PDCD1 and cancer: Immunotherapy targeting cytotoxic T lymphocyte antigen 4 (CTLA4), programmed cell death-ligand 1 (PD-L1), or programmed cell death 1 (PD-1) have become effective and frequently-used ways in the treatment of various cancers (Herbst et al., 2019; Pires da Silva, 2021; Sacco, 2021).