CTLA4 and cancer: A fascinating field is that of anti-tumor immunotherapy, based on the understanding that tumor cells activate immune checkpoints such as molecular programmed death receptor-1 (PD-1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) signaling pathways to inhibit T lymphocyte activation and thus escape from immune surveillance, known as “immune brake.” Checkpoint inhibitors (CPIs) reactivate T lymphocytes to recognize cancer cells by blocking CTLA-4 or PD-1, and are therefore effective in numerous types of cancer.