Transcriptome profiling of the normal breast of women at either high- or average risk for breast cancer [methyl-capture]

Epigenetic mechanisms such as DNA methylation are important regulators of gene expression and are frequently dysregulated early in breast carcinogenesis. The relationship between DNA methylation aberrations in normal breast tissue and breast cancer risk remains unclear. Disease-free breast tissue cores donated by high-risk (Tyrer-Cuzick lifetime risk ≥20%) and 78 average-risk women were obtained from the Susan G. Komen Tissue Bank and processed for whole methylome and whole transcriptome profiling. We identified 1355 CpGs that were differentially methylated between high- and average-risk breast tissues (ΔZ>0.5, FDR<0.05). Hypomethylated CpGs were overrepresented in high-risk tissue and were found predominantly (68%) in non-coding regions. Hypermethylated CpG sites were found equally in the gene body and non-coding regions. Transcriptomic analysis identified 67 differentially expressed genes (fold change≥2, FDR<0.05, 17 down 50 up), involved in chemokines signaling, metabolism and estrogen biosynthesis. Methylation-expression correlations revealed 6 epigenetically regulated genes in high-risk breast. This is the first gene expression/DNA methylation analysis of normal breasts from women at either high or average risk of breast cancer. Our discovery of epigenetically regulated genes associated with breast cancer risk using a unique resource of normal breast samples opens the doors to a deeper understanding of the process of cancer initiation and provides an opportunity to mechanistically dissect breast cancer susceptibility and risk-associated molecular alterations. The study cohorts includes 165 women at either average or high risk for breast cancer according to the Tyrer Cuzick risk assessment score. Fresh frozen breast tssue cores were processed for RNA/DNA extraction. Methyl-capture was then employed to obtain the methylome profiling, while RNAseq was used to obtain the transcriptome profing of each sample