Abstract 5751: Dietary cholesterol promotes steatohepatitis-related hepatocellular carcinoma by inducing aberrant gene expression in metabolism and mutations in calcium signaling
Authors: Liang Qiaoyi Jessie , Teoh Narcissus , Xu Lixia , Farrell Geoffrey , Yu Jun 
Published: August 2018

Abstract
Background and Aims: Dietary cholesterol and nonalcoholic steatohepatitis (NASH) are risk factors for hepatocellular carcinoma (HCC), but their molecular mechanisms are undefined.
Methods: We investigated the effects of cholesterol on NASH and HCC in diethylnitrosamine-injected mice fed high-fat diets with or without high cholesterol. mRNA microarray and whole-exome sequencing analyses were applied for expressional and genetic aberrations. Identified molecular changes were validated in 37 human NASH-HCCs.
Results: Whereas non-cholesterol-fed mice developed simple steatosis, high-cholesterol-fed mice developed NASH, with inflammatory, metabolic and oncogenic genes upregulated in NASH versus steatosis. In cholesterol-induced NASH, HCCs were larger and more numerous than in non-cholesterol-induced steatosis. Although similar numbers of differentially expressed genes were identified between NASH- and steatosis-HCCs, more pathways were found to be uniquely affected in NASH-HCCs, including calcium signaling, insulin signaling, cell adhesion, and axon guidance. In addition, significantly more nonsynonymous somatic mutations occurred in NASH-HCCs (335±84/sample) than steatosis-HCCs (43±13/sample) (P&lt;0.05). Integrated analysis demonstrated that genetic and expressional alterations in NASH-HCCs uniquely affected distinct genes pertinent to five pathways of calcium signaling, insulin signaling, cell adhesion, axon guidance and metabolism. Twelve aberrantly expressed genes in murine NASH-HCC were verified in human NASH-HCC, including metabolism-related genes ALDH18A1, CAD, CHKA, POLD4, PSPH, SQLE and CFD. Among the 80 recurrent mutations particular in murine NASH-HCCs, 21 were also recurrently mutated in human NASH-HCCs, including potential mutational cancer drivers MTOR and SDK1, and three calcium signaling-related genes (RYR1, CACNA1H and RYR2). With calcium signaling affected most significantly by mutations in murine NASH-HCCs, we further verified that calcium signaling was significantly dysregulated by 19 recurrently mutated genes in human NASH-HCCs (n=37), 11 of which encode calcium channel proteins (RYR1, RYR2, CACNA1B, CACNA1E, CACNA1H, CACNA1I, GRIN2C, ATP2A2, ATP2B4, SLC8A1 and ITPR3). RYR1 was mutated most frequently in both murine (4/5) and human (13.5%) NASH-HCCs, with loss-of-function stop-gain/truncating mutations; silencing of RYR1 promoted hepatocyte growth.
Conclusions: Dietary cholesterol causes NASH by dysregulating genes involved in inflammation and metabolism, and promotes NASH-HCC by inducing oncogenic expression and mutations. We identified novel aberrant gene expression, mutations and core oncogenic pathways that contribute to cholesterol-associated NASH-HCC in mice that are relevant to human NASH-HCC.
Citation Format: Qiaoyi Jessie Liang, Narcissus Teoh, Lixia Xu, Geoffrey Farrell, Jun Yu. Dietary cholesterol promotes steatohepatitis-related hepatocellular carcinoma by inducing aberrant gene expression in metabolism and mutations in calcium signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5751.