【作者】 梁培禾；

【导师】 靳风烁；

【作者基本信息】 第三军医大学 ， 外科学， 2006， 博士

【摘要】 肿瘤的形成、生长、浸润和转移均有赖于血流提供养分，新生血管化的强度限制／决定了肿瘤生长速度。因此，抗血管新生被认为是恶性肿瘤极有力的治疗手段。自Judah Folkmanl971年在《新英格兰医学杂志》上发表题为《Tumor anagiogensis：Therapeutic implications》的、具有开创性意义的文章以来，经过近四十年的发展，关于肿瘤血管新生及抗血管新生治疗的研究取得了令人瞩目的成果，大量研究表明这种治疗方法具有“两高（高靶向性、高作用效率）、两低（低副反应、低耐药比例）”的特点，在动物实验中显示出良好的效果，但应用于人体后疗效却不尽如人意，主要问题是由于药物分子代谢特性等限制，常需大量、长期给药，副反应大为增加；此外，目前也缺少相对成熟的治疗方案和疗效评估体系。 相比之下，激发机体针对肿瘤新生血管内皮细胞的特异性主动免疫反应，则可形成直接的杀伤效应，从而抑制和破坏新生血管的形成，具有作用持久、效率高、避开了肿瘤细胞产生的免疫抑制效应等优势。实现这一方案首先需选择肿瘤和正常内皮细胞表达有明显差异、免疫系统能够识别的靶抗原。Flk-1（即血管内皮细胞生长因子受体-2，vascular endothelial cell growth factor receptor-2，VEGFR-2）在成人正常内皮细胞表达极低，多数组织中检测不到，而在血管新生过程中增殖的内皮细胞上则高度表达，是目前公认的肿瘤内皮细胞较好的分子标志和靶抗原。但Flk-1属自身抗原，研究人员面临如何才能增强其免疫原性，打破免疫耐受激发有效免疫应答的难题。上个世纪90年代后期发现2-3个串联的补体C3裂解片段C3d具有强烈的免疫佐剂效应，可大大提高抗原的免疫原性，为克服这一障碍提供了有力的工具。本研究利用了补体领域的这一重要发现，引入C3d作为分子内佐剂，制备了含有Flk-1胞外段265bp-2493bp(Flk-1_{extraeellular domain}，Flk-1_ECD和串联的3个C3d（C3d3）融合基因的DNA疫苗，并利用动物模型初步观察了该疫苗对膀胱肿瘤生长的抑制效应，为开发安全、有效的肿瘤抗血管新生疫苗打下了基础。主要的研究内容及结果如下：更多还原

【Abstract】 The close relationship between tumor progression and its angiogenesis was first hypothesized by Folkman in 1971. Accumulating evidence has clearly shown that angiogenesis played an essential role in the development of various solid tumors and affected its growth and metastasizing dramatically. Therefore, tumor angiogenesis is potentially an important therapeutic target which has been actively studied during the last decade.The strategy of inhibition of tumor angiogenesis has been proved to be extremely effective in animal experiments. However, translation of these strategies to a clinical setting has proven difficult, in part due to toxicities of the drugs. Another obstacle is the delivery of sufficient amounts of bioavailable drugs. In most cases, chronic long-term delivery of high doses is necessary to achieve a clinical response.One strategy to circumvent the hurdles has been to take advantage of inherent immune response to selectively target tumor neovascularization, thereby eliminating the need for long-term expensive delivery of high doses of potentially toxic agents. Appropriate target antigen is the key factor to the success of this strategy. Vascular endothelial growth factor(VEGF) and its receptor vascular endothelial growth factor receptor 2 (VEGFR-2, also known as Flk-1) play a critical role in the regulation of normal and pathological angiogenesis. Flk-1, which has a more restricted expression on proliferating tumor endothelial cells, provides an optimization selection. But Flk-1 is self-antigen. A major challenge is to break the immune tolerance and induce a robust, long-lived T cell-mediated immunity which leads to an effective suppression of tumor angiogenesis. Luckily, in 90s of the last century, an important discover in the research area of complement provided a novel approach to solve this tough question. This discover was that C3d, a fragment of complement C3 component, can influence the acquired immune response by binding to its receptor CR2/CD21, on B lymphocytes and other antigen-presenting cells (APC). Dempsey et al. found that the fusion of three copies of C3d (C3d3) to hen egg lysozyme, a model antigen, increased the efficiency of immunizations by more than 1000-fold. The development of vaccines containing the更多还原