Lately, a series of clinical trials with fully humanized monoclonal antibodies that are capable of blocking the inhibitory signaling pathways mediated through the inhibitory T cell surface receptors, CTLA-4 and PD-1—usually referred to as immune checkpoint inhibition (ICI)—and immunotherapy with a patient’s own T cells retooled to express a set of chimeric antigen receptor (CAR) exhibiting antibody specificities have shown durable complete remissions as well as prolongation of survival of patients with certain types of cancer [4, 5] and have emerged as remarkable success stories. This evidence concerns the gene CTLA4 and cancer.