In HCC patients who responded to anti-programmed cell death protein 1 (PD-1) immunotherapy, Bacteroidetes remained the most common gut bacteria with increased levels of Ruminococcacae and Akkermansiamuciniphila after treatment which is in contrast to patients who did not respond to anti-PD-1 therapy and had increasing levels of Proteobacteria after treatment, which became the most common taxon by the 12th week after treatment [3,27]. The gene discussed is PDCD1; the disease is hepatocellular carcinoma.