An Epigenomic Approach to Therapy for Tamoxifen-Resistant Breast Cancer

Cell Res. 2014 Jul;24(7):809-19. doi: 10.1038/cr.2014.71. Epub 2014 May 30.

Abstract

Tamoxifen has been a frontline treatment for estrogen receptor alpha (ERα)-positive breast tumors in premenopausal women. However, resistance to tamoxifen occurs in many patients. ER still plays a critical role in the growth of breast cancer cells with acquired tamoxifen resistance, suggesting that ERα remains a valid target for treatment of tamoxifen-resistant (Tam-R) breast cancer. In an effort to identify novel regulators of ERα signaling, through a small-scale siRNA screen against histone methyl modifiers, we found WHSC1, a histone H3K36 methyltransferase, as a positive regulator of ERα signaling in breast cancer cells. We demonstrated that WHSC1 is recruited to the ERα gene by the BET protein BRD3/4, and facilitates ERα gene expression. The small-molecule BET protein inhibitor JQ1 potently suppressed the classic ERα signaling pathway and the growth of Tam-R breast cancer cells in culture. Using a Tam-R breast cancer xenograft mouse model, we demonstrated in vivo anti-breast cancer activity by JQ1 and a strong long-lasting effect of combination therapy with JQ1 and the ER degrader fulvestrant. Taken together, we provide evidence that the epigenomic proteins BRD3/4 and WHSC1 are essential regulators of estrogen receptor signaling and are novel therapeutic targets for treatment of Tam-R breast cancer.

Publication types

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

MeSH terms

  • Animals
  • Azepines / therapeutic use
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / genetics
  • Cell Cycle Proteins
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm / drug effects*
  • Epigenomics
  • Estradiol / analogs & derivatives
  • Estradiol / therapeutic use
  • Estrogen Receptor alpha / biosynthesis
  • Estrogen Receptor alpha / physiology*
  • Female
  • Fulvestrant
  • Histone-Lysine N-Methyltransferase / metabolism*
  • Humans
  • Mice
  • Nuclear Proteins / physiology
  • RNA-Binding Proteins / physiology
  • Repressor Proteins / metabolism*
  • Signal Transduction / drug effects
  • Tamoxifen / pharmacology
  • Tamoxifen / therapeutic use*
  • Transcription Factors / physiology
  • Triazoles / therapeutic use

Substances

  • (+)-JQ1 compound
  • Azepines
  • BRD3 protein, human
  • BRD4 protein, human
  • Cell Cycle Proteins
  • Estrogen Receptor alpha
  • Nuclear Proteins
  • RNA-Binding Proteins
  • Repressor Proteins
  • Transcription Factors
  • Triazoles
  • estrogen receptor alpha, human
  • Tamoxifen
  • Fulvestrant
  • Estradiol
  • Histone-Lysine N-Methyltransferase
  • NSD2 protein, human