CD4 and neoplasm: TGF-β signaling has dual functions in cancer: (i) as a tumor suppressor to mediate growth arrest and apoptosis in cancer cells (antitumor)52, 53, and (ii) as a potent immunosuppressive agent to suppress both innate and adaptive immune responses comprising of CD4+ effector T cells (Th1 and Th2), CD8+ cytotoxic T cells (CTLs), NK cells and antigen presenting cells, as well as to stimulate the generation of regulatory T cells which inhibit effector T cell functions (protumor)54.