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Reverse Yeast Two-hybrid System to Identify Mammalian Nuclear Receptor Residues that Interact with Ligands and/or Antagonists
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Reverse Yeast Two-hybrid System to Identify Mammalian Nuclear Receptor Residues that Interact with Ligands and/or Antagonists

Published on: November 15, 2013

Nuclear receptor conformation, coregulators, and tamoxifen-resistant breast cancer

J D Graham1, D L Bain, J K Richer

  • 1Department of Medicine, University of Colorado School of Medicine, Denver, CO 80262, USA. dinny.graham@uchsc.edu

Steroids
|December 8, 2000
PubMed

Insights

Tamoxifen resistance in breast cancer may be linked to changes in nuclear receptor coregulators. Understanding these factors could reveal new therapeutic targets for overcoming resistance to endocrine therapy.

Area of Science:

  • Endocrinology
  • Molecular Biology
  • Oncology

Background:

  • Tamoxifen resistance is a major challenge in breast cancer treatment, even with continued estrogen receptor (ER) expression.
  • Tamoxifen acts as a mixed antagonist, possessing both agonist and antagonist properties.
  • Resistance may arise from tamoxifen exhibiting more agonist-like properties, potentially stimulating tumor growth.

Purpose of the Study:

  • To investigate the role of nuclear receptor coregulators in tamoxifen resistance.
  • To identify proteins influencing tamoxifen's agonist and antagonist activities.
  • To explore the correlation between coregulator levels and tamoxifen sensitivity in breast tumors.

Main Methods:

  • Utilized a mixed antagonist-biased two-hybrid screening to identify coregulators.
  • Conducted transcriptional studies to assess the impact of N-CoR and L7/SPA on tamoxifen and RU486 activity.
  • Employed quantitative RT-PCR to measure transcript levels of coregulators (N-CoR, SMRT, L7/SPA, SRC-1) in tumor samples.

Main Results:

  • Identified N-CoR (nuclear receptor corepressor) and L7/SPA (coactivator) as key proteins influencing nuclear receptor activity.
  • N-CoR suppressed agonist properties of tamoxifen and RU486, while L7/SPA enhanced them.
  • Preliminary data suggest that relative levels of these coregulators may influence tamoxifen's agonist/antagonist balance.

Conclusions:

  • The balance of agonist and antagonist properties of mixed antagonists like tamoxifen may be determined by coregulator expression levels.
  • Tumor sensitivity to tamoxifen might be regulated by a complex interplay of transcription factors.
  • Further research is needed to fully understand these transcription factors and their role in endocrine therapy resistance.

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