Identification of transcriptome profiles for the DNA‐damaging agents bleomycin and hydrogen peroxide in L5178Y mouse lymphoma cells

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Abstract
It is believed that some aspects of genotoxicity are associated with changes in the transcription levels of certain genes, especially those involved in DNA repair and cell cycle control. Additionally, it is hypothesized that chemicals sharing a common mode of genotoxicity should exhibit similar changes in gene expression. We have evaluated these hypotheses by analyzing transcriptome profiles of mouse lymphoma L5178Y/TK+/− cells treated with bleomycin and hydrogen peroxide, two mutagens that produce genotoxicity by generating reactive free radicals. The cells were treated for 4 hr and RNA was isolated at the end of the treatment and after a 20 hr recovery. Transcriptome analyses were performed using the Clontech Mouse 1.2K cDNA microarray (1,185 genes) and hybridization with a 32[P]‐labeled probe. Of the genes examined, each mutagen altered the expression (1.5‐fold or greater) of only two genes after the 4 hr treatment. In cells allowed to recover for 20 hr after treatment, bleomycin and hydrogen peroxide altered the expression of 8 and 5 genes, respectively. Many of the altered genes have some association with apoptosis. Of these genes, three (the genes encoding granzyme A, integrin beta 7, and 45 kDa calcium‐binding protein precursor) were in common between chemical treatments. The expression of DNA repair and cell cycle controlling genes present on the array was not affected by the treatments. These results show that bleomycin and hydrogen peroxide both have unique and commonly regulated genes that have the potential to serve as biomarkers of exposure to agents causing DNA damage by free radical mechanisms. Environ. Mol. Mutagen. 42:19–25, 2003.