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Updated: Jun 7, 2025
10:36
Systems Biology of Metabolic Regulation by Estrogen Receptor Signaling in Breast Cancer
Published on: March 17, 2016
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Estrogens and breast cancer
J Kim1, P N Munster2
1Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indiana University Melvin and Bren Simon Comprehensive Cancer Center, Indianapolis, USA.
Summary
Progestogens, not estrogens, are the main drivers of hormone-related breast cancer risk. Estrogen therapy alone may offer benefits for menopausal women and survivors, with progestin being the key risk factor.
Area of Science:
- Endocrinology
- Oncology
- Women's Health
Background:
- Estrogens are traditionally linked to increased breast cancer risk.
- Emerging evidence implicates progestogens (progesterone or progestins) as the primary hormonal drivers of breast cancer risk.
- Estrogens may indirectly increase risk by upregulating progesterone receptors.
Purpose of the Study:
- To re-evaluate the role of estrogens versus progestogens in breast cancer risk.
- To assess the safety and benefits of estrogen-alone hormone replacement therapy (HRT).
- To explore the impact of estrogen in specific contexts like assisted reproductive technology (ART) and in BRCA1/2 carriers.
Main Methods:
- Review of large-scale clinical studies, including hormonal contraceptive use and the Women's Health Initiative (WHI) trials.
- Analysis of experimental evidence on hormonal signaling pathways.
- Examination of data from assisted reproductive technology (ART) and antiestrogen therapies.
Main Results:
- Hormonal contraceptives' breast cancer risk is primarily linked to progestins, not estrogens.
- Estrogen-plus-progestin HRT increases breast cancer risk; estrogen-alone HRT shows minimal impact or potential benefit.
- Estrogen-alone HRT in the WHI trials suggests a benefit.
- Estrogen during ART has minimal adverse effects on breast cancer risk.
- Inhibition of progesterone signaling is key for antiestrogen efficacy.
Conclusions:
- Progestogens are the primary hormonal drivers of breast cancer risk, not estrogens.
- Estrogen-alone HRT offers benefits for menopausal women and may be beneficial for breast cancer survivors and young BRCA1/2 carriers.
- Estrogen therapy, particularly without progestin, is likely beneficial for various women's health aspects.
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