氧/活性氧纳米传输体系的构建及其对恶性实体肿瘤缺氧的作用及调控机制研究

The hypoxia microenvironment in solid tumors significantly accelerates the deterioration and metastasis of tumors, as well as makes them highly resistant to chemo- and radiotherapy, which has been a knotty problem for tumor therapy. It may represent an efficient strategy for improving the therapeutic effect of solid tumors by elevating the partial pressure of oxygen (PO2) or increasing the concentration of reactive oxygen species (ROS) in hypoxia solid tumors. Herein, this project is proposed to fabricate a series of tumor-targeted delivery nanosystems which responsively release oxygen or ROS in tumor cells/tissues, and to investigate their effects and modulation mechanism on the hypoxia microenvironment of solid tumors. Specifically, organic peroxides, inorganic peroxides or endoperoxides will be anchored on the silica nanocarriers (prepared in our previous work) and functional compounds will be modified on these nanocarriers to fabricate the oxygen/ROS delivery nanosystems. These nanosystems are aimed to be delivered selectively into tumors by targeting modification of the nanosystems with peptides. In order to guarantee their stability in the transportation processes and controlled-release of oxygen or ROS in the focal areas of tumors, the fabrication procedures of these nanosystems will be explored and the mechanism of the generation of oxygen/ROS will be illustrated elaborately. Additionally, both in vitro and in vivo hypoxia tumor models will be built and the effects of the nanosystems on the hypoxia tumor microenvironment as well as the sensitization effects of the nanosystems on the doxorubicin-based chemotherapy of hypoxia tumors will be discussed. Significantly, the underlying modulation mechanisms of the nanosystems on the hypoxia tumor microenvironment will be further explored. These oxygen/ROS delivery nanosystems may represent a creative and effective way for the amelioration of hypoxia microenvironments in solid tumors. The ultimate goal of this study is to improve the clinical therapy efficiency of malignant solid tumors.

缺氧是制约恶性实体肿瘤疗效的关键“瓶颈”问题之一。究其原因，缺氧可显著加快肿瘤的恶性转变和转移，同时使肿瘤对化疗、放疗的敏感性明显降低。通过改善缺氧肿瘤的氧分压或提高其活性氧浓度，有望成为提高恶性实体肿瘤疗效的有效途径。鉴于此，本项目拟以前期工作制备的介孔氧化硅纳米材料为载体，通过负载高活性的有机、无机或内过氧化物，并对材料进行功能化合物修饰构建氧/活性氧纳米传输体系，以实现其在肿瘤缺氧微环境内的氧/活性氧响应性释放。在此基础上，研究体系的过氧化物负载工艺，实现其体外稳定性及体内氧/活性氧的释放可控性，揭示其产生氧/活性氧的物理化学机制；建立肿瘤缺氧实验模型，探究体系在体外、体内对缺氧肿瘤氧合状态的调控作用，并评价其对阿霉素治疗缺氧肿瘤的化疗增敏作用，阐明体系对肿瘤缺氧的调控作用及机制。本项目的完成有望为改善实体肿瘤缺氧微环境提供一种崭新思路。本研究的最终目标是提高恶性实体肿瘤的临床疗效。

骨肉瘤作为一种典型的实体肿瘤，具有易转移、对放/化疗不敏感等问题。虽然大部分骨肉瘤可以通过手术切除，但是针对部分复杂部位骨肉瘤难以手术切除，部分骨肉瘤患者不满足手术要求等临床问题，需要开发新的、更有效的治疗方法。基于此，本项目开发了一种新型的超声可激活的氧气和活性氧共释放纳米复合材料体系用于系统调控肿瘤的缺氧微环境并用于敏化声动力学疗法对于缺氧恶性实体肿瘤的治疗效果。体内动物实验发现，纳米复合材料FHPLP与超声波协同作用下，裸鼠皮下肿瘤体积明显缩小，组织学染色实验发现肿瘤内凋亡细胞明显增加，细胞增殖明显降低，且实验组肿瘤组织内的p53蛋白表达明显增高，说明FHPLP与超声波协同作用激活了细胞内的凋亡通路。此外，本项目开发了一种超声激活的纳米药物，该纳米药物释放出的高铁酸盐能有效地与水以及肿瘤细胞中过度表达的过氧化氢和谷胱甘肽反应，实现肿瘤复氧和肿瘤组织中谷胱甘肽的耗竭。复氧可下调肿瘤细胞缺氧诱导因子和多药耐药基因/转运体P-糖蛋白的表达，使以凋亡为基础的阿霉素化疗更为敏感。更重要的是，来自纳米药物的外源性铁代谢引发细胞内Fenton反应，导致活性氧的过度产生和肿瘤细胞铁依赖性的铁中毒性死亡。此外，谷胱甘肽耗竭使谷胱甘肽过氧化物酶4（GPX4，铁死亡的一个重要调控靶点）失活，抑制脂质过氧化物的减少，并加强细胞的铁死亡。本项目构建的氧/活性氧传输体系为提高乏氧实体肿瘤的临床疗效提供了新思路和重要的研究基础。另一方面，本项目通过在生物相容性的介孔二氧化硅纳米载体中合成过氧化钙，然后组装热敏材料二十烷和聚乙二醇，构建了一种超声响应的纳米释氧系统。通过在大鼠体内建立心梗模型，给予大鼠纳米释氧系统处理后，心梗下心肌细胞的存活率大大提高，梗死心肌组织的损伤也减小了。该超声波响应的纳米释氧体系有望为急性心肌梗死的治疗提供一种有效方法。