This study revealed that the microbiome composition might have an impact on anti-PD-1 immunotherapy, patients with favorable gut microbiome like Ruminococcaceae or Faecalibacterium might have an enhancing antitumor immune response, and this antitumor immune response was related to more antigen presentation in the periphery and improved effector T cell function in the tumor microenvironment. The gene discussed is PDCD1; the disease is neoplasm.