Human Cancer Biology Expression of Serotonin Receptors in Human Hepatocellular Cancer Christopher Soll 1 , Marc-Oliver Riener 2,4 , Christian Eugen Oberkofler 1 , Claus Hellerbrand 3 , Peter J. Wild 2 , Michelle L. DeOliveira 1 , and Pierre-Alain Clavien 1 Abstract Purpose: Serotonin is a well-known neurotransmitter and vasoactive substance. Recent research indicates that serotonin contributes to liver regeneration and promotes tumor growth of human hepato- cellular cancer. The aim of this study is to investigate the expression of serotonin receptors in hepatocellular cancer and analyze their potential as a cytotoxic target. Experimental Design: Using a tissue microarray and immunohistochemistry, we analyzed the expres- sion of serotonin receptors in the liver from 176 patients with hepatocellular carcinoma, of which nontumor tissue was available in 109 patients. Relevant clinicopathologic parameters were compared with serotonin receptor expression. Two human hepatocellular cancer cell lines, Huh7 and HepG2, were used to test serotonin antagonists as a possible cytotoxic drug. Results: The serotonin receptors 1B and 2B were expressed, respectively, in 32% and 35% of the patients with hepatocellular cancer. Both receptors were associated with an increased proliferation index, and receptor 1B correlated with the size of the tumor. Serotonin antagonists of receptors 1B and 2B consistently decreased viability and proliferation in Huh7 and HepG2 cell lines. Conclusion: We identified two serotonin receptors that are often overexpressed in human hepatocel- lular cancer and may serve as a new cytotoxic target. Clin Cancer Res; 18(21); 5902–10. Ó2012 AACR. Introduction Hepatocellular carcinoma (HCC) is the 5th most fre- quent cancer (1) and has become the 3rd leading cause of cancer-related death worldwide (2). To face this global health problem, the investigation of new molecular targets is necessary to develop new treatment strategies. Recent in vitro and in vivo studies have suggested that serotonin (5HT) contributes to the tumor growth in a variety of cancer including cholangiocarcinoma (3, 4), colon cancer (5), and HCC (6). Within the liver, 5HT was found to be implicated in the pathogenesis of liver fibrosis (7, 8), nonalcoholic steatotic hepatitis (9), and viral hep- atitis (10); all these conditions are involved in the tumor- igenesis of HCC. We have recently proposed that 5HT, through its 5HT2B receptor, may represent a potential target in HCC (6). We observed that the inhibition of 5HT2B receptors leads to cell death of hepatocellular cancer cells in vitro and decreased tumor growth in a subcutaneous tumor model in mice. At the cellular level, 5HT acts predominantly via G- protein coupled receptors. The availability of 7 receptor classes including 14 subtypes of serotonin receptors reflect the diversity of the serotonergic actions (11). Within these subtypes, 5HT receptors (1A, 1B, 2A, 2B, and 7) are widely distributed in the human gastrointestinal tract and are involved in normal liver function and disease (12, 13). In contrast, 5HT receptors 4 and 5 are not or only poorly expressed in the liver (14, 15). In this study, the expression of different serotonin receptors was analyzed in specimens obtained from 176 patients with HCC using immunohistochemistry (IHC) on a tissue microarray (TMA). Receptor expression was compared between nontumoral and tumoral tissue in 109 patients, in whom nontumor tissue was available. We tested whether the expression of serotonin receptors in HCC correlated to the phenotype of the tumor and a variety of clinicopathologic parameters. From these data, we conducted experiments in human cell lines of HCC to investigate the cytotoxic effect of antagonizing serotonin receptors. Patients and Methods Patients One hundred seventy-six patients with HCC who under- went surgery between 1992 and 2007 in Z€ urich, Switzerland Authors' Affiliations: Departments of 1 Surgery and 2 Pathology, Swiss Hepato-Pancreato-Biliary (HPB) Center, University Hospital Zurich, Zurich, Switzerland; 3 Department of Gastroenterology, University of Regensburg, Regensburg, Germany; and 4 Institute of Pathology, University Hospital Erlangen, Erlangen, Germany Note: C. Soll and M.-O. Riener contributed equally. Corresponding Author: Pierre-Alain Clavien, Department of Surgery, University Hospital Zurich, Raemistrasse 100, 8091 Zurich, Switzerland. Phone: 41-44-255-3300; Fax: 41-44-255-4449; E-mail: clavien@access.uzh.ch doi: 10.1158/1078-0432.CCR-11-1813 Ó2012 American Association for Cancer Research. Clinical Cancer Research Clin Cancer Res; 18(21) November 1, 2012 5902 Research. on September 29, 2021. © 2012 American Association for Cancer clincancerres.aacrjournals.org Downloaded from Published OnlineFirst October 19, 2012; DOI: 10.1158/1078-0432.CCR-11-1813