PDCD1 and hepatocellular carcinoma: We performed a research on Pubmed/Medline, Cochrane library and Scopus using the following keywords “HCC” OR “hepatocellular carcinoma” OR “liver cancer” AND “PD-L1” OR “TMB” OR “MSI” OR “MMR” OR “DDR” OR “gut microbiome” OR “predictive biomarkers” OR “predictors of response” AND “pembrolizumab” OR “PD-L1” OR “immune checkpoint inhibitors” OR “immunotherapy” OR “PD-1 inhibitor” OR “atezolizumab” OR “durvalumab” OR “tremelimumab” OR “nivolumab”.