Molecular mechanism of diet-induced carcinogenesis

摘要 近年来非酒精性脂肪肝的发病率急剧增加 导致NASH（非酒精性肝炎）患病率的增加。 脂肪性肝炎）和相关并发症，如肝硬化和肝细胞癌 癌症（HCC）。在美国，NASH正在成为HCC的主要风险因素， 有效的治疗。与HBV/HCV诱导的HCC不同， NASH相关HCC的发病机制。我们使用了 HCC小鼠模型，其中100%小鼠喂养胆碱缺乏和氨基酸定义 （CDAA）饮食在22周时形成NASH，在65-75周时在约75%的小鼠中形成自发性HCC 周此外，这些小鼠表现出明确的病理变化， 类似于人类HCC的进展。我们研究的一个关键发现是， miR-155（一种促炎性microRNA）从早期阶段开始持续上调， 喂食与NASH发展相关的CDAA饮食。值得注意的是，miR-155是 在人类NASH和HCC患者中升高，其水平是NASH和HCC的独立预测因子。 肝癌患者预后差，无复发生存。我们假设 肝细胞和枯否细胞（肝脏中的炎性细胞）中miR-155的上调， 在NASH和HCC中起因果作用。这一建议是基于新的发现， (i)miR-155敲除（KO）小鼠表现出减少的炎症和脂血症， 早在4周喂养CDAA饮食，和（ii）zerumbone（ZER），倍半萜品 一种来自食用姜的植物化学物质抑制了自发的和饮食诱导的 小鼠炎症反应和培养中的HCC细胞生长， 下调miR-155。为了验证我们的假设， 而ZER治疗将抑制NASH和HCC，我们将追求以下3个目标。 1（a）阐明miR-155在饮食诱导的NASH的起始和进展中的作用 和HCC，以及（B）通过聚焦于 miR-155靶点。2（a）研究过表达miR-155的小鼠的易感性 在肝细胞中或在肝细胞+枯否细胞中，以饮食诱导的NASH和HCC，和（B） 通过鉴定其细胞来阐明差异发病机制的潜在机制 具体目标类型。3.通过以下方式探索ZER的预防/治疗潜力：（a）评估 其针对HCC细胞的抗肿瘤发生潜力，（B）测试其抗炎功能 在小鼠中，和（c）阐明其功能的分子基础。

ABSTRACT 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.