Tamoxifen(TAM) is one of the most effective endocrine treatment for estrogen receptor(ER)-positive breast cancer, however drug resistance greatly limits benefit of it. Our purpose is to uncover the role of Beclin 1 in tamoxifen resistance and prognosis of ER positive breast cancer. We established a tamoxifen resistant ER-positive breast cancer cell subline MCF-7R presenting with higher Beclin 1 and human epidermal growth factor receptor 2(HER2) levels than MCF-7. Silencing Beclin 1 decreased levels of HER2 and significantly promoted TAM sensitivity of MCF-7 and MCF-7R in vitro. Overexpression of HER2 could reverse TAM sensitivity, which was formerly increased in Beclin 1 downregulated cell. Beclin 1 level was not only positively correlated with level of HER2 but also negatively correlated with overall survival of ER-positive breast cancer patients. Using bioinformatic methods, Beclin 1 mRNA was found to be negatively correlated with overall survival in breast cancer patients receiving TAM treatment. This study indicated for the first time that lower HER2 expression by Beclin 1 downregulation contributes to alteration of tamoxifen sensitivity and low Beclin 1 predicts favorable outcome in ER-positive breast cancer.
[1]Fudan Univ, Shanghai Canc Hosp, Dept Radiat Oncol, Shanghai, Peoples R China;
[2]Zhejiang Univ, Sch Med, Affiliated Hosp 1, Dept Surg Oncol, Hangzhou, Zhejiang, Peoples R China;
[3]Shanghai Jiao Tong Univ, Shanghai Chest Hosp, Dept Thorac Surg, Shanghai, Peoples R China;
[4]Zhejiang Canc Hosp, Dept Med Oncol, Hangzhou, Zhejiang, Peoples R China;
[5]Zhejiang Univ, Clin Res Ctr, Sch Med, Affiliated Hosp 2, Hangzhou, Zhejiang, Peoples R China
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