肿瘤细胞与炎性微环境双靶向响应性纳米载药系统的构建及其用于肿瘤联合治疗的研究

Tumor inflammatory microenvironment is the basis for tumor cells to survive and resist treatment, and plays a key role for poor tumor prognosis. M2 type tumor-associated macrophages (TAMs) are the main participants for tumor inflammation, inhibition of TAMs activity is of great significance to reshape tumor inflammatory microenvironment to improve the prognosis. In this project, a combination therapeutic strategy of dual targeting to both tumor cells and TAMs is therefore raised for anticancer therapy. Based on modification of tumor cells and TAMs-specific legumain-activable targeting peptides (LAT) and legumain-cleavable PEG chain, a tumor cells and TAMs dual-targeting and double layer-responsive nanocarrier delivery system has been constructed for combined anticancer therapy, to achieve synergy of targeted treatment of both tumor cells and tumor-associated inflammatory microenvironment. . The outer layer of PEG shielding effect and the deactivation of LAT targeting effect can enable the nanocarriers to effectively avoid non-specific MPS elimination to extend the blood circulation. After reaching tumor site by EPR effect, the outer PEG layer of nanocarriers was cleaved and the LAT targeting effect was activated specifically by the legumain overexpressed on both tumor cells and TAMs, thus achieving the dually targeted delivery and the combination treatment. Through this study, it can provide beneficial references for the combined anticancer therapy with tumor inflammatory microenvironment.

肿瘤炎性微环境是肿瘤细胞赖以存活和抵御治疗的基础，是肿瘤预后不良的关键所在。M2型巨噬细胞（TAM）是肿瘤相关炎症最主要的参与者，抑制TAM活性对重塑肿瘤炎性微环境，改善化疗预后具有重要意义。本项目因此提出联合肿瘤细胞和TAM靶向治疗策略，设计对肿瘤细胞和TAM的特异性legumain酶可激活靶向肽LAT作为配体，辅以legumain酶可裂解PEG链双层修饰，构建高效的具有肿瘤细胞和TAM双靶向响应性的纳米载药系统应用于肿瘤联合治疗，以实现肿瘤与炎性微环境靶向治疗的协同效果。纳米载体利用legumain酶可裂解PEG链外层屏蔽效应和LAT靶向“钝化”作用避免正常单核巨噬细胞系统非特异性吞噬，延长体循环时间；同时利用肿瘤特异性legumain酶裂解脱除PEG链和“活化”LAT靶向作用，有效实现联合靶向肿瘤细胞和TAM递药和治疗效果。通过本项目研究，为联合肿瘤与炎性微环境靶向治疗提供有益思路。

肿瘤炎性微环境被普遍认为是导致肿瘤术后化疗耐药和预后不良的根本因素。肿瘤相关M2型巨噬细胞（TAMs）是肿瘤微环境炎症最主要的参与者，抑制TAMs活性对于重塑肿瘤炎性微环境，改善化疗预后具有重要意义。本项目针对性提出联合肿瘤和TAMs治疗策略，旨在构建一种新型高效的肿瘤细胞与TAMs双靶向多功能纳米递药平台用于抗肿瘤联合治疗及作用机制研究。重点考察了纳米载体表面Legumain酶可激活ATpep配体和PEG双功能化修饰对于其靶向肿瘤和TAMs特异性和递送效率的影响，以及以紫杉醇（PTX）和CSF-1R抑制剂（PLX3397）为联合用药模型，研究了纳米载体不同的PTX/PLX3397联用比例和释药模式对于抗肿瘤联合治疗协同效应的影响。研究结果表明使用Legumain酶敏感可激活促吞噬肽（ATpep）相比促吞噬肽（Tpep）修饰可以显著提高纳米载体对于肿瘤和TAMs靶向特异性以及使用Legumain酶敏感可脱落的PEG双修饰可以进一步有效改善纳米载体对于肿瘤和TAMs靶向递送效率。当PTX与PLX3397用药比例为1：2（w/w）时，二者联合给药表现出最为显著的协同治疗效果。构建智能响应型PLX/Ps@HATpep NPs程序释药纳米粒通过优先释放CSF-1R抑制剂PLX3397药物，而后通过还原型谷胱甘肽（GSH）激活Ps前药释放细胞毒性PTX药物，可以有效实现免疫/化学协同抗肿瘤治疗效果。综上，本项目研究为临床上肿瘤术后化疗联合炎性微环境靶向CSF-1R抑制剂治疗肿瘤提供有益的思路和理论指导。