Somatostatin Receptor Based PET Imaging of Gene Transfer

基于生长抑素受体的基因转移 PET 成像

• 批准号: 6856960
• 负责人: Buck E. Rogers
• 金额: $ 31.84万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-06-01 至 2009-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6856960
• 关键词: G protein; aminohydrolases; athymic mouse; bioimaging /biomedical imaging; biological signal transduction; cell surface receptors; gene expression; gene therapy; hormone receptor; imaging /visualization /scanning; ligands; polymerase chain reaction; positron emission tomography; radiochemistry; radiopharmacology; radiotracer; reporter genes; single photon emission computed tomography; site directed mutagenesis; somatostatin

DESCRIPTION (provided by applicant): Gene therapy trials would benefit from the ability to determine the location, magnitude, and change in magnitude over time of the expression of delivered genes. Thus far, gene transfer efficiency has been evaluated by obtaining tissue biopsies at predetermined times post treatment. This method of determining gene transfer efficiency is undesirable due to its invasiveness and its inability to generate a global picture of gene transfer, since it is limited to the small piece of tissue(s) examined. Numerous groups have been developing methods for non-invasively imaging gene transfer. We have utilized the human somatostatin receptor subtype 2 (hSSTR2) as a reporter gene along with various radiolabeled somatostatin analogs for gamma ray imaging of gene transfer. However, this system is limited by 1) overexpression of hSSTR2 may have an impact on cell physiology and homeostasis; 2) hSSTR2 is endogenously expressed on certain human tissues; and 3) somatostatin analogs are eliminated through the kidneys which can interfere with signal detection. Therefore, we hypothesize that the hSSTR2 reporter system can be improved through modification of the receptor itself by uncoupling the receptor from G proteins and through the development of novel targeting ligands that recognize a novel epitope inserted into hSSTR2. The first Aim will investigate the ability of somatostatin analogs radiolabeled with positron emitters to quantify different levels of hSSTR2 expression, in vitro and in vivo. The second Aim will construct diabodies and minibodies targeted toward an alternative epitope inserted into hSSTR2 and evaluate these constructs in a manner similar to the somatostatin analogs in Aim 1. These first two Aims are intended to determine the most optimal radiopharmaceutical as a reporter probe for PET imaging. The third Aim will focus on making and evaluating mutants of hSSTR2 that uncouple the receptor from G proteins. The final Aim will use the best mutant hSSTR2 (developed in Aim 3) and the most optimal radiopharmaceutical to determine the activity and efficacy of a therapeutic gene. This is intended to demonstrate that the system can be used to non-invasively detect therapeutic gene transfer through PET imaging. This proposal should result in improvement of the existing hSSTR2 reporter system for imaging gene transfer.

描述（由申请人提供）： 基因治疗试验将受益于确定所传递基因表达的位置、大小以及大小随时间变化的能力。到目前为止，已经通过在治疗后预定时间获取组织活检来评估基因转移效率。这种确定基因转移效率的方法是不受欢迎的，因为它具有侵入性并且无法生成基因转移的全局图，因为它仅限于检查的小块组织。许多团体一直在开发非侵入性成像基因转移的方法。我们利用人类生长抑素受体亚型 2 (hSSTR2) 作为报告基因以及各种放射性标记的生长抑素类似物，用于基因转移的伽马射线成像。然而，该系统受到以下限制：1）hSSTR2的过度表达可能对细胞生理学和稳态产生影响； 2) hSSTR2在某些人体组织中内源表达； 3) 生长抑素类似物通过肾脏消除，这会干扰信号检测。因此，我们假设 hSSTR2 报告系统可以通过受体本身的修饰（通过将受体与 G 蛋白解偶联）以及通过开发识别插入 hSSTR2 的新表位的新靶向配体来改进。第一个目标将研究用正电子发射体放射性标记的生长抑素类似物在体外和体内定量不同水平的 hSSTR2 表达的能力。第二个目标将构建针对插入 hSSTR2 中的替代表位的双抗体和微型抗体，并以与目标 1 中的生长抑素类似物类似的方式评估这些构建体。前两个目标旨在确定作为 PET 报告探针的最佳放射性药物成像。第三个目标将集中于制备和评估 hSSTR2 突变体，使受体与 G 蛋白解偶联。最终目标将使用最好的突变体 hSSTR2（在目标 3 中开发）和最优化的放射性药物来确定治疗基因的活性和功效。这是为了证明该系统可用于通过 PET 成像非侵入性地检测治疗性基因转移。该提案应改进现有的用于成像基因转移的 hSSTR2 报告系统。