多靶点肝靶向脂质体递药系统的构建及其抗肝癌作用机制研究

Liver cancer (hepatocellular carcinoma, HCC) is one of the most common disease with a high mortality. Chemotherapy is the main treatment for cancer. However, due to the limited drug accumulation in tumor site and high toxic side effects for healthy tissue, the chemotherapy for HCC shows little clinical benefit or few prolonged survivals as compared to no treatment. Therefore, development of an effective hepatic targeted drug delivery system (HTDDS) is extremely important to improve the drug efficacy to hepatic cancer cells, and reduce toxic side effects systematically. In this study, we try to construct the glycyrrhetinic (GA) receptor and αvβ3 receptor-mediated long circulating liposomes (LCL) using GA and cRGD as targeting ligands (GA and cRGD modified LCL,GA/cRGD-LCL). The aim is to get a highly selective HTDDS through delivering chemotherapeutic agents to both hepatic tumor cells and hepatic tumor vasculature. The new lipid derivative(GA modified pegylated dioleoylphosphatidylethanolamine,GA-PEG-DOPE) will be synthesized. A novel dual-ligand pegylated liposomes will be constructed. The cellular uptake and cytotoxicity of the liposomes in HepG2 cells and human umbilical vein endothelial cells (HUVEC) will be evaluated.The tumor distribution of liposomes in nude mice bearing HepG2 hepatoma will be observed using MRI. The physicochemical properties,stability and in vitro drug release of the GA/cRGD-LCL encapsulated doxorubicin (GA/cRGD-LCL-Dox) will be studied. The tissue distribution and antitumor effects of GA/cRGD-LCL-Dox will be evaluated in HepG2 tumor-bearing nude mice.This study will provide theoretical and practical foundation for the further research of the novel HTDDS. In this study, a novel HTDDS modified with two ligands to target both liver tumor cells and liver tumor blood vessels is designed. This new attempt will provide a new way for the treatment of HCC.

肝癌是严重危害人类健康的常见病之一。构建对肝肿瘤有特异性的靶向递药系统，将化疗药物定向输送至肝肿瘤部位以达到高效低毒的目的一直是医药工作者努力研究的课题。本项目拟在合成新型甘草次酸-聚乙二醇-二油酰基磷脂酰乙醇胺脂质衍生物（GA-PEG-DOPE）的基础上，以阿霉素为模型药物，利用甘草次酸（GA）对肝肿瘤细胞表面的甘草次酸受体、环多肽cRGD对肝肿瘤细胞表面和肿瘤新生血管内皮细胞膜上的整合素αvβ3受体的特异性亲和力，构建甘草次酸和环多肽cRGD双配体修饰的新型肝靶向长循环脂质体，旨在通过对肝肿瘤细胞和肿瘤血管的多靶点靶向及EPR效应，得到一种高效肝肿瘤靶向递药系统。通过研究所构建的双配体空白脂质体体内外对肝癌细胞及肿瘤血管内皮细胞的靶向性和载药脂质体体内外性质及其抗瘤活性，探讨所构建新型脂质体的靶向规律及其靶向治疗的作用机制，为开拓肝癌治疗新途径提供理论依据和新思路。

本课题的目的是构建一种靶向治疗肝癌的双靶点脂质体递药系统。首先以甘草次酸(GA)和二油酰基磷脂酰乙醇胺(DOPE)为原料合成了GA-DOPE脂质衍生物，利用GA对肝肿瘤细胞表面的甘草次酸受体、环多肽cRGD对肝肿瘤细胞表面和肿瘤新生血管内皮细胞膜上的整合素ανβ3受体的特异性亲和力，构建甘草次酸和环多肽cRGD双配体修饰的新型肝靶向阿霉素长循环脂质体，旨在通过对肝肿瘤细胞和肿瘤血管的多靶点靶向及EPR效应，形成一种高效肝肿瘤靶向递药系统。本论文设计并合成了两种靶体GA-DOPE和DSPE-PEG-cRGD，构建了GA/cRGD双配体修饰的荧光探针标记的脂质体，研究了该脂质体在HepG2肝癌细胞的摄取情况及荷瘤裸鼠活体成像进行了研究，结果显示GA/cRGD双配体修饰的脂质体较单一配体修饰的脂质体和未经配体修饰的脂质体对HepG2肝癌细胞和肝肿瘤组织具有更强的靶向性；同时制备了GA/cRGD双配体修饰的阿霉素脂质体（GA/cRGD-LP-DOX），对其体外细胞毒性、体内药动学参数及组织分布、荷瘤裸鼠的抑瘤活性进行了评价。结果显示所制备的GA/cRGD-LP-DOX的粒径为 (92.04 ± 0.4) nm，Zeta电位(-32.9 ± 2.0) mV。体外细胞毒性实验显示双配体修饰的阿霉素脂质体的IC50比单一配体修饰的阿霉素脂质体IC50值小，体内抑瘤活性试验显示GA/cRGD-LP-DOX给药组抑瘤效率较单一配体修饰的阿霉素脂质体抑瘤活性更强，荷瘤裸鼠的生存周期更长。