Formate Supplementation Enhances Antitumor CD8+ T-cell Fitness and Efficacy of PD-1 Blockade

Metabolic support, in the form of formate supplementation, combined with anti-PD-1 improves antitumor CD8+ T-cell fitness and tumor control, revealing a strategy that can be used to extend the benefits of anti-PD-1 therapy. Abstract 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. Significance: 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. See related commentary by Lin et al., p. 2507. This article is featured in Selected Articles from This Issue, p. 2489