Although we have not observed an effect of Smad7 on the ability of TGF-β to stimulate the MAPK pathway in osteosarcoma cells (suggesting a crucial role of the TGF-β/Smad cascade in osteosarcoma progression), the role of TGF-β/MAPK pathways cannot be ruled out. This evidence concerns the gene TGFB1 and osteosarcoma.