PDCD1 and gastric cancer: Multiple ICIs, including antibodies that target programmed cell death protein 1 (PD-1), programmed death-ligand 1 (PD-L1), or cytotoxic T lymphocyte antigen 4 (CTLA4), have been approved for the treatment of a variety of advanced malignancies, including non-small cell lung cancer (NSCLC) (1), skin cutaneous melanoma (SKCM) (2), gastric cancer (3), and bladder urothelial carcinoma (BLCA) (4).