氧化还原响应性7-乙基-10-羟基喜树碱靶向纳米输送体系的制备及其克服肿瘤耐药性的研究

Development of targeted drug delivery systems based on macromolecule synthesis and nanotechnology has provided novel strategies to improve anti-cancer treatments. Especially, the tumor microenvironment-responsive delivery systems, e.g. pH-responsive, ROS-responsive and GSH-responsive, hold great promise to enhance targeted drug release in a controlled manner. Disulfide bond remains stable in physiological conditions, but could be hydrolyzed in response to high level of intracellular GSH, thus providing the opportunity of designing GSH-responsive nano-drug delivery systems in which drug moleculars are conjugated with the carriers through disulfide bonds. There are several drawbacks for the clinical application of CPT-11. Moreover, 7-ethyl-10-hydroxy camptothecin (SN38), the active metabolite of CPT-11, can not be directly applied for clinics due to its extremely low water solubility. It has been reported that high level of intracellular GSH and overexpression of drug transporters, such as BCRP and in some cases P-gp as well, play crucial roles in the development of drug resistance to CPT-11/SN38. Recently, our group has reported and characterized two novel redox-responsive PEG-SN38 prodrugs, OEG-SN38 and OEG-2S-SN38. In this project, we will further design and synthesize another PEG-SN38 prodrug, PEG-S-S-SN38, in which SN38 is conjugated to PEG via responsive disulfide bonds. Furthermore, we will encapsulate drug transporter inhibitors (Ko143, tetrandrine) into the self-assembling PEG-SN38 nanoparticles. Through establishment of various sensitive/resistant tumor models, these targeted PEG-SN38 nanodrugs, carrying either SN38 alone or in combination with drug transporter inhibitor, will be extensively studied for their redox-responsive drug release, anti-tumor effect and the capability of reversing drug resistance in vitro and in vivo. The proposed study may lead to the development of redox-responsive targeted drug delivery systems useful for clinical cancer treatment and may promote the clinical application of drug transporter inhibitors.

肿瘤组织内含有高活性氧自由基，且细胞内还原性谷胱甘肽(GSH)的浓度较血液及细胞外显著升高，这为构建氧化还原响应性靶向药物输送体系奠定了基础。二硫键在生理环境中保持稳定，但可被细胞内GSH所降解。CPT-11存在多种缺陷，其活性产物7-乙基-10-羟基喜树碱(SN38)因水溶性差无法直接应用。CPT-11/SN38耐药性与细胞内GSH升高、耐药相关蛋白过表达有关。本项目在课题组近期报道两种氧化还原响应性PEG-SN38纳米前药基础上，进一步合成二硫键连接的PEG-S-S-SN38；以三种PEG-SN38前药为载体制备SN38与耐药逆转剂的联合输送体系；利用多种体内外模型，研究SN38单药及联合药物输送体系的氧化还原响应性、抗癌及逆转耐药性的能力及关键机制。项目的开展为研制能克服CPT-11/SN38多种缺陷及耐药性的SN38输送体系、解决耐药逆转剂临床应用困难的困境奠定重要理论和实验基础。

肿瘤组织内含有高活性氧自由基，且细胞内还原性谷胱甘肽(GSH)的浓度较血液及细胞外显著升高，这为构建氧化还原响应性靶向药物输送体系奠定了基础。二硫键在生理环境中保持稳定，但可被细胞内GSH所降解。化疗药物CPT-11存在多种缺陷限制其临床应用，而其活性代谢产物7-乙基-10-羟基喜树碱（SN38）因水溶性和稳定性差等原因无法直接应用。此外，研究发现CPT-11/SN38的耐药性与细胞内GSH升高及耐药蛋白过表达有关。本项目在课题组近期报道两种氧化还原响应性PEG-SN38前药的基础上，设计和合成借二硫键连接的新型前药PEG-S-S-SN38，并以其为载体进一步构建SN38与小分子耐药逆转剂的联合输送体系，对获得的单药及联合载药体系进行系统表征；构建并利用多种表达不同耐药蛋白水平的肿瘤模型，研究新型SN38单药及联合药物输送体系的体内外抗肿瘤及逆转耐药性的能力，探索内在机制。此外，项目组制备并探索了粒径、主动靶向基团CRGDK对新型SN38前药PEG2.4K-p(HEMASN38)3K药物动力学、体内外肿瘤靶向能力及抗肿瘤疗效的影响。本项目的研究工作不仅成功获得了多种新型SN38单药及共输送联合载药体系，并通过系统的实验研究，证实相关前药具有优异的体内外抗肿瘤及逆转耐药性的能力，可能与其多重环境响应性释药等特性有关。其中，联合共输送体系能够特异性地有效逆转BCRP高表达肿瘤的耐药性。项目的研究工作为研制能克服CPT-11/SN38多种固有缺陷、逆转耐药性的新型SN38输送体系，以及解决小分子耐药逆转剂临床应用困难的瓶颈问题奠定重要的理论和实验基础。