microRNA-374a suppresses colon cancer progression by directly reducing CCND1 to inactivate the PI3K/AKT pathway

Abstract

// Yiyu Chen 1, 2, * , Jingwen Jiang 1, * , Mengyang Zhao 2, * , Xiaojun Luo 1 , Zixi Liang 1, 2 , Yan Zhen 2 , Qiaofen Fu 2 , Xiaojie Deng 1, 2 , Xian Lin 1 , Libo Li 1 , Rongcheng Luo 1 , Zhen Liu 2, 3 , Weiyi Fang 1, 2 1 Cancer Center, Traditional Chinese Medicine-Integrated Hospital of Southern Medical University, Guangzhou, PR China 2 Cancer Research Institute, Southern Medical University, Guangzhou, PR China 3 Department of Pathology, School of Basic Medicine, Guangzhou Medical College, Guangzhou, PR China * These authors contributed equally to this work Correspondence to: Weiyi Fang, email: fangweiyi1975@163.com Zhen Liu, email: narcissus_jane@163.com Rongcheng Luo, email: luorc01@163.com Keywords: miR-374a, CCND1, CRC, PI3K/AKT pathway, EMT Received: September 05, 2015      Accepted: April 24, 2016      Published: May 12, 2016 ABSTRACT microRNA-374a (miR-374a) exhibits oncogenic functions in various tumor types. Here we report that miR-374a suppresses proliferation, invasion, migration and intrahepatic metastasis in colon adenocarcinoma cell lines HCT116 and SW620. Notably, we detected that PI3K/AKT signaling and its downstream cell cycle factors including c-Myc, cyclin D1 (CCND1), CDK4 and epithelial-mesenchymal transition (EMT)-related genes including ZEB1, N-cadherin, Vimentin, Slug, and Snail were all significantly downregulated after miR-374a overexpression. Conversely, cell cycle inhibitors p21 and p27 were upregulated. Expression of E-cadherin was only decreased in HCT116, without any obvious differences observed in SW620 cells. Furthermore, luciferase reporter assays confirmed that miR-374a could directly reduce CCND1. Interestingly, when CCND1 was silenced or overexpressed, levels of pPI3K, pAkt as well as cell cycle and EMT genes were respectively downregulated or upregulated. We examined miR-374a levels by in situ hybridization and its correlation with CCND1 expression in CRC tumor tissues. High miR-374a expression with low level of CCND1 was protective factor in CRC. Together these findings indicate that miR-374a inactivates the PI3K/AKT axis by inhibiting CCND1, suppressing of colon cancer progression.