The Value of DNA Methylation Analysis in Basic, Initial Toxicity Assessments

DNA methylation is an epigenetic mechanism regulating pat-terns of gene expression. Our goal was to see if the assessment of DNA methylation might be a useful tool, when used in conjunction with initial, basic in vitro tests, to provide a more informative preliminary appraisal of the toxic potential of chemicals to prior-itize them for further evaluation. We sought to give better indica-tions of a compound’s toxic potential and its possible mechanism of action at an earlier time and, thereby, contribute to a rational approach of an overall reduction in testing by making improved early decisions. Global and GC-rich patterns of DNA methylation were evaluated along with more traditional cytolethality measure-ments, e.g., cytolethality and genotoxicity assessments, on rat hepatoma (H4IIE) cells. The relative toxic potential of model compounds camptothecin, 5-fluorouracil, rotenone, and stauro-sporine was estimated by employing DNA methylation assess