When paired with PD-L1, PD-1 blocked the conduction of molecules downstream of the TCR signaling pathway by phosphorylating intracellular tyrosine residues, which inhibited cytokine secretion and effector T-cell proliferation and function (59).49 Notably, PD-1 not only induces leukemia-specific CTL-mediated cytolysis but also interferes with IFN-γ-mediated cytotoxic effects through STAT3- and caspase-7-dependent pathways (60). This evidence concerns the gene PDCD1 and leukemia.