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递送基因表达的时间级，幅度和变化的能力。到目前为止，已经通过在治疗后预定时间获得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由于其侵入性和无法产生基因转移的全局图像而不受欢迎，因为它仅限于检查的一小块组织。许多组一直在开发非侵入性成像基因转移的方法。我们已经利用了人的生长抑素受体亚型2（HSSTR2）作为记者基因，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。但是，该系统受到1）HSSTR2的过表达可能会对细胞生理和稳态产生影响； 2）HSSTR2在某些人体组织上内源表达； 3）通过肾脏消除生长抑素类似物，这可能会干扰信号检测。因此，我们假设可以通过将受体本身的修饰通过从G蛋白中解脱出受体本身，并通过开发新的靶向配体识别插入HSSTR2中的新型表位来改善HSSTR2报告基因系统。第一个目标将研究用正电子发射器放射性标记的生长抑素类似物的能力，以量化不同水平的HSSTR2表达，体外和体内。第二个目标将构建针对插入HSSTR2的替代表位的糖尿病生和小型生物，并以类似于AIM 1中的生长抑素类似物的方式评估这些构建体。这些前两个目标旨在确定最佳的放射性放射线药物作为宠物成像的记者探针。第三个目标将集中于制造和评估HSSTR2的突变体，使受体与G蛋白不同。最终目的将使用最佳的突变体HSSTR2（在AIM 3中开发）和最佳的放射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非侵入性检测通过PET成像的治疗基因转移。该提案应改善现有的HSSTR2报告基因转移基因转移。