Aberrant DNA Methylation of MicroRNA Genes in Hepatocellular Carcinoma (HCC)

描述（申请人提供）：启动子DNA甲基化导致肿瘤抑制基因沉默是肿瘤发生的重要机制，包括在肝细胞癌（HCC）中。MicroRNAs （miRNAs）作为基因表达的关键调控因子，在细胞增殖、分化和凋亡过程中起着至关重要的作用。在其启动子区域含有cpg岛的肿瘤抑制mirna也可能对甲基化介导的沉默敏感。先前的研究发现，肿瘤抑制mirna （miR-1-1、miR-124和miR-203）的表达失调可能是由于DNA甲基化异常。这些有限的数据是从不同的动物模型、癌细胞系或少量冷冻肿瘤组织的研究中获得的。许多具有肿瘤抑制功能的mirna的甲基化状态在很大程度上是未知的，特别是那些在肝组织中特异性表达的mirna （miR-122、miR-152、miR-194、miR-199和miR-215）。我们的假设是肿瘤抑制miRNA基因的DNA甲基化是影响相关成熟miRNA表达的共同事件，有助于HCC肿瘤和非肿瘤组织的区分。两个具体目的是：(1)检测一组肿瘤抑制miRNA基因在HCC肿瘤组织中的DNA甲基化水平是否明显高于邻近的非肿瘤组织，并检测乙型肝炎病毒（HBV）和丙型肝炎病毒（HCV）相关HCC的miRNA甲基化水平是否不同；(2)研究显示显著甲基化改变的miRNA基因亚组是否与相关成熟miRNA表达下调相关。一项病例研究将在哥伦比亚大学医学中心使用一个完善的、福尔马林固定、石蜡包埋（FFPE）的美国HCC患者组织库进行。本研究共有120例组织学证实的肝癌伴肿瘤及邻近非肿瘤组织和HBV/HCV感染的病例。这项初步研究将为了解miRNA基因甲基化在区分HCC恶性组织和非肿瘤组织中的作用提供有价值的初步数据。由于表观遗传改变的可逆性，这些甲基化标记物在改善风险评估、早期诊断和预后预测方面具有潜在的临床应用价值，甚至可能改善治疗。小灵通398/2590 （Rev. 06/09）页延续格式页

DESCRIPTION (provided by applicant): Tumor suppressor gene silencing by promoter DNA methylation is an important mechanism of tumorigenesis, including in hepatocellular carcinoma (HCC). MicroRNAs (miRNAs), as key regulators of gene expression, play a critical role in cell proliferation, differentiation and apoptosis. Tumor suppressive miRNAs harboring CpG-islands in their promoter regions may also be sensitive to methylation-mediated silencing. Previous studies found that the deregulated expression of tumor suppressive miRNAs (miR-1-1, miR-124, and miR-203) might be due to aberrant DNA methylation. These limited data were obtained from different animal models, cancer cell lines or from a study of a small number of frozen tumor tissues. The methylation status of many miRNAs with tumor suppressive functions is largely unknown, especially for those specifically expressed in liver tissues (miR-122, miR-152, miR-194, miR-199 and miR-215). Our hypothesis is that DNA methylation in tumor suppressive miRNA genes is a common event influencing relevant mature miRNA expression, and contributes to differentiate HCC tumor and non-tumor tissues. The two specific aims are: (1) To examine whether a panel of tumor suppressive miRNA genes have significantly higher levels of DNA methylation in HCC tumor tissues compared with adjacent non-tumor tissues, and test whether the miRNA methylation levels are different for hepatitis B virus (HBV) and hepatitis C virus (HCV)-related HCC; (2) To examine whether a subgroup of miRNA genes showing significant methylation alterations are associated with the down-regulation of relevant mature miRNA expression. A case-only study will be conducted using a well-established, formalin- fixed, paraffin-embedded (FFPE) tissue bank of US HCC patients at Columbia University Medical Center. Totally, 120 histologically confirmed HCC cases with tumor and adjacent non-tumor tissues and HBV/HCV infection data are available for the current study. This pilot study will provide valuable preliminary data to understand the role of miRNA gene methylation in distinguishing HCC malignant tissue from non-tumor tissues. These methylation markers have potential clinical applications to improve risk assessment, early diagnosis and prognostic prediction, and may even possibly improve treatment because of the reversible nature of epigenetic changes. PHS 398/2590 (Rev. 06/09) Page Continuation Format Page PUBLIC HEALTH RELEVANCE: Aberrant DNA methylation is a frequent event occurring early in HCC tumorigenesis. This pilot study will provide initial evidence on the critical role of tumor suppressive miRNA genes' methylation and expression in identifying HCC malignant tissue. It will provide preliminary data to support expanded epidemiological studies that should lead to long term improvements in HCC risk assessment, early diagnosis and efficient treatment.