Frequent in-frame somatic deletions activate gp130 in inflammatory hepatocellular tumours

Inflammatory hepatocellular adenomas (IHCA) are benign liver tumours defined by the presence of inflammatory infiltrates and by the elevated expression of inflammatory proteins in tumour hepatocytes1,2. Here we show a striking activation of the IL6 signalling pathway in this tumour type, and sequencing candidate genes pinpointed this response to somatic gain-of-function mutations in the IL6ST gene that encodes the signalling co-receptor gp130. Indeed, ~70% of IHCA harbour small in-frame deletions that target the binding site of gp130 for IL6, and expression of the most frequent gp130 mutant, Delta-STVY190, in hepatocellular cells activates STAT3 in absence of ligand. Further, analysis of hepatocellular carcinomas revealed rare gp130 alterations always accompanied by ß-catenin-activating mutations, suggesting a cooperative effect of these signalling pathways in the malignant conversion of hepatocytes. The recurrent gain-of-function gp130 mutations in these human hepatocellular adenomas explains their inflammatory phenotype, and suggest that similar alterations may occur in other inflammatory epithelial tumours with STAT3 activation. HG-U133A Affymetrix GeneChipTM arrays were used to compare the expression profiles of 4 Inflammatory hepatocellular adenomas (IHCA) and 4 non related non-tumor livers. RNA labelling, hybridization and analysis were carried out following the manufacturer’s instructions (Affymetrix, Santa Clara, CA). Raw data were obtained by using Microarray Suite 5.0 (MAS5) software, embedded in the Affymetrix GeneChip Operating Software (Santa Clara, USA); the resulting raw numerical data (CEL files) - available as supplementary files - collected from 8 Affymetrix GeneChips were pre-processed for normalization and filtering as described in [Rebouissou et al., J Biol Chem 2007, 282(19):14437-46, PMID: 17379603; Rebuissou et al., J Hepatol 2008, 49(1):61-71. PMID: 18466996 and Rebuissou et al., in preparation].