PDCD1 and gastric cancer: Immune checkpoint inhibitors (ICIs), which inhibit coinhibitory molecules such as cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), programmed cell death protein-1 (PD-1), and the related programmed death-ligand 1 (PD-L1) [6,7,8], often administered to gastric cancer patients include pembrolizumab (anti-PD-1 monoclonal antibody) and cadonilimab (anti-PD-1/CTLA-4 bispecific antibody), etc. Clinical data have revealed that nivolumab combined with platinum-based or/and fluoropyrimidine-based chemotherapy can effectively improve the survival of AGC patients [9,10].