PDCD1 and neoplasm: Tumor cells express programmed cell-death 1 ligand (PD-L1) and the cluster of differentiation 86 (CD86) protein binds to immune-checkpoint receptors programmed cell-death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) of CD8+ T-cell to inhibit host immune responses [17].