PDCD1 and neoplasm: ICIs, including anti-cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), anti-programmed cell death protein-1 (PD-1), and anti-PD-ligand 1 (PD-L1), have shown higher efficacy against some solid tumors by clearing the inhibitory pathways that block effective anti-tumor T-cell responses [3–5] and are a recent promising cancer treatment.