Molecular mechanism of diet-induced carcinogenesis

描述（由申请人提供）：近年来，西方世界非酒精性脂肪性肝病的发病率急剧增加，导致NASH（非酒精性脂肪性肝炎）及其相关并发症如肝硬化和肝细胞癌（HCC）的患病率增加。在美国，NASH正在成为HCC的主要危险因素，但没有有效的治疗方法。与HBV/ hcv诱导的HCC不同，nash相关HCC的发病机制知之甚少。我们使用了一个小鼠肝癌模型，其中100%的小鼠喂食缺乏胆碱和氨基酸（CDAA）饮食，在22周内发生NASH，约75%的小鼠在65-75周内发生自发性HCC。此外，这些小鼠表现出明确的病理变化，与人类HCC的进展明显相似。我们研究的一个关键发现是miR-155（一种促炎microRNA）在喂食CDAA饮食的早期阶段持续上调，这与NASH的发展相关。值得注意的是，miR-155在人类NASH和HCC患者中升高，其水平是HCC患者预后不良和无复发生存的独立预测因子。我们假设肝细胞和库普弗细胞（肝脏中的炎症细胞）中miR-155的上调在NASH和hcc中起因果作用。该建议基于以下新发现：(i) miR-155敲除（KO）小鼠在喂食CDAA饮食后4周就表现出炎症和甘油三酯血症的减少；（ii） zerumbone (ZER)，一种来自可食用生姜的倍半萜萜类植物化学物质，抑制小鼠自发和饮食诱导的炎症反应以及培养中的HCC细胞生长，并导致miR-155的下调。为了验证我们的假设，即操纵miR-155水平和使用ZER治疗将抑制NASH和HCC，我们将追求以下3个目标。1 (a)利用miR155KO小鼠阐明miR-155在饮食诱导的NASH和HCC的发生和进展中的作用，(b)通过关注miR-155靶点确定其潜在机制。2 (a)研究在肝细胞或肝细胞+Kupffer细胞中过表达miR-155的小鼠对饮食诱导的NASH和HCC的易感性；(b)通过鉴定其细胞类型特异性靶点阐明其差异发病机制。3. 通过(a)评估其对HCC细胞的抗肿瘤潜力，(b)在小鼠中测试其抗炎功能，(c)阐明其功能的分子基础，探索ZER的预防/治疗潜力。

DESCRIPTION (provided by applicant): The dramatic increase in recent years in the incidence of non-alcoholic fatty liver disease in the Western world has led to an increase in the prevalence of NASH (non-alcoholic steatohepatitis) and associated complications such as cirrhosis and hepatocellular cancer (HCC). In USA, NASH is emerging as a major risk factor for HCC with no effective therapy. Unlike HBV/HCV-induced HCC, very little is known about the mechanism(s) underlying the pathogenesis of NASH-associated HCC. We have used a mouse model of HCC in which 100% mice fed choline-deficient and amino acid defined (CDAA) diet develop NASH by 22 weeks and spontaneous HCC in ~75% mice by 65-75 weeks. Further, these mice exhibit well-defined pathological changes that are markedly similar to the progression of HCC in humans. A key finding from our study is the consistent upregulation of miR-155, a proinflammatory microRNA, from an early stage of feeding CDAA diet that correlates with development of NASH. Notably, miR-155 is elevated in human NASH and HCC patients and its level is an independent predictor of poor prognosis and recurrence-free survival in HCC patients. We hypothesize that upregulation of miR-155 in hepatocytes and Kupffer cells (inflammatory cells in the liver), plays a causal role in NASH and HCCs. This proposal is based on the novel findings that (i) miR-155 knockout (KO) mice exhibit reduced inflammation and triglyceridemia as early as 4 weeks of feeding CDAA diet, and (ii) zerumbone (ZER), a sesquiterpine phytochemical from an edible ginger suppressed both spontaneous and diet-induced inflammatory responses in mice and HCC cell growth in culture and caused downregulation of miR-155. To test our hypothesis that manipulation of miR-155 levels and treatment with ZER will inhibit NASH and HCC, we will pursue the following 3 aims. 1 (a) Elucidate the role of miR-155 in initiation and progression of diet-induced NASH and HCC using miR155KO mice, and (b) identify the underlying mechanism by focusing on miR-155 targets. 2 (a) Investigate the susceptibility of mice overexpressing miR-155 in hepatocytes or in hepatocytes+Kupffer cells to diet induced NASH and HCC, and (b) elucidate the underlying mechanism of differential pathogenesis by identifying its cell type specific targets. 3. Explore preventive/therapeutic potential of ZER by (a) assessing its anti-tumorigenic potential against HCC cells, (b) testing its anti-inflammatory function in mice, and (c) elucidating the molecular basis of its function.