PDCD1 and cancer: Immunotherapy is changing the prognosis of some cancer patients through the use of monoclonal antibodies that block immune checkpoints (immune checkpoint blockade, ICKB), such as cytotoxic T lymphocyte antigen-4 (CTLA-4/CD28) and/or programmed cell death 1 (PD-1)/PD-1 ligand (PD-L1) axes.