Imaging of O6-Alkylguanine-DNA Alkyltransferase

O6-烷基鸟嘌呤-DNA 烷基转移酶的成像

• 批准号: 6542181
• 负责人: GANESAN VAIDYANATHAN
• 金额: $ 30.8万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-30 至 2006-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6542181
• 关键词: CHO cells; DNA repair; SDS polyacrylamide gel electrophoresis; alkylating agents; analog; antineoplastics; athymic mouse; chemotherapy; drug resistance; fluorine; high performance liquid chromatography; imaging /visualization /scanning; iodine; methylguanine DNA methyltransferase; positron emission tomography; radiochemistry; radiotracer; single photon emission computed tomography; transfection

DESCRIPTION (provided by applicant): Chemotherapy, especially alkylator chemotherapy, is one of the primary modes for the treatment of cancer; however, the response rate is often low. A major reason for poor prognosis in many patients is the development of drug resistance, resulting in tumor regrowth and eventual patient death. The drug resistance is due to the repair of DNA lesions, generated by alkylation of guanine and thymine residues by the alkylating agents, by the repair protein O6 alkyl-DNA alkyltrasferase (AGT). AGT repairs the lesions by transferring the alkyl groups from the modified DNA to a cysteine in its active site. This is a suicidal process as there is no mechanism to regenerate the protein and hence the resistance, or alternatively the therapeutic efficacy, depends on the amount of AGT content in the tumor. A means to noninvasively quantitate tumor AGT will go a long way in the planning of alkylator chemotherapy, monitoring the effect of drugs on AGT levels during the therapeutic course, and in the development of newer alkylator chemotherapeutic agents. Benzylguanine (BG) has been shown to be an excellent inactivator of AGT and there are several clinical trials in progress evaluating the use of BG to deplete AGT prior to chemotherapy. The long-term objective of this proposal is to develop radioiodine- or 18F-labeled BG analogues useful in the noninvasive mapping of AGT by scintigraphic imaging. BG containing fluorine at the 4-position of its benzyl group (4-FBG) has already been shown to be an excellent analogue of BG. Methods will be developed for the 18F-labeling of 4-FBG as well as radioiodinated BG derivatives. While it may be possible to demonstrate the proof of principle using these compounds, efforts will also be directed in the development of better analogues that are easier to prepare, more potent, and will have higher metabolic stability, and longer tumor retention. Among the compounds considered are the derivatives of 4-benzyloxy-2,6-diamino-5-nitro/nitroso-pyrimidine, and various BG derivatives with substituents at its C-8 and N-9 positions. Novel unlabeled compounds will be first evaluated for their AGT inactivating ability using Chinese hamster ovary (CHO) cells transfected with AGT. Labeled compounds will be evaluated for their binding with pure AGT and for their uptake and retention in AGT-containing cells. Their in vitro metabolism also will be studied. Correlativity of tumor AGT content and tumor uptake of labeled BG analogues will be Established. Primarily, TE-67 1 human medulloblastoma xenografts will be utilized for these studies. Tumor uptake as a function of drug concentration and time will be studied. Potential metabolites, especially in the tumor, will be determined. Again, the correlativity between tumor uptake and tumor AGT content will be investigated in xenograft models as well. In summary, this proposal seeks to determine whether the development of a suitable agent for the imaging of tumor AGT will facilitate chemotherapy planning, thereby improving the outcome of alkylator chemotherapy. Subsequently these tracers will be evaluated in athymic mice hosting xenografts. Primarily, TE-671 human medulloblastoma xenografts will be utilized for these studies. Tumor uptake as a function of drug concentration and time will be studied. Potential metabolites, especially in the tumor, will be determined. Again, the correlativity between tumor uptake and tumor AGT content will be investigated in xenograft models as well. In summary, this proposal seeks to determine whether the development of a suitable agent for the imaging of tumor AGT will facilitate chemotherapy planning, thereby improving the outcome of alkylator chemotherapy.

描述（由申请人提供）：化学疗法，尤其是烷基化疗，是治疗癌症的主要模式之一。但是，响应率通常很低。许多患者预后不良的主要原因是耐药性的发展，导致肿瘤再生和最终患者死亡。耐药性是由于DNA病变的修复，该病变是由烷基化剂，通过修复蛋白O6烷基-DNA烷基转移酶（AGT）对鸟嘌呤和胸腺嘧啶残基产生的。 AGT通过将烷基从修饰的DNA转移到其活性部位的半胱氨酸来修复病变。这是一个自杀过程，因为没有机制可以再生蛋白质，因此耐药性或治疗功效取决于肿瘤中AGT含量的量。非侵入性定量肿瘤AGT的一种手段将在烷基化疗计划，监测药物对治疗过程中AGT水平的影响以及较新的烷基化学治疗剂的发展。苯甲胺（BG）已被证明是AGT的极好的灭活剂，并且正在进行多项临床试验，以评估BG在化学疗法之前耗尽AGT的使用。该提案的长期目标是开发用于通过闪烁图成像对AGT无创映射有用的放射性碘或18F标记的BG类似物。 BG在其苄基组（4-FBG）的4位处含有氟的BG已被证明是BG的极好类似物。将开发用于4-FBG和放射性腐蚀的BG衍生物的18F标记的方法。虽然有可能使用这些化合物证明原理的证明，但努力也将针对更好的类似物的发展，这些类似物更容易准备，更有效，并且具有更高的代谢稳定性，并且保留了更长的肿瘤。在考虑的化合物中，有4-苯甲酰氧基-2,6-二氨基-5-硝基/硝基苯胺的衍生物，以及具有C-8和N-9位置的各种BG衍生物。新型未标记化合物将首先评估使用AGT转染的中国仓鼠卵巢（CHO）细胞的AGT灭活能力。标记的化合物将与纯AGT结合以及它们在含Agt细胞中的摄取和保留率进行评估。 还将研究他们的体外代谢。将建立肿瘤AGT含量和肿瘤吸收的相关性。首先，TE-67 1人类髓母细胞瘤异种移植物将用于这些研究。将研究肿瘤吸收作为药物浓度和时间的函数。将确定潜在的代谢产物，尤其是在肿瘤中。同样，在异种移植模型中也将研究肿瘤摄取和肿瘤AGT含量之间的相关性。总而言之，该提案旨在确定开发合适的肿瘤成像药物是否会促进化学疗法计划，从而改善烷基化疗的结果。 随后，这些示踪剂将在托有异种移植物的无性小鼠中进行评估。 首先，将使用TE-671人类髓母细胞瘤异种移植物用于这些研究。 将研究肿瘤吸收作为药物浓度和时间的函数。 将确定潜在的代谢产物，尤其是在肿瘤中。 同样，在异种移植模型中也将研究肿瘤摄取和肿瘤AGT含量之间的相关性。 总而言之，该提案旨在确定开发合适的肿瘤成像药物是否会促进化学疗法计划，从而改善烷基化疗的结果。