Epigenetic Changes of the ESR1 Gene in Breast Tissue of Healthy Women: A Missing Link with Breast Cancer Risk Factors?

Reproductive history and obesity are among the well-recognized risk factors in the development of breast cancer, which are partially mediated by the increased exposure of breast tissues to estrogens. However, only a few studies have investigated the link between these risk factors and the pattern of methylation signatures in the breast tissue of healthy women. The role of the estrogen receptor 1 (ESR1) gene hypermethylation is reportedly important in the development of breast cancer. Thus, it is speculated that such ESR1 epigenetic changes may be influenced or shaped by obesity and reproductive history-related factors before and during breast carcinogenesis. Breast samples were collected from 120 cancer-free women who had undergone cosmetic mammoplasty. DNA was extracted from the breast tissues and, then, the methylation levels at the promoter and exon 1 regions of the ESR1 gene CpG island were determined by using the methylated DNA immunoprecipitation-quantitative PCR assay. The methylation level of the ESR1 promoter observed in women with a body mass index (BMI) ≥30 kg/m (p ≤ 0.001) was higher than in the subgroups of women of BMI