PDCD1 and cancer: The United States Food and Drug Administration has approved several immunotherapeutic agents for cancer treatment, such as cytotoxic T‐lymphocyte‐associated protein 4 (CTLA‐4) antibodies, programmed cell death 1 (PD‐1) inhibitors and programmed cell death 1 ligand 1 (PD‐L1) inhibitors.7, 8