Finally, we showed that Smad7, SD-208, and halofuginone strongly affect the ability of the primary bone tumor to develop lung metastases, mainly by their ability to block the capacity of TGF-β1 to stimulate osteosarcoma migration and invasion, as previously described in the context of melanoma bone metastasis [93,94,95]. This evidence concerns the gene TGFB1 and osteosarcoma.