Lynn BCD, Bodelon C, Pfeiffer RM, et al. - Among cancer-free, uniparous and lactating US black (n = 57) and white (n = 82) women, ages 19 to 44, researchers assessed the links between genome-wide DNA methylation levels in breast milk and breast cancer risk factors, including race, to ultimately reveal the impact of this reproductive stage on a woman's risk for breast cancer as well as its potential contribution to racial differences in breast cancer. They found that statistically significant links with race and lactation duration were shown in epigenetic analysis in breast milk. A total of 284 CpG sites were found to be related to race, of these, hypermethylation of 242 was noted in black women. Hypomethylation of all 227 CpG sites related to lactation duration was seen in women who lactated longer. In IPA analysis of differentially methylated promoter region CpGs by race and lactation duration, they found enrichment for networks involved in carcinogenesis. The links between DNA methylation and lactation duration could provide insight into its role in reducing breast cancer risk. Social, behavioral, or other factors associated with breast cancer may be mediated by epigenetic links with race. These links may also offer a better understanding of potential mechanisms underlying racial differences in breast cancer incidence.