调控肿瘤相关成纤维细胞的多肽自组装纳米载体的设计及抗肿瘤机制研究

Fibrotic stroma is a physical scaffold for soluble growth factors capable of influencing tumor cell growth, survival, and motility, and this fibrotic stroma also provides physical barriers to inhibit the distribution and penetration of various antitumor drugs. Cancer-associated fibroblasts (CAFs), a predominant stromal cell type in the tumor microenvironment, are the principal source of fibrosis in the stroma, induce tumor fibrosis and alter composition and physiochemical properties of extracellular matrix (ECM), and interact closely with tumor cells to create a tumor-facilitated environment that stimulates local tumor growth and distant metastasis. Specific expression and unique properties make CAFs a potentially attractive therapeutic and diagnostic target in the tumor microenvironment. It is now known that fibrogenesis is a dynamic process that is potentially reversible, at least in its early stage. Consequently, inhibiting the development of fibrosis through regulating CAFs may be a specific and efficient strategy to downregulate fibrogenesis of ECM, leading to enhanced drug perfusion and improved tumor therapeutic efficiency.. Peptides and peptide derivatives, owing to their biocompatibility, chemical versatility, and biological recognition abilities, have been widely utilized as building blocks to construct multifunctional nanostructures for drug delivery and release. Herein, based on previous studies, we will develop some peptide self-assembled nanomaterials with the ability of CAFs targeting and efficient destruction of tumor cells. The strategies will be effective to downregulate fibrogenesis of ECM and decrease the stromal barrier, improve the chemotherapeutic drug delivery for the treatment of CAF-rich solid tumors, and reduce side-effects of chemotherapeutic drugs. The nanocarriers might be also potentially applicable for the delivery of a broad spectrum of poorly soluble chemotherapeutic drugs, being able to greatly enhance tumor targeting and drug delivery efficacy, in establishing an efficient treatment of a broad range of cancers. By targeting CAFs in the tumor microenvironment and improving cellular uptake of tumor cells, these studies lay a foundation for further development of such combination strategy for drug delivery against a wide range of solid tumors. Furthermore, our study will give a new insight for precise control of peptide self-assembly. This concept, therefore, has significant implications in understanding the interactions of nanostructures with biological systems and assisting in the nanocarriers construction mediated by peptide self-assembly, with great potential for the development of clinical therapeutics using nanomedicine.

本项目主要研究以调控肿瘤相关成纤维细胞(CAFs)的生物医学功能为导向的多肽纳米结构的设计及组装过程。通过合理设计多肽序列、并对侧链进行改性和修饰的手段，构建新型多肽自组装纳米载体。选择CAFs为治疗靶点，构建对肿瘤微环境特异高表达的蛋白水解酶响应的多肽自组装纳米载体，实现抗纤维化药物对CAFs的靶向输运、以及在肿瘤微环境中进行酶响应的药物可控释放，通过调控CAFs下调肿瘤微环境ECM的纤维化程度；进一步利用特异性靶向肿瘤细胞并能高效进入细胞的多肽自组装纳米载体包载化疗药物，提高抗肿瘤纳米药物在肿瘤组织中的渗透效率。并将揭示多肽功能纳米结构的自组装及多肽-药物复合体系的共组装机理；阐明组装体的结构与其生物医学功能之间的构效关系。从而削弱并有效控制肿瘤的恶性发展，发挥更加高效、长效、安全的抗肿瘤疗效，为通过调控CAFs实现肿瘤（胰腺癌和前列腺癌）治疗的关键科学目标奠定实验与理论基础。

恶性肿瘤是目前危害人类健康的主要杀手，目前仍需要更为有效的的手段去解决肿瘤治疗的难题。肿瘤相关成纤维细胞（CAFs）是肿瘤微环境中主要的间质细胞成分，在塑造肿瘤基质微环境的过程中起着重要的作用。本项目以CAFs为治疗靶点，结合纳米药物的优势为切入点提出治疗策略，有望成为克服肿瘤治疗瓶颈的有效手段。CAFs大量分泌细胞外基质主要成分而形成的间质屏障是我们首先关注的一个问题。根据肿瘤组织高表达基质金属蛋白酶-2（MMP-2）的特点，我们设计了MMP-2响应型两亲性多肽，并以多肽、磷脂等生物材料为基本组装单元，通过分子自组装构筑了MMP-2响应型吡非尼酮脂质体。经过对多肽和磷脂组装的优化，吡非尼酮脂质体在体外细胞水平和体内动物模型上均实现了特异地、高效地响应释放。通过降低CAFs的ECM分泌，纳米药物清除了间质屏障，从而有效地增强了化疗药物和小分子探针在肿瘤部位的渗透。此外，对CAFs活化程度的抑制也可直接产生抑制肿瘤转移的作用。我们根据CAFs特异表达成纤维细胞活化蛋白（FAP-α）的特点，设计了靶向FAP-α的纳米基因载体，利用该载体对CAFs表达的关键趋化因子12（CXCL12）进行沉默。该纳米药物在沉默CXCL12表达的同时，也降低了CAFs活化状态，抑制了CAFs相关的肿瘤细胞迁移、侵袭和内皮细胞迁移、成管等功能。通过降低肿瘤细胞转移能力和降低肿瘤组织血管密度，该纳米药物有效地抑制了肿瘤转移。综上所述，我们设计了两种以CAFs为靶点的纳米药物系统。从CAFs的两大生物学功能：间质屏障和促进转移入手，一方面，通过减少CAFs分泌的ECM解决了化疗药物实体瘤渗透不足的问题。另一方面，通过降低CAFs分泌细胞因子的能力，有效地抑制了肿瘤转移。我们以调控CAFs为目的的纳米药物设计为纳米医学在肿瘤治疗领域的应用提供新的思路。