1253 Exercise-induced microbial folate metabolite enhances CD8 T cell antitumor immunity and promotes immunotherapy efficacy

Background

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 antitumor effects remain obscure. Here, we show for the first time that exercise-induced changes to the microbiota are a key mechanism by which exercise promotes antitumor immunity via a previously undefined mechanism.

Methods

In this study, we use a mouse treadmill running model to define the mechanisms by which exercise enhances tumor immunity and ICI efficacy in a translationally relevant BRAF^v600E melanoma tumor model which is ICI resistant.

Results

We first show that exercise-mediated tumor suppression relies upon adaptive immunity, specifically CD8 T cells, and an intact specific-pathogen-free microbiota in our model. Strikingly, we show that the compositionally distinct exercised microbiota is sufficient to confer tumor suppression, but must be metabolically active to do so, suggesting a key role for metabolites produced by the exercised microbiota. Accordingly, we find that exercise-microbiota produced metabolites are sufficient to restrain tumor growth in vivo and act directly on CD8 T cells to promote antitumor effector function in vitro. Through targeted and untargeted metabolomics approaches, we identify that exercise changes metabolic output of the microbiota by increasing bacterial folate (vitamin B9) metabolism. Accordingly, formate, a short-chain fatty acid and known intermediate of folate metabolism, is enriched in cecum contents and serum of exercised mice. Excitingly, we identify that the bacterial enzyme pyruvate formate lyase, required for bacterial formate synthesis, is significantly enriched in feces of immunotherapy responder patients across eight different study cohorts. In our model, we find that oral administration of formate alone is sufficient to restrain tumor growth, promote tumor antigen specific CD8 T cell effector function, and enhance immunotherapy efficacy in in a manner dependent on Nuclear Factor Erythroid 2-related factor 2 (Nrf2) signaling. Lastly, we demonstrate that Nrf2 signaling is required for the exercise-mediated antitumor effect in vivo.

Conclusions

Through this study, we have unveiled a previously unrecognized mechanism in which exercise, by modulating the production of a microbiota metabolite, improves ICI efficacy in melanoma. Our study will motivate a new line of investigations as it provides a rational mechanistic basis to design novel exercise, precision dietary, and microbial metabolite combinatorial therapeutic strategies to determine the clinical antitumor effect of microbial Nrf2 agonists, such as formate, in immunotherapy-resistant cancer patients.

Ethics Approval

This study was performed in accordance with the policies set forth by the University of Pittsburgh Institutional Animal Care and Use Committee.