CTLA4 and cancer: Monoclonal antibodies specific for cytotoxic T lymphocyte-associated antigen 4 (CTLA4) are a form of experimental immunotherapy for treatment of patients with advanced cancers, including melanoma, prostate cancer, renal cell carcinoma, non-Hodgkin's lymphoma, colorectal carcinoma, non-small lung breast cancer, and pancreatic cancer [5].