June 2022 EMM Editor's Choice Article

The June 2022 EMM Editor’s Choice Article is “A new imaging platform (iScreen) allows for the concurrent assessment of micronucleus induction and genotoxic mode of action in human A375 cells” (https://doi.org/10.1002/em.22496) by Xiaowen SunElizabeth RubitskiRichard A. SpellmanMaria Engel, and Maik Schuler.

The work of Sun and co-workers introducing iScreen, a novel multiplexed image analysis platform for in vitro micronucleus assessment and genotoxic mode of action determination. The platform utilizes adherent human melanoma (A375) cells and incorporates micronuclei (MN) identification, centromere detection in MN, and DNA damage response biomarkers. To validate the platform, authors used 12 compounds in total, covering four genotoxicity classes (nongenotoxicant [apoptosis inducer], clastogen, and two types of aneugens, - tubulin binder and aurora inhibitor), with three chemicals per class. Using a custom image analysis algorithm, the platform first discriminates between genotoxicant and nongenotoxicant by quantifying micronucleus induction, then examining  centromere protein A (CENPA) signals within the micronuclei to distinguish between aneugens and clastogens, then uses phosphorylated histone H2AX Ser139 (γH2AX) staining to confirm clastogenicity, and finally, discriminates between aneugens that bind tubulin from those that affect aurora kinases by analyze changes in phosphorylated histone3 Ser10 (pH 3) and increases in polyploidy in mitotic cells. Authors were able to correctly classify all compounds and showed quantitative agreement with MicroFlow® data from TK6 cells using benchmark dose-response analysis. The platform definitely offers excellent alternative for genotoxicity testing in drug development. Furthermore, with additional validation exercises (e.g., testing in other cell lines and using larger compound set, as currently planned by the authors) iScreen may also offer important mechanistic insights for other applications, such as human health risk assessment of chemicals.

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