Clinical Significance of Promoter Hypermethylation of ERβ and RARβ2 in Tumor and Serum DNA in Indian Breast Cancer Patients

To determine concordance of promoter hypermethylation of ER beta (estrogen receptor beta) and RAR beta 2 (retinoic acid receptor beta 2) in tumor and circulating DNA of Indian breast cancer patients and their association with clinicopathologic parameters and disease prognosis. ER beta and RAR beta 2 methylation was analyzed by methylation-specific PCR in the tumors and circulating DNA of 100 patients with invasive ductal breast carcinoma. Promoter hypermethylation was associated with the expression of the encoded protein in tumors by immunohistochemistry, and their prognostic utility was explored in a follow-up study. Significant correlation was observed between promoter hypermethylation of ER beta (r = + 0.77; p a parts per thousand currency sign 0.001) and RAR beta 2 (r = + 0.85; p a parts per thousand currency sign 0.001) in tumors and paired sera. No association was found between ER beta and RAR beta 2 promoter hypermethylation and loss of protein expression. Kaplan-Meier survival curve showed loss of ER beta expression, and RAR beta 2 promoter hypermethylation was associated with poor overall survival (OS) (p = 0.03, p = 0.001). Breast cancer patients showing concurrent hypermethylation of ER beta and RAR beta 2 had a significantly shorter median OS (p = 0.02), underscoring that hypermethylation of these two genes may serve as an adverse prognosticator for breast carcinoma. Methylation status of ER beta and RAR beta 2 in serum could potentially be used to predict invasive ductal breast carcinoma. Furthermore, concurrent ER beta and RAR beta 2 methylation as well as loss of ER beta expression may serve as a good prognostic marker.