The tumor microenvironment (TME) restricts antitumor CD8+ T-cell function and immunotherapy responses. Cancer cells compromise the metabolic fitness of CD8+ T cells within the TME, but the mechanisms are largely unknown. Here we demonstrate that one-carbon (1C) metabolism is enhanced in T cells in an antigen-specific manner. Therapeutic supplementation of 1C metabolism using formate enhances CD8+ T-cell fitness and antitumor efficacy of PD-1 blockade in B16-OVA tumors. Formate supplementation drives transcriptional alterations in CD8+ T-cell metabolism and increases gene signatures for cellular proliferation and activation. Combined formate and anti–PD-1 therapy increases tumor-infiltrating CD8+ T cells, which are essential for enhanced tumor control. Our data demonstrate that formate provides metabolic support to CD8+ T cells reinvigorated by anti–PD-1 to overcome a metabolic vulnerability in 1C metabolism in the TME to further improve T-cell function.


This study identifies that deficiencies in 1C metabolism limit the efficacy of PD-1 blockade in B16-OVA tumors. Supplementing 1C metabolism with formate during anti–PD-1 therapy enhances CD8+ T-cell fitness in the TME and CD8+ T-cell–mediated tumor clearance. These findings demonstrate that formate supplementation can enhance exhausted CD8+ T-cell function.

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