TGFB1 and cancer: Immunosuppressive mechanisms regulated by Tregs leading to immunological tolerance and ignorance of cancer are as follows: 1) releasing soluble or membranous repressive cytokines such as interleukin-10 (IL-10), interleukin-35 (IL-35) and transforming growth factor-β (TGF-β), which can kill effector T cells (18).