PDCD1 and cancer: Recent study also demonstrated that in humans, the oxaliplatin responder cancer patients exhibited a higher amount of serum butyrate than did non-responders, which could also increase ID2 expression and function of human CD8+ T cells in the absence of anti-PD-1 therapy.26 Consistent with previous studies suggesting that butyrate regulates CD8+ T cell antitumor immunity,26,27 we showed that the microbial metabolite butyrate promotes anti-PD-1 immunotherapy efficacy through CD8+ T cell-dependent antitumor immunity.