There are two studies that highlight the key role of the intestinal microbiota in mediating tumor response to immune checkpoint inhibitors: (1) The antitumor efficacy of CTLA-4 antibody depended on the immunostimulatory effect of intestinal microbiota, in which distinct bacterial species could promote the maturation of intratumoral dendritic cells and induced interleukin-12-dependent Th1 immune response14. The gene discussed is CTLA4; the disease is neoplasm.