Abstract |
The interactions of 16 alpha-hydroxyestrone (16 alpha-OHE1), a metabolite of estradiol (E2), with estrogen receptors (ERs) were compared in this study to the classic E2-receptor mechanism in human breast cancer cells MCF-7 in culture. When MCF-7 cells were incubated with radioinert 16 alpha-OHE1 or its 3H-labeled form for 4 weeks, the estrogen bound extensively and irreversibly in a time-dependent fashion to nuclear protein species that correspond to the ER. Here we show that the interactions of 16 alpha-OHE1 with the ER are different from those of E2 with the receptor. Dissociation of tritiated E2-ER or 16 alpha-OHE1-ER complexes, salt extraction, DNase and proteinase K digestion, and ethanol treatment demonstrated that the binding of 16 alpha-OHE1 to the ER corresponds to two different forms: a classical noncovalent interaction similar to that of E2, and a covalent adduct formation between the metabolite and the ER. These complexes localized preferentially in nuclear matrix components as revealed by cell fractionation and probing with a monoclonal anti-ER antibody. [3H]16 alpha-OHE1-ER complexes analyzed by polyacrylamide gel electrophoresis demonstrated a radiolabeled band at approximately 66 kDa that was absent when the exposure of cells was done in the presence of E2 in competition and that was also absent in [3H]E2 incubations. The present results when considered together with our previous findings of elevated activities of estrogen 16 alpha-hydroxylase, the enzyme responsible for the formation of 16 alpha-OHE1, in breast cancer patients and in women at enhanced risk for the disease, suggest that covalent modification of the ER may be one mechanism of malignant transformation in estrogen target tissues.
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Authors | G E Swaneck, J Fishman |
Journal | Proceedings of the National Academy of Sciences of the United States of America
(Proc Natl Acad Sci U S A)
Vol. 85
Issue 21
Pg. 7831-5
(Nov 1988)
ISSN: 0027-8424 [Print] United States |
PMID | 3186693
(Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)
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Chemical References |
- Antibodies, Monoclonal
- Hydroxyestrones
- Receptors, Estradiol
- 16-hydroxyestrone
- Estrone
- Estradiol
- Steroid 16-alpha-Hydroxylase
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Topics |
- Antibodies, Monoclonal
- Breast Neoplasms
(metabolism)
- Cell Division
- Cell Line
- Cell Nucleus
(metabolism)
- Electrophoresis, Polyacrylamide Gel
- Estradiol
(metabolism)
- Estrone
(analogs & derivatives)
- Humans
- Hydroxyestrones
(metabolism)
- Receptors, Estradiol
(metabolism)
- Steroid 16-alpha-Hydroxylase
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