The Anti-Estrogen Hydroxytamoxifen Is a Potent Antagonist in a Novel Yeast System

Abstract

The budding yeast Saccharomyces cerevisiae has been used extensively as a biological 'test tube' to study the regulation of the human estrogen receptor (ER) alpha. However, anti-estrogens, which are of great importance as therapeutic agents and research tools, fail to antagonize the activation by estrogen in yeast. Here, we have surveyed the antagonistic potential of five different anti-estrogens of diverse chemical nature. While they all act as agonists for wild-type ERalpha, we have established a novel yeast assay system for anti-estrogens, in which at least the commonly used anti-estrogen hydroxytamoxifen is a potent antagonist.

A Bacterial Biosensor of Endocrine Modulators

“…5 For example, a yeast-based transcriptional assay that successfully recognizes the antagonistic activity of 4-hydroxytamoxifen has been reported, but failed to do so with other partial or pure estrogen antagonists. 27 Similarly, another gene transcription assay in yeast was able to show inhibitory effects only for the partial estrogen antagonist nafoxidine. 28 A possible explanation for this limitation may be that yeast cells tend to selectively uptake estrogen agonist compounds over estrogen antagonists.…”

Antiestrogenic and antigenotoxic activity of bee pollen from Cystus incanus and Salix alba as evaluated by the yeast estrogen screen and the micronucleus assay in human lymphocytes

“…Estrogenic/antiestrogenic activity of pollen samples was tested using the Saccharomyces cerevisiae yeast strain RMY326 containing the human estrogen receptor a and a Xenopus laevis vitellogenin ERE sequence linked to the lacZ reporter gene encoding for the enzyme b-galactosidase [58]. The induction of transcription of the reporter gene by the complex receptoreligand was detected and quantified by spectrophotometry (ULTROSPEC Ò 2100 pro, Amersham Pharmacia Biotech).…”

“…Samples that were able to inhibit the activity of the natural ligand E 2 led to a dose-dependent decrease in b-gal expression, that was associated with a concurrent decrease in the rate of change in the colour of the medium. The drug 4-OHT (SigmaeAldrich, Milano, Italy), widely regarded as a partial antagonist of estrogen activity in yeast [58,61], was added at final concentration ranging from 0.00387 mg/ml up to 3.87 mg/ml to E 2 and used as a reference control to measure antiestrogenic activity. E 2 , 4-OHT and tested samples were dissolved in DMSO (DMSO:water, 1:1 for extract 2 samples) and added to the yeast culture so that the concentration of solvent did not exceed 1% (v/v).…”

Determination of trace endocrine disruptors in ultrapure water for laboratory use by the yeast estrogen screen (YES) and chemical analysis (GC/MS)

“…For this study an in vitro assay using the Saccharomyces cerevisiae yeast strain RMY326 [21] containing a plasmid expressing the human estrogen receptor ␣ (hER␣) and a reporter plasmid carrying an estrogen responsive element (ERE) bound to the lacZ reporter gene encoding for the enzyme ␤-galactosidase (␤-gal) was used. The yeast strain was kindly supplied by Prof. D. Picard, University of Geneva.…”

“…The drug 4-OHT, widely regarded as an antagonist of the estrogen action in yeast [21,24,25], was used as a control to measure the inhibitory activity.…”