PDCD1 and neoplasm: Nevertheless, the expression of ICM leads to immune escape of tumor cells and some of these ICMs (particularly the cytotoxic T lymphocyte antigen (Ag)-4 (CTLA-4), programmed cell death-1 (PD-1) and its ligand (PD-L1)) are now being blocked by monoclonal antibodies (mAbs) [353–355].