ER beta splice variant expression in four large cohorts of human breast cancer patient tumors

作者：Wimberly Hallie; Han Gang; Pinnaduwage Dushanthi; Murphy Leigh C; Yang Xiaohong Rose; Andrulis Irene L; Sherman Mark; Figueroa Jonine; Rimm David L^*

来源：Breast Cancer Research and Treatment, 2014, 146(3): 657-667.

DOI：10.1007/s10549-014-3050-3

• Estrogen receptors
• Breast cancer prognosis and prediction
• Triple-negative breast cancer
• Quantitative immunofluorescence
• Antibody validation

Though the role of Estrogen Receptor (ER)alpha in breast cancer has been studied extensively, there is little consensus about the role of alternative ER isoform ER beta in breast cancer biology. ER beta has significant sequence homology to ER alpha but is located on a different chromosome and maintains both overlapping and unique functional attributes. Five variants exist, resulting from alternative splicing of the C-terminal region of ER beta. The relevance of ER beta variants in breast cancer outcomes and response to therapy is difficult to assess because of conflicting reports in the literature, likely due to variable methods used to assess ER beta in patient tumors. Here, we quantitatively assess expression of ER beta splice variants on over 2,000 breast cancer patient samples. Antibodies against ER beta variants were validated for staining specificity in cell lines by siRNA knockdown of ESR2 and staining reproducibility on formalin-fixed paraffin-embedded tissue by quantitative immunofluorescence (QIF) using AQUA technology. We found antibodies against splice variants ER beta 1 and ER beta 5, but not ER beta 2/cx, which were sensitive, specific, and reproducible. QIF staining of validated antibodies showed both ER beta 1 and ER beta 5 QIF scores, which have a normal (bell shaped) distribution on most cohorts assessed, and their expression is significantly associated with each other. Extensive survival analyses show that ER beta 1 is not a prognostic or predictive biomarker for breast cancer. ER beta 5 appears to be a context-dependent marker of worse outcome in HER2-positive and triple-negative patients, suggesting an unknown biological function in the absence of ER alpha.

• 出版日期2014-8