Tissue-Specific Radiation Sensitization of Prostate Cancer by Aptamer-Targeted siRNA Knock-Down of DNA Repair Pattiway

本项目的长期目标是提高放射治疗前列腺癌（PCa）的治疗指数。放射治疗是临床局限性PCa的两种主要治疗方法之一，也是与较高级别、分期和/或PSA相关的局部晚期疾病的主要治疗方法。虽然放射和手术的成功率对于低度器官局限性疾病都很高，但估计晚期疾病的十年无病生存率低于50%。因此，改善临床定位的高阶段和/或等级前列腺癌患者的治疗的手段将显著降低该疾病的发病率和死亡率。为了解决这个问题，我们开发了前列腺靶向RNA干扰（RNAi）药物，选择性抑制前列腺细胞中的DNA修复途径。通过RNA适体A10-3实现组织特异性靶向，其结合细胞表面上的前列腺特异性膜抗原（PSMA），然后内化到细胞中。然后通过细胞RNAi机制加工缀合的短发夹RNA（shRNA），导致特异性DNA修复mRNA和蛋白质的敲低。在上一个资助周期中，我们证明了这些药物直接注射到肿瘤中时，可显著增强外照射放射治疗的治疗指数。在这里，我们建议继续发展这一战略，产生化学合成的适体-siRNA辐射增敏剂，并评估其安全性作为前列腺内注射剂的I期临床试验。除了这个翻译目的，我们将进行临床前研究，以确定适体-siRNA放射增敏剂是否有效后静脉注射。如果成功，这种给药模式将为放射增敏局部晚期PCa提供一种次要途径，它将提供一种新的方法来提高外照射放射治疗对骨痛管理的疗效，最后它将提供一种方法来提高全身靶向放射治疗的疗效。

The long term objective of this project is to improve the therapeutic index of radiation therapy for the treatment of prostate cancer (PCa). Radiation therapy is one of two primary treatments for clinically-localized PCa and is the principal therapy for locally-advanced disease associated with a higher grade, stage and/or PSA. While the success rate for both radiation and surgery is high for low-grade organ-confined disease, the estimated ten year disease-free-survival for advanced disease is less than 50%. Therefore, a means to improve the treatment of patients with clinically-localized high stage and/or grade prostate cancer would significantly decrease the morbidity and mortality of this disease. To address this we developed prostate-targeted RNA interference (RNAi) agents that selectively inhibit DNA repair pathways in prostate cells. Tissue-specific targeting was achieved through an RNA aptamer, A10-3, which binds to the Prostate Specific Membrane Antigen (PSMA) on the cellular surface and is then internalized into cells. The conjugated short hairpin RNAs (shRNAs) are then processed by cellular RNAi machinery, leading to knockdown of specific DNA repair mRNA and proteins. In the previous funding cycle we demonstrated that these agents, when directly injected into the tumor, significantly enhance the therapeutic index of external beam radiation therapy. Here we propose to continue the development of this strategy by generating chemically synthesized aptamer-siRNA radiation sensitizing agents and evaluating their safety as intraprostatically injected agents in a Phase I clinical trial. In addition to this translational aim, we will perform pre-clinical studies to determine whether the aptamer-siRNA radiation sensitizing agents are effective following intravenous injection. If successful, this mode of administration would provide a secondary route for radio-sensitizing locally advanced PCa, it would provide a novel means to improve the efficacy of external beam radiation therapy for the management of bone pain, and finally it would provide a means to enhance the efficacy of systemically targeted radiotherapeutics.