CTLA4 and cancer: Advances in the understanding of anti-cancer immunity has resulted in the successful use of immunotherapies against a number of cancers with checkpoint inhibitor antibodies such as the anti-CTLA-4 antibody Ipilumimab,(YervoyTM) and anti-PD1 antibodies Pembrolizumab, (KetrudaTM) and Nivolumab, (OpdivoTM) becoming FDA approved for a number of cancers (1).