Investigation of epigenetic profiles in exfoliated mammary epithelial cells retrieved from lactating women

Breast cancer is one of the most diagnosed cancer among Turkish women and mortality rate is higher for the younger women. As the breast cancer is a heterogenous disease, identification of the underlying molecular mechanisms of the epidemiologically established risk factors for the breast cancer provide us the possible strategies for prevention and early detection. Hypermethylation of the promoter region of the tumor suppressor genes is a hallmark of the breast cancer and it can be used as a biomarker for the indicator of the breast cancer risk and tool for the diagnosis. Human breast milk is rich in mammary epithelial source and suitable for DNA methylation analysis. Fresh milk samples were collected from lactating women residing in Marmara region, mainly Istanbul. Pyrosequencing analysis was carried on DNA promoter methylation assessment for the six tumor suppressor genes which are PYCARD, CDH1, SFRP1, GSTP1, RBP1 and RASSF1A. The methylation scores were generally found as unmethylated state. DNA methylation analysis results showed that age is significantly positively related with methylation rate of the all CpG sites of RASSF1A, many CpG sites of the PYCARD and sixth and seventh CpG region of the GSTP1 promoter methylation. Statistically positive relationship was found between BMI of the lactating women and fifth CpG of the CDH1 and RASSF1A. Age of the first birth was found as statistically positive with all CpG sites of the RASSF1A and GSTP1 promoter methylation. Statistically higher methylation rate was found in many CpG regions of the PYCARD for women using the intrauterine devices. Significantly higher methylation rate for RBP1 was also seen among participants who had family history of breast and ovarian cancer. Significantly higher methylation percentage for RASSF1A was also detected among women who has family history of ovarian cancer. Dietary habits including dairy, fish, egg and poultry consumption were also significantly linked with methylation rate in several CpG region of PYCARD, CDH1, SFRP1, GSTP1, RBP1 and RASSF1A. In conclusion, breast milk is valuable biological sample for monitoring of early molecular modifications in breast tissue.