Identifying Compounds with Genotoxicity Potential Using Tox21 High-Throughput Screening Assays.

Area of Science:

• Toxicology
• Genetics
• Biochemistry

Background:

• Genotoxicity assessment is crucial for toxicological profiling.
• The Tox21 Program evaluated over 10,000 compounds using high-throughput screening (HTS).

Purpose of the Study:

• To assess the utility of five quantitative high-throughput screening (qHTS) assays for genotoxicity evaluation.
• To compare qHTS results with standard genotoxicity assays.
• To develop predictive models for genotoxicity.

Main Methods:

• Utilized five qHTS assays measuring DNA damage/repair indicators (p53 activation, ATAD5, H2AX phosphorylation, DT40 cell cytotoxicity).
• Compared qHTS data with bacterial mutation, in vitro chromosomal aberration, and in vivo micronucleus assays.
• Developed predictive models using Tox21 assay data and QSAR models.

Main Results:

• Each qHTS assay detected distinct DNA damage response components; >70% of active compounds were assay-specific.
• qHTS assays showed low sensitivity (max 40% detection of known genotoxicants) compared to standard assays.
• Ranking by qHTS potency enriched for genotoxicants up to 12-fold, enabling prioritization.
• Predictive models achieved up to 0.83 accuracy, with stress-response pathway data being most informative.

Conclusions:

• Current qHTS genotoxicity assays cannot replace traditional methods due to low sensitivity.
• qHTS assays are valuable for prioritizing chemicals for further genotoxicity investigation.
• Integrated qHTS data, predictive models, and QSAR improved chemical prioritization for genotoxicity characterization.