Matrix Metalloproteinase-9 (MMP-9; also known as gelatinase B), a zinc-dependent endopeptidase belonging to the MMP family. MMP-9 is secreted by various cell types including neutrophils, macrophages, and tumor cells. Its primary physiological and pathological function is the degradation of extracellular matrix (ECM) components, such as collagen IV and gelatin. In cancer, MMP-9 plays a multifaceted role in tumor progression, angiogenesis, invasion, and metastasis by remodeling the tissue stroma to facilitate cancer cell spread. In inflammation, it contributes to tissue damage and immune cell recruitment.