MMP9 and neoplasm: In contrast to MMP-2, which is constantly expressed in non-malignant cells and tumor cells, MMP-9 is strongly associated with the malignant progression of various cancers and is highly inducible in response to a variety of stimuli, including transforming growth factor beta (TGF-β), epidermal growth factor (EGF), phorbol 12-myristate 13-acetate (PMA), ultraviolet radiation, and oncogenes [6,7,8].