One of the most successful approaches to mount CD8+ T cell-mediated anti-tumor immune reaction is the administration of checkpoint inhibitors, i.e., blocking antibodies against inhibitory checkpoint receptors (e.g., PD-1 and CTLA4) or ligands (e.g., PD-L1) (Farkona et al., 2016; Khalil et al., 2016). This evidence concerns the gene PDCD1 and neoplasm.