Quantifying Epigenetic Changes Induced by Chemical Exposure Using the epi-TK Assay.

Area of Science:

• Epigenetics and Toxicology
• Molecular Biology
• Chemical Safety Assessment

Background:

• Epigenetic modifications regulate gene expression and cellular identity.
• Chemicals can cause cancer via epigenetic alterations, independent of DNA damage.
• Standard genotoxicity assays lack specific epigenetic evaluation.

Purpose of the Study:

• To develop a simple, cost-effective, and quantitative reporter assay for chemically induced epigenetic alterations.
• To establish a method for evaluating epigenetic toxicity in chemical safety frameworks.
• To enable sensitive detection of epigenetic state transitions.

Main Methods:

• Development of the epi-TK assay using an engineered human lymphoblastoid cell line (mTK6).
• Site-specific methylation of the endogenous thymidine kinase (TK) gene promoter to achieve transcriptional repression.
• Quantification of TK revertant colonies after chemical exposure to detect epigenetic perturbations.

Main Results:

• The epi-TK assay successfully detected epigenetic alterations induced by a DNA methyltransferase 1 inhibitor (GSK3484862).
• The assay demonstrated sensitive and quantitative detection of epigenetic state transitions.
• The method allowed bi-directional detection of epigenetic changes, including DNA demethylation and histone modification alterations.

Conclusions:

• The epi-TK assay provides a practical and quantitative platform for evaluating epigenetic toxicity.
• This assay is suitable for routine testing and comparative assessment of multiple compounds.
• The epi-TK assay has potential applications in chemical safety assessment frameworks.