The potential role of estrogen receptor β2 in breast cancer

Endocrine therapy is provided to all patients with estrogen receptor (ER)-positive breast cancer, but only a subset of them derives clinical benefit. The discovery of ER beta and its five isoforms added another layer of complexity in the regulation of estrogen activity in breast cancer cells. Two large retrospective studies showed conflicting results with regard to the prognostic value of the different ER beta isoforms in patients treated with tamoxifen in an adjuvant setting. This study tested the hypothesis that ER beta 1 and, or ER beta 2 are correlated with clinical outcome. We identified patients with breast cancer who had undergone surgery at Bucheon St. Mary's Hospital, the Catholic University of Korea, between January 2004 and March 2006. We evaluated 101 consecutive cases for ER beta 1 and ER beta 2 expression using immunohistochemical staining and obtained other clinicopathology by reviewing medical records. ER beta 1 was expressed in 81.2% (79 of 97) and ER beta 2 was expressed in 50.5% (51 of 101) of primary breast cancer tissues. Disease-free survival (DFS) and overall survival (OS) of patients with cancers expressing ER beta 2 was significantly worse. Moreover, in subgroup analysis according to the tamoxifen treatment, ER beta 2 expression was significantly associated with shorter DFS of tamoxifen-treated patients. This study indicates that breast cancer with ER beta 2 expression was associated with worse DFS and OS, especially in tamoxifen treated patients. Our results suggest a role for ER beta 2 as an independent prognostic marker and might serve as a new therapeutic target. (C) 2015 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.