PDCD1 and cancer: Recently, cytotoxic T lymphocyte-associated protein-4 (CTLA-4, CD152), programmed death-1 (PD-1, CD279) and its ligand PD-L1 (CD274, B7-H1), lymphocyte activating gene-3 (LAG-3, CD233), T cell immunoglobulin and mucin-domain containing-3 (TIM-3, CD366) have been identified as crucial targets in cancer treatment (47).