With respect to immune checkpoints associated with tumor cell immune evasion, such as CTLA-4, PD-1, PD-L1, T-cell immunoglobulin and ITIM domain (TIGIT) (35), lymphocyte activation gene 3 (LAG-3) (36), and T-cell immunoglobulin-3 (TIM-3) (36), these inhibitory receptors/ligands inhibit the antitumor immune response by altering their expression levels (37) (Figure 1). This evidence concerns the gene PDCD1 and neoplasm.