Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

Background A significant percentage of estrogen receptor (ER)-positive breast cancers are resistant to tamoxifen therapy. Seven in Absentia Homolog 2 (SIAH2), an E3 ubiquitin protein ligase, has been shown to be associated with resistance to antiestrogens. We sought to assess its role in the resistance of a breast cancer cell line, MCF-7, to the ER antagonist, tamoxifen. Materials and methods A bioinformatic approach was used for the analysis of SIAH2 expression in breast cancer. MCF-7 and MDA-MB-231, which are ER-positive and -negative breast cancer cell lines, respectively, were used for in vitro studies. SIAH2 and ER-α were selectively knocked down in these cell lines with small-interfering RNAs. Knockdowns were confirmed with Western blot analysis and quantitative real-time polymerase chain reaction. Cells with SIAH2 knockdown were treated with tamoxifen and compared with controls. Results Knockdown of SIAH2 followed by treatment with tamoxifen resulted in a significant decrease in the sensitivity of treated ER-positive cells. Of note, knockdown of SIAH2 resulted in downregulation of ER-α, whereas knockdown of ER-α had minimal effect on SIAH2. Consistent with this result, the bioinformatic analysis of clinical data revealed that SIAH2 expression is significantly correlated with ER positivity in human breast cancers, and low SIAH2 expression is associated with a poorer response to tamoxifen. Conclusions SIAH2 appears to be an important modulator of tamoxifen sensitivity in ER-positive MCF-7 cells, mediated, at least in part, through regulation of ER-α expression. Low expression of SIAH2 may be one of the mechanisms that contribute to tamoxifen resistance in human breast cancer. © 2014 Elsevier Inc. All rights reserved.

Original publication




Journal article


Journal of Surgical Research

Publication Date





203 - 209