Tamoxifen-resistant breast cancer cells possess cancer stem-like cell properties

• Published in: Chinese medical journal Vol. 126; no. 16; pp. 3030 - 3034
• Main Authors: Liu, Hui, Zhang, Heng-wei, Sun, Xian-fu, Guo, Xu-hui, He, Ya-ning, Cui, Shu-de, Fan, Qing-xia
• Format: Journal Article
• Language: English
• Published: China Department of Oncology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, China%Department of Breast, Affiliated Cancer Hospital of Zhengzhou University, Zhengzhou, Henan 450008, China 30.08.2013
• Subjects: Animals; Antineoplastic Agents, Hormonal - pharmacology; Breast Neoplasms - drug therapy; Breast Neoplasms - pathology; Drug Resistance, Neoplasm; Epithelial-Mesenchymal Transition; Female; Humans; MCF-7 Cells; MCF7细胞; Mice; mRNA水平; Neoplastic Stem Cells - drug effects; Tamoxifen - pharmacology; 乳腺癌细胞; 他莫昔芬; 实时定量RT-PCR; 生物学特性; 肿瘤干细胞; 诱导阻力; breast cancer; epithelial-mesenchymal transition; tamoxifen resistance; cancer stem cells
• ISSN: 0366-6999; 2542-5641
• DOI: 10.3760/cma.j.issn.0366-6999.20130227

Background Cancer stem cells （CSCs） are the cause of cancer recurrence because they are resistant to conventional therapy and contribute to cancer growth and metastasis.Endocrinotherapy is the most common breast cancer therapy and acquired tamoxifen （TAM） resistance is the main reason for endocrinotherapy failure during such therapy.Although acquired resistance to endocrine treatment has been extensively studied,the underlying mechanisms are unclear.We hypothesized that breast CSCs played an important role in TAM-induced resistance during breast cancer therapy.Therefore,we investigated the biological characteristics of TAM-resistant （TAM-R） breast cancer cells.Methods Mammosphere formation and tumorigenicity of wild-type （WT） and TAM-R MCF7 cells were tested by a mammosphere assay and mouse tumor xenografts respectively.Stem-cell markers （SOX-2,OCT-4,and CD133） and epithelial-mesenchymal transition （EMT） markers were tested by quantitative real-time （qRT）-PCR.Morphological observation was performed to characterize EMT.Results After induction of TAM resistance,TAM-R MCF7 cells exhibited increased proliferation in the presence of TAM compared to that of WT MCF7 cells （P ＜0.05）,indicating enhanced TAM resistance of TAM-R MCF7 cells compared to that of WT MCF7 cells.TAM-R MCF7 cells showed enhanced mammosphere formation and tumorigenicity in nude mice compared to that of WT MCF7 cells （P ＜0.01）,demonstrating the elevated CSC properties of TAM-R MCF7 cells.Consistently,qRT-PCR revealed that TAM-R MCF7 cells expressed increased mRNA levels of stem cell markers including SOX-2,OCT-4,and CD133,compared to those of WT MCF7 cells （P ＜0.05）.Morphologically,TAM-R MCF7 cells showed a fibroblastic phenotype,but WT MCF7 cells were epithelial-like.After induction of TAM resistance,qRT-PCR indicated that MCF7 cells expressed increased mRNA levels of Snail,vimentin,and N-cadherin and decreased levels of E-cadherin,which are considered as EMT characteristics （P ＜0.05）.Conclusion TAM-R MCF7 cells possess CSC characteristics and may be responsible for TAM resistance during breast cancer therapy.