CD274 and neoplasm: PD-1 (also known as CD279) is expressed on activated T cells and engages with either of its two ligands (PD-L1, also known as CD274/B7-H1 or PD-L2, also known as CD273/B7-DC) on tumor cells or other immune cells in tumor microenvironment (TME), leading to T cell dysfunction and tumor immune evasion6–8.