Bombesin修饰的纳米粒肿瘤靶向性及靶向递药效果研究

Nanoparticles can be used as carriers to take chemotherapy drugs targeting to tumors via the enhanced permeability and retention (EPR) effect, which displays great advantages in tumor-targeted therapy. However, the EPR effect largely depends on the degree of tumor vascularization and porosity of tumor vessels. Therefore, it is still difficult to achieve specific tumor targeting if only relying on EPR effect. Attachment of tumor targeting moieties to the nanoparticles could enhance their targeting ability. We have demonstrated that Bombesin can bind to tumor cells with high affinity and specificity. Besides, conjugation of Bombesin to toxin molecules can significantly enhance their cytotoxicity to tumor cells. Subsequently, we found that Bombesin could increase the celluar uptake of nanoparticles in tumor cells, which indicates that attachment of Bombesin to nanoparticles may enhance their targeting ability. In this project, we will test the hypothesis in detail that nanoparticles grafted with Bombesin could target the tumors and could further enhance the antitumor efficacy of chemotherapy drugs. Hence, this work will evaluate the possibly of targeted delivery of anticancer drugs by Bombesin-grafted nanoparticles. This natural tumor-homing peptide Bombesin has the advantage of small size and high affinity. By attachment of Bombesin to nanoparticles, it is expected to develop the highly specific, no/low toxic and water-soluble targeting carriers with independent intellectual property rights for efficient delivery of anticancer drugs to tumor cells.

纳米粒通过EPR效应可携带化疗药物，靶向肿瘤组织，在肿瘤靶向治疗中显示出极大优势。然而EPR效应受肿瘤血管化程度及血管孔径影响大，因此，仅依靠EPR效应难以实现对肿瘤的特异性靶向。采用肿瘤细胞特异性识别分子修饰纳米粒，可提高纳米粒的肿瘤靶向性。项目前期证实Bombesin不仅高亲和、高选择结合肿瘤细胞，还能携带杀伤分子选择性杀伤肿瘤细胞。后续研究发现Bombesin的修饰提高了肿瘤细胞对纳米粒的摄取，提示Bombesin可增强纳米粒的肿瘤靶向能力。本项目拟进一步采用Bombesin修饰纳米粒，确定其对肿瘤靶向性的增强作用及包载化疗药物的体内外抗肿瘤效果，评价将其开发为新型靶向递药纳米粒的可能性。项目选择的天然肿瘤导向肽Bombesin具有分子小、亲和力强等优点，采用Bombesin修饰纳米粒，可望推出系列自主产权、高选择性、无/低毒、水溶性的靶向递药纳米粒，为肿瘤靶向治疗提供新选择。

纳米粒在增加药物溶解性、药物缓释、改善化疗药物临床疗效、低毒/无毒等方面显示出极大优势。然而，其对肿瘤组织的被动靶向受肿瘤血管通透性影响大，因此，常导致纳米粒药物向肿瘤部位递送不足。采用能特异性识别肿瘤组织的导向肽（如Bombesin）修饰纳米粒，可能提高纳米粒的肿瘤靶向性。肿瘤导向肽iRGD不仅可通过其环肽序列识别肿瘤部位integrin受体，还可继而与neuropilin-1组织穿透性受体结合，介导药物对肿瘤组织的靶向和穿透。更重要的是，iRGD可不与纳米粒进行共价连接，协同给药即可增强纳米粒对肿瘤的靶向性。不仅省去了Bombesin多肽与纳米粒连接的工艺，避免了共价连接操作过程引起的纳米粒不稳定性；而且载药纳米粒与iRGD的比例可根据需要进行切换，临床使用更加方便。与游离紫杉醇（PTX）相比，纳米粒包载的紫杉醇（PLGA-PTX）保留了PTX对结肠癌细胞的杀伤活性，同时在相同浓度下对正常细胞杀伤能力较弱。PLGA-PTX可诱导肿瘤细胞凋亡，使细胞周期停滞在G2/M期，有效抑制了肿瘤细胞的侵袭和转移。PLGA-PTX与iRGD协同用药体外未增强纳米粒对肿瘤细胞的毒性。在荷人结肠癌小鼠模型中，肿瘤组织血管丰富并高表达integrin受体和neuropilin-1受体；iRGD协同给药，增加了纳米粒在肿瘤部位的富集，使纳米粒从肿瘤组织血管中渗透进入瘤体实质，并显示出更强的抗肿瘤作用。这些结果说明，肿瘤导向肽iRGD可促进纳米粒向肿瘤部位的递送，进而增强了纳米粒的抗肿瘤效果。