Insulin induces a transcriptional activation of epiregulin, HB-EGF and amphiregulin, by a PI3K-dependent mechanism: identification of a specific insulin-responsive promoter element

Biochem Biophys Res Commun. 2007 Mar 23;354(4):885-91. doi: 10.1016/j.bbrc.2007.01.047. Epub 2007 Jan 18.


Previously we have shown that insulin-stimulation of RT4 bladder cancer cells leads to increased proliferation, which require HER1 activation, and is accompanied by increased mRNA expression of the EGF-ligands heparin-binding EGF-like growth factor (HB-EGF), amphiregulin (AR), and epiregulin (EPI) [D. Ornskov, E. Nexo, B.S. Sorensen, Insulin-induced proliferation of bladder cancer cells is mediated through activation of the epidermal growth factor system, FEBS J. 273 (2006) 5479-5489]. In the present paper, we have investigated the molecular mechanism leading to this insulin-induced expression. We monitored the decay of mRNA after inhibiting transcription with Actinomycin D and demonstrated that the insulin-mediated increase was not caused by enhanced mRNA stability. In untreated cells, HB-EGF mRNA was the least stable, whereas AR and EPI mRNA decayed with slower kinetics. However, promoter analysis of HB-EGF and EPI demonstrated that insulin stimulated transcription. Studies on the EPI promoter identified the insulin-responsive element to be located in the region -564 to -365bp. This region contains potential binding sites for the transcription factors SP1, AP1, and NF-kappaB. Interestingly, all three transcription factors can be activated by PI3K. We demonstrate that the insulin-induced expression of HB-EGF, AR, and EPI mRNA is completely prevented by the specific PI3K inhibitor Wortmannin, suggesting an involvement of the PI3K.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amphiregulin
  • Androstadienes / pharmacology
  • EGF Family of Proteins
  • Epidermal Growth Factor / metabolism*
  • Epiregulin
  • Glycoproteins / metabolism*
  • Heparin-binding EGF-like Growth Factor
  • Humans
  • Insulin / pharmacology*
  • Intercellular Signaling Peptides and Proteins / metabolism*
  • Phosphatidylinositol 3-Kinases / physiology*
  • Phosphoinositide-3 Kinase Inhibitors
  • Promoter Regions, Genetic / drug effects*
  • RNA, Messenger / metabolism
  • Transcription, Genetic / drug effects
  • Urinary Bladder Neoplasms / metabolism
  • Wortmannin


  • AREG protein, human
  • Amphiregulin
  • Androstadienes
  • EGF Family of Proteins
  • EREG protein, human
  • Epiregulin
  • Glycoproteins
  • HBEGF protein, human
  • Heparin-binding EGF-like Growth Factor
  • Insulin
  • Intercellular Signaling Peptides and Proteins
  • Phosphoinositide-3 Kinase Inhibitors
  • RNA, Messenger
  • Epidermal Growth Factor
  • Wortmannin