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Cell Death Differ. 2018 Feb;25(2):406-420. doi: 10.1038/cdd.2017.176. Epub 2017 Nov 10.

A miR-20a/MAPK1/c-Myc regulatory feedback loop regulates breast carcinogenesis and chemoresistance.

Author information

1
Program of Innovative Cancer Therapeutics, Division of Hepatobiliary and Pancreatic Surgery, Department of Surgery, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang Province 310003, China.
2
Breast Center, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang Province 310003, China.
3
Department of Breast Surgery, the First Affiliate Hospital of Zhejiang Chinese Medical University, Hangzhou 310014, China.
4
Key Laboratory of Combined Multi-Organ Transplantation, Ministry of Public Health, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang Province 310003, China.
5
Clinical Research Center, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang Province 310003, China.
6
Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425, USA.

Abstract

Chemoresistance often leads to the failure of breast cancer treatment. MicroRNAs (miRNAs) play an important role in the progression and chemoresistance of cancer. However, because of the complexity of the mechanisms of chemoresistance and the specificity of miRNA regulation in different cell types, the function of miR-20a in breast cancer chemoresistance is still unclear. Here, by using miRNA microarray and high-content screening techniques, we found that miR-20a/b were significantly downregulated in breast cancer tissues compared with normal breast tissues, and low miR-20a/b expression was correlated with poor survival in breast cancer patients. Ectopic overexpression of miR-20a sensitized breast cancer cells to a broad spectrum of chemotherapy drugs and suppress their proliferation both in vitro and in vivo. Further study demonstrated that miR-20a directly targeted the 3'untranslated region of MAPK1, and thus downregulated the expression of P-gp and c-Myc by inhibiting the MAPK/ERK signaling pathway, whereas c-Myc can bind to the promoter region of the miR-20a gene to promote the expression of miR-20a. Together, our study identified a novel miR-20a/MAPK1/c-Myc feedback loop that regulates breast cancer growth and chemoresistance. These findings suggest that miR-20a synergizing with anticancer drugs will be a promising treatment strategy, especially for chemoresistant patients.

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