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）和相关并发症（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的主要风险因素，但没有有效的治疗方法。与HBV/HCV诱导的HCC不同，对NASH相关HCC的发病机制知之甚少。我们使用了HCC小鼠模型，其中100%喂食胆碱缺乏和氨基酸限定（CDAA）饮食的小鼠在22周时发生NASH，约75%的小鼠在65-75周时发生自发性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，从喂食CDAA饮食的早期阶段开始，miR-155（一种促炎性microRNA）的一致上调与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，并且其水平是HCC患者中不良预后和无复发生存的独立预测因子。我们假设miR-155在肝细胞和枯否细胞（肝脏中的炎性细胞）中的上调在NASH和HCC中起因果作用。该提议基于以下新发现：（i）miR-155敲除（KO）小鼠早在喂食CDAA饮食4周时就表现出炎症和脂血症减少，以及（ii）zerumbone（ZER），一种来自可食用生姜的倍半萜类植物化学物质，可抑制小鼠中自发和饮食诱导的炎症反应以及培养物中的HCC细胞生长，并导致miR-155下调。为了验证我们的假设，即操纵miR-155水平和用ZER治疗将抑制NASH和HCC，我们将追求以下3个目标。1（a）使用miR-155 KO小鼠阐明miR-155在饮食诱导的NASH和HCC的起始和进展中的作用，以及（B）通过关注miR-155靶点来鉴定潜在机制。2（a）研究在肝细胞或肝细胞+枯否细胞中过表达miR-155的小鼠对饮食诱导的NASH和HCC的易感性，和（B）通过鉴定其细胞类型特异性靶标来阐明差异发病机制的潜在机制。3.通过以下方式探索ZER的预防/治疗潜力：（a）评估其针对HCC细胞的抗肿瘤潜力，（B）在小鼠中测试其抗炎功能，以及（c）阐明其功能的分子基础。

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.