MMP9 and osteosarcoma: In addition to a TGF-β1 inhibitory element at −474 bp and 4 potential AP-1 binding elements, the functional AP-1 site at position −79 is essential for basal and jun/Fos induced expression in HT-1080 and osteosarcoma cells [119], three functional PEA3/Ets binding sites localise between −599 and −531 are also involved in basal gelatinase B/MMP-9 transcription [119,120].