MMP9 and osteosarcoma: In addition, a strong positive correlation between p-Axl and matrix metalloproteinase (MMP)-9 expression was confirmed in these osteosarcoma patients,66 and proteins of the MMP family are involved in the breakdown of extracellular matrix associated with metastasis.70 All these results implicate Gas6/Axl in osteosarcoma, and further basic and clinical studies are needed to investigate whether the inhibition of Gas6/Axl could lead to positive results.