Sturgeon SR, Sela DA, Browne EP, et al. - Given a link may exist between white blood cell (WBC) DNA and breast cancer risk, and 250 individual CpG sites that were differentially methylated between breast cancer cases and non-cases were revealed in a case-cohort analysis nested in the prospective Sister Study, researchers herein assessed five of the top 40 CpG sites in a case control analysis nested in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial Cohort. They analyzed 297 breast cancer cases and 297 frequency-matched controls. They found elevated breast cancer risk in relation to a one-unit increase in percent methylation in ERCC1 in proximate WBC DNA. However, a one-unit increment in percent methylation in ERCC1 in distant WBC DNA was identified to be inversely related to breast cancer risk. Findings revealed an absence of a convincing pattern between DNA methylation in the five CpG sites and breast cancer risk.