Targeting TF/CD44v6 for In Vivo Nano-generated alpha-therapy of Ovarian Cancer

描述（由申请人提供）：本研究的目的是使用放射性标记的工程肽支架，使用匹配的203 Pb/212 Pb体内α粒子发生器开发敏感的卵巢癌诊断和治疗（治疗诊断）剂。a粒子的高线性能量转移显著高于通常用于治疗的b粒子发射放射性核素。虽然早期卵巢癌的存活率很高，但晚期疾病往往是致命的。卵巢癌的预后差是由于诊断复杂，这是由于疾病发展基本上无症状，存在侵袭性转移细胞，以及缺乏疾病阶段的生物标志物。我们建议靶向癌特异性的TF糖抗原和卵巢癌生物标志物CD 44 v6，一种透明质酸（HA）受体CD 44的肿瘤特异性剪接变体。CD 44 v6糖基化导致HA结合和内化增加，导致大量信号传导事件。TF二糖显示在CD 44上，可能在癌症特异性v6区域，并且与侵袭和转移相关。假设靶向该TF/CD 44 v6糖表位将提供α粒子辐射的特异性定位 用于成像和治疗的放射性。所采用的靶向载体将是25个氨基酸的铁调素的工程化衍生物，其结合TF/CD 44 v6并与抗体或小肽相比表现出最佳的体内性质，包括高的体内稳定性和通过肾脏的快速清除，从而增加肿瘤保留并减少非靶器官辐射。延长的生物利用度和对健康组织的最小暴露可以通过HA的递送来进一步实现，以确保TF/CD 44 v6肽的内化。本研究的具体目的是：1）筛选和表征TF/CD 44 v6-avid噬菌体展示衍生肽; 2）将TF/CD 44 v6-avid肽生物工程化到铁调素支架中，并表征生物素化和1，4，7，10-四氮杂环十二烷-1，4，7，10-四乙酸（DOTA）缀合形式的体外卵巢癌细胞结合特性;和3）测定212 Pb和203 Pb标记的肽缀合物在人卵巢癌异种移植小鼠体内的药代动力学、生物分布和肿瘤靶向能力。HA处理对放射性标记的铁调素肽支架的肿瘤保留的影响将通过生物分布研究来确定。为了可视化肿瘤归巢，将用203 Pb标记肽构建体用于单光子发射计算机断层扫描成像。所提出的用α-粒子标记的肽支架体内靶向卵巢癌对于卵巢癌的成像和治疗具有广泛的适用性，这是重要的，因为早期卵巢癌通常是无症状的，晚期卵巢癌通常是致命的。此外，所提出的技术可以应用于靶向和杀死其他癌细胞，特别是因为TF存在于>80%的腺癌上。

DESCRIPTION (provided by applicant): The goal of this research is to use radiolabeled engineered peptide scaffolds for development of sensitive ovarian carcinoma diagnostic and therapeutic (theranostic) agents using a matched pair 203Pb/212Pb in vivo α-particle generator. The high linear energy transfer of a-particle is significantly higher than that of b-particle emittng radionuclides commonly used for therapy. Although the survival rates of early stage ovarian cancer are high, late stage disease is often fatal. The poor prognosis of ovarian cancer results from complicated diagnosis due to a largely asymptomatic disease development, the presence of aggressive metastatic cells, as well as a lack of biomarkers for disease stages. We propose to target the carcinoma-specific Thomsen- Friedenreich (TF) glycoantigen and the ovarian carcinoma biomarker CD44v6, a tumor-specific splice variant of the hyaluronic acid (HA) receptor CD44. CD44v6 glycosylation results in increased HA binding and internalization, leading to a multitude of signaling events. TF disaccharide is displayed on CD44, likely in the cancer-specific v6 region and is associated with invasion and metastasis. It is hypothesized that targeting this TF/CD44v6 glycoepitope will afford the specific localization of a-particle radiation radioactivity to tumors for both imaging and therapy. The targeting vehicle employed will be an engineered derivative of 25 amino acid hepcidin that binds TF/CD44v6 and exhibits optimum in vivo properties compared to antibodies or small peptides, including high in vivo stability and rapid clearance through the kidney, thereby increasing tumor retention and reducing non-target organ radiation. Prolonged bioavailability and minimal exposure to healthy tissues may be further accomplished by delivery of HA to ensure internalization of the TF/CD44v6 peptide. The specific aims of the proposed research are to 1): select and characterize TF/CD44v6-avid phage display derived peptides; 2) bioengineer TF/CD44v6-avid peptide(s) into hepcidin scaffolds and characterize biotinylated and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated forms for their in vitro ovarian cancer cell binding properties; and 3) determine the pharmacokinetics, biodistribution and tumor-targeting ability of both 212Pb and 203Pb-labeled peptide conjugates in vivo in human ovarian carcinoma xenografted mice. The effect of HA treatment on the tumor retention of the radiolabeled hepcidin peptide scaffold will be determined by biodistribution studies. In order to visualize tumor homing, the peptide construct will be labeled with 203Pb for single photon emission computed tomography imaging. The proposed in vivo targeting of ovarian cancers with a-particle labeled peptide scaffolds has wide applicability for the imaging and treatment of ovarian cancer, which is important because early ovarian cancer is often asymptomatic and late stage ovarian cancer is usually fatal. Further, the technology proposed can be applied to target and kill other cancer cells, especially since TF is present on >80% of adenocarcinomas.