatment with the antireovirus. Furthermore, the combination treatment of oral anticancer reovirus with PD-1 and CTLA-4 immune checkpoint inhibitors in a mouse model of colon cancer induced complete remission of the tumor and induced long-term anticancer immunity.

“This study is significant in that it shows that oral oncolytic reovirus is an effective and potent anticancer immunotherapy strategy, suggesting the possibility of a new cancer treatment,” Professor Kim said. “Oral oncolytic virus administration is expected to be particularly effective for digestive cancers, including colon and liver cancer.”

The findings were published in the prestigious journal Nature Communications (IF=14.7).