RNA Therapeutics for Pancreatic Cancer

描述（由申请人提供）：绝大多数胰腺癌患者仅靠切除无法治愈。标准治疗与低反应率和适度的生存改善有关，迫切需要更有效的治疗方法。适配体是一类治疗性核酸（RNA或DNA）分子，它特异性地结合现有的靶蛋白。核酸适体是通过大型组合文库的迭代筛选过程产生的，这些文库可以被修改为核酸酶抗性。适配体可以通过与靶蛋白结合而产生直接的治疗作用。此外，与细胞表面受体结合的适体可以被表达这些受体的细胞内化，并用于递送其他治疗货物。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度表达的靶标的适体可用于选择性地向胰腺癌细胞递送细胞毒性物质，如小干扰rna （sirna）或化疗药物。我们有两个具体目标：具体目标#1：利用针对复杂靶点的选择策略来确定新的胰腺癌靶点。适体介导递送的理想靶标是在所有胰腺癌细胞表面高表达、有效内化且不在正常细胞表面表达的靶标。利用复杂靶标（如整个癌细胞或肿瘤组织）的选择策略允许适体选择自己的靶标。这一目标包括对整个胰腺癌细胞的体外筛选，以及对胰腺癌异种移植和基因工程小鼠胰腺癌模型的体内筛选。我们将通过鉴定其特定的蛋白质和细胞靶标来表征选定的适体。因此，这一目标有可能同时确定新的靶标和介导其递送的药物。被胰腺癌细胞内化的适体将在Aim #2中进一步评估。特定目标#2：利用胰腺癌细胞内化的适体特异性递送sirna和其他治疗货物。我们有初步的数据表明，结合EGFR的RNA适体和结合核仁蛋白的DNA适体被胰腺癌细胞内化。在Aim #1中鉴定新的适体的同时，我们将利用这些现有的适体来优化K-ras sirna和吉西他滨聚合物进入细胞的结构。然后，我们将使用在Aim #1中发现的适体和在Aim #2的第一部分获得的货物技术来制定更具体和有效的结构，以在体外和体内将K-ras sirna和吉西他滨聚合物输送到胰腺癌细胞中。

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.