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: 7015559
• 负责人: Buck E. Rogers
• 金额: $ 29.7万
• 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/7015559
• 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递送基因表达的位置、幅度和幅度随时间的变化的能力。到目前为止，基因转移效率已经通过在治疗后预定时间获得组织活检来评估。这种确定基因转移效率的方法是不希望的，因为它的侵入性和它不能产生基因转移的全局图像，因为它限于所检查的小块组织。许多研究小组一直在开发非侵入性成像基因转移的方法。我们已经利用人生长抑素受体亚型2（hSSTR 2）作为报告基因沿着与各种放射性标记的生长抑素类似物用于基因转移的γ射线成像。然而，该系统受到以下限制：1）hSSTR 2的过表达可能对细胞生理学和体内平衡产生影响; 2）hSSTR 2在某些人体组织上内源性表达;和3）生长抑素类似物通过肾脏消除，这可能干扰信号检测。因此，我们假设hSSTR 2报告系统可以通过受体本身的修饰来改善，通过将受体从G蛋白上解偶联，以及通过开发识别插入hSSTR 2的新表位的新型靶向配体。第一个目标将调查的能力，生长抑素类似物放射性标记的正电子发射体定量不同水平的hSSTR 2的表达，在体外和体内。第二个目标将构建靶向插入hSSTR 2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最佳放射性药物作为PET成像的报告探针。第三个目标将集中于制造和评估hSSTR 2的突变体，其将受体与G蛋白解偶联。最终的目标将使用最好的突变hSSTR 2（在目标3中开发）和最佳的放射性药物来确定治疗基因的活性和功效。这旨在证明该系统可用于通过PET成像非侵入性检测治疗性基因转移。这一建议应导致现有的hSSTR 2报告系统的成像基因转移的改善。