Recently, the advances of immunotherapy have revolutionized cancer therapy and reinvigorated research in cancer immunology.[7] Immune checkpoint inhibitors (ICIs), such as anti‐PD‐1 (anti‐Programmed cell death 1),[8, 9] anti‐PD‐L1 (anti‐programmed death ligand 1)[10] and anti‐CTLA‐4 (anti‐cytotoxic T lymphocyte‐associated protein 4),[8, 10] have demonstrated durable clinical responses across multiple types of cancer. Here, PDCD1 is linked to cancer.