Characterization of a novel invasion-related gene in Glioblastoma

描述（由申请人提供）： 多形性胶质母细胞瘤是胶质瘤中恶性程度最高的一种，占退伍军人所有原发性脑肿瘤的30%。虽然手术技术的进步已经允许切除高达99%的可见肿瘤，但由于肿瘤细胞的侵袭性生长超出了原发性肿瘤病灶或边缘，肿瘤总是会复发。了解这些肿瘤细胞分散的分子事件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，使用最先进的技术，例如数字核型分析，我们以高分辨率绘制了原发性GBM肿瘤的基因组图谱，并确定了位于染色体1p36.32上的粘附连接相关蛋白1（AJAP 1）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AJAP 1在大量GBM原发性肿瘤中表达缺失的临床意义，深入了解其缺失的机制，了解其在肿瘤细胞分散中的作用，并探索其调节肿瘤细胞迁移活性的机制。这些研究的依据来自以下观察结果：1）AJAP 1位于染色体1p36.3上的热点区域，该区域在GBM中经常丢失，2）AJAP 1编码参与蛋白复合物形成的关键跨膜蛋白，该蛋白复合物在细胞-细胞和细胞-细胞外基质相互作用中起重要作用，3）在初步研究中，我们证明了在高达25%的原发性GBM肿瘤中AJAP 1表达的丧失，4）使用几种GBM细胞系，我们提供了初步证据，即超甲基化可能是GBM细胞中AJAP 1表达丧失的重要机制，5）我们观察到GBM患者中AJAP 1表达缺失与生存率差之间存在显著相关性，以及6）我们的初步数据显示AJAP 1表达缺失增加肿瘤细胞迁移，并且其重建降低肿瘤细胞侵袭性。基于这些重要的观察结果，我们假设AJAP 1在GBM细胞中作为一种新的分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潜力，并有助于GBM的侵袭性临床行为。 具体目标#1将表征具有相关临床数据的大量原发性GBM中AJAP 1表达丧失的机制。具体目标#2将表征AJAP 1表达对体外和体内GBM细胞迁移活性的调节。具体目标#3将表征AJAP 1缺失对GBM中肿瘤细胞迁移的影响的分子机制。我们相信，这些研究的结果将促进基于分子的治疗的发展，靶向GBM中肿瘤细胞迁移的机制，并可以提供新的手术治疗模式。

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.