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An In Vitro Dormancy Model of Estrogen-sensitive Breast Cancer in the Bone Marrow: A Tool for Molecular Mechanism Studies and Hypothesis Generation
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An In Vitro Dormancy Model of Estrogen-sensitive Breast Cancer in the Bone Marrow: A Tool for Molecular Mechanism Studies and Hypothesis Generation

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AIB1:ERα transcriptional activity is selectively enhanced in aromatase inhibitor-resistant breast cancer cells

Jane O'Hara1, Damir Vareslija, Jean McBryan

  • 1Endocrine Oncology Research Group, Department of Surgery and Epidemiology, Royal College of Surgeons in Ireland, University College Dublin, Dublin, Ireland.

Clinical Cancer Research : an Official Journal of the American Association for Cancer Research
|May 3, 2012
PubMed
Abstract

Insights

Aromatase inhibitor resistance in breast cancer involves the ER coactivator AIB1. AIB1 promotes aggressive tumor phenotypes by altering estrogen receptor target gene regulation, impacting treatment efficacy.

Area of Science:

  • Oncology
  • Molecular Biology
  • Endocrinology

Background:

  • Aromatase inhibitors (AIs) are effective for estrogen receptor (ER)-positive breast cancer.
  • ER target gene dysregulation contributes to endocrine therapy resistance.
  • AIB1, an ER coactivator, is linked to breast cancer initiation and endocrine resistance.

Purpose of the Study:

  • Investigate AIB1's role in ER target gene deregulation during AI resistance.
  • Determine AIB1's impact on AI-resistant breast cancer phenotypes.

Main Methods:

  • Utilized tissue microarrays from breast cancer patients.
  • Developed cell line models resistant to the AI letrozole.
  • Analyzed ERα/AIB1 promoter recruitment and target gene expression (pS2, Myc, cyclin D1).

Main Results:

  • AIB1 expression correlated with disease recurrence and reduced disease-free survival in AI-treated patients.
  • In letrozole-resistant cells, ERα/AIB1 upregulated classic ER targets (pS2, Myc) constitutively.
  • Cyclin D1 regulation by ERα/AIB1 remained sensitive to letrozole, potentially via JNK signaling.

Conclusions:

  • AIB1 plays a significant role in AI-resistant breast cancer.
  • A novel ERα/AIB1 gene regulation mechanism contributes to aggressive tumor development.
  • Findings suggest AIB1 as a potential therapeutic target in resistant breast cancer.

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