Indeed, overexpression of the Smad inhibitor Smad7, or the systemic injection of SD208, an inhibitor of TβRI kinase, inhibits the TGF-β signaling cascade and thus reduces the expression of TGF-β-regulated metastatic genes and the ability of TGF-β to stimulate migration and invasion of osteosarcoma cells [11]. This evidence concerns the gene SMAD7 and osteosarcoma.