Modulation of MAPK pathways and cell cycle by replicating hepatitis B virus: Factors contributing to hepatocarcinogenesis q Ruth Chin 1 , Linda Earnest-Silveira 1 , Bernd Koeberlein 2 , Susanne Franz 3 , Hanswalter Zentgraf 3 , Xuebin Dong 4,5 , Eric Gowans 4,5 , C.-Thomas Bock 2 , Joseph Torresi 1, * 1 Department of Medicine, CCREID, Royal Melbourne Hospital, University of Melbourne, Post Office, Parkville, Vic. 3050, Australia 2 Department of Molecular Pathology, University Hospital of Tuebingen, Germany 3 Applied Tumor Virology, German Cancer Research Center (DKFZ), Heidelberg, Germany 4 Burnet Institute, AMREP, Prahran, Vic., Australia 5 Department of Microbiology, Monash University, Vic., Australia Background/ Aims: Chronic infection with the hepatitis B virus (HBV) is strongly associated with the development of hepatocellular carcinoma but the mechanism by which this occurs is unknown. Numerous studies have focused on the HBV X protein showing that it activates signal transduction pathways while few have investigated these changes in HBV-replicating hepatocytes. Methods: We utilized the recombinant adenovirus system to deliver a replication competent HBV genome into Huh7 and primary marmoset hepatocytes (PMH) to examine the effects of active viral replication on the regulation of Ras-ERK sig- nal transduction and related pathways. Results: Huh7 cells and PMHs replicating HBV demonstrated significant upregulation in phosphorylated ERK, Akt, c- myc together with increased p53, cyclin B1 and p21 cip1 expression and cell cycle progression to G2 phase in the absence of increased cell proliferation. Phosphorylation of the key cell survival kinase, Akt, was significantly increased, resulting in increased serine phosphorylation of the downstream target, GSK3-b. Conclusions: These results demonstrated simultaneous activation of the MAP Kinase and Akt pathways in HBV-repli- cating hepatocytes that resulted in dysregulation in the control of cell cycle progression and which help explain the early pathogenic mechanisms that underlie malignant transformation associated with chronic hepatitis B infection. Ó 2007 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved. Keywords: Hepatitis; Carcinoma; Cell signaling 0168-8278/$32.00 Ó 2007 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jhep.2007.03.025 Received 3 December 2006; received in revised form 5 March 2007; accepted 6 March 2007; available online 18 April 2007 Associate Editor: F. Zoulim q The authors who have taken part in this study declared that they have no relationship with the manufacturers of the product involved either in the past or present and did not receive funding from the manufacturers to carry out their research. * Corresponding author. Tel.: +61 3 8344 3262; fax: +61 3 93471863. E-mail addresses: rchin@unimelb.edu.au (R. Chin), lindae@unimelb.edu.au (L. Earnest-Silveira), Bernd.Koeberlein@med.uni-tuebingen.de (B. Koeberlein), susanne-franz@web.de (S. Franz), h.zentgraf@dkfz-heidelberg.de (H. Zentgraf), xuebin@burnet.edu.au (X. Dong), gowans@burnet. edu.au (E. Gowans), thomas.bock@med.uni-tuebingen.de (C.-Thomas Bock), josepht@unimelb.edu.au (J. Torresi). Abbreviations: HBV, hepatitis B virus; MAPK, mitogen activated protein kinases; ERK, extracellular signal-regulated kinases; SAPK/JNK, stress-activated protein kinases/NH2-terminal-Jun kinases. www.elsevier.com/locate/jhep Journal of Hepatology 47 (2007) 325–337