TGFB1 and neoplasm: These include the inefficient processing and presentation of tumor antigens, the upregulation of negative costimulatory ligands that induce T cell anergy and expand the regulatory cell populations, the production of immunosuppressive molecules, such as Fas-L, TGF-β, CTLA-4, and PD-1/PD-L1, the increased expression of the immunosuppressive enzyme indoleamine 2,3-dioxygenase, the downregulation of MHC-I molecules on the cell surface, and the impairment of antigen presentation [21].