Detection of Tumor Hypoxia by Non-invasive Nuclear Imaging Methods

这个项目的总体目标是提高我们对肿瘤的机制和过程的理解 乏氧图像用核方法获得。为了实现这一目标，我们将使用含有低氧的肿瘤模型， 诱导型报告基因，以允许通过光学和核成像方法侵入性地或非侵入性地可视化由缺氧诱导的分子事件的级联。具体地，在缺氧响应元件HRE的控制下，报告基因构建体HRE-tkeGFP（单纯疱疹病毒1型胸苷激酶tk和增强的绿色荧光蛋白eGFP的融合基因）表达的肿瘤内分布将用微PET、数字放射自显影和荧光显微镜成像。由于报告基因是在HRE的控制下，我们可以确定初始缺氧诱导事件的分布，并提供肿瘤缺氧生物学与其他缺氧相关终点和替代物之间的联系。具体地，将报告基因表达的分布与内源性（例如HIF-1 α和Ca9）和外源性（例如哌莫硝唑和EF5）缺氧相关标志物的模式进行比较，如通过免疫组织化学（IHC）分析所评估的， 此外，报告基因表达的microPET和放射自显影图像也将与 正在进行临床评价的外源性PET缺氧显像剂：18 F-FMISO、18 F-EF5和124 I-IAZGP。在连接缺氧诱导的分子事件PET图像，这项研究提供了第一个直接验证的非侵入性缺氧成像。作为参考，我们将使用物理探针进行肿瘤内pO-2测量，并与图像进行空间配准。然后，我们将应用这些技术来量化干预措施的效果，包括碳/高压氧呼吸以及放射治疗后的再氧合调节缺氧的影响。 最后，我们建议开发各种来源的数据的空间共配准方法：PET、放射自显影和核磁共振图像、pO2探针数据、肿瘤组织学和内源性或外源性标志物的免疫组化分析，相信来自互补方法的组合数据集将改善对肿瘤缺氧的评估。

The overall goal of this project is to improve our understanding of the mechanisms and processes underlying tumor hypoxia images obtained with nuclear methods. Towards this goal, we shall use tumor models that contain a hypoxia inducible reporter gene to allow the cascade of molecular events induced by hypoxia to be either invasively or non-invasively visualized by optical and nuclear imaging methods. Specifically, the intra-tumor distribution of the expression of the reporter gene construct HRE-tkeGFP (the fusion gene of the herpes simplex virus type 1 thymidine kinase tk and the enhanced green fluorescence protein eGFP), under the control of the hypoxia responsive element HRE will be imaged with microPET, digital autoradiography and fluorescence microscopy. Because the reporter gene is under the control of the HRE, we can determine the distribution of the initial hypoxia-induced event and provide a link between the biology of tumor hypoxia and other hypoxia-associated endpoints and surrogates. Specifically, the distributions of reporter gene expression will be compared with patterns of endogenous (e.g. HIF-1alpha and Ca9) and exogenous (e.g. pimonidazole and EF5) hypoxia-associated markers, as assessed by immunohistochemical (IHC) analysis, In addition, microPET and autoradiography images of reporter gene expression will also be compared to the images of exogenous PET hypoxia imaging agents that are under clinical evaluation: 18F-FMISO, 18F-EF5 and 124I-IAZGP. In linking hypoxia-induced molecular events to PET images, this study provides the first direct validation of non-invasive hypoxia imaging. As a reference, we shall use physical probes to perform intra-tumoral pO-2 measurements that are spatially co-registered with the images. We shall then apply these techniques to quantify the effect of interventions that modulate the effects of hypoxia including carbogen/hyperbaric oxygen breathing as well as re-oxygenation following radiation treatment. Finally, we propose to develop methods for spatial co-registration of the data from various sources: PET, autoradiography and NMR images, pO2 probe data, tumor histology and IHC analysis of endogenous or exogenous markers, with the belief that the combined datasets from complementary methods will lead to an improved assessment of tumor hypoxia.