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Updated: Jun 19, 2026
09:07
Detecting the Ligand-binding Domain Dimerization Activity of Estrogen Receptor Alpha Using the Mammalian Two-Hybrid Assay
Published on: December 19, 2018
A hypersensitive estrogen receptor alpha mutation that alters dynamic protein interactions
Matthew H Herynk1, Torsten Hopp, Yukun Cui
1Lester and Sue Smith Breast Center, Baylor College of Medicine, One Baylor Plaza, Mailstop 600, Houston, TX 77030, USA.
Breast Cancer Research and Treatment
|October 21, 2009
Summary
A specific mutation in estrogen receptor alpha (ERalpha), K303R, drives hypersensitive breast cancer tumor growth and estrogen-independent regrowth. This ERalpha mutation impacts coactivator interactions and promoter activity.
Area of Science:
- Molecular Endocrinology
- Cancer Biology
- Genetics
Background:
- Estrogen receptor alpha (ERalpha) is a key regulator of cell growth and is implicated in human breast cancer.
- ERalpha activity is tightly controlled by various mechanisms, including posttranslational modifications and coactivator interactions.
- A previously identified K303R mutation in ERalpha's hinge region alters its regulation and enhances in vitro growth.
Purpose of the Study:
- To investigate the in vivo impact of the K303R ERalpha mutation on tumor growth and estrogen dependency.
- To elucidate the molecular mechanisms underlying the hypersensitive tumor growth associated with the K303R ERalpha mutation.
Main Methods:
- MCF-7 breast cancer cells stably expressing either wild-type ERalpha or K303R mutant ERalpha were xenografted into nude mice.
- Tumor growth dynamics were monitored under varying estrogen concentrations, including withdrawal and subsequent re-administration.
- Mechanistic studies involved assessing estrogen binding affinity, coactivator interactions (SRC family, p300), and promoter occupancy (pS2) for mutant ERalpha.
Main Results:
- Tumors expressing K303R ERalpha exhibited accelerated growth compared to wild-type ERalpha tumors in the presence of low estrogen.
- Upon estrogen withdrawal, K303R ERalpha tumors showed significant regression, but approximately half regrew independently of estrogen.
- The K303R mutation did not alter estrogen binding affinity but increased interactions with SRC coactivators, enhancing SRC-3 and p300 recruitment to the pS2 promoter, indicating a loss of negative regulation by the F domain.
Conclusions:
- The K303R ERalpha mutation confers hypersensitivity to estrogen, promoting accelerated tumor growth and enabling estrogen-independent tumor recurrence in vivo.
- This mutation disrupts normal ERalpha regulation, leading to enhanced coactivator recruitment and prolonged promoter occupancy, driving aggressive tumor behavior.
- The K303R ERalpha mutation represents a significant factor in hormonal regulation of breast cancer progression and promoter dynamics.
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