Importantly, we showed that Smad7 overexpression in osteosarcoma cells or the treatment of mice with the TβRI inhibitor SD-208 inhibits the development of lung metastases demonstrating that the inhibition of TGF-β/Smad signaling pathway may represent a promising therapeutic strategy against tumor progression of osteosarcoma specifically against the development of lung metastases [11]. Here, SMAD7 is linked to osteosarcoma.