An assay for the detection of xenoestrogens based on a promoter containing overlapping EREs.

Xenoestrogens could be implicated in the decrease of male fertility and in the increased incidence of testicular and breast cancers in humans. To predict their deleterious effects, various in vivo or in vitro tests have been proposed to assay the xenoestrogenic activity. We have designed an assay for the detection of xenoestrogens based on a novel estrogen responsive unit formed by two overlapping estrogen response elements (overEREs). This construct is able to mediate a synergistic activation of transcription by 17ss-estradiol. We have used the overERE unit to assay the estrogenic activity of synthetic compounds, mostly organochlorine compounds. By using the overERE construct, we were able to detect the estrogenic activity of compounds at concentrations 10- to 100-fold lower than a single ERE (i.e., we detected the estrogenic effect of endosulfan at a concentration of 10(-5) M with ERE, whereas the overERE unit allowed us to detect a significant estrogenic activity of endosulfan at a lower concentration (10(-6) M). Some compounds did not exhibit any estrogenic activity when tested with a classical ERE, whereas they were potent xenoestrogens when the overERE was used (i.e., Betanal). The assays we have developed are very sensitive and can be performed quickly. Moreover, because the promoter that we used contains only an overlapping ERE as a regulatory unit, the interference of the tested molecules with other regulatory pathways can be avoided.