Clinical significance of promoter hypermethylation of ERβ and RARβ2 in tumor and serum DNA in Indian breast cancer patients.

Abstract

To determine concordance of promoter hypermethylation of ERβ (estrogen receptor β) and RARβ2 (retinoic acid receptor β2) in tumor and circulating DNA of Indian breast cancer patients and their association with clinicopathologic parameters and disease prognosis. ERβ and RARβ2 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 ERβ (r = + 0.77; p ≤ 0.001) and RARβ2 (r = + 0.85; p ≤ 0.001) in tumors and paired sera. No association was found between ERβ and RARβ2 promoter hypermethylation and loss of protein expression. Kaplan-Meier survival curve showed loss of ERβ expression, and RARβ2 promoter hypermethylation was associated with poor overall survival (OS) (p = 0.03, p = 0.001). Breast cancer patients showing concurrent hypermethylation of ERβ and RARβ2 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 ERβ and RARβ2 in serum could potentially be used to predict invasive ductal breast carcinoma. Furthermore, concurrent ERβ and RARβ2 methylation as well as loss of ERβ expression may serve as a good prognostic marker.