7 PRECLINICAL CHARACTERIZATION OF PRO 206, AN ORALLY ACTIVE SMALL-MOLECULE HEPATITIS C (HCV) ENTRY INHIBITOR

Inflammatory hepatocellular adenomas (IHCA) are benign liver tumours defined by the presence of inflammatory infiltrates and by an overexpression of inflammatory proteins.IHCA are usually developed in women and their occurrence is frequently associated with obesity and alcohol intake.Recently, we identified somatic mutations activating gp130 in 60% of IHCA (Rebouissou et al, Nature, in press), thus defining gp130 as a new oncogene in human tumors.The aim of this work was to evaluate frequency of gp130 mutations in a wide series of tumors.Method: A series of 400 well-characterised hepatocellular tumors was screened including hepatocellular adenomas, carcinomas, hepatocholangio-carcinoma, fibrolamellar carcinomas and intra-hepatic cholangiocarcinomas. 100 tumors from different organs were also collected.To search for mutations, gp130 exons were screened in all samples and function of 7 different mutants was analysed in HEP3B.Results: We identified a somatic mutation in 65% of the IHCA including 24 different small in-frame deletions or duplications.Spectrum of mutations shows that mutations clearly target the IL-6 binding site in gp130.We further demonstrated that the expression of the most frequent gp130 mutants in HEP3B cells activates STAT3 in absence of IL-6.We searched for possible interaction and cooperation of gp130 activation with other pathways altered in hepatocellular adenoma.HNF1a inactivation and gp130 activation were mutually exclusive in HCA (P < 10 -4 ).By contrast, in half of the b-catenin activating HCA, we identified a gp130-activating mutation.For two IHCA associated with a malignant transformation, both an activating gp130 and b-catenin mutations were found.Further, analysis of 220 hepatocellular carcinomas revealed rare gp130 alterations in all cases accompanied by b-catenin-activating mutations, suggesting a cooperative effect of these signalling pathways in the malignant transformation of hepatocytes.Conclusion: This is the first identification of gp130 somatic activating mutations in human tumors; this finding reinforces the role of inflammation in hepatocarcinogenesis and particularly in the malignant transformation of HCA.Moreover, gp130 mutations enable to refine the molecular classification of hepatocellular tumors in human.