SMAD7 and melanoma: Since IFN-γ also induces the expression of SMAD-7, an antagonistic SMAD, which prevents the interaction of SMAD-3 with the TGF-β receptor [33], therefore, we guess the increased SMAD-7 in tumor cells may bind to the TGF-β-receptor complex, preventing its interaction with, and phosphorylation of SMAD-3 [36,37], which may result in inhibition of melanoma growth and metastasis in mice.