As positive controls, SB431542 and LDN193189 inhibitors completely abolished TGF-β1-induced SMAD3 phosphorylation and BMP-6-mediated activation of SMAD1/5/9, respectively, in both SW1353 and Hs 819.T chondrosarcoma cell lines (Fig. 4f, lanes 4–7 and 11–14). Here, SMAD1 is linked to chondrosarcoma.