CTLA4 and neoplasm: Numerous studies discovered several negative costimulatory molecules such as the programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) axis, lymphocyte activation gene-3 (LAG3), cytotoxic T lymphocyte associated antigen-4 (CTLA4), T-cell immunoglobulin and mucin domain protein 3 (TIM3), which participate to inhibit T cells and enable different tumor cells to singly or jointly escape (3, 12–14).