Impact of Epigenome-Wide Methylation and Breast Cancer Recurrence in Women Tested Negative for BRCA Genes: The Breast Methylation Risk (BREMERI) Study

Background and Aim: DNA methylation may contribute to a worsening in breast cancer (BC). Methods: We conducted a matched case–control study to investigate the contribution of DNA methylation (DNAm) in breast cancer recurrence risk. Genome-wide DNAm profiles were generated from peripheral white blood cells (WBC) collected post-surgery from women with primary breast cancer BRCA wild-type, using Illumina Infinium HumanMethylationEPIC array. Cases had to experience recurrence of breast cancer or death and were matched to controls (subjects without recurrence, ratio 1:2) by age at diagnosis (+/− 5 years) and follow-up duration. Results: We identified three differentially methylated regions between the groups. Cases showed two hypomethylated regions, one upstream of the vtRNA2–1 gene (estimate −0.30, p-value < 0.005), and one in the 5′ UTR region of the FGFR2 gene (estimate −0.34, p-value < 0.028), whereas one, upstream of the RUFY1 gene (estimate 0.32, p-value < 0.015), was hypermethylated. Additionally, we identified two methylation signals, recognised as predictors of biochemical traits. The chemokine ligand 21 (unadjusted p-value < 0.03) and insulin receptor expression (unadjusted p-value < 0.04) were higher in cases than in controls. Conclusions: Our exploratory study suggests that specific DNA methylation patterns in WBCs, particularly in genes related to cellular proliferation, invasion, and glucose homeostasis, may be associated with the risk of breast cancer recurrence in BRCA wild-type women. If validated in larger cohorts, these circulating signatures may serve as blood-based biomarkers to improve risk stratification and guide tailored treatment strategies.