Radionuclide-based Molecular Imaging of the DNA Repair Protein AGT

DNA 修复蛋白 AGT 的放射性核素分子成像

• 批准号: 7779968
• 负责人: GANESAN VAIDYANATHAN
• 金额: $ 19.31万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-03-01 至 2011-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7779968
• 关键词: Active Sites; Adverse effects; Affect; Alkylating Agents; Alkylating Antineoplastic Agents; Benzene; Binding; Brain Neoplasms; Cell Line; Cell Nucleus; Clinical; Coupled; Cysteine; DNA; DNA lesion; DNA repair protein; Deoxyguanosine; Development; Drug resistance; Economics; Effectiveness; Goals; Guanine; Image; Imaging Techniques; In Vitro; Individual; Iodine; Label; Laboratories; Lesion; Malignant Neoplasms; Malignant neoplasm of brain; Methods; Modeling; Monitor; Nuclear; Nude Mice; O(6)-Methylguanine-DNA Methyltransferase; O(6)-benzylguanine; Outcome; Patients; Play; Positioning Attribute; Positron-Emission Tomography; Process; Proteins; Radioisotopes; Radiolabeled; Role; Survival Rate; Techniques; Therapeutic; Time; Tracer; Triage; Tumor Cell Nuclei; Work; Xenograft Model; Xenograft procedure; alkyl group; alternative treatment; base; cancer therapy; cancer type; chemotherapy; design; functional group; in vivo; molecular imaging; mouse model; neoplastic cell; protein aminoacid sequence; public health relevance; radiotracer; repaired; single photon emission computed tomography; stem; suicidal; tool; tumor; tumor growth; tumor xenograft; uptake

DESCRIPTION (provided by applicant): Alkylator chemotherapy plays a significant role in the treatment of brain tumors and other malignancies. However, its effectiveness is all too often limited by drug resistance, which leads to lethal growth of tumors despite further rounds of alkylator chemotherapy. Drug resistance to alkylator chemotherapy is primarily due to the repair of induced O6-alkylguanine DNA lesions by the protein alkylguanine-DNA alkyltransferase (AGT). There is a well-established inverse correlation between tumor AGT content and therapeutic outcome; generally, survival rates are higher when the AGT content of tumor is below a threshold. We hypothesize that it should be possible to decide whether to administer alkylator chemotherapy in individual patients based on noninvasive imaging of tumor AGT levels prior to therapy. The goal of this work is to develop radiolabeled agents that will allow assessment of AGT levels using SPECT or PET imaging. We propose to synthesize radioiodinated derivatives of O6- benzylguanine (BG), a potent AGT inactivating agent, coupled to nuclear localizing peptide sequences (NLS) to enhance delivery of the labeled substrate to the cell nucleus where AGT is predominantly present. These labeled agents will be evaluated in vitro using pure AGT and AGT-expressing cell lines and in vivo using xenograft models. The specific aims are: 1. To synthesize benzylguanine derivatives and their NLS conjugates. 2. To evaluate the radiolabeled benzylguanines and their NLS conjugates for binding to pure AGT and in tumor cells in vitro. 3. To evaluate AGT-specific radiolabeled agents developed in athymic mouse xenograft models. A successful agent for the molecular imaging of AGT could be an important tool that can be used to avoid unnecessary chemotherapy; in addition to the economic benefits, it can spare patients from the major side effects of alkylator chemotherapy, and allow them to be triaged earlier to alternative treatments. PUBLIC HEALTH RELEVANCE: The goal of this project is to develop radiolabeled tracers that can be utilized as molecular imaging agents for the noninvasive assessment of the DNA repair protein alkylguanine-DNA alkyltransferase (AGT) in brain cancers and other tumors. AGT is primarily responsible for the drug resistance that frequently compromises the effectiveness of alkylator-based chemotherapy of many cancers. Because drug resistance is a major road block in the cancer treatment process, the availability of a molecular imaging technique to quantify AGT will have a significant clinical impact. With such a technique, chemotherapy can be personalized because it should be possible to predict which patients will benefit from chemotherapy and which will not. This will help avoid treating patients for whom alkylator chemotherapy will be largely ineffective, sparing them of unwarranted side effects and expense, and providing an earlier rationale for seeking alternative treatments that might be more successful, given their AGT status.

描述（由申请人提供）：烷化剂化疗在脑肿瘤和其他恶性肿瘤的治疗中发挥着重要作用。然而，其有效性常常受到耐药性的限制，尽管进行了进一步的烷化剂化疗，仍会导致肿瘤致命的生长。对烷化剂化疗的耐药性主要是由于蛋白质烷基鸟嘌呤-DNA 烷基转移酶 (AGT) 修复了诱导的 O6-烷基鸟嘌呤 DNA 损伤。肿瘤 AGT 含量与治疗结果之间存在明确的负相关关系；一般来说，当肿瘤的AGT含量低于阈值时，存活率较高。我们假设，应该可以根据治疗前肿瘤 AGT 水平的无创成像来决定是否对个体患者进行烷化剂化疗。这项工作的目标是开发放射性标记药物，以便使用 SPECT 或 PET 成像评估 AGT 水平。我们建议合成 O6- 苄基鸟嘌呤 (BG) 的放射性碘化衍生物，这是一种有效的 AGT 灭活剂，与核定位肽序列 (NLS) 偶联，以增强标记底物向主要存在 AGT 的细胞核的递送。这些标记试剂将使用纯 AGT 和表达 AGT 的细胞系进行体外评估，并使用异种移植模型进行体内评估。具体目标是： 1.合成苄基鸟嘌呤衍生物及其NLS缀合物。 2. 评估放射性标记的苄基鸟嘌呤及其 NLS 缀合物在体外与纯 AGT 和肿瘤细胞中的结合。 3. 评估在无胸腺小鼠异种移植模型中开发的 AGT 特异性放射性标记药物。成功的 AGT 分子成像试剂可能成为避免不必要化疗的重要工具；除了经济效益之外，它还可以使患者免受烷化剂化疗的主要副作用，并使他们能够更早地接受替代治疗。公共健康相关性：该项目的目标是开发放射性标记示踪剂，可用作分子成像剂，对脑癌和其他肿瘤中的 DNA 修复蛋白烷基鸟嘌呤-DNA 烷基转移酶 (AGT) 进行无创评估。 AGT 是造成耐药性的主要原因，这种耐药性常常会损害许多癌症基于烷化剂的化疗的有效性。由于耐药性是癌症治疗过程中的主要障碍，因此量化 AGT 的分子成像技术的可用性将产生重大的临床影响。通过这种技术，化疗可以个性化，因为应该可以预测哪些患者将从化疗中受益，哪些患者不会。这将有助于避免治疗烷化剂化疗在很大程度上无效的患者，使他们免受不必要的副作用和费用，并为考虑到他们的 AGT 状态而寻求可能更成功的替代疗法提供早期理由。