基于核酸适体的靶向性组合药物体系构建研究及肿瘤耐药性调控

Drug resistance arises from complicated mechanisms in tumor cells, and leads to the failure of cancer treatments. Chemotherapy regimens that combine several anticancer drugs working in different mechanisms can minimize the effect of drug resistance during the cancer treatment. The efficacy of regimens will be largely improved when the molecules are conjugated with a targeting ligand to reduce toxicity while increase synergistic effect. Based on our previously established automated modular synthesis of aptamer-drug conjugate, we hypothesize that aptamer is an ideal ligand for construction of targeted regimens. As a proof of the concept, anticancer drugs camptothecins and combretastatins are converted into corresponding pharmaceutical modules by organic synthesis. From the modules, two drugs are covalently linked to a strand of aptamer in a solid-phase synthesizer with high efficiency and controllability. The sequence of aptamer, the linker between drugs and backbone, and the dose can be readily adjusted by programmable automated synthesizer. Fluorescent labeling and imaging techniques are used to study the targeting property, endocytosis and distribution of the conjugates. Inhibitory activity of the conjugates against drug-resistant breast cancer cell is to be investigated with well-established cell lines and animal models. This project provides the design and synthetic method of a novel drug combinations by integration of targeting ligand together. Biological studies may provide theoretical guide and experimental evidence for developing new anticancer drugs.

肿瘤耐药产生途径多、机制复杂，通常导致癌症治疗失败。临床实践证明，使用组合药物的化疗联合方案可减少耐药对癌症治疗的影响。将药物与配体偶联可降低联合方案毒副作用并增强药物协同作用，以显著提高对耐药肿瘤的药效。基于在核酸适体-药物偶联物合成上的研究基础，我们提出核酸适体是构建靶向性联合方案理想配体的假说。作为验证，选择将不同抗癌机制的喜树碱与考布他汀通过有机合成转化为相应的药用模块，应用该模块在固相合成仪上高效、可控地构建相应的核酸适体-组合药物偶联物。核酸适体序列、药物之间的链接形式与各个药物配比可方便地经由程序化、自动化合成仪进行调节。应用荧光标记与成像技术，研究偶联物的靶向性、内吞机制与分布情况。通过乳腺癌耐药细胞与动物模型，研究偶联物对耐药性肿瘤抑制活性。本项目设计一类新型靶向性组合药物，拟开展相应药物库的构建方法研究，并进行生物学研究作为理论指导与实验依据，最终发现新的抗癌药物。

耐药通常导致癌症治疗失败主要原因之一，而临床实践证明，使用组合药物的化疗联合方案可减少耐药对癌症治疗的影响。将药物分子与靶向配体偶联可进一步降低副作用并增强药物协同作用，以提高对肿瘤的药效。前期研究结果表明，基于核酸适体-药物偶联物的靶向药物递送体系可用于降低毒副作用。本项目研究在已有5-氟尿嘧啶、吉西他滨等药用固相模块的基础上，结合计算化学、化学生物学及生物技术等手段，设计并合成包含喜树碱、SN-38及紫杉醇等常规肿瘤治疗药物分子的核酸适体-药物偶联物体系，并进行作用机制研究与联合用药评估；项目还针对核酸类药物在活体内代谢快的瓶颈，进一步引入人工碱基对核酸结构进行优化研究。项目的实施，展示了在靶向药物递送系统的核酸适体-药物偶联物中如何一体式连接多个药物分子，以应对耐药问题；同时通过疏水碱基调控与白蛋白作用力，开发出延长核酸适体-药物偶联物血液循环时间的新技术，将促进核酸适体-药物偶联物在临床的应用。