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Systems Biology of Metabolic Regulation by Estrogen Receptor Signaling in Breast Cancer
10:36

Systems Biology of Metabolic Regulation by Estrogen Receptor Signaling in Breast Cancer

Published on: March 17, 2016

ErbB receptor signaling and therapeutic resistance to aromatase inhibitors

Incheol Shin1, Todd Miller, Carlos L Arteaga

  • 1Department of Cancer Biology, Vanderbilt-Ingram Comprehensive Cancer Center, Vanderbilt University School of Medicine, University Medical Center, 2220 Pierce Avenue, Nashville, TN 37232, USA.

Clinical Cancer Research : an Official Journal of the American Association for Cancer Research
|February 10, 2006
PubMed

Insights

HER-2 overexpression in breast cancer cells promotes resistance to letrozole by enabling estrogen receptor (ER) signaling independent of hormone levels. This suggests new therapeutic targets for overcoming aromatase inhibitor resistance.

Area of Science:

  • Oncology
  • Molecular Biology
  • Endocrinology

Background:

  • Aromatase inhibitors like letrozole are standard treatments for estrogen receptor-positive breast cancer.
  • Resistance to aromatase inhibitors is a significant clinical challenge.
  • HER-2 overexpression is implicated in various cancer pathologies and treatment resistance.

Purpose of the Study:

  • To investigate the impact of HER-2 overexpression on letrozole resistance in MCF-7 breast cancer cells.
  • To elucidate the molecular mechanisms underlying HER-2-mediated resistance to aromatase inhibitors.

Main Methods:

  • Stable expression of cellular aromatase and HER-2 in MCF-7 cells.
  • Measurement of estrogen receptor (ER)-mediated transcriptional reporter activity.
  • Assessment of cell proliferation.
  • Chromatin immunoprecipitation (ChIP) assays to analyze protein-DNA interactions.

Main Results:

  • HER-2 overexpression led to a >2-fold increase in ER-mediated transcription upon androstenedione treatment.
  • Letrozole failed to inhibit androstenedione-induced transcription and proliferation in HER-2-overexpressing cells.
  • HER-2 overexpression promoted ligand-independent association of ERalpha coactivators (AIB-1, CBP) with the pS2 gene promoter.

Conclusions:

  • Ligand-independent coactivator recruitment to estrogen-responsive promoters, driven by HER-2 overexpression, may contribute to letrozole resistance.
  • Targeting HER-2 signaling or coactivator recruitment could be a strategy to overcome letrozole resistance in breast cancer.

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