PDCD1 and colorectal carcinoma: For example, doxorubicin has been demonstrated to cooperate with ICIs specific for PD-L1, programmed cell death 1 (PDCD1, best known as PD-1), cytotoxic T lymphocyte-associated protein 4 (CTLA4) or CD96 in immunocompetent mice bearing subcutaneous 4T1 mammary carcinomas [24] or CT26 colorectal carcinomas (CRCs) [25, 26].