Reactive oxygen species induce phosphorylation of serine 118 and 167 on estrogen receptor alpha

Breast Cancer Res Treat. 2009 Nov;118(2):269-79. doi: 10.1007/s10549-008-0221-0. Epub 2008 Oct 21.

Abstract

Estrogen receptor alpha (ERalpha) is a well-known target for signaling pathways originating from growth factor receptors. Reactive oxygen species (ROS) can induce activation of extracellular response kinase 1/2 (Erk1/2) and protein kinase B (Akt). Both kinases have been implicated in the phosphorylation of serine 118 and serine 167 on ERalpha, respectively. This activity may lead either to ligand-independent activation of ERalpha or down-regulation of ERalpha and may contribute to development of the resistance to endocrine therapy. Treatment of MCF-7 human breast cancer cells with glucose oxidase (GO, 0.1 un/ml) induced transient phosphorylation of serine 118 and serine 167. The increase in expression of p-ser118-ERalpha was 355 +/- 98% (mean +/- SD) and of p-ser167-ERalpha was 632 +/- 355%. These effects were enhanced in Her2 over-expressing MCF7 cells. ERalpha expression declined to 63 +/- 20% within the first 90 min of treatment and was below 10% 24 h later. ROS induced phosphorylation of ERalpha resulted in decreased expression of pS2 and progesterone receptor. Activation of Erk1/2 and Akt was transient with highest levels of Erk1/2 being 595 +/- 143% and p-Akt 311 +/- 125%. Inhibition of Erk1/2 by U0126 (10 microM) decreased p-ser118-ERalpha by 51.7 +/- 8.5% and decreased p-ser167-ERalpha by 41.9 +/- 16.9% whereas inhibition of Akt by LY294002 (20 microM) and wortmannin (500 nM) or by siRNA knock-down, had no effect on p-ser167-ERalpha expression. Our data show for the first time that ROS can induce post-translational modifications of ERalpha at serine 118 and serine 167, and may lead to ERalpha down-regulation in human breast cancer cells. Both the phosphorylation and consequent down-regulation of ERalpha may be a mechanism associated with development of endocrine therapy resistance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • Breast Neoplasms / metabolism*
  • Cell Line, Tumor
  • Down-Regulation
  • Estrogen Receptor alpha / metabolism*
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Female
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • Phosphorylation
  • Protein Processing, Post-Translational
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA, Small Interfering
  • Reactive Oxygen Species / metabolism*
  • Receptor, ErbB-2 / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Serine / metabolism
  • Signal Transduction / physiology*
  • Transfection

Substances

  • Estrogen Receptor alpha
  • RNA, Small Interfering
  • Reactive Oxygen Species
  • Serine
  • Receptor, ErbB-2
  • Proto-Oncogene Proteins c-akt
  • Extracellular Signal-Regulated MAP Kinases