New imaging agents for studying gene expression

用于研究基因表达的新型成像剂

• 批准号: 7093967
• 负责人: Hank F Kung
• 金额: $ 22.93万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-04-01 至 2008-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7093967
• 关键词: enzymes; gene expression; neoplasm /cancer; nucleosides

DESCRIPTION (provided by applicant): We propose to develop F-18 and 1-123 labeled nucleosides as selective substrates of herpes simplex thymidine kinase (HSV1-TK) in conjunction with positron computed tomography (PET). Introduction of HSV1- TK in tumor followed by gancyclovir (GCV) treatment has been successfully tested as a suicide gene therapy for cancer therapy. Labeled nucleosides (such as [1-123/124]FIAU and [F-18JFHBG) selectively targeting the HSV1-TK enzyme are useful as reporter probes for measuring HSV1-tk gene expression in vivo by PET or SPECT imaging. Based on this approach, HSV1-tk gene expression can also be used as a surrogate marker gene for expression of other genes (transgenes) determined by the labeled nucleosides as in vivo imaging probes. The objective of this project is to design, synthesize and characterize a series of novel labeled nucleosides, 2'-deoxyuridine and FIAU analogs (group A and B), as superior imaging agents for measuring in vivo gene expression. Currently, [F-18]FIAU is more effective for imaging HSV1-TK; but the synthesis of this F-18 probe is very long and difficult. [F-18]FHBG is easier to prepare, but only effective for imaging a mutant HSV1-TK(sr39). The purposes of developing these novel nucleosides are: 1) to prepare F-18 radiolabeled group A and B nucleosides 2). to identify improved F-18 nucleoside probes with desired in vivo kinetics for higher target to non-target ratio and a higher selectivity between the human TK vs viral HSV1-TK enzyme and 3) to test the correlation between gene expression and probe-uptake in a doxycycline inducible HSV1-TK expressing cell line. It is likely that the new probes can be selectively phosphorylated by the viral enzyme, as such they may be superior for measuring the concentration of HSV1-TK enzyme levels in the tumor cells. They will have several useful properties: ability to cross the cell membrane and a minimum influence from other metabolic steps of nucleosides and nucleotides. Efforts will be made to select tracers predominantly trapped in the targeted cells by the native HSV1-TK only, and confounding signals from other processes from native hTK1 and hTK2 enzymes are minimized. In conjunction with PET, these new imaging agents may enhance our ability to measure tk gene expression in vivo; thus, they may enhance the probability of developing new gene therapy approaches for various diseases.

描述（由申请人提供）：我们建议结合正电子计算机断层扫描（PET）开发F-18和1-123标记核苷作为单纯疱疹胸苷激酶（HSV1-TK）的选择性底物。在肿瘤中引入 HSV1-TK，然后进行更昔洛韦 (GCV) 治疗，已成功测试作为癌症治疗的自杀基因疗法。选择性靶向 HSV1-TK 酶的标记核苷（例如 [1-123/124]FIAU 和 [F-18JFHBG）可用作通过 PET 或 SPECT 成像测量体内 HSV1-tk 基因表达的报告探针。基于这种方法，HSV1-tk基因表达也可以用作替代标记基因，用于由标记核苷作为体内成像探针确定的其他基因（转基因）的表达。该项目的目标是设计、合成和表征一系列新型标记核苷、2'-脱氧尿苷和 FIAU 类似物（A 组和 B 组），作为测量体内基因表达的优质成像剂。目前，[F-18]FIAU对HSV1-TK成像更有效；但这种F-18探针的合成过程非常漫长且困难。 [F-18]FHBG 更容易制备，但仅对突变型 HSV1-TK(sr39) 的成像有效。开发这些新型核苷的目的是：1）制备F-18放射性标记的A和B组核苷2）。鉴定具有所需体内动力学的改进的 F-18 核苷探针，以实现更高的靶标与非靶标比率以及人 TK 与病毒 HSV1-TK 酶之间的更高选择性，以及 3) 测试基因表达与探针摄取之间的相关性多西环素诱导型 HSV1-TK 表达细胞系。新探针很可能可以被病毒酶选择性磷酸化，因此它们可能更适合测量肿瘤细胞中 HSV1-TK 酶水平的浓度。它们将具有几个有用的特性：穿过细胞膜的能力以及核苷和核苷酸其他代谢步骤的影响最小。我们将努力选择主要仅由天然 HSV1-TK 捕获在靶细胞中的示踪剂，并将来自天然 hTK1 和 hTK2 酶的其他过程的混杂信号降至最低。与 PET 结合，这些新的显像剂可以增强我们测量体内 tk 基因表达的能力；因此，它们可能会提高开发针对各种疾病的新基因治疗方法的可能性。