CTLA4 and cancer: Cancer immunotherapy using monoclonal antibodies against the immune checkpoint proteins, including PD-1 (and its ligand PD-L1) and CTLA-4, has demonstrated unprecedented therapeutic benefits and brought out a major breakthrough in oncology, helping to realize long-term durable responses in a subset of patients with multiple types of advanced cancers [30,31,32,33,34,35,36,37,38].