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Updated: May 12, 2026

Detecting the Ligand-binding Domain Dimerization Activity of Estrogen Receptor Alpha Using the Mammalian Two-Hybrid Assay
09:07

Detecting the Ligand-binding Domain Dimerization Activity of Estrogen Receptor Alpha Using the Mammalian Two-Hybrid Assay

Published on: December 19, 2018

Estrogen receptor-α variant, ER-α36, is involved in tamoxifen resistance and estrogen hypersensitivity

Xiantian Zhang1, Zhao-Yi Wang

  • 1Department of Medical Microbiology, Creighton University Medical School, Criss III, Room 352, 2500 California Plaza, Omaha, Nebraska 68178, USA. zywang@creighton.edu

Endocrinology
|April 3, 2013
PubMed

Insights

Tamoxifen (TAM) resistance in estrogen receptor-positive breast cancer is linked to elevated ER-α36 levels. Targeting ER-α36 may overcome TAM resistance and improve patient outcomes.

Area of Science:

  • Oncology
  • Molecular Biology
  • Endocrinology

Background:

  • Tamoxifen (TAM) is a standard treatment for estrogen receptor (ER)-positive breast cancer.
  • Tumor resistance to TAM therapy is a significant clinical challenge, with underlying molecular mechanisms not fully elucidated.
  • ER-α36, a variant of ER-α, has been implicated in reduced patient response to TAM therapy.

Purpose of the Study:

  • To investigate the role and mechanism of ER-α36 in tamoxifen resistance in ER-positive breast cancer.
  • To determine if elevated ER-α36 expression contributes to TAM resistance.
  • To explore potential therapeutic strategies targeting ER-α36.

Main Methods:

  • Analysis of ER-α36 concentrations in TAM-treated breast cancer patients and cell lines.
  • Overexpression and knockdown (short hairpin RNA) of ER-α36 in MCF7 breast cancer cells.
  • Assessment of TAM sensitivity in cells with varying ER-α36 levels.
  • Western blot analysis to detect phosphorylation of AKT and ERK kinases.

Main Results:

  • TAM treatment increased ER-α36 concentrations in breast cancer cells.
  • Cells with high ER-α36 expression (endogenous or forced) exhibited resistance to TAM.
  • Down-regulation of ER-α36 restored TAM sensitivity in resistant cells.
  • TAM activated AKT phosphorylation in ER-α36-expressing cells.
  • High ER-α36 levels led to hypersensitivity to estrogen, activating ERK phosphorylation.

Conclusions:

  • Elevated ER-α36 concentration is a key mechanism driving tamoxifen resistance in ER-positive breast cancer.
  • ER-α36 mediates TAM resistance through activation of AKT and ERK signaling pathways.
  • Targeting ER-α36 presents a promising therapeutic strategy for overcoming TAM resistance in breast cancer patients.

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