title: ERβ splice variant expression in four large cohorts of human breast cancer patient tumors.
abstract: Though the role of Estrogen Receptor (ER)α in breast cancer has been studied extensively, there is little consensus about the role of alternative ER isoform ERβ in breast cancer biology. ERβ has significant sequence homology to ERα 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 ERβ. The relevance of ERβ 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 ERβ in patient tumors. Here, we quantitatively assess expression of ERβ splice variants on over 2,000 breast cancer patient samples. Antibodies against ERβ 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 ERβ1 and ERβ5, but not ERβ2/cx, which were sensitive, specific, and reproducible. QIF staining of validated antibodies showed both ERβ1 and ERβ5 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 ERβ1 is not a prognostic or predictive biomarker for breast cancer. ERβ5 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 ERα.
authors.affiliation: Department of Pathology, Yale University School of Medicine, BML116, 310 Cedar Street, PO Box 208023, New Haven, CT, 06520-8023, USA.
authors.forename: Hallie
authors.initials: H
authors.lastname: Wimberly
authors.forename: Gang
authors.initials: G
authors.lastname: Han
authors.forename: Dushanthi
authors.initials: D
authors.lastname: Pinnaduwage
authors.forename: Leigh C
authors.initials: LC
authors.lastname: Murphy
authors.forename: Xiaohong Rose
authors.initials: XR
authors.lastname: Yang
authors.forename: Irene L
authors.initials: IL
authors.lastname: Andrulis
authors.forename: Mark
authors.initials: M
authors.lastname: Sherman
authors.forename: Jonine
authors.initials: J
authors.lastname: Figueroa
authors.forename: David L
authors.initials: DL
authors.lastname: Rimm
mesh_terms: D000328:Adult; D000368:Aged; D017398:Alternative Splicing / Q000235:genetics; D015331:Cohort Studies; D047628:Estrogen Receptor alpha / Q000235:genetics; D047629:Estrogen Receptor beta / Q000096:biosynthesis* / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D061986:MCF-7 Cells; D008875:Middle Aged; D011379:Prognosis; D020033:Protein Isoforms / Q000096:biosynthesis* / Q000235:genetics; D034741:RNA, Small Interfering; D064726:Triple Negative Breast Neoplasms / Q000235:genetics* / Q000473:pathology
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D020033:Protein Isoforms; D034741:RNA, Small Interfering