To provide a comprehensive analysis of small molecule genotoxic potential we have developed and validated an automated, high-content, high throughput, image-based in vitro Micronucleus (IVM) assay. This assay simultaneously assesses micronuclei and multiple additional cellular markers associated with genotoxicity. Acoustic dosing (≤ 2 mg) of compound is followed by a 24-h treatment and a 24-h recovery period. Confocal images are captured [Cell Voyager CV7000 (Yokogawa, Japan)] and analysed using Columbus software (PerkinElmer). As standard the assay detects micronuclei (MN), cytotoxicity and cell-cycle profiles from Hoechst phenotypes. Mode of action information is primarily determined by kinetochore labelling in MN (aneugencity) and γH2AX foci analysis (a marker of DNA damage). Applying computational approaches and implementing machine learning models alongside Bayesian classifiers allows the identification of, with 95% accuracy, the aneugenic, clastogenic and negative compounds within the data set (Matthews correlation coefficient: 0.9), reducing analysis time by 80% whilst concurrently minimising human bias. Combining high throughput screening, multiparametric image analysis and machine learning approaches has provided the opportunity to revolutionise early Genetic Toxicology assessment within AstraZeneca. By multiplexing assay endpoints and minimising data generation and analysis time this assay enables complex genotoxicity safety assessments to be made sooner aiding the development of safer drug candidates.

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The detection of aneugenic chemicals is important due to the implications of aneuploidy for human health. Aneuploidy can result from chromosome loss or nondisjunction due to chromosome mis-segregation at anaphase. Frequently, aneugens are detected using the in vitro micronucleus assay (IVM), with either centromere or kinetochore labeling. However, this method does not consider nondisjunction, the suggested predominant mechanism of spindle poison induced aneugenicity in primary human lymphocytes. Therefore, the IVM may be relatively insensitive in detecting aneuploidy. To investigate whether chromosome distribution analysis, specifically of nondisjunction, using chromosome-specific centromeric probes provides a more sensitive assay for aneugen detection, six reference aneugens with differing modes of action were tested on human lymphoblastoid TK6 cells. The results show that chromosome loss is a substantial part of the process leading to aneuploidy in TK6 cells. This differs from previous studies on human lymphocytes where nondisjunction has been described as the major mechanism of aneugenicity. However, in the current study more cells and types of aneugenic damage were analyzed. Although compound specific effects on nondisjunction were identified, chromosome distribution analysis did not provide increased sensitivity for the detection of aneugens: For the six reference aneugens examined, chromosome loss was shown at the same concentrations or lower than nondisjunction, even when nondisjunction levels were comparatively high. Therefore, in TK6 cells methods that detect chromosome loss, eg, the IVM, provide a more sensitive technique for the detection of aneugens than the measurement of nondisjunction.

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