DNA Methylation Patterns in Rat Mammary Carcinomas Induced by Pre- and Post-Pubertal Irradiation

Several lines of evidence indicate one's age at exposure to radiation strongly modifies the risk of radiation-induced breast cancer. We previously reported that rat mammary carcinomas induced by pre- and post-pubertal irradiation have distinct gene expression patterns, but the changes underlying these differences have not yet been characterized. The aim of this investigation was to see if differences in CpG DNA methylation were responsible for the differences in gene expression between age at exposure groups observed in our previous study. DNA was obtained from the mammary carcinomas arising in female Sprague-Dawley rats that were either untreated or irradiated (γ-rays, 2 Gy) during the pre- or post-pubertal period (3 or 7 weeks old). The DNA methylation was analyzed using CpG island microarrays and the results compared to the gene expression data from the original study.