Methylation in the estrogen receptor alpha (ESRα) promoter is an epigenetic abnormality in breast cancer (BCa) and hypermethylation results in the loss of ER expression. We used pyrosequencing to investigate whether there is a direct link between aberrant methylation in P0/P1 promoters of ESRα and risk of progression of benign fibrocystic and fibroadenoma tumors to BCa. Our results showed a significant elevated level of DNA methylation in ESRα P1 promoter (p=0.0001) in fibroadenoma compared to ER-negative BCa tumors, and 2-fold increased ESRα expression in fibrocystic and fibroadenoma benign tissues. In addition, the methylation level of HIN-1 and RASSF1A promoters were elevated in ER-positive compared to ER-negative BCa (p-value <0.5). ANOVA Mixed Model revealed significantly higher methylation levels in the promoter of RASSF1A for fibroadenoma and ER-positive BCa (p=0.004) compared to ER-negative BCa. Tumors with unclassified molecular subtype (ER-positive, PR-negative, HER2-negative) had elevated levels of methylation (p=0.046) in the P0 promoter compared with luminal B (ER-positive, PR-positive, HER2-positive) tumors. Grade 3 tumors showed a borderline association with ESRα P1 promoter methylation when compared with grade 2 tumors (p=0.056). Our results demonstrate a highly methylated ESRα P0 promoter occurs in the initial stages of breast carcinogenesis while methylation in the P1 promoter occurs at later stages/grades of BCa with poor prognosis. Therefore, methylation of ESRα promoter and other tumor-related genes could serve as potential biomarkers for prediction of fibroadenoma, known to have elevated risk of progressing to BCa.

Yasmine Kanaan is an Associate Professor at Howard University College of Medicine and Howard University Cancer Center in Washington DC, USA. She is an educator and has trained many doctoral students in her laboratory and served on numerous dissertation committees. She has published over 110 manuscripts and abstracts on breast and prostate cancer research in peer-reviewed journals; and has been an invited speaker in several national and international venues to present her research. The goals of her research studies are to identify ethnicity specific markers for breast cancer progression and develop a more tailored treatment approach that leads to better management of breast cancer in African American women.