In cancer, despite expression of MHC I-associated molecules with “foreign cancer” antigens, PD-L1 found on these cells continue to suppress T-cells through PD-L1: PD-1 interactions, and some tumor cells may even increase the expression of PD-L1 on the cell surface to enhance this immune suppression (Friss et al., 1989). This evidence concerns the gene PDCD1 and neoplasm.