The immunosuppressive network is also mediated through the immune checkpoint (IC) molecule programmed cell death ligand 1 (PD-L1), which is expressed in tumor cells, and the immune response by CTLs is down-regulated via programmed cell death 1 (PD-1) by PD-L1 in tumor cells or cytotoxic T lymphocyte–associated antigen 4 in antigen-presenting cells [28]. This evidence concerns the gene PDCD1 and neoplasm.