The recent development of immune checkpoint inhibitors (ICIs) [mainly including anti-programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) and anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4)] has revolutionized treatment of all cancer types, resulting in durable responses and acceptable toxicities [2]. The gene discussed is CTLA4; the disease is cancer.