Is oestrogen receptor- β a predictor of endocrine therapy responsiveness in human breast cancer?

    1. Peter H Watson2
    1. 1Manitoba Institute of Cell Biology, Departments of Biochemistry and Medical Genetics and
    2. 2Pathology, University of Manitoba, and Cancer Care Manitoba Winnipeg, Canada R3E 0V9
    1. (Requests for offprints should be addressed to L C Murphy; Email: lcmurph{at}


    The role of oestrogen receptor (ER) β in human breast cancer remains unclear. However, it is now apparent that when considering ER β in human breast cancer it is important to recognise two ER β expressing groups, one in which ER β is co-expressed with ER α and the other where ERβ is expressed alone. Emerging data support different functions between ER β when it is expressed alone and when it is co-expressed with ER α. With regard to the latter group (ER α +/ER β +), there are now 9 out of 10 retrospective clinical outcome studies published, that support the hypothesis that increased expression of ER β is associated with increased likelihood of response to endocrine therapy. The data strongly support undertaking prospective studies to determine if the addition of ERβ to ER α is clinically beneficial and whether to include both ER β and ER α when establishing clinically relevant cut-offs for defining ER status.

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