DNA methylation in paired breast epithelial and white blood cells from women undergoing reduction mammoplasty.

BACKGROUND: The extent to which white blood cell (WBC) DNA methylation provides information on the status of breast epithelial cell DNA is unknown. PATIENTS AND METHODS: We examined the correlation between methylation in Ras-association domain family-1 gene (RASSF1), a tumor-suppressor gene, and methylation in repetitive elements in paired sets of DNA from WBC and breast epithelial cells collected from 32 women undergoing reduction mammoplasty. RESULTS: We observed no evidence of correlation in methylation levels for ALU, long interspersed nuclear element-1 (LINE1) or juxtacentromeric satellite-2 (SAT2) (r=0.02 for LINE1, p=0.98; r=0.28 for ALU, p=0.12; r=0.26 for SAT2, p=0.17) for matched sets of DNA from WBC and breast epithelial cells. Variability in these markers across individuals and in the same tissue was low. Five women had an average methylation level above 5% for RASSF1 in breast epithelial cell DNA; however, average methylation levels in WBC DNA for these women were all below 1%. CONCLUSION: Methylation patterns in WBC DNA did not reflect methylation patterns in the breast.