PDCD1 and neoplasm: In addition, upregulated expression of the immune checkpoints cytotoxic T lymphocyte-associated antigen 4 (CTLA4), programmed cell-death-1 (PD-1), programmed cell-death ligand-1 (PD-L1), lymphocyte activation gene 3 (LAG3) and indoleamine 2,3-dioxygenase (IDO) was noted in MSI tumours [34•].