Role of matrix metalloproteinase-9 in transforming growth factor-β1-induced epithelial-mesenchymal transition in esophageal squamous cell carcinoma.

Epithelial-mesenchymal transition (EMT) is thought to be a crucial event during the early metastasis of tumor cells. Transforming growth factor (TGF)-β1 is involved in the process of EMT in a variety of human malignancies. Matrix metalloproteinase (MMP)-9 plays an important role in tumor invasion and metastasis, and its expression is regulated by various growth factors, including TGF-β1, in different cell types.