Hepatocyte growth factor induced up-regulations of VEGF through Egr-1 in hepatocellular carcinoma cells

The potential role of hepatocyte growth factor (HGF) in the regulation of angiogenesis factors in hepatoma cells is not widely appreciated. We investigated the role of HGF-induced activation of a transcription factor, Egr-1, in the expression of pro-angiogenic factors. Genes associated with angiogenesis induced by HGF were screened by using cDNA microarray technology in hepatocellular carcinoma cell lines, HepG2 and Hep3B. Expression levels of Egr-1, vascular endothelial growth factor (VEGF), and interleukin (IL)-8 were further confirmed by real time RT-PCR and Western blot analysis. Roles of Egr-1 in the levels of HGF-induced up-regulations of VEGF and IL-8 were measured by knockdown of Egr-1 with Egr-1 shRNA and chromatin immunoprecipitation assay. The levels of Egr-1, VEGF and IL-8 were up-regulated in cells treated with HGF. HGF-induced up-regulations of Egr-1, VEGF, and IL-8 were inhibited by the pretreatment with an MEK inhibitor, PD098059. HGF-induced up-regulation of VEGF and IL-8 were repressed by Egr-1 knockdown. HGF enhanced the binding activity of Egr-1 to the VEGF promoter in control cells, but not in the Egr-1-shRNA cells. No constitutive and inducible Egr-1 binding activities to the IL-8 promoter were observed in control and Egr-1-shRNA cells. Egr-1 knockdown reduced the luciferase activities increased by HGF not in the IL-8 promoter, but in the VEGF promoter. Egr-1 might play an important role in the up-regulation of VEGF and IL-8 induced by HGF and contribute to HGF-mediated angiogenesis, which might be promising targets for hepatocellular carcinoma therapy.