KLF8 promotes tumorigenesis, invasion and metastasis of colorectal cancer cells by transcriptional activation of FHL2

Abstract

// Qingqing Yan 1 , Wenjing Zhang 1 , Yao Wu 1 , Meiyan Wu 1 , Mengnan Zhang 1 , Xinpeng Shi 1 , Jinjun Zhao 2 , Qingzhen Nan 1 , Ye Chen 1 , Long Wang 3 , Tianming Cheng 1 , Jiachu Li 4 , Yang Bai 1 , Side Liu 1 , Jide Wang 1 1 Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, China 2 Department of Rheumatism, Nanfang Hospital, Southern Medical University, Guangzhou, China 3 Division of Vascular Interventional Radiology, Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China 4 Department of Oncology, The First Affiliated Hospital of Chongqing Medical University, China Correspondence to: Jide Wang, e-mail: jidewang55@163.com Side Liu, e-mail: liuside@163.com Keywords: KLF8, EMT, FHL2, metastasis, colorectal cancer Abbreviations: EMT, epithelial-to-mesenchymal transition; FHL2, four-and-a-half LIM-only protein 2; RLU, relative luciferase unit; ATCC, american type culture collection; ChIP, chromatin immunoprecipitation Received: December 10, 2014      Accepted: July 03, 2015      Published: July 15, 2015 ABSTRACT The transcription factor Krüppel-like factor (KLF)8 plays an important role in the formation of several human tumors, including colorectal cancer. We recently identified four-and-a-half LIM protein 2 (FHL2) as a critical inducer of the epithelial-to-mesenchymal transition (EMT) and invasion. However, the molecular mechanism by which KLF8 affects FHL2-mediated tumor proliferation, EMT and metastasis remains unknown. Here, we showed that KLF8 overexpression promoted EMT and metastatic phenotypes. KLF8 expression was stimulated by transforming growth factor (TGF)-β1. Moreover, KLF8 acted as a potential EMT inducer by stimulating vimentin expression and inducing a loss of E-cadherin in stable KLF8-transfected cells. KLF8 overexpression induced a strong increase in FHL2 expression, and a positive correlation between the expression patterns of KLF8 and FHL2 was observed in CRC cells. Promoter reporter and chromatin immunoprecipitation (ChIP) assays demonstrated that KLF8 directly bound to and activated the human FHL2 gene promoter. However, siRNA-mediated repression of FHL2 in KLF8-overexpressing cells reversed the EMT and the proliferative and metastatic phenotypes. In vivo , KLF8 promoted FHL2-mediated proliferation and metastasis via orthotopic implantation. Taken together, this work identified KLF8-induced FHL2 activation as a novel and critical signaling mechanism underlying human breast/colorectal cancer invasion and metastasis.