Immunotherapy is an important treatment for gastric cancer; immune checkpoint inhibitors (ICIs) include cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), programmed death 1 (PD-1), and programmed death ligand 1 (PD-L1), and more progress has been made in the clinical research of advanced gastric cancer. The gene discussed is CTLA4; the disease is gastric cancer.