PDCD1 and cancer: In recent years, the advent of immunotherapies, including immune checkpoint inhibitors (ICIs), has brought new hope to cancer patients, such as anti-programmed cell death 1 (PD-1)/L1 antibodies, anticytotoxic T lymphocyte-associated antigen-4 (CTLA-4) antibodies, and anti-lymphocyte-activating gene-3 (LAG3) antibodies (4–6).