PDCD1 and cancer: Programmed death-ligand 1 (PD-L1) is a type 1 transmembrane protein encoded by the human CD274 gene that is overexpressed in some types of cancer (Salmaninejad et al., 2019), and PD-1 is an inhibitory receptor encoded by the PDCD1 gene that is located on the surface of all T cells (LaFleur et al., 2018).