Oncogenic role of the frizzled-7/b-catenin pathway in hepatocellular carcinoma Philippe Merle 1,2 , Miran Kim 1 , Marc Herrmann 1 , Anand Gupte 1 , Lydie Lefranc ¸ois 2 , Sophia Califano 1 , Christian Tre ´po 2 , Shinji Tanaka 3 , Ludmila Vitvitski 2 , Suzanne de la Monte 1 , Jack R. Wands 1, * 1 Department of Medicine and Pathology, Brown Medical School, The Liver Research Center, Providence, 55 Claverick St., 4th Floor, Providence, RI 02903, Rhode Island 02903, USA 2 Inserm U271, Virus des Hepatites et Pathologies Associees, Lyon, France 3 Department of Gastroenterological Surgery, National Cancer Center, Fukuoka, Japan Background/Aims: The molecular mechanisms of hepatocarcinogenesis remain largely unknown. Previous studies suggest that activation of the Wnt/b-catenin pathway is important during hepatocyte transformation but the role of Frizzled receptor (FZD) in this process has not been defined. Here we investigate activation of this pathway by FZD using transgenic hepatocellular carcinoma (HCC) murine models. Methods: We employed single (c-myc, SV40-Tag) and established double [insulin receptor substrate-1 (IRS-1/c-myc) and hepatitis Bx protein (X/c-myc)] transgenic lines and all developed HCC. Expression of 9 FZD was measured by real time RT-PCR and Western blot analysis. Phosphorylation and cellular accumulation of b-catenin were assessed in both dysplastic tissue and tumors. We investigated the effect of a dominant negative (DN) FZD7 on TCF transcriptional activity in a SV40 derived HCC cell line. Results: FZD7 was highly overexpressed at the mRNA and protein level(s) in HCC and occurred in dysplasia. Upregulation of FZD7 was associated with reduced phosphorylation of b-catenin and led to nuclear accumulation in HCC tumors. Ectopic expression of a DN FZD7 construct decreased TCF transcriptional activity in tumor cells. Conclusions: These observations suggest that upregulation of FZD7 receptors in association with activation of the canonical Wnt/b-catenin pathway is a common molecular event in HCC. q 2005 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved. Keywords: Signaling; Frizzled receptors; Liver dysplasia; Hepatocellular carcinoma 1. Introduction Hepatocellular carcinoma (HCC) is one of the most frequent fatal malignancies worldwide [1]. It occurs at a high rate in Asia and Africa [2] and has been gradually increasing in Western countries as well [3,4]. Although major environmental risks have been identified such as chronic hepatitis B and C virus infection, exposure to aflatoxin B1, alcohol consumption and anabolic steroids, the molecular mechanisms of hepatocarcinogenesis remain largely unknown [5,6]. More recently, the observation of aberrant activation of the Wnt/b-catenin pathway as manifested by cellular and nuclear accumulation of this protein due to mutations of the b-catenin gene has contributed to a better understanding of pathogenesis [7,8]. However, additional studies estimate that 46% of hepatic adenomas and between 35 and 80% of HCC have aberrant b-catenin cellular accumulation, not associated with mutations affecting the b-catenin gene. In addition, Journal of Hepatology 43 (2005) 854–862 www.elsevier.com/locate/jhep 0168-8278/$30.00 q 2005 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jhep.2005.05.018 Received 2 December 2004; received in revised form 13 May 2005; accepted 16 May 2005; available online 21 June 2005 * Corresponding author. Tel.:C1 401 444 5031; fax: C1 401 444 6194. E-mail address: jack_wands_md@brown.edu (J.R. Wands).