Angiotensin II promotes EMT of hepatocellular carcinoma cells through high mobility group protein B1 mediated by E4F1

To screen for specific transcription factors (TFs) that induce expression of the HMGB1 promoter in response to stimulation by Ang-II. A HMGB1 overexpressing vector and small interfering (si)RNA were constructed and used to transfect the three HCC cell lines used in scratched monolayer wound healing and Transwell assays. Chromatin immunoprecipitation (ChIP) assays were used to confirm the relationship between a specific TF and the HMGB1 promoter. Invasion and migration by HMGB1 overexpressing HCC cells after treatment with Ang-II were significantly increased compared to negative controls (NC); E-cadherin was down-regulated while vimentin was up-regulated. However, compared with NC, invasion and migration by HMGB1 siRNA HCC cells stimulated by Ang-II were not altered; the expression of E-cadherin and vimentin was also unaltered. Nineteen TFs were predicted by Promoter 2.0 Prediction Server and TFsitescan. Real-time qPCR was used to evaluate TF expression levels. E4F1 was the only TF abnormally elevated in all three HCC cell lines when stimulated by Ang-II. WB and ChIP assays revealed high expression of E4F1 compared to other TFs in cells stimulated by Ang-II. E4F1 is activated by Ang-II and binds to the HMGB1 promoter region to promote HMGB1 expression; it then enhances Ang-II to induce HCC cell invasion and migration, and EMT.