CTLA4 and neoplasm: In the TME, tumor cells produce VEGF-A, which is able to increase programmed cell death 1 (PD-1), cytotoxic T-lymphocyte associated protein 4 (CTLA-4), and T cell immunoglobulin and mucin-domain containing-3 (TIM-3) on the CD8+ T cell surface, inducing T cell exhaustion [72], participating in the establishment of an immunosuppressive microenvironment.