Characterization of a novel invasion-related gene in Glioblastoma

描述(由申请人提供)： 项目概述多形性胶质母细胞瘤是恶性程度最高的胶质瘤，占退伍军人所有原发脑肿瘤的30%。虽然外科技术的进步使99%的可见肿瘤得以切除，但肿瘤总是由于侵袭性的肿瘤细胞生长超出原发灶或边缘而复发。对这些肿瘤细胞扩散的分子事件的了解将对这种普遍致命的疾病具有巨大的临床潜力和影响。最近，我们利用最先进的技术，如数字核型分析，以高分辨率绘制了原发性GBM肿瘤的基因组图谱，并发现位于染色体1p36.32上的黏附连接相关蛋白1(AJAP1)基因的表达缺失是GBM中常见的分子事件。我们的目标是探索AJAP1在大量GBM原发肿瘤中表达缺失的临床意义，了解其缺失的机制，了解其在肿瘤细胞扩散中的作用，并探讨其调节肿瘤细胞迁移活性的机制。这些研究的基本原理来自以下观察：1)AJAP1位于染色体1p36.3上的热点区域，在GBM中经常丢失；2)AJAP1编码一种关键的跨膜蛋白，参与形成在细胞-细胞和细胞-细胞外基质相互作用中发挥重要作用的蛋白质复合体；3)在初步研究中，我们证明了AJAP1在多达25%的原发GBM肿瘤中表达缺失；4)我们使用几个GBM细胞系，提供了初步证据，表明AJAP1高甲基化可能是导致GBM细胞AJAP1表达缺失的重要机制，5)我们观察到AJAP1缺失与GBM患者生存不良之间的显著相关性6)我们的初步数据显示，AJAP1的表达缺失增加了肿瘤细胞的迁移，其重组降低了肿瘤细胞的侵袭力。基于这些关键的观察，我们假设AJAP1在GBM细胞中作为一种新的弥散相关细胞膜蛋白发挥作用，其表达的缺失或下调增加了这些肿瘤细胞的迁移能力，并有助于GBM的侵袭性临床行为。具体目标#1将描述AJAP1在大量原发胶质瘤中表达缺失的机制，并与临床数据相关联。特定目的#2将表征AJAP1表达对GBM细胞体外和体内迁移活性的调节。具体目的#3将描述AJAP1缺失对基底膜肿瘤细胞迁移的影响的分子机制(S)。我们相信，这些研究的结果将有助于开发针对基底膜肿瘤细胞迁移机制的分子疗法，并可能为手术提供新的辅助治疗方式。 公共卫生相关性： 项目简介在过去的十年里，超过15万名退伍军人被诊断出患有脑瘤。最常见的原发脑肿瘤是基底节细胞瘤。即使在人类已知的最激进的医疗护理下，GBM患者也会在大约一年内死亡。任何治疗上的突破都将恢复人类数年的生命，并减少数百万美元的医疗支出。基于分子的、基因途径特异性的癌症治疗正日益成为现实，并将是治愈GBM所必需的。我们已经确定了一个潜在的与GBM弥散相关的新基因，该基因在GBM肿瘤细胞的高迁移和侵袭性中起着关键作用。

DESCRIPTION (provided by applicant): Project Summary Glioblastoma multiforme, the most malignant grade of glioma, represents up to 30% of all primary brain tumors in veterans. Although advances in surgical techniques have allowed removal of up to 99% of the visible tumor; the tumor always recurs due to aggressive tumor cell growth beyond the primary tumor focus or margin. The understanding of the molecular events that underly the dispersion of the cells of these tumors would have enormous clinical potential and impact on this universally fatal disease. Recently, using a state-of-the-art technologies, e.g. digital karyotyping, we mapped the genomic landscape of primary GBM tumors at a high resolution and identified the isolated loss of expression of the Adherens Junctional Associated Protein 1 (AJAP1) gene, located on chromosome 1p36.32, as a frequent molecular event in GBMs. Our goal in this proposal is to explore the clinical implications of the loss of expression of AJAP1 in a large set of GBM primary tumors, to gain insights into the mechanisms underlying its loss, to understand its role in tumor cell dispersion, and to explore the mechanisms by which it modulates tumor cell migratory activity. The rationale for these studies derive from the following observations: 1) AJAP1 is located in a hotspot region on chromosome 1p36.3 that is frequently lost in GBM, 2) AJAP1 encodes for a key transmembrane protein involved in formation of a protein complex that plays an important role in cell-cell and cell-extracellular matrix interactions, 3) in preliminary studies, we demonstrated loss of AJAP1 expression in up to 25% of primary GBM tumors, 4) using several GBM cell lines, we provided preliminary evidence that hypermethylation may be an important mechanism underlying the loss of AJAP1 expression in GBM cells, 5) we observed a significant correlation between AJAP1 loss and poor survival in GBM patients, and 6) our preliminary data showed that loss of AJAP1 expression increases tumor cell migration, and its reconstituion decreases tumor cell invasiveness. Based on these critical observations, we hypothesize that AJAP1 functions as a novel dispersion-associated cell membrane protein in GBM cells and that loss or downregulation of its expression increases the migratory potential of these tumor cells and contributes to the aggressive clinical behavior of GBM. Specific aim #1 will characterize mechanisms of loss of AJAP1 expression in a large number of primary GBMs with linked clinical data. Specific aim #2 will characterize the modulation of AJAP1 expression on the migratory activity of GBM cells in vitro and in vivo. Specific aim #3 will characterize the molecular mechanism(s) underlying the effects of AJAP1 loss on tumor cell migration in GBM. We believe that the results of these studies will facilitate the development of molecular-based therapies that target mechanisms of tumor cell migration in GBM and could provide novel adjunctive therapeutic modalities to surgery. PUBLIC HEALTH RELEVANCE: Project Narrative Over the past decade, more than 150,000 veterans were diagnosed with a brain tumor. The most common primary brain tumor was GBM. GBM patients die within about 1 year, even with the most aggressive medical care known to mankind. Any therapeutic breakthrough will restore years of human life and decrease millions of dollars in healthcare expenditures. Molecular-based, gene pathway specific cancer therapies are becoming an increasing reality and will be necessary for curing GBM. We have identified a potential novel dispersion-related gene for GBM that plays a critical role in the high migratory and invasive nature of GBM tumor cells.