Antibiotics inhibit the clinical benefits of ICIs in advanced cancer patients, and transplantation of fecal microbiota (FMT) from cancer patients who respond to ICIs into GF or antibiotic-treated mice can improve the antitumor effect of PD-1 blockade, whereas FMT from nonresponders cannot improve the efficacy of PD-1 (255). Here, PDCD1 is linked to cancer.