CTLA4 and cancer: The launch of immune checkpoint inhibitors (ICPIs) including the first cytotoxic T-lymphocyte antigen 4 (CTLA-4) blocking antibody ipilimumab in 2011[3] and programmed death receptor 1 or ligand 1 (PD-1/PD-L1) blocking antibodies pembrolizumab and nivolumab in 2014[4, 5] represents the substantive progress in the field and boosts immunotherapy as a new standard therapy for many cancer types.