Xu et al investigated transforming growth factor β1 and hepatocyte growth factor (HGF) protein secretion by esophageal squamous epithelial cells and stromal fibroblasts in esophageal carcinogenesis using immunohistochemical assay.[47] Results showed that the expression levels of alpha-smooth muscle actin, transforming growth factor β1, and HGF increased significantly in the order of normal, LGIN, HGIN, and ESCC. This evidence concerns the gene HGF and esophageal squamous cell carcinoma.