miR-340 and ZEB1 negative feedback loop regulates TGF-β- mediated breast cancer progression

// Li-Kun Hou 1, 2, 3, * , Yue Yu 1, 2, 3, * , Ye-Gong Xie 1, 2, 3 , Jie Wang 1, 2, 3 , Jie-Fei Mao 1, 2, 3 , Bin Zhang 1, 2, 3 , Xin Wang 1, 2, 3 , Xu-Chen Cao 1, 2, 3 1 The First Department of Breast Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Tianjin 300060, China 2 Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China 3 Key Laboratory of Breast Cancer Prevention and Therapy, Tianjin Medical University, Ministry of Education, Tianjin 300060, China * These authors contributed equally to this work Correspondence to: Xu-Chen Cao, e-mail: caoxuchen@tmu.edu.cn Keywords: miR-340, ZEB1, TGF-β, EMT, breast cancer Received: October 27, 2015      Accepted: March 06, 2016      Published: March 27, 2016 ABSTRACT MicroRNAs act as key regulators in carcinogenesis and progression in various cancers. In present study, we explored the role of miR-340 in the breast cancer progression. Our results showed that overexpression of miR-340 inhibits breast cancer cell proliferation and invasion, whereas depletion of miR-340 promotes breast cancer progression. Molecularly, ZEB1 was identified as a target gene of miR-340 and miR-340 suppressed the expression of ZEB1 by directly binding to the 3′-UTR of ZEB1. Furthermore, ZEB1 transcriptionally suppresses miR-340 expression. The negative feedback loop regulated TGF-β-mediated breast cancer progression. In conclusion, our data suggested that miR-340 acted as a tumor suppressor in breast cancer progression.