RNA Therapeutics for Pancreatic Cancer

描述（由申请人提供）：绝大多数胰腺癌患者仅通过切除术无法治愈。标准疗法与低反应率和生存率的适度改善相关，迫切需要更有效的疗法。适体是一类治疗性核酸（RNA或DNA）分子，其特异性结合现有靶蛋白。适体是通过大的组合文库的迭代筛选过程产生的，所述组合文库可以针对核酸酶抗性进行修饰。适体可以具有通过结合其蛋白质靶标介导的直接治疗效果。此外，与细胞表面受体结合的适体可以被表达那些受体的细胞内化，并用于递送其他治疗性货物。我们的总体假设是，结合相对于正常细胞在胰腺癌细胞上过表达的靶标的适体可用于选择性地将细胞毒性货物，如小干扰RNA（siRNA）或化疗剂递送至胰腺癌细胞。我们有2个具体目标：具体目标#1：利用针对复杂靶点的选择策略来识别新的胰腺癌靶点。适体介导的递送的理想靶点是在所有胰腺癌的表面上高度表达、有效内化并且在正常细胞的表面上不表达的靶点。利用复杂靶点如体内完整癌细胞或肿瘤组织的选择策略允许适体选择它们自己的靶点。该目的包括针对整个胰腺癌细胞的体外选择以及针对胰腺癌异种移植物和胰腺癌的基因工程小鼠模型的体内选择。我们将通过鉴定其特异性蛋白质和细胞靶点来表征选定的适体。因此，这一目标有可能同时确定新的目标和中介交付给他们的代理。将在目标#2中进一步评价被胰腺癌细胞内化的适体。具体目标#2：利用被胰腺癌细胞内化的适体用于siRNA和其他治疗性货物的特异性递送。我们有初步的数据表明，结合EGFR的RNA适体和结合核仁素的DNA适体被胰腺癌细胞内化。在目标#1中鉴定新适体的同时，我们将利用这些现存的适体来优化用于将K-ras siRNA和吉西他滨聚合物递送到细胞中的构建体。然后，我们将使用目标#1中发现的适体和目标#2第一部分中获得的货物技术来配制更特异和有效的构建体，以在体外和体内将K-ras siRNA和吉西他滨聚合物递送到胰腺癌细胞中。

DESCRIPTION (provided by applicant): The vast majority of patients with pancreatic cancer are not cured by resection alone. Standard therapies are associated with low response rates and modest improvements in survival, and there is a dire need for more effective therapies. Aptamers are a class of therapeutic nucleic acid (RNA or DNA) molecules, which specifically bind to existing target proteins. Aptamers are generated by an iterative screening process of large combinatorial libraries that can be modified for nuclease resistance. Aptamers can have direct therapeutic effects mediated by binding their protein targets. In addition, aptamers that bind to cell surface receptors can be internalized by cells expressing those receptors and be utilized to deliver other therapeutic cargo. Our global hypothesis is that aptamers that bind targets over-expressed on pancreatic cancer cells relative to normal cells can be used to selectively deliver cytotoxic cargo, such as small interfering RNAs (siRNAs) or chemotherapeutic agents, to pancreatic cancer cells. We have 2 specific aims: Specific Aim #1: To utilize selection strategies against complex targets to identify new pancreatic cancer targets. The ideal target for aptamer-mediated delivery is one that is highly expressed on the surface of all pancreatic cancers, efficiently internalized, and not expressed on the surface of normal cells. Selection strategies utilizing complex targets such as whole cancer cells or tumor tissue in vivo allow the aptamers to choose their own targets. This aim includes in vitro selection against whole pancreatic cancer cells as well as in vivo selection against pancreatic cancer xenografts and genetically engineered mouse models of pancreatic cancer. We will characterize selected aptamers by identifying their specific protein and cellular targets. This aim therefore has the potential to simultaneously identify novel targets and the agents to mediate delivery to them. Aptamers that are internalized by pancreatic cancer cells will be further evaluated in Aim #2. Specific Aim #2: To utilize aptamers that is internalized by pancreatic cancer cells for specific delivery of siRNAs and other therapeutic cargo. We have preliminary data demonstrating that a RNA aptamer that binds EGFR and a DNA aptamer that binds nucleolin are internalized by pancreatic cancer cells. In parallel with the identification of new aptamers in Aim #1, we will utilize these extant aptamers to optimize constructs for delivery of K-ras siRNAs and gemcitabine polymers into cells. Then, we will use aptamers discovered in Aim #1 with the cargo technology gained in the first part of Aim #2 to formulate more specific and effective constructs to deliver K-ras siRNAs and gemcitabine polymers into pancreatic cancer cells in vitro and in vivo.