Opposing effects of estradiol- and testosterone-membrane binding sites on T47D breast cancer cell apoptosis
- Department of Experimental Endocrinology, University of Crete, School of Medicine, P.O. Box 2208, Heraklion, GR-71003 (Greece)
- Department of Pharmacology, University of Crete, School of Medicine, Heraklion, 71003 (Greece)
- Department of Biochemistry, University of Crete, School of Medicine, Heraklion, 71003 (Greece)
- Department of Pathology, University of Crete, School of Medicine, Heraklion, 71003 (Greece)
Classical steroid mode of action involves binding to intracellular receptors, the later acting as ligand-activated nuclear transcription factors. Recently, membrane sites for different steroids have been also identified, mediating rapid, non-genomic, steroid actions. Membrane sites for estrogen and androgen have been found in a number of different cell types, bearing or not classical intracellular receptors. In the present study, with the use of radioligand binding, flow cytometry and confocal laser microscopy, we report that T47D human breast cancer cells express specific and saturable membrane receptors for both estrogen (K {sub D} 4.06 {+-} 3.31 nM) and androgen (K {sub D} 7.64 {+-} 3.15 nM). Upon activation with BSA-conjugated, non-permeable ligands (E{sub 2}-BSA and testosterone-BSA), membrane estrogen receptors protect cells from serum-deprivation-induced apoptosis, while androgen receptors induce apoptosis in serum-supplemented T47D cells. In addition, co-incubation of cells with a fixed concentration of one steroid and varying concentrations of the other reversed the abovementioned effect (apoptosis for androgen, and anti-apoptosis for E{sub 2}), suggesting that the fate of the cell depends on the relative concentration of either steroid in the culture medium. We also report the identification of membrane receptors for E{sub 2} and androgen in biopsy slides from breast cancer patients. Both sites are expressed, with the staining for membrane E{sub 2} being strongly present in ER-negative, less differentiated, more aggressive tumors. These findings suggest that aromatase inhibitors may exert their beneficial effects on breast cancer by also propagating the metabolism of local steroids towards androgen, inducing thus cell apoptosis through membrane androgen receptor activation.
- OSTI ID:
- 20717615
- Journal Information:
- Experimental Cell Research, Vol. 307, Issue 1; Other Information: DOI: 10.1016/j.yexcr.2005.02.027; PII: S0014-4827(05)00093-5; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0014-4827
- Country of Publication:
- United States
- Language:
- English
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