Abstract 461: Distinctive molecular traits of hepatocellular carcinoma in patients with non-alcoholic steatohepatitis

Background and aim: Non-alcoholic steatohepatitis (NASH) is emerging as one of the leading risk factors for hepatocellular carcinoma (HCC), but its molecular pathogenesis is still ill-defined. This study aims to identify unique molecular traits that differentiate NASH-HCC from other aetiologies through an integrative molecular characterization. Methods: A total of 225 tissue samples were collected, including samples from 125 biopsied/transplanted NASH patients; and 100 resected/transplanted NASH-HCC patients. Molecular characterization of FFPE samples, comprised expression array (n=53 NASH-HCC; n=74 NASH), whole exome sequencing (n=50 NASH-HCC), and SNP array (n=44 NASH-HCC). Publicly available data from HCV/HBV/alcohol-related HCCs were used to identify NASH-HCC distinctive traits. Results: NASH-HCC patients compared to NASH non-HCC patients were prevalently males (82% vs 42%, p<0.001), older (67 years vs 54, p<0.01), with higher diabetes incidence (72% vs 50%, p=0.004), hypertension (80% vs 52%, p<0.01) and cirrhosis (69% vs 29%, p<0.001). Analysis of the transcriptome showed enrichment of liver metabolism pathways in NASH livers, whereas NASH-liver tissues of HCC cases were characterized by inflammation (TNFα-NFkβ, IL6, STAT3), epithelial-mesenchymal transition (TGFβ1), proliferation (AKT, mTOR), and poor-prognosis liver signatures (p<0.05). Gene expression profiles of NASH-HCC tumours demonstrated that they can be classified in proliferation (50%) and non-proliferation (50%) molecular classes, as in non-NASH HCC. Mutational profiling of NASH-HCC tumours identified 4 genes with mutations in ≥10% of cases: TERT (52%), CTNNB1 (28%), TP53 (18%) and the TGFβ-receptor ACVR2A (10%). Interestingly, mutations in ACVR2A were three times more prevalent in NASH-HCC (n=100) than in viral/alcohol-related HCC (n=624)(2.6%, p<0.05). Functional impact of ACVR2A mutations is currently being investigated. Finally, unsupervised clustering of mutational signatures showed that NASH-HCC tumours are clustered in 2 groups, enriched in liver-cancer signatures #16 (44%) and #5(22%), respectively; and that a third cluster (15%) was enriched in signature #3, which is novel in liver cancer. By comparing these results with the clustering of mutational profiles from viral/alcohol-related HCCs, we identified the signature#3-cluster as specific of NASH-HCC. Conclusions: Non-tumour liver tissue of NASH-HCC patients is characterized by a cancer-field enriched in inflammatory, epithelial-to-mesenchymal transition and proliferation signalling pathways. NASH-HCC tumours showed a high frequency of ACVR2A mutations (10%), and a novel cancer mutational signature #3 (15%), suggesting genotoxic factors specifically associated to this entity. Citation Format: Sara Torrecilla, Roser Pinyol, Huan Wang, Carla Montironi, Carmen Andreu-Oller, Wei Qiang Leow, Agrin Moeini, Claudia Oliveira, Venancio Avancini Ferreira Alves, Anja Lachenmayer, Stephanie Roessler, Beatriz Minguez, Peter Schirmacher, Paolo Boffetta, Jean-François Dufour, Swan N Thung, Andrew Uzilov, Flair Jose Carrilho, Charissa Chang, Daniela Sia, Josep M Llovet. Distinctive molecular traits of hepatocellular carcinoma in patients with non-alcoholic steatohepatitis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 461.