Investigation of tumor suppressive miR-148a in IDH mutant gliomas

描述(由申请人提供)：目前脑胶质瘤仍不能用目前可用的放射和化疗方法治愈。对胶质瘤的深入分子表征揭示了丰富的分子多样性的异常，这引发了人们的希望，即我们可以通过将最有希望的靶点转化为个性化的治疗方法来显著影响这种疾病。这项建议通过研究一种新的靶点miR-148A的肿瘤抑制机制直接满足了这一需求，该靶标是通过PI的实验室建立的创新和强大的DNA甲基化分析策略确定的。虽然还没有在胶质瘤中进行研究，但miRNA-148A正在其他癌症中作为一种肿瘤抑制miRNA出现。作为抑制基因表达的非编码小RNA，miRNAs在癌症机制中发挥着关键作用，并作为其自身或其调控的基因提供新的治疗靶点。广泛的癌症组织基因组特征揭示了广泛存在的异常DNA CpG岛甲基化，这可能与某些miRNAs的表观遗传沉默有关。最近发现的异柠檬酸脱氢酶(IDH)突变不仅被认为是继发性胶质瘤的生物标志物，而且代表了胶质瘤发生的起始事件。我们对IDHMUT胶质瘤的研究有助于识别IDHMUT相关的全基因组高甲基化特征，胶质瘤-CpG岛甲基化表型(G-CIMP)，这在正常组织或IDH野生型胶质瘤中不存在。这导致了一个被广泛接受但尚未得到支持的假说，即G-CIMP通过沉默肿瘤抑制基因和/或参与分化的基因在胶质瘤的形成中发挥关键作用。因此，我们假设IDHMUT相关的DNA高甲基化可能会沉默胶质瘤中重要的肿瘤抑制miRNAs的表达。如我们的初步数据所示，我们使用无偏甲基化图谱在G-CIMP的背景下识别高甲基化的miRNA基因，在这些候选基因中，miRNA-148A似乎不仅具有肿瘤抑制特性，而且还直接调节参与DNA甲基化维持的关键基因DNMT1。在这项提案中，我们测试了中心假设，即IDHMUT导致肿瘤抑制基因miR-148A的表观遗传沉默，并且miR-148A的重新表达为胶质瘤的治疗提供了一种新的策略，特别是对于IDHMUT亚群。为此，我们的目标是：1)研究IDH突变与miR148A下调的分子基础；2)建立miR-148A下游抑制肿瘤的靶基因；3)探索miR-148A在IDHMUT胶质瘤中的治疗潜力。这些目标将结合无偏见的高分辨率甲基化分析技术、广泛的患者组织资源和包括患者来源的神经胶质瘤神经球细胞在内的各种细胞模型来实现。上述目标的实现将对基于修复缺陷miRNAs的胶质瘤新的定制治疗方法的开发做出重大贡献。

DESCRIPTION (provided by applicant): Gliomas presently remain incurable with currently available radiation and chemotherapeutic modalities. Intensive molecular characterization of gliomas have revealed a rich molecular diversity of aberrations that give rise to the hope that we can significantly impact this disease through translation of the most promising targets into personalized therapies. This proposal directly addresses this need by investigating the tumor suppressive mechanism of a novel target, miR-148a, identified using an innovative and powerful DNA methylation profiling strategy established in the PI's laboratory. Although not yet studied in glioma, miRNA-148a is emerging as a tumor suppressive miRNA in other cancers. As small non-coding RNAs that suppress gene expression, miRNAs occupy key roles in cancer mechanisms and provide emerging therapeutic targets as either themselves or genes they regulate. Extensive genomic characterization of cancer tissue has revealed the widespread presence of aberrant DNA CpG island methylation, which can be associated with the epigenetic silencing of some miRNAs. The recently discovered isocitrate dehydrogenase (IDH) mutation is thought not only to provide a biomarker of secondary gliomas but also represent an initiating event in gliomagenesis. Our research in IDHMUT gliomas has contributed to the recognition of an IDHMUT-associated genome-wide hypermethylation profile, glioma-CpG island methylator phenotype (G-CIMP), that is not found in normal tissue or IDH wild-type gliomas. This has led to a widely accepted but as yet unsupported hypothesis that G-CIMP occupies a pivotal role in gliomagenesis through silencing of tumor suppressive genes and/or genes involved in differentiation. Thus, we hypothesized that IDHMUT-associated DNA hypermethylation may silence the expression of important tumor-suppressive miRNAs in glioma. As shown in our preliminary data, we used unbiased methylation profiling to identify hypermethylated miRNA genes in the context of G-CIMP, and among these candidates, miRNA-148a appears not only to have tumor suppressive properties but also to directly regulate DNMT1, a key gene involved in DNA methylation maintenance. In this proposal, we test the central hypotheses that IDHMUT causes epigenetic silencing of the tumor suppressive miR-148a and that re-expression of miR-148a provides a novel strategy for glioma treatment, particularly for the IDHMUT subset. To do so, the aims are: 1) to investigate the molecular basis linking IDH mutation and miR148a downregulation, 2) to establish miR-148a downstream target genes contributing to tumor suppression, and 3) to explore the therapeutic potential of miR-148a in IDHMUT glioma. These aims will be accomplished combining an unbiased high-resolution methylation profiling technique, extensive patient tissue resources, and a variety of cell models including patient-derived glioma neurospheres cells. Accomplishment of the stated aims will have a significant contribution towards the development of novel tailored treatments for gliomas based on restoration of deficient miRNAs.