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

描述（由申请人提供）：胶质瘤目前仍然无法治愈，目前可用的放射和化疗方式。神经胶质瘤的密集分子表征揭示了畸变的丰富分子多样性，这给我们带来了希望，即我们可以通过将最有希望的靶点转化为个性化治疗来显著影响这种疾病。该提案通过研究新靶点miR-148 a的肿瘤抑制机制直接解决了这一需求，该靶点是使用PI实验室建立的创新且强大的DNA甲基化分析策略鉴定的。尽管尚未在神经胶质瘤中进行研究，但miRNA-148 a正在其他癌症中作为肿瘤抑制性miRNA出现。作为抑制基因表达的小的非编码RNA，miRNA在癌症机制中占据关键作用，并作为其自身或其调节的基因提供新兴的治疗靶点。对癌症组织的广泛基因组表征揭示了异常DNA CpG岛甲基化的广泛存在，其可与一些miRNA的表观遗传沉默相关。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，而且也代表了胶质瘤发生的起始事件。我们在IDHMUT胶质瘤中的研究有助于识别IDHMUT相关的全基因组超甲基化谱，胶质瘤-CpG岛甲基化表型（G-CIMP），这在正常组织或IDH野生型胶质瘤中没有发现。这导致了一个被广泛接受但尚未得到支持的假设，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发生中发挥关键作用。因此，我们假设IDHMUT相关的DNA高甲基化可能沉默胶质瘤中重要的肿瘤抑制性miRNA的表达。正如我们的初步数据所示，我们使用无偏甲基化分析来鉴定G-CIMP背景下的高甲基化miRNA基因，在这些候选基因中，miRNA-148 a似乎不仅具有肿瘤抑制特性，而且直接调节DNMT 1，这是参与DNA甲基化维持的关键基因。在这个提议中，我们测试了中心假设，即IDHMUT导致肿瘤抑制性miR-148 a的表观遗传沉默，并且miR-148 a的再表达为神经胶质瘤治疗提供了一种新的策略，特别是对于IDHMUT子集。为此，目的是：1）研究IDH突变和miR 148 a下调的分子基础，2）建立有助于肿瘤抑制的miR-148 a下游靶基因，3）探索miR-148 a在IDHMUT胶质瘤中的治疗潜力。这些目标将通过结合无偏倚的高分辨率甲基化分析技术、广泛的患者组织资源和各种细胞模型（包括患者来源的胶质瘤神经球细胞）来实现。所述目标的实现将对基于缺陷miRNA的恢复的神经胶质瘤的新型定制治疗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.