Dynamic multimodal imaging of tumor hypoxia and vascular profiles in glioblastoma

描述（由申请人提供）：多形性胶质母细胞瘤（GBM）是最常见、最致命的颅内肿瘤，对传统的多模式治疗具有高度耐药性。这些肿瘤的特征是血管生成深度、血脑屏障（BBB）破坏、血管源性水肿以及缺氧和坏死区域，这些已被证明与局部肿瘤控制、无病生存和总生存呈负相关。有相当多的轶事证据表明，肿瘤内缺氧赋予放射抵抗。然而，由于缺乏可靠的体内监测方法，在GBM中，动态的肿瘤内氧状态仍未得到测试。我们开发了一种利用生物发光报告系统监测肿瘤内缺氧的遗传策略。通过将缺氧诱导因子1a-萤火虫荧光素酶（HIF-1a-ODD-luc）引入各种GBM细胞，包括患者新鲜GBM肿瘤分离的细胞，并富集细胞表面标志物CD133，我们将能够通过生物发光成像（BLI）实时监测原位GBM模型的肿瘤缺氧情况。我们还建议开发基于交错T2- （BOLD，血氧水平依赖）和T1-（组织氧水平依赖）加权序列的MRI技术，用于评估肿瘤氧合，包括基线缺氧，空间异质性和对原位GBM模型干预反应的动力学。此外，将通过动态敏感性对比（DSC）和动态对比增强（DCE） MRI评估血管灌注、血脑屏障状态与缺氧的相关性。最近有报道称，在抗血管生成和化疗药物辅助治疗后，GBM患者的总生存期和无进展生存期有所增加。然而，潜在的机制仍不清楚。我们假设肿瘤缺氧和血管的体内多模态成像将增强我们对有效抗血管生成的病理生理机制的理解，并进一步促进联合放疗或化疗的优化。该项目的主要目标是整合多模态成像获得的肿瘤缺氧和血管系统的多个参数，以与肿瘤侵袭性相关，并了解抗血管生成治疗临床获益的病理生理机制。影像学结果将与灌注、血管密度和缺氧的组织学和免疫组织化学研究以及药物的药理研究相关联。本课题目标的成功实现将增强我们对临床胶质母细胞瘤的认识，并为未来化疗与放疗联合的新型临床治疗方案奠定基础。

DESCRIPTION (provided by applicant): Glioblastoma multiform (GBM) is the most common and lethal intracranial cancer, and highly resists to conventional multimodal therapies. These tumors are characterized by profound angiogenesis, disrupted blood-brain-barrier (BBB), vasogenic edema, as well as regions of hypoxia and necrosis, which have been shown to correlate negatively with local tumor control, disease free survival and overall survival. There is considerable anecdotal evidence that intra-tumoral hypoxia confers radiation resistance. However, in the absence of a reliable method of monitoring, in vivo, the dynamic intra-tumoral oxygen status, has remained untested in GBM. We have developed a genetic strategy to monitor intra-tumoral hypoxia using a bioluminescence reporter system. By introducing the Hypoxia-inducible-factor1a-firefly luciferase (HIF-1a-ODD-luc) to various GBM cells including the cells isolated from fresh GBM tumors of patient and enriched for the cell surface marker CD133, we will be able to monitor real-time tumor hypoxia in orthotopic GBM model by bioluminescent imaging (BLI). We also propose to develop MRI techniques based on an interleaved T2- (BOLD, blood oxygen level dependent) and T1- (tissue oxygen level dependent) weighted sequence for assessing tumor oxygenation, including baseline hypoxia, spatial heterogeneity and dynamics of response to interventions in orthotopic GBM model. Moreover, correlation of vascular perfusion, BBB status with hypoxia will be evaluated by dynamic susceptibility contrast (DSC) and Dynamic contrast enhanced (DCE) MRI. Recent gains in overall survival as well as progression free survival of GBM patients have been reported following adjuvant treatment with antiangiogenic and chemotherapeutic agents. However, the underlying mechanisms remain unclear. We hypothesize that in vivo multimodal imaging of tumor hypoxia and vasculature will enhance our understanding of pathophysiological mechanisms of effective antiangiogenesis and further facilitate optimization of combined radiotherapy or chemotherapy. The major goal of this project is to integrate multiple parameters of tumor hypoxia and vasculature acquired by multimodal imaging to correlate with tumor aggressiveness and understand pathophysiological mechanism underlying the clinical benefits from antiangiogenic treatment. The imaging findings will be correlated with histological and immunohistochemical studies of perfusion, vascular density and hypoxia, as well as pharmacological study of drug. Successful accomplishment of the goals of this project will enhance our understanding of clinical glioblastoma and lay the foundation for future novel clinical treatment regimens towards chemotherapy in combination with radiotherapy. PUBLIC HEALTH RELEVANCE: Glioblastoma multiform (GBM) is the most common and lethal intracranial cancer, and highly resists to conventional multimodal therapies. These tumors are characterized by profound angiogenesis, disrupted blood-brain-barrier, vasogenic edema, as well as regions of hypoxia and necrosis, which have been shown to correlate negatively with clinical outcome. We propose to apply bioluminescent imaging (BLI), based on a hypoxia reporter gene, and a novel MRI approach to assessing dynamic change of intra-tumor hypoxia and vascular characteristics in orthotopic GBM models, and to further understand pathophysiological mechanisms underlying the clinical benefits from antiangiogenic agents such as bevacizumab.