CTLA4 and neoplasm: All of the above immune checkpoint molecules, including cytotoxic T lymphocyte antigen 4 (CTLA-4) or programmed cell death-1 (PD-1) and its ligands (PD-L1 and PD-L2) are known to be expressed on tumor-infiltrating lymphocytes (TILs) as well as some tumor cells (6).