PDCD1 and cancer: Notably, the expression of immune checkpoint genes, including programmed cell death protein 1 (PD-1), programmed cell death ligand 1 (PD-L1), and Cytotoxic T-lymphocyte antigen number 4 (CTLA-4), was significantly lower in tumors with a high CHP score in nearly all cancer types (i.e., in 25, 27 or 28 of 33, respectively) (Figure 2E), as was the CTL score and the IFN-γ signature (Figure 2F) (Supplementary Table 5).