PDCD1 and melanoma: Interestingly, the blocking antibodies (ipilimumab and nivolumab) of co-suppressing molecules cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) in immune cells have emerged to be quite promising in treating immunity-associated malignancies such as melanoma.