The Role of MicroRNA in Hepatocarcinogenesis

描述（由申请人提供）：我们的长期目标是推进我们对微rna （miRNAs）在肝癌发生中的作用的理解。mirna是高度保守的-19-25核苷酸的非编码rna，部分在植物和动物中表达，主要参与基因沉默。在动物中，miRNAs的功能要么是通过靶基因3'- utr上多个非重叠位点的不完美互补碱基配对，要么是通过介导靶mrna的降解。只有少数mirna的生物学功能是已知的。最近的研究表明，这些mirna的表达在不同来源的人类癌症中受到不同的调控，其中一些mirna的靶点作为癌基因或肿瘤抑制基因。许多mirna以组织特异性的方式表达，在人类癌症中显着改变。该项目的目的是阐明肝脏特异性微RNA （mir-122a）在肝癌发生中的作用。肝细胞癌是世界上第五大最常见的癌症，也是导致癌症相关死亡的第三大原因。通过miRNA微阵列分析，我们观察到叶酸/甲基缺乏大鼠诱导的多阶段肝癌发生过程中一些miRNA的差异调控。其中，丰富的肝脏特异性miRNA mir-122a的表达在所有肿瘤中均显著下调。将这项研究扩展到人原发性肝细胞癌，发现肿瘤中mir-122的表达显著降低。在本研究中，我们将探讨mir-122a在肝细胞分化和肝癌发生中的作用。本研究的具体目的是：1)通过实时RT-PCR或northern blot分析，在大量人类HCC中检测mir- 122a的表达，以确定其下调是否为特定病因HCC的特征；2)通过反义寡核苷酸确定mir-122a是否参与小鼠ES细胞或大鼠肝细胞的肝细胞分化；3)研究其在非表达的人肝癌细胞系中过表达是否抑制培养和锚定独立生长或促进细胞凋亡。希望本研究能够建立mir-122a作为肝细胞癌的生物标志物，为肝癌治疗提供新的分子靶点。此外，该提案与NCI， NIDDK和NIAAA等多个研究所在肝细胞癌的病因，预防和治疗方面设定的使命/目标非常吻合。

DESCRIPTION (provided by applicant): Our long term objective is to advance our understanding of the role of micro RNAs (miRNAs) in hepatocarcinogenesis. miRNAs are highly conserved -19-25 nucleotides noncoding RNAs some of expressed in plants and animals, are primarily involved in gene silencing. In animals, miRNAs function either by imperfect complimentary base pairing at multiple non-overlapping sites on 3'-UTRs of target genes or by mediating degradation of target mRNAs. The biological function of only a few miRNAs is known. Recent studies have shown that the expression of the miRNAs are differentially regulated in human cancers of different origins and the targets of some of the miRNAs act as oncogenes or tumor suppressor genes. Many miRNAs are expressed in a tissue-specific manner that is markedly altered in human cancers. The objective of this project is to elucidate the role of a liver specific micro RNA (mir-122a) in hepatocarcinogenesis. Hepatocellular carcinoma is the fifth most prevalent cancer in the world and is the third leading cause of cancer related death. Using miRNA microarray analysis we observed differential regulation of some miRNAs during the multistage hepatocarcinogenesis process induced in folate/methyl-deficient rats. Among these the expression of mir-122a, an abundant liver specific miRNA, was significantly down regulated in all tumors. Extension of this study to human primary hepatocellular carcinomas showed dramatic decrease in mir-122 expression in tumors. In the present study we will explore the role of mir-122a in hepatocyte differentiation and hepatocarcinogenesis. The specific aims of the present proposal are to: 1) measure expression of mir- 122a by real time RT-PCR or northern blot analysis in a large number of human HCCs to determine whether its down regulation is characteristic of HCC of specific etiology; 2) determine whether mir-122a is involved in hepatocyte differentiation in mouse ES cells or rat hepatocytes by antisense oligo and 3) investigate whether its overexpression in nonexpressing human hepatocellular carcinoma cell lines inhibits growth in culture and anchorage independent growth or promotes apoptosis. It is hoped that this study could establish mir-122a as a biomarker for hepatocellular carcinomas that can provide novel molecular target for liver cancer therapy. Further, this proposal fits well with the mission/goals set forth by multiple institutes that include NCI, NIDDK and NIAAA n the etiology, prevention and treatment of hepatocellular carcinomas.