Using in vitro high throughput screening assays to identify potential endocrine-disrupting chemicals - PubMed (original) (raw)

doi: 10.1289/ehp.1205065. Epub 2012 Sep 28.

David J Dix, Keith A Houck, Thomas B Knudsen, Matthew T Martin, Keith W McLaurin, David M Reif, Kevin M Crofton, Amar V Singh, Menghang Xia, Ruili Huang, Richard S Judson

Affiliations

Using in vitro high throughput screening assays to identify potential endocrine-disrupting chemicals

Daniel M Rotroff et al. Environ Health Perspect. 2013 Jan.

Abstract

Background: Over the past 20 years, an increased focus on detecting environmental chemicals that pose a risk of adverse effects due to endocrine disruption has driven the creation of the U.S. Environmental Protection Agency (EPA) Endocrine Disruptor Screening Program (EDSP). Thousands of chemicals are subject to the EDSP; thus, processing these chemicals using current test batteries could require millions of dollars and decades. A need for increased throughput and efficiency motivated the development of methods using in vitro high throughput screening (HTS) assays to prioritize chemicals for EDSP Tier 1 screening (T1S).

Objective: In this study we used U.S. EPA ToxCast HTS assays for estrogen, androgen, steroidogenic, and thyroid-disrupting mechanisms to classify compounds and compare ToxCast results to in vitro and in vivo data from EDSP T1S assays.

Method: We implemented an iterative model that optimized the ability of endocrine-related HTS assays to predict components of EDSP T1S and related results. Balanced accuracy was used as a measure of model performance.

Results: ToxCast estrogen receptor and androgen receptor assays predicted the results of relevant EDSP T1S assays with balanced accuracies of 0.91 (p < 0.001) and 0.92 (p < 0.001), respectively. Uterotrophic and Hershberger assay results were predicted with balanced accuracies of 0.89 (p < 0.001) and 1 (p < 0.001), respectively. Models for steroidogenic and thyroid-related effects could not be developed with the currently published ToxCast data.

Conclusions: Overall, results suggest that current ToxCast assays can accurately identify chemicals with potential to interact with the estrogenic and androgenic pathways, and could help prioritize chemicals for EDSP T1S assays.

PubMed Disclaimer

Conflict of interest statement

The views expressed in this article are those of the authors and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency (EPA). Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

The authors declare they have no actual or potential competing financial interests.

Figures

Figure 1

Figure 1

Overlap between EDSP T1S assays and ToxCast phase I assays by endocrine MOAs. Abbreviations: A, androgen; E, estrogen; NA, not applicable; T, thyroid. Colors indicate the type of endocrine MOA data.

Figure 2

Figure 2

Illustration of the balanced optimization model used to analyze predictive capacity of endocrine-related ToxCast assays. Multiple assays and study reports were available for each chemical–MOA combination. (A) Snapshot of a step in this modeling/optimization process, in which chemical X is positive in three of five HTS assays and two of three guideline reports. In this example, the dynamic HTS threshold is at least two positive assays and the guideline threshold is at least 50% positive reports, so chemical X is considered a true positive (TP). With less than two positive assays, chemical X would be a false negative (FN); < 50% positive reports would produce a false positive (FP); and if both were negative according to this criteria, chemical X would be a true negative (TN). (B) Method for tabulating results for all chemicals (e.g., chemical X would be counted in the TP portion of the contingency table) to arrive at an estimate of balanced accuracy for each set of threshold parameters.

Figure 3

Figure 3

Forest plot illustrating the performance—as measured by sensitivity, specificity, and BA—of ToxCast endocrine-related assays for predicting outcomes captured in EDSP/OECD guideline studies. Symbols represent the optimal BA obtained across all threshold combinations and the corresponding sensitivity and specificity at the same threshold. Gray boxes indicate 95% confidence intervals around permuted BA distributions. Analyses designated “All” include all available assays for the stated endocrine MOA. A value of > 50% “required guideline positives” indicates that > 50% of the studies had to report a positive result for a chemical to be considered a positive in the analysis. If the “required guideline positives” value is 1, any study reporting a positive resulted in the chemical being considered positive in the analysis. A separate analysis compared only uterotrophic and Hershberger analyses (right). The tests listed on the left represent replicate MOA with test conditions annotated under “Required HTS Positives” and “Required guideline positives.”

Figure 4

Figure 4

Forest plot illustrating the performance—as measured by sensitivity, specificity, and BA—of ToxCast endocrine-related assays for predicting outcomes captured in non-guideline endocrine studies. Symbols represent the optimal BA obtained across all threshold combinations and the corresponding sensitivity and specificity at the same threshold. Gray boxes indicate 95% confidence intervals around permuted BA distributions. A value of > 50% “required non-guideline positives” indicates that > 50% of the studies had to report a positive result for a chemical to be considered a positive in the analysis. If the “required non-guideline positives” value is 1, any study reporting a positive resulted in the chemical being considered positive in the analysis. The tests listed on the left represent replicate MOA with test conditions annotated under “Required HTS Positives” and “Required non-guideline positives.”

References

    1. Andersen HR, Vinggaard AM, Rasmussen TH, Gjermandsen IM, Bonefeld-Jørgensen EC. Effects of currently used pesticides in assays for estrogenicity, androgenicity, and aromatase activity in vitro. Toxicol Appl Pharmacol. 2002;179(1):1–12. - PubMed
    1. Ankley GT, Giesy JP. Pensacola, FL: SETAC Press, 349–367; 1998. Endocrine disruptors in wildlife: a weight of evidence perspective. In: Principles and Processes for Evaluating Endocrine Disruption in Wildlife (Kendall R, Dickerson R, Giesy J, Suk W, eds.)
    1. Bigsby R, Chapin RE, Daston GP, Davis BJ, Gorski J, Gray LE, et al. Evaluating the effects of endocrine disruptors on endocrine function during development. Environ Health Perspect. 1999;107(suppl 4):613–618. - PMC - PubMed
    1. Birnbaum LS, Fenton SE. Cancer and developmental exposure to endocrine disruptors. Environ Health Perspect. 2003;111:389–394. - PMC - PubMed
    1. Blystone CR, Furr J, Lambright CS, Howdeshell KL, Ryan BC, Wilson VS, et al. Prochloraz inhibits testosterone production at dosages below those that affect androgen-dependent organ weights or the onset of puberty in the male Sprague Dawley rat. Toxicol Sci. 2007;97(1):65–74. - PubMed

MeSH terms

Substances

LinkOut - more resources