PDCD1 and cancer: Inhibitors of programmed cell death protein 1 (PD-1) and its associated ligand (PD-L1) as medicines of immunotherapy, the most promising treatment for cancers (Tang J, 2018; Cancer Research Institute, 2022), have been used for non-small-cell lung cancer (Brahmer et al., 2015; Jia et al., 2018; Gao et al., 2019), Hodgkin’s lymphoma (Ansell et al., 2015; Jia et al., 2018; Gao et al., 2019), and others in recent years.