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Hong Fang,¹ Weida Tong,² Roger Perkins,² Ana M. Soto,³ Nancy V. Prechtl,³ Daniel M. Sheehan¹

¹Division of Genetic and Reproductive Toxicology, National Center for Toxicological Research (NCTR), Jefferson, Arkansas, USA
²R.O.W. Sciences, Inc., Jefferson, Arkansas, USA
³Tufts University School of Medicine, Department of Anatomy and Cellular Biology, Boston, Massachusetts, USA

Abstract

Substances that may act as estrogens show a broad chemical structural diversity. To thoroughly address the question of possible adverse estrogenic effects, reliable methods are needed to detect and identify the chemicals of these diverse structural classes. We compared three assays--in vitro estrogen receptor competitive binding assays (ER binding assays) , yeast-based reporter gene assays (yeast assays) , and the MCF-7 cell proliferation assay (E-SCREEN assay) --to determine their quantitative agreement in identifying structurally diverse estrogens. We examined assay performance for relative sensitivity, detection of active/inactive chemicals, and estrogen/antiestrogen activities. In this examination, we combined individual data sets in a specific, quantitative data mining exercise. Data sets for at least 29 chemicals from five laboratories were analyzed pair-wise by X-Y plots. The ER binding assay was a good predictor for the other two assay results when the antiestrogens were excluded (r² is 0.78 for the yeast assays and 0.85 for the E-SCREEN assays) . Additionally, the examination strongly suggests that biologic information that is not apparent from any of the individual assays can be discovered by quantitative pair-wise comparisons among assays. Antiestrogens are identified as outliers in the ER binding/yeast assay, while complete antagonists are identified in the ER binding and E-SCREEN assays. Furthermore, the presence of outliers may be explained by different mechanisms that induce an endocrine response, different impurities in different batches of chemicals, different species sensitivity, or limitations of the assay techniques. Although these assays involve different levels of biologic complexity, the major conclusion is that they generally provided consistent information in quantitatively determining estrogenic activity for the five data sets examined. The results should provide guidance for expanded data mining examinations and the selection of appropriate assays to screen estrogenic endocrine disruptors. Key words: antiestrogens, chemical structure, data mining, endocrine disruptors, E-SCREEN assay, estrogens, estrogen receptor competitive binding assay, estrogen receptors, MCF-7 cell proliferation assay, species sensitivity, yeast-based reporter gene assay. Environ Health Perspect 108:723-729 (2000) . [Online 26 June 2000]

http://ehpnet1.niehs.nih.gov/docs/2000/108p723-729fang/ abstract.html

Address correspondence to H. Fang, Division of Genetic and Reproductive Toxicology, National Center for Toxicological Research (NCTR) , 3900 NCTR Road, Jefferson, AR 72079 USA. Telephone: (870) 543-7538. Fax: (870) 543-7382. E-mail: hfang@nctr.fda.gov

H.F. received postdoctoral support from the Oak Ridge Institute for Science and Education Program, supported by the U.S. Department of Energy and the U.S. Food and Drug Administration (FDA) . This work was supported in part by the Office of Women's Health (FDA) and National Institutes of Health grant ES-08314 (A.M.S.) . We thank W. Owens for reviewing the manuscript.

Received 21 September 1999 ; accepted 11 April 2000.