Abstract 1175: Exercise-induced microbial vitamin B9 metabolite drives CD8 T cell antitumor immunity and promotes ICI efficacy in preclinical melanoma

Abstract A sedentary lifestyle significantly increases the risk of cancer. In contrast, exercise has been associated with enhanced antitumor immunity and improved immune checkpoint inhibitor (ICI) efficacy in cancers like melanoma. However, the mechanisms through which exercise mediates this antitumor effect remain obscure. Here, we demonstrate for the first time that exercise-induced changes to the microbiota are a critical mechanism by which exercise enhances antitumor immunity through a previously unrecognized pathway. First, we show exercise-mediated tumor restraint depends on both adaptive immunity, specifically CD8 T cells, and on the gut microbiota. We found that the compositionally distinct exercised microbiota is sufficient to confer tumor suppression and enhance Tc1 effector function. Through untargeted metabolomics coupled with a machine learning approach, we reveal that exercise promotes microbial vitamin B9 metabolism, leading to enrichment of microbial vitamin B9 metabolite formate. We demonstrate that formate directly enhances Tc1 effector function in vitro, promotes tumor antigen-specific Tc1 immunity, and improves ICI efficacy in vivo. We found that transcription factor Nuclear Factor Erythroid 2-related factor 2 (Nrf2) is required for formate-mediated enhancement of Tc1 function in vitro and the exercise-mediated antitumor effect in vivo. Translationally relevant, we found that the enzymatic ability of microbes to produce formate is linked with human ICI response in melanoma. Additionally, we show that the high-formate-producing healthy human microbiota is superior in its ability to restrain tumor growth and enhance Tc1 effector function when compared to a low-formate-producing healthy human microbiota or the native murine microbiota in a preclinical melanoma model. Through this study, we unveil a previously unrecognized mechanism in which exercise, by modulating the production of a microbiota metabolite, promotes antitumor Tc1 immunity and ICI efficacy in melanoma. This work will unleash multiple new avenues of investigation, as the impact of the exercised microbiota on host immunity is currently unexplored. We believe that this work will provide a rational mechanistic basis to design novel precision dietary and microbial therapeutics that will help tune host immunity in cancer and other immune conditions, with the ultimate goal of reproducing exercise-associated benefits for sedentary patients. Citation Format: Catherine M. Phelps, Colin Laughlin, Yue Zhang, Surya Pandey, Nate Willis, Aaron Rosen, Jake Shapira, Alex C. McPherson, Amanda Lee, Tingting Duan, Daphne Rodriguez Jimenez, Simran K. Randhawa, Lee Hedden, Karl-Heinz Wagner, Sebastien Winter, Jishnu Das, Joeseph F. Pierre, Giorgio Trinchieri, Marlies Meisel. Exercise-induced microbial vitamin B9 metabolite drives CD8 T cell antitumor immunity and promotes ICI efficacy in preclinical melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1175.