Evaluating the utility of the MSTI assay results in predicting compound promiscuity and cytotoxicity

Authors

• L Kruger
• DK Ngan
• T Xu
• L Zhang
• M Xia
• A Simeonov
• R Huang

Abstract

Background: Non-specific reactive chemicals often interfere with the interpretation of high throughput assay results because of their promiscuity and/or cytotoxicity. Having a high-throughput assay to identify such compounds is necessary to efficiently rule out potential assay artifacts. The MSTI, (E)-2-(4-mercaptostyrl)-1,3,3-trimethyl-3H-indol-1-ium, assay uses a thiol-containing fluorescent probe to screen for electrophile reactivity and could potentially be used to determine non-specific reactive compounds.
Methods: The Tox21 10K compound library was previously screened against a panel of ~80 cell-based assays as well as the biochemical-based MSTI assay. In this study, we compared the MSTI assay activity of the Tox21 10K compounds with their promiscuity and cytotoxicity as reflected by their activities across the Tox21 assay panel to determine: 1) if this assay is predictive of a compound’s promiscuity and cytotoxicity and 2) what chemical features create inconsistent results between the MSTI assay activity and promiscuity/cytotoxicity (false negatives and positives).
Results: We found that the MSTI assay can predict a chemical’s promiscuity/cytotoxicity with a 0.55 sensitivity and 0.97 specificity. Out of 3407 unique compounds evaluated, there were 92 false positive and 227 false negative results. Several structural features such as carbonyl groups and alkyl halides were identified to be apparent in 76% (p=1.4E-07) and 19% (p=4.3E-06) of the false positives and negatives, respectively.
Conclusions: The results of this analysis will help identify the potential pitfalls of this high-throughput assay and allow researchers to identify if a compound will be cytotoxic and/or promiscuous in an efficient manner.

Scientific Focus Area: Computational Biology

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