Browsing by Subject "endocrine resistance"

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    Expression levels of SF3B3 correlate with prognosis and endocrine resistance in estrogen receptor-positive breast cancer
    (Nature Publishing Group, 2015-05) Gökmen-Polar, Yesim; Neelamraju, Yaseswini; Goswami, Chirayu P.; Gu, Xiaoping; Nallamothu, Gouthami; Janga, Sarath Chandra; Badve, Sunil; Department of Pathology and Laboratory Medicine, IU School of Medicine
    De novo or acquired resistance to endocrine therapy limits its utility in a significant number of estrogen receptor-positive (ER-positive) breast cancers. It is crucial to identify novel targets for therapeutic intervention and improve the success of endocrine therapies. Splicing factor 3b, subunit 1 (SF3B1) mutations are described in luminal breast cancer albeit in low frequency. In this study, we evaluated the role of SF3B1 and SF3B3, critical parts of the SF3b splicing complex, in ER-positive endocrine resistance. To ascertain the role of SF3B1/SF3B3 in endocrine resistance, their expression levels were evaluated in ER-positive/endocrine-resistant cell lines (MCF-7/LCC2 and MCF-7/LCC9) using a real-time quantitative reverse transcription PCR (qRT-PCR). To further determine their clinical relevance, expression analysis was performed in a cohort of 60 paraffin-embedded ER-positive, node-negative breast carcinomas with low, intermediate, and high Oncotype DX recurrence scores. Expression levels of SF3B1 and SF3B3 and their prognostic value were validated in large cohorts using publicly available gene expression data sets including The Cancer Genome Atlas. SF3B1 and SF3B3 levels were significantly increased in ERα-positive cells with acquired tamoxifen (MCF-7/LCC2; both P<0.0002) and fulvestrant/tamoxifen resistance (MCF-7/LCC9; P=0.008 for SF3B1 and P=0.0006 for SF3B3). Expression levels of both MCF-7/LCC2 and MCF-7/LCC9 were not affected by additional treatments with E2 and/or tamoxifen. Furthermore, qRT-PCR analysis confirmed that SF3B3 expression is significantly upregulated in Oncotype DX high-risk groups when compared with low risk (P=0.019). Similarly, in publicly available breast cancer gene expression data sets, overexpression of SF3B3, but not SF3B1, was significantly correlated with overall survival. Furthermore, the correlation was significant in ER-positive, but not in ER-negative tumors.
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    HOXB7 is an ERα cofactor in the activation of HER2 and multiple ER target genes leading to endocrine resistance
    (American Association for Cancer Research, 2015-09) Jin, Kideok; Park, Sunju; Teo, Wei Wen; Korangath, Preethi; Cho, Sean Soonweng; Yoshida, Takahiro; Győrffy, Balázs; Goswami, Chirayu Pankaj; Nakshatri, Harikrishna; Cruz, Leigh-Ann; Zhou, Weiqiang; Ji, Hongkai; Su, Ying; Ekram, Muhammad; Wu, Zhengsheng; Zhu, Tao; Polyak, Kornelia; Sukumar, Saraswati; Surgery, School of Medicine
    Why breast cancers become resistant to tamoxifen despite continued expression of the estrogen receptor alpha (ERα) and what factors are responsible for high HER2 expression in these tumors remains an enigma. HOXB7 ChIP analysis followed by validation showed that HOXB7 physically interacts with ERα, and that the HOXB7-ERα complex enhances transcription of many ERα target genes including HER2. Investigating strategies for controlling HOXB7, our studies revealed that MYC, stabilized via phosphorylation mediated by EGFR-HER2 signaling, inhibits transcription of miRNA-196a, a HOXB7 repressor. This leads to increased expression of HOXB7, ER-target genes and HER2. Repressing MYC using small molecule inhibitors reverses these events, and causes regression of breast cancer xenografts. The MYC-HOXB7-HER2 signaling pathway is eminently targetable in endocrine-resistant breast cancer.