Oncogenic potential of histone-variant H2A.Z.1 and its regulatory role in cell cycle and epithelial-mesenchymal transition in liver cancer.

// Hee Doo Yang 1, 3, * , Pum-Joon Kim 2, * , Jung Woo Eun 1, 3 , Qingyu Shen 1, 3 , Hyung Seok Kim 1, 3 , Woo Chan Shin 1, 3 , Young Min Ahn 4 , Won Sang Park 1 , Jung Young Lee 1 , Suk Woo Nam 1, 3, 5 1 Laboratory of Oncogenomics, Department of Pathology, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea 2 Department of Cardiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea 3 Functional RNomics Research Center, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea 4 Department of Kidney System, College of Oriental Medicine, Kyung Hee University, Seoul 02447, Republic of Korea 5 Cancer Evolution Research Center, The Catholic University of Korea, Seoul 06591, Republic of Korea * These authors contributed equally to this work Correspondence to: Suk Woo Nam, e-mail: swnam@catholic.ac.kr Keywords: H2A.Z.1, cell cycle, epithelial-mesenchymal transition, liver cancer Received: September 14, 2015      Accepted: January 23, 2016      Published: February 04, 2016 ABSTRACT H2A.Z is a highly conserved H2A variant, and two distinct H2A.Z isoforms, H2A.Z.1 and H2A.Z.2, have been identified as products of two non-allelic genes, H2AFZ and H2AFV . H2A.Z has been reported to be overexpressed in breast, prostate and bladder cancers, but most studies did not clearly distinguish between isoforms. One recent study reported a unique role for the H2A.Z isoform H2A.Z.2 as a driver of malignant melanoma. Here we first report that H2A.Z.1 plays a pivotal role in the liver tumorigenesis by selectively regulating key molecules in cell cycle and epithelial-mesenchymal transition (EMT). H2AFZ expression was significantly overexpressed in a large cohort of hepatocellular carcinoma (HCC) patients, and high expression of H2AFZ was significantly associated with their poor prognosis. H2A.Z.1 overexpression was demonstrated in a subset of human HCC and cell lines. H2A.Z.1 knockdown suppressed HCC cell growth by transcriptional deregulation of cell cycle proteins and caused apoptotic cell death of HCC cells. We also observed that H2A.Z.1 knockdown reduced the metastatic potential of HCC cells by selectively modulating epithelial-mesenchymal transition regulatory proteins such as E-cadherin and fibronectin. In addition, H2A.Z.1 knockdown reduced the in vivo tumor growth rate in a mouse xenograft model. In conclusion, our findings suggest the oncogenic potential of H2A.Z.1 in liver tumorigenesis and that it plays established role in accelerating cell cycle transition and EMT during hepatocarcinogenesis. This makes H2A.Z.1 a promising target in liver cancer therapy.