Underexpression of LKB1 tumor suppressor is associated with enhanced Wnt signaling and malignant characteristics of human intrahepatic cholangiocarcinoma

// Jinghan Wang 1,2 , Keqiang Zhang 2 , Jinhui Wang 3 , Xiwei Wu 3 , Xiyong Liu 2 , Bin Li 1 , Yan Zhu 4 , Yong Yu 1 , Qingbao Cheng 1 , Zhenli Hu 4 , Chao Guo 3 , Shuya Hu 2 , Bing Mu 3 , Chun-Hao Tsai 5 , Jie Li 2 , Lynne Smith 2 , Lu Yang 3 , Qi Liu 2 , Peiguo Chu 6 , Vincent Chang 7 , Baihe Zhang 1 , Mengchao Wu 1 , Xiaoqing Jiang 1 and Yun Yen 2,8 1 The First Department of Biliary Surgery, Eastern Hepatobiliary Surgical Hospital, The Second Military Medical University, Shanghai, China 2 Department of Molecular Pharmacology, City of Hope National Medical Center, Duarte, California, USA 3 The Integrative Genomics Core lab of Department of Molecular Medicine, City of Hope National Medical Center, Duarte, California, USA 4 Changhai Hospital, The Second Military Medical University, Shanghai, China 5 Department of Orthopedic Surgery, School of Medicine, China Medical University, Taichung, Taiwan 6 Department of Pathology, City of Hope National Medical Center; Duarte, California, USA 7 Program for Translation Medicine, Taipei Medical University, Taipei, Taiwan 8 PhD Program of Cancer Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan Correspondence to: Yun Yen, email: // Xiaoqing Jiang, email: // Keqiang Zhang, email: // Keywords : intrahepatic cholangiocarcinoma (ICC), liver kinase B1 (LKB1), global transcriptional profiling, Wnt/β-catenin, recurrence and metastasis Received : February 28, 2015 Accepted : May 13, 2015 Published : May 27, 2015 Abstract Intrahepatic cholangiocarcinoma (ICC) is a rare and highly aggressive malignancy. In this study, we identified the presence of gene deletion and missense mutation leading to inactivation or underexpression of liver kinase B1 (LKB1) tumor suppressor and excluded the involvement of LKB1 gene hypermethylation in ICC tissues. Immunohistochemical analysis showed that LKB1 was underexpressed in a portion of 326 ICC tissues compared to their adjacent normal tissues. By statistical analysis underexpression of LKB1 in ICC tissues significantly correlated with poor survival and malignant disease characteristics in ICC patients. Moreover, we showed that knockdown of LKB1 significantly enhanced growth, migration, and invasion of three LKB1-competent ICC cell lines. Global transcriptional profiling analysis identified multiple malignancy-promoting genes, such as HIF-1α , CD24 , Talin1 , Vinculin , Wnt5 , and signaling pathways including Hedgehog, Wnt/β-catenin, and cell adhesion as novel targets of LKB1 underexpression in ICC cells. Furthermore, knockdown of LKB1 gene expression dramatically enhanced Wnt/β-catenin signaling in ICC cells, while an inverse correlation between LKB1 and nuclear β-catenin was observed in ICC tissues. Our findings suggest a novel mechanism for ICC carcinogenesis in which LKB1 underexpression enhances multiple signaling pathways including Wnt/β-catenin to promote disease progression.