MMP9 and cancer: Tumor metastasis is a multistep process by which cancer cells disseminate long distances from the primary site to form secondary tumors [73] and is regulated by proteins associated with metastasis, such as vascular endothelial growth factor (VEGF), urokinase plasminogen activator (uPA), matrix metalloproteinase 2 (MMP-2), and matrix metalloproteinase 9 (MMP-9) [74].