ER?1: characterization, prognosis, and evaluation of treatment strategies in ER?-positive and -negative breast cancer.
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ABSTRACT: The role and clinical value of ER?1 expression is controversial and recent data demonstrates that many ER? antibodies are insensitive and/or non-specific. Therefore, we sought to comprehensively characterize ER?1 expression across all sub-types of breast cancer using a validated antibody and determine the roles of this receptor in mediating response to multiple forms of endocrine therapy both in the presence and absence of ER? expression.Nuclear and cytoplasmic expression patterns of ER?1 were analyzed in three patient cohorts, including a retrospective analysis of a prospective adjuvant tamoxifen study and a triple negative breast cancer cohort. To investigate the utility of therapeutically targeting ER?1, we generated multiple ER?1 expressing cell model systems and determined their proliferative responses following anti-estrogenic or ER?-specific agonist exposure.Nuclear ER?1 was shown to be expressed across all major sub-types of breast cancer, including 25% of triple negative breast cancers and 33% of ER-positive tumors, and was associated with significantly improved outcomes in ER?-positive tamoxifen-treated patients. In agreement with these observations, ER?1 expression sensitized ER?-positive breast cancer cells to the anti-cancer effects of selective estrogen receptor modulators (SERMs). However, in the absence of ER? expression, ER?-specific agonists potently inhibited cell proliferation rates while anti-estrogenic therapies were ineffective.Using a validated antibody, we have confirmed that nuclear ER?1 expression is commonly present in breast cancer and is prognostic in tamoxifen-treated patients. Using multiple breast cancer cell lines, ER? appears to be a novel therapeutic target. However, the efficacy of SERMs and ER?-specific agonists differ as a function of ER? expression.
SUBMITTER: Reese JM
PROVIDER: S-EPMC4196114 | biostudies-literature | 2014 Oct
REPOSITORIES: biostudies-literature
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