Abstract.
In the last decades, substances with estrogenic activity have been dispersed into the environment. Xenoestrogens act by binding to estrogen receptors, ligand-regulated transcription factors, for which two subtypes have been described, Er-α and Er-β, which are often coexpressed at variable amounts in different tissues. We investigated variations in the expression of Er-α and Er-β mRNAs following treatment with four xenoestrogens (bisphenol A, 4-tert octylphenol, 2-hydroxybiphenyl, 4-hydroxybiphenyl) and with 17β-estradiol in estrogen-sensitive (T47D) and estrogen-insensitive (BT20) breast cancer cell lines. Although to a variable extent, both estradiol and the tested xenoestrogens increased the expression of Er-β mRNA, whereas a slight effect on Er-α was observed only in T47D cells. Upregulation of Er-β expression by estradiol and xenoestrogens was observed only in the presence of detectable Er-α protein levels. These findings indicate a regulatory role for ER-β in ER-α-mediated transcription and a role for ER-β in mediating xenoestrogen toxicity.
Keywords: Key words. Xenoestrogen; Er-β; ER-α; breast cancer; RT-PCR.
Footnotes
Received 5 November 2002; received after revision 12 December 2002; accepted 23 January 2003
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