CTLA4 and neoplasm: Tregs and MDSCs express cytotoxic T lymphocyte-associated protein 4 (CTLA-4) and PDL1 and produce immunosuppressive cytokines (IL-10 and transforming growth factor beta (TGF-β)) that inhibit the proliferation, activation and effector function of CTLs and NK cells, while M2 macrophages and N2 neutrophils secrete pro-angiogenic factors (vascular endothelial growth factor (VEGF), TGF-β, prostaglandin E2 (PGE2)), which induce the generation of new blood vessels, enabling enhanced tumor growth and progression [1,3,6].