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Estrogen receptor mutagenesis and hormone resistance
1Division of Medical Oncology, University of Texas Health Science Center, San Antonio 78284-78841.
Cancer
|August 1, 1994
Summary
A new estrogen receptor (ER) variant lacking hormone-binding capacity was discovered. This variant may cause tamoxifen resistance in ER-positive breast cancer patients.
Area of Science:
- Endocrinology
- Molecular Biology
- Oncology
Background:
- A truncated estrogen receptor (ER) variant, lacking the hormone-binding domain due to exon 5 deletion, has been identified.
- This variant exhibits dominant-positive activity in the absence of hormones.
- Initially found in ER-negative tumors, it is now coexpressed with wild-type ER in many ER-positive tumors.
Purpose of the Study:
- To investigate the clinical significance of the exon 5 ER variant coexpressed with the wild-type receptor.
- To determine the functional impact of the exon 5 ER variant on tamoxifen sensitivity in ER-positive breast cancer cells.
Main Methods:
- Transfection of the exon 5 ER variant into ER-positive MCF-7 breast cancer cells.
- Coexpression analysis of the variant with the wild-type ER.
- Assessment of tamoxifen sensitivity in transfected cells.
Main Results:
- MCF-7 cells expressing equivalent levels of the variant and wild-type ER became resistant to tamoxifen's growth-inhibitory effects.
- The exon 5 ER deletion variant's coexpression with wild-type ER is linked to tamoxifen resistance.
Conclusions:
- The exon 5 ER deletion variant may play a role in clinical tamoxifen resistance.
- This variant could contribute to hormone independence in ER-positive breast cancer.