Loss of miR-200b promotes invasion via activating the Kindlin-2/integrin β1/AKT pathway in esophageal squamous cell carcinoma: An E-cadherin-independent mechanism

// Hai-Feng Zhang 1, 3 , Abdulraheem Alshareef 3 , Chengsheng Wu 3 , Shang Li 4 , Ji-Wei Jiao 1 , Hui-Hui Cao 2 , Raymond Lai 3 , Li-Yan Xu 1, 2 , En-Min Li 1 1 The Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou, Guangdong, China 2 Institute of Oncologic Pathology, Shantou University Medical College, Shantou, Guangdong, China 3 Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada 4 College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, Heilongjiang, China Correspondence to: En-Min Li, e-mail: nmli@stu.edu.cn Li-Yan Xu, e-mail: lyxu@stu.edu.cn Raymond Lai, e-mail: rlai@ualberta.ca Keywords: miR-200, E-cadherin, invasion, prognosis, esophageal squamous cell carcinoma Received: May 04, 2015      Accepted: August 07, 2015      Published: August 20, 2015 ABSTRACT Our previous studies have shown that loss of miR-200b enhances the invasiveness of esophageal squamous cell carcinoma (ESCC) cells. However, whether the miR-200-ZEB1/2-E-cadherin regulatory cascade, a master regulator of epithelial-to-mesenchymal transition (EMT), is involved in the regulation of ESCC invasion remains elusive. Here, we show that miR-200b represses ESCC cell invasion in vivo without altering the expression of E-cadherin and vimentin, two surrogate markers of EMT. However, an inverse correlation was observed between the expression levels of miR-200b and ZEB1/2 in both ESCC cell lines ( n = 7, P < 0.05) and ESCC tumor samples ( n = 88, P < 0.05). Methylation of E-cadherin gene was found to block the regulation of E-cadherin by the miR-200b-ZEB1/2 axis, indicating that an E-cadherin-independent mechanism can mediate the biological function of miR-200b in ESCC. We revealed that miR-200b suppresses the integrin β1-AKT pathway via targeting Kindlin-2 to mitigate ESCC cell invasiveness. In two independent cohorts of ESCC samples ( n = 20 and n = 53, respectively), Kindlin-2 expression positively correlated with the activation status of both the integrin signaling pathway and the PI3K-AKT signaling pathway (both P < 0.01). These data highlight that suppression of the Kindlin-2-integrin β1-AKT regulatory axis is an alternative mechanism underlying the tumor suppressor function of miR-200b in ESCC.