MicroRNA-30a increases tight junction protein expression to suppress the epithelial-mesenchymal transition and metastasis by targeting Slug in breast cancer

// Chia-Wei Chang 1 , Jyh-Cherng Yu 2 , Yi-Hsien Hsieh 1 , Chung-Chin Yao 3 , Jui-I Chao 4 , Po-Ming Chen 1 , Hsiao-Yen Hsieh 1 , Chia-Ni Hsiung 5 , Hou-Wei Chu 5 , Chen-Yang Shen 5, 6 , Chun-Wen Cheng 1, 7 1 Institute of Biochemistry, Microbiology and Immunology, Chung Shan Medical University, Taichung, Taiwan 2 Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan 3 Department of Surgery, Chung Shan Medical University Hospital, Taichung, Taiwan 4 Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan 5 Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan 6 College of Public Health, China Medical University, Taichung, Taiwan 7 Clinical Laboratory, Chung Shan Medical University Hospital, Taichung, Taiwan Correspondence to: Chun-Wen Cheng, e-mail: cwcheng@csmu.edu.tw Chen-Yang Shen, e-mail: bmcys@ibms.sinica.edu.tw Keywords: breast cancer metastasis, EMT, miR-30a, slug, claudin Received: August 07, 2015 Accepted: February 10, 2016 Published: February 24, 2016 ABSTRACT The epithelial-to-mesenchymal (EMT) transition is a prerequisite for conferring metastatic potential during tumor progression. microRNA-30a (miR-30a) expression was significantly lower in aggressive breast cancer cell lines compared with non-invasive breast cancer and non-malignant mammary epithelial cell lines. In contrast, miR-30a overexpression reversed the mesenchymal appearance of cancer cells to result in a cobblestone-like epithelial phenotype. We identified Slug, one of the master regulators of EMT, as a target of miR-30a using in silico prediction. Reporter assays indicated that miR-30a could bind to the 3'-untranslted region of Slug mRNA. Furthermore, we linked miR-30a to increased expression of claudins, a family of tight junction transmembrane proteins. An interaction between Slug and E-box in the claudin promoter sequences was reduced upon miR-30a overexpression, further leading to reduction of filopodia formation and decreased invasiveness/metastasis capabilities of breast cancer cells. Consistently, delivery of miR-30a in xenografted mice decreased tumor invasion and migration. In patients with breast cancer, a significantly elevated risk of the miR-30a low /CLDN2 low / FSCN high genotype was observed, linking to a phenotypic manifestation of larger tumor size, lymph node metastasis, and advanced tumor stage among patients. In conclusion, the miR-30a/Slug axis inhibits mesenchymal tumor development by interfering with metastatic cancer cell programming and may be a potential target for therapy in breast cancer.