Chemoprevention of Gliomas using Nitrones with Anti-c-Met Activity

描述(由申请人提供)： 本项目致力于建立α-苯基-叔丁基硝酮(PBN)的作用机制，在不同肿瘤分级的实验啮齿动物模型中抑制胶质瘤的形成。我们有很有希望的初步数据，清楚地表明PBN在体内、在肿瘤植入之前或在肿瘤形成后可能是一种有效的抗肿瘤药物。我们的假设是c-Met，一种肝细胞生长因子(分散因子)的酪氨酸激酶受体，在恶性胶质瘤的形成中起着不可或缺的作用，而PBN治疗后c-Met水平的改变抑制了胶质瘤的形成。恶性胶质瘤的重要特征包括侵袭性行为和血管生成。C-Met被认为是许多脑肿瘤恶性进展过程中的介质，包括细胞增殖、细胞侵袭、细胞凋亡和血管生成。在美国，每年大约有15,000名患者死于胶质母细胞瘤。由于胶质瘤的浸润性，手术很少有效。尽管有现代的诊断和治疗，胶质母细胞瘤患者的中位生存期不超过15个月。一种潜在的化学预防性药物可以抑制胶质瘤的生长，甚至完全根除胶质瘤，这将对发展为恶性肿瘤的患者带来巨大的好处。体内磁共振方法非常适合于跟踪肿瘤生长、血管生成以及c-Met水平的变化，c-Met水平可作为预测胶质瘤预后的标志。我们目前使用非侵入性体内磁共振成像(MRI)方法来检测肿瘤形态、肿瘤血管形成或血管生成(使用MR血管成像(MRA))，并有关于c-Met表达的初步数据(使用分子靶向MRI)。此外，我们还使用了分子生物学方法(Western blots、免疫荧光组织学)和组织学肿瘤分级，以与磁共振成像、血管造影和分子靶向数据相关联。该项目将评估PBN预防恶性胶质瘤形成和发展的能力，使用c-Met击倒胶质瘤细胞克隆，并结合体内分子靶向MRI新技术，在不同肿瘤级别的大鼠脑胶质瘤中体内检测c-Met。Fisher 344大鼠脑内种植C6(形成II级或III级肿瘤)或RG2(形成更具侵袭性的III级或IV级肿瘤)胶质瘤细胞作为胶质瘤模型。具体目标1将评估两种胶质瘤模型(C6和RG2)中c-Met的水平；特定目标2将确定PBN作为c-Met抑制因子在预防胶质瘤生长和形成中的有效性，并利用c-Met基因敲除胶质瘤模型进一步阐明c-Met在胶质瘤形成中的作用；特殊目标3将开发和验证改进的MRI方法用于体内检测c-Met的表达。目前适用于恶性胶质瘤介入治疗的药物很少。除了抑制c-Met外，PBN的其他有希望的特征是它是口服生物利用的，并且它能够穿越血脑屏障(BBB)。PBN似乎是一个很有前途的候选药物，它可以有效地防止胶质瘤的形成，并可能作为人类多形性胶质母细胞瘤的化学预防药物。我们有初步数据表明，PBN(α-苯基-叔丁基硝酮)似乎是一种很有前途的候选药物，它可以有效地防止胶质瘤的形成，并可能作为人类多形性胶质母细胞瘤的化学预防药物。我们的假设是，c-Met是一种酪氨酸激酶受体，在恶性胶质瘤的形成中起着不可或缺的作用，而PBN能够降低c-Met的水平，从而抑制胶质瘤的形成。该项目将评估PBN预防恶性胶质瘤形成和发展的能力，使用c-Met击倒胶质瘤细胞克隆来阐明c-Met的作用，并结合新的体内分子靶向磁共振成像(MRI)技术，在不同肿瘤级别的大鼠脑胶质瘤中体内检测c-Met。

DESCRIPTION (provided by applicant): This project is focused on establishing the mechanism of alpha-phenyl-tert-butyl nitrone (PBN), in its ability to inhibit glioma formation in experimental rodent models that vary in tumor grade. We have promising preliminary data that clearly demonstrates that PBN can potentially be an effective anti-tumor agent in vivo, prior to tumor implantation, or once a tumor has formed. Our hypothesis is that c-Met, a tyrosine kinase receptor for the hepatocyte growth factor (scatter factor) plays an integral role in the formation of malignant gliomas, and that altered c-Met levels from PBN treatment suppresses glioma formation. Important hallmarks of malignant gliomas include their invasive behavior and angiogenesis. c-Met is thought to be a mediator in many of the processes of malignant brain tumor progression, including cell proliferation, cell invasion, apoptosis and angiogenesis. Approximately 15,000 patients in the U.S.A. die with glioblastomas per year. Due to the infiltrative nature of gliomas, surgery is rarely effective. Despite modern diagnostics and treatments the median survival time for patients with glioblastomas does not exceed 15 months. A potential chemo-preventative agent that can suppress glioma growth or even eradicate gliomas entirely would be of tremendous benefit to patients that develop malignant tumors. In vivo magnetic resonance (MR) methods are ideally suited to follow changes in tumor growth, angiogenesis, as well as the assessment of c- Met levels which can be used as a marker for predicting the prognosis of gliomas. We currently use non-invasive in vivo MR imaging (MRI) methods to detect tumor morphology, tumor vasculature or angiogenesis (using MR angiography (MRA)), and have preliminary data on c-Met expression (using molecular-targeted MRI). In addition we use molecular biology methods (Western blots, immunofluorescence histology) and histological tumor grading, to correlate with MR imaging, angiography and molecular targeted data. This project will assess PBN in its ability to prevent malignant glioma formation and development, use c-Met knockdown glioma cell clones, and incorporate novel in vivo molecular-targeted MRI techniques for in vivo detection of c-Met in intracranial rat gliomas varying in tumor grades. Intracerebral implantation of rat C6 (forming grade II or III tumors) or RG2 (forming more aggressive grade III or IV tumors) glioma cells will be used in Fisher 344 rats as the glioma models. Specific aim 1 will be to assess the levels of c-Met in the 2 glioma models (C6 and RG2); specific aim 2 will be to establish the effectiveness of PBN as a c-Met suppressor in preventing glioma growth and formation, and to use c-Met knockdown glioma models to further elucidate the role of c-Met in glioma formation; and specific aim 3 will be to develop and validate improved MRI methods for in vivo detection of c-Met expression. There are very few existing agents that are currently applicable for the intervention of malignant gliomas. Other promising characteristics of PBN, in addition to c-Met suppression, are that it is orally bio-available, and it is able to cross the blood-brain-barrier (BBB). PBN seems to be a promising candidate in its ability to be an effective agent against glioma formation, and may be useful as a chemo-preventative agent against glioblastoma multiforme in humans. We have preliminary data that PBN (alpha-phenyl-tert-butyl nitrone) seems to be a promising candidate in its ability to be an effective agent against glioma formation, and may be useful as a chemo-preventative agent against glioblastoma multiforme in humans. Our hypothesis is that c-Met, a tyrosine kinase receptor, plays an integral role in the formation of malignant gliomas, and that PBN is able to decrease c-Met levels, resulting in the suppression of glioma formation. This project will assess PBN in its ability to prevent malignant glioma formation and development, use c-Met knockdown glioma cell clones to elucidate the role of c-Met, and incorporate novel in vivo moleculartargeted MRI (magnetic resonance imaging) techniques for in vivo detection of c-Met in intracranial rat gliomas varying in tumor grades.