TGF-β is a multipotent growth factor family: the TGF-β superfamily can exert multiple functions in a cell/tissue-specific manner. Depending upon the isoforms (1, 2, 3, and the BMPs and activins), the TGF-β superfamily can promote cell proliferation, differentiation, cell cycle arrest, apoptosis and/or transformation in a time- and system-dependent manner. However, whether all these roles are directly or indirectly related to the EMT or not still remains to be investigated.