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

描述（由申请人提供）：启动子DNA甲基化导致的肿瘤抑制基因沉默是肿瘤发生的重要机制，包括肝细胞癌（HCC）。microRNAs（miRNAs）作为基因表达的关键调控因子，在细胞增殖、分化和凋亡中发挥着重要作用。在其启动子区域中含有CpG岛的肿瘤抑制性miRNA也可能对甲基化介导的沉默敏感。先前的研究发现，肿瘤抑制性miRNA（miR-1-1、miR-124和miR-203）的表达失调可能是由于异常的DNA甲基化。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，特别是对于在肝组织中特异性表达的那些（miR-122、miR-152、miR-194、miR-199和miR-215）。我们的假设是，肿瘤抑制性miRNA基因中的DNA甲基化是影响相关成熟miRNA表达的常见事件，并且有助于区分HCC肿瘤和非肿瘤组织。这两个具体目标是：（1）检测一组肿瘤抑制性miRNA基因在HCC肿瘤组织中与邻近非肿瘤组织相比是否具有显著更高的DNA甲基化水平，并测试miRNA甲基化水平对于B型肝炎病毒（HBV）和丙型肝炎病毒（HCV）相关的HCC是否不同;（2）研究一组miRNA基因甲基化改变是否与成熟miRNA表达下调有关。将使用哥伦比亚大学医学中心完善的福尔马林固定石蜡包埋（FFPE）美国HCC患者组织库进行仅病例研究。共有120例经组织学证实的HCC病例，有肿瘤和邻近非肿瘤组织以及HBV/HCV感染数据可用于本研究。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。这些甲基化标志物具有潜在的临床应用，以改善风险评估，早期诊断和预后预测，甚至可能改善治疗，因为表观遗传变化的可逆性。PHS 398/2590（Rev.06/09）

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