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Carcinoma cells metastasis to distant organs through blood vessels is a mainly leading cause of death in cancer patients.Hematogenous metastasis is a complex multistep process [1].The key step is that tumor cells invade vessel wall into interstitial space during blood-borne cancer metastasis.Matrix metalloproteinases facilitate tumor cell invasion through proteolysing the extracellular matrix (ECM).MMP-9 possesses the ability of degrading the gelatin, a component of ECM and the specific substrate of MMP-9, which facilitates tumor cell extravasation [2].