CTLA4 and neoplasm: VEGF contributes to the pro-tumor immunosuppressive microenvironment by inhibiting dendritic cell maturation, accumulating myeloid-derived suppressor cells, and inducing T regulatory cells (T reg), as well as increasing the expression of inhibitory receptors on cytotoxic CD8+ T cells, including programmed cell death protein 1 (PD-1), cytotoxic T lymphocyte associated protein 4 (CTLA-4), T cell immunoglobin and mucin domain containing protein 3 (TIM-3), and lymphocyte activation gene 3 (LAG-3) [28,29].