(593am) Comparison of Estrogenic Properties of Small Molecules Across Several Species Using Biosensors

Estrogenic compounds have important pharmaceutical and toxicological properties.  As pharmaceuticals, these compounds can be used to treat several types of cancer, including breast, pancreatic and testicular cancer.  As trace contaminants in the environment, estrogens have been linked to health risks, such as decreased ages of puberty onset in girls.  Using engineered Escherchilia coli biosensors, we have developed an assay that eliminates the initial need for animal testing, in evaluating potentially estrogenic compounds.  The bacterial biosensor relies on an engineered protein consisting of an intein with an inserted estrogen receptor beta (ERβ) ligand-binding domain, and a thymidylate synthase (TS) reporter enzyme.  Culturing the E.coli biosensor strain in thymine-less media allows for identification of estrogenic compounds based on growth phenotype.  The assay is able to distinguish between ERβ agonists and antagonists.  By comparing the effect of a compound on different biosensors with different animal ERβ receptors, the difference in estrogenicity between several test compounds across several species can be determined. The current set-up is a 96-well plate system, but this setup can be adapted for high-throughput screening of unknown toxins.  We verified this system by constructing dose-response curves using thirty compounds, determining the EC50 for each compound, and comparing it to literature regarding the compound.  The EC50 value was then used to make cross-strain comparisons.  In all we tested the estrogenic responses for our test library of 30 compounds against eight animal species.  Results indicate that the potential risk of endocrine disruption for some compounds may vary from species to species, while other compounds have a more consistent risk level.