TGFB1 and osteosarcoma: The biochemical blockade of MAPK pathway abolishes TGF-β induction of MMP13 in human breast cancer cell lines [33], and the inhibition of the MAPK pathways reduces TGFB1-stimulated MMP13 expression in the rat osteosarcoma cell line (UMR 106-01) [35], favouring the SMAD-independent pathway for enhanced MMP13 expression in OA cartilage.