Abstract 6690: Gut microbial metabolite butyrate facilitates antitumor efficacy of telomerase-specific oncolytic adenovirus via MHC-I and cGAS-STING pathway activation

Abstract Introduction: Gut microbiota has been reported to have a potential to modulate tumor sensitivity to chemo- or immuno-therapies although the underlying mechanism is still unclear. Oncolytic virotherapy is a promising antitumor treatment that selectively induces oncolytic cell death in tumor cells. We have previously developed OBP-702, a telomerase-specific oncolytic adenovirus armed with the p53 tumor suppressor gene, highlighting potent antitumor effects across different cancer types. To explore the potential of gut microbial metabolites, particularly butyrate, in augmenting the antitumor efficacy of oncolytic virotherapy. Materials and Methods: We assessed the synergistic antitumor effects of butyrate and OBP-702 in cytotoxic assay using two human (HCT116, SW48) and two murine (CT26, MC38) colorectal cancer cell lines in vitro, and the in vivo antitumor effects in subcutaneous tumor models using HCT116 and CT26. We explored underlying mechanisms of the synergistic effects, focusing on the influences of butylate on viral infectivity via Coxsackie-Adenovirus Receptor (CAR) and integrins, and antitumor immunity via tumor MHC-I expression and CD8-positive T cells. Results: Butyrate and OBP-702 showed potent synergistic effects in all four cell lines in vitro, and the combination suppressed tumor growth significantly in HCT116 and CT26 subcutaneous tumors compared to each monotherapy. These synergistic effects were produced by butyrate increasing the potential of OBP-702 by enhancing viral infection efficiency via upregulating expressions of CAR and integrins on tumor cells. Butyrate also increased MHC-I expression on tumor cells by activating the cGAS-STING pathway, leading to increased CXCL10 expression, which led to activation of antitumor immunity through recruitment of CD8-positive T cells in tumor tissues. The synergistic effects of butyrate and OBP-702 were proved in an orthotopic colorectal tumor model with liver metastases using CT26 cells expressing luciferase, in which this combination not only reduced tumor growth, but also improved survival by activating antitumor immunity via CD8-positive T cells. Conclusion: Butyrate and OBP-702 showed synergistic antitumor effects via activation of systemic antitumor immunity in addition to direct effects of butyrate on viral cytotoxic potential, which provides valuable insights into the development of innovative cancer treatment strategies. Citation Format: Masaki Sakamoto. Gut microbial metabolite butyrate facilitates antitumor efficacy of telomerase-specific oncolytic adenovirus via MHC-I and cGAS-STING pathway activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6690.