细胞载体介导纳米药物复合物精准归巢肿瘤及其抗肿瘤作用的系统研究

The targeted drug delivery systems have common bottlenecks such as inadequate targeting ability for the tumor and its metastases, and difficult to in-depth throughout the tumor tissue. In our previous studies, RGD-/PEG-PAMAM-DOX (RGD-PPCD and PPCD) nanoconjugates with targeting and acid-triggered DOX release had been systematically studied. Both mesenchymal stem cells (MSCs) and neural stem cells (NSCs) have extensive tumoritropism. To further enhance the targeted efficacy of the nanoconjugates, MSCs and NSCs used as cell carriers will incorporate the nanoconjugates via three methods,including cellar uptake, noncovalent and covalent bond forming in cell surface.Through in vitro and in vivo experiments,the effect of three drug-loaded methods on stability, bioactivity and in vivo fate will be systematically studied and evaluated. Sequentially，the MSCs/NSCs- nanoconjugates will be optimize in order to construct a novel targeted drug delivery system with the specific tropism for tumor and local drug release into tumor. After intravenous and / or intratumoral injection, the stem cells enhanced the targeting and antitumor effect of nanoconjugates will be primarily investigated. It is expected that the MSCs/NSCs-nanoconjugates will migrate toward the primary tumor and its metastases more efficiently and delivery DOX with wider distribution in tumor tissues compared with stem cells and nanoconjugates. The increased DOX intratumoral distribution will further contributed to significantly enhanced tumor-cell apoptosis. The achievement of the project would suggest that stem cell therapy combined with nanotechnology could be a promising tool to efficiently deliver drugs to tumors and a potential strategy to overcome the shortcomings of drug delivery nanosystem. Furthermore, it will lay a solid foundation for stem cells-based cancer therapy and provide prospects for their clinical translation.

目前抗肿瘤靶向递药系统存在的瓶颈问题是靶向和深入肿瘤组织的程度难有突破性提高，本研究组前期研究中建立的酸敏性释药RGD-/PEG-PAMAM-阿霉素(RGD-PPCD和PPCD) 靶向纳米复合物也存在此问题。鉴于间充质干细胞（MSCs）和神经干细胞(NSCs) 具有定向归巢于肿瘤的独特优势，本项目提出以MSCs和NSCs为细胞载体，通过细胞内吞、膜表面非共价和共价结合三种方式，分别装载PPCD和RGD-PPCD，构建一新型MSC/NSCs-纳米复合物靶向递药系统。通过体内外实验，系统研究和评价不同载药方式对干细胞-纳米复合物的稳定性、生物活性及体内命运的影响；与干细胞和纳米复合物比较，重点探讨干细胞-纳米复合物递药系统精准归巢肿瘤、瘤内定位释药进而发挥更高效抗肿瘤作用的优势。本项目的研究将为以干细胞为载体设计更高效的肿瘤靶向递药系统提供实验和理论依据，为干细胞最终应用于临床治疗奠定基础。

本项目以骨髓间充质干细胞（MSCs）为细胞载体，分别采用内吞入胞、膜表面非共价和共价结合三种载药策略，装载课题组前期研究的RGD修饰或未修饰的阿霉素-树枝状聚合物纳米复合物（PPCD 和 RGD-PPCD），进而构建了不同类型的干细胞-纳米复合物递药系统，通过系统的体内外研究和评价，最终优选了两种MSCs-纳米复合物递药系统，一是采用自然吞噬方式装载PPCD和RGD-PPCD，构建了MSCsRGD-/PPCD干细胞递药系统，载药后的MSCs仍保持了干细胞的活力和肿瘤趋向性，成功实现了精准、高效治疗脑胶质瘤的研究目标。进一步地，采用了一种国内外首创的装载策略，即内吞和膜结合双模式载药，构建了一种最大化载药的MSCs-纳米复合物递药系统，该策略解决了目前干细胞载药量有限难以实现在动物耐受范围内进行全身给药的问题。该系统通过全身给药用于转移性肺癌的治疗，呈现了极高的肺部蓄积水平，进而获得了最强的抗肿瘤活性。总之，与纳米药物相比， MSCs 具有肿瘤定向迁移能力与更强的肿瘤组织渗透能力，可以将药物定向运送到肿瘤部位，并穿透肿瘤实质，深入到组织内部释放药物。本项目利用 MSCs 这一特性， 改善 了RGD-/PPCD 的靶向效力，进一步增加了药物在肿瘤内的分布和蓄积。体内实验证实了 MSCs 优于复合物的抗肿瘤作用，并具有更好的安全性。与 MSCsDOX 相比，由于复合物本身的缓释作用和纳米大分子的优势， MSCsRGD-/PPCD 表现出了更好的肿瘤内分布和更强的治疗效果。研究基本上按计划完成了总体目标，已达到预期研究成果。