Polymer and Lipid-based Nanomedicine of Synergistic Drug Combination for Improving Chemotherapy of Multidrug Resistant Breast Cancer
Keywords: Biological Barrier
Cancer
Drug Combination
Multidrug Resistance
Nanoparticle
Synergy

Chemotherapy is a primary treatment modality for metastatic cancer. The development of multifactorial multidrug resistance (MDR), however, remains a significant obstacle contributing to treatment failure. The goal of this thesis is to investigate an emerging polymer-lipid hybrid nanoparticle (PLN) system for co-delivering synergistic drug combinations to overcome both macro- and microscopic biological barriers associated with MDR that blocks the effectiveness of chemotherapy. Based on our previous research on PLN for drug combination delivery, this thesis is intended to answer three questions: 1) can PLN synchronize the pharmacokinetics and ratio-metrically co-deliver high concentrations of a synergistic drug combination into tumor tissue? 2) Can PLN enhance intracellular drug delivery to the site of drug action e.g., the nucleus? 3) Can PLN overcome the plasma membrane rigidity and target mitochondria that are responsible for apoptosis dysregulation in MDR cancer cells? Results from this thesis show that compared to the drug combination in free solution, PLN synchronized pharmacokinetics and co-delivered two DNA damaging drugs, doxorubicin (DOX) and mitomycin C (MMC), to breast tumors at high concentrations at their synergistic ratios. Compared to clinically used liposomal or free solution of DOX, PLN moderated DOX-induced cardiotoxicity in vivo and enhanced local DOX bioavailability as evidenced by the highest intracellular accumulation and nuclear localization in vitro and tumor cell apoptosis in vivo. A new PLN formulation co-encapsulating poly-unsaturated fatty acid docosahexaenoic acid (DHA) and MMC effectively reduced MDR-associated rigidity of cytoplasmic membrane, enhanced drug and nanoparticle uptake, enabled synergistic reaction of MMC and DHA, and subsequently damaged mitochondria through elevated oxidative stress. These rationally designed PLN formulations resulted in superior efficacy against MDR breast cancer cells. The findings in this thesis substantiate PLN as a promising platform for nanoscale co-delivery of synergistic drug combinations and suggest powerful strategies for future design of nanomedicine for overcoming multifactorial MDR in cancer. 联合化疗是治疗转移性癌症的主要方式,但是化疗后肿瘤产生多药耐药性 (multidrug resistance, MDR)是导致肿瘤化疗失败的重要原因之一。 因此,为了克服与 MDR 相关的 宏观和微观生物屏障,从而促进联合化疗的疗效并且降低其毒副作用,该 课题旨在设计一种新型的高分子材料 - 脂质混合纳米颗粒(Polymer-Lipid Hybrid Nanoparticles, PLN)来用于输送具有协同疗效的药物组合。根据我们过去的研究表明, PLN 作为纳米载体具有同时载入数种药物分子的优越性能。 该课题从目前 MDR 肿瘤治 疗的方案和 PLN 潜在临床转化应用的两个方面入手,研究以下三个问题: 1) 从宏观毒药物动力学(adsorption,distribution,metabolism,andelimination,ADME) 的角度,PLN 在血液循环的过程中是否具有同步药代动力, 并且将所载入的协同 组合药物靶向输送到肿瘤组织的能力? 2) 从微观MDR肿瘤细胞的角度,PLN是否可以逆转P-糖蛋白外排泵(P-glycoprotein efflux transporter)介导的肿瘤 MDR, 从而增强癌细胞内药物的浓度, 并且将药物准 确高效的输送到药理作用分布的特定范围,比如细胞核内双链 DNA? 3) 从微观更细化的 MDR 肿瘤亚细胞的角度, 与药物敏感的肿瘤细胞相比较,P-gp 过 度表达的 MDR 肿瘤细胞有较高的细胞膜弯曲刚度, 因此对于作用与癌细胞内的药 物和其药物载体是一个巨大的通透性屏障。PLN 是否能够降低 MDR 细胞膜弯曲刚 度, 其后以线粒体(mitochondria)凋亡途径为靶点杀灭癌细胞? 该课题的研究结果表明,在原位乳腺肿瘤小鼠模型中, 经尾静脉注射的PLN能显著富 集分布在肿瘤组织, 之后进入癌细胞按照最优化协同比率控释两种同时携带的抗肿瘤药 物阿霉素 (doxorubicin) 和丝裂霉素C (mitomycin C)。相比于临床上使用的脂质体 doxorubicin (Liposomal doxorubicin, DOXIL®/Caelyx®) 或游离doxorubicin (Adriamycin®) PLN显著提高了doxorubicin在细胞核的积累。 更重要的是PLN增加了doxorubicin在肿瘤 细胞中的生物药效率(bioavailability),从而增强癌细胞DNA双链的断裂和凋亡(apoptosis)。原位乳腺肿瘤小鼠实验表明同时携带doxorubicin 和 mitomycin C PLN有效抑制了MDR乳 腺肿瘤生长并且没有任何毒副作用。 含有ω-3不饱和脂肪酸(docosahexaenoic acid, DHA ) PLN 明显降低P-gp介导的MDR肿瘤细胞膜的弯曲刚度,增强了MDR肿瘤细胞对 mitomycin C摄取。 随后MMC和DHA协同作用所产生的活性氧(reactive oxygen species, ROS) 通过升高氧化应激破坏线粒体, 从而到达对MDR乳腺肿瘤氧化损伤。该研究成果 对阐明PLN作为新型先进纳米药物载体改善联合化疗的作用机制和研发转化新型靶向抗肿 瘤新药都具有重要意义。