CTLA4 and cancer: Most recently, immunotherapy specific to malignancies has been such an exciting breakthrough that Drs. James P. Allison and Tasuku Honjo have received the 2018 Nobel Prize in Physiology or Medicine for their contributions to the field of cancer immunotherapy and identification of the immune checkpoint proteins [e.g., programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1), cytotoxic T lymphocyte associated antigen-4 (CTLA-4)] that usually act as a brake on the immune system.