Rodrigo B Interiano1, Jun Yang2, Adrian L Harris3, Andrew M Davidoff4. 1. Department of Surgery, St. Jude Children's Research Hospital, Memphis, Tennessee; Department of Surgery, University of Tennessee Health Science Center, Memphis, Tennessee. 2. Department of Surgery, St. Jude Children's Research Hospital, Memphis, Tennessee. 3. Department of Oncology, The Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK. 4. Department of Surgery, St. Jude Children's Research Hospital, Memphis, Tennessee; Department of Surgery, University of Tennessee Health Science Center, Memphis, Tennessee. Electronic address: andrew.davidoff@stjude.org.
Abstract
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.
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.
Authors: Hongjuan Zhao; Anita Langerød; Youngran Ji; Kent W Nowels; Jahn M Nesland; Rob Tibshirani; Ida K Bukholm; Rolf Kåresen; David Botstein; Anne-Lise Børresen-Dale; Stefanie S Jeffrey Journal: Mol Biol Cell Date: 2004-03-19 Impact factor: 4.138
Authors: Jianfei Qi; Koh Nakayama; Robert D Cardiff; Alexander D Borowsky; Karen Kaul; Roy Williams; Stan Krajewski; Dan Mercola; Philip M Carpenter; David Bowtell; Ze'ev A Ronai Journal: Cancer Cell Date: 2010-07-13 Impact factor: 31.743