Attenuation of estrogen receptor alpha (ERalpha) signaling by selenium in breast cancer cells via downregulation of ERalpha gene expression

Breast Cancer Res Treat. 2005 Aug;92(3):239-50. doi: 10.1007/s10549-005-3203-5.


Numerous studies have shown that selenium provides beneficial effects as a cancer chemoprevention agent. Although long-term intervention trials failed to confirm selenium protection against breast cancer in humans because of insufficient cases, the evidence of effective selenium chemoprevention in animal mammary tumor models or human breast cancer cells is substantial and convincing. The present study demonstrates that the selenium compound methylseleninic acid (MSA) inhibits estrogen receptor alpha (ERalpha) signaling in ER-positive MCF-7 breast cancer cells as evidenced by decreased estradiol-dependent cell growth and gene expression. MSA diminishes estradiol induction of endogenous ER-regulated pS2 and c-myc genes as well as the expression of an ER-regulated reporter gene. A major mode of MSA action on ER signaling is through a downregulation of ERalpha gene expression that precedes a decrease in ERalpha protein level. This study provides a mechanism driven rationale for using selenium as a chemopreventive agent for women at high risk for developing breast cancer or as a therapeutic strategy for ER-positive breast cancer.

Publication types

  • Evaluation Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Breast Neoplasms / drug therapy*
  • Cell Line, Tumor
  • Down-Regulation*
  • Estradiol / metabolism
  • Estrogen Receptor alpha / antagonists & inhibitors*
  • Female
  • Gene Expression Regulation, Neoplastic / drug effects*
  • Humans
  • Organoselenium Compounds / pharmacology*
  • Signal Transduction / drug effects


  • Estrogen Receptor alpha
  • Organoselenium Compounds
  • Estradiol
  • methylselenic acid