以Fascin1为靶标的靶向体内树突状细胞的前列腺癌疫苗设计及其免疫效果评价

Dendritic cells (DCs) are the most potent professional antigen-presenting cells of the immune system. DCs-based vaccines are considered as a promising approach for the immunotherapy of cancer. However, there are still many challenges in clinical trials, including unsatisfied therapeutic efficiency, immune tolerance, and so on. In this study, the properties of Fascin1 protein, prostate stem cell antigen (PSCA), and vascular endothelial growth factor (VEGF) were analyzed based on previous researches on DCs biology and prostate cancer. Among them, Fascin1 is highly expressed in mature DCs; PSCA is a prostate cancer associated antigen; and VEGF is a cytokine and highly expressed in tumor patients. Therefore, Fascin1, PSCA and VEGF have been chosen as the immunotherapeutic targets and their specific recombinant antibodies will be isolated respectively. Subsequently, bispecific antibodies fused with anti-PSCA and anti-VEGF antibodies will be constructed and expressed to disturb the immunosuppressive tumor microenvironment and improve the immune functions of DCs. Simultaneously, the prostate cancer vaccine will be obtained by fused the anti-Fascin1 antibody with prostate cancer specific antigen peptide (PSA146-154). Then, the vaccine will directly target to DCs in vivo and induce specific immune responses against prostate cancer. Thus, this study will focus on enhancing the immune effects of in vivo DCs-targeting vaccine for prostate cancer through the synergistic effects of passive immunotherapy. It may provide a new strategy for tumor immunotherapy, and also has great significance for the fundamental researches and clinical application.

树突状细胞（dendritic cells, DCs）是目前所知功能最强大的专职抗原提呈细胞，基于DCs的肿瘤疫苗被认为是一种极具发展潜力的免疫治疗方法，但现阶段在临床试验过程中还存在疗效不理想和免疫耐受等许多问题。基于此，本项目在课题组以前的工作基础上，选择成熟DCs中高表达的Fascin1蛋白、前列腺干细胞抗原（PSCA）以及肿瘤患者体内高表达的血管内皮生长因子（VEGF）为靶标制备特异重组抗体，利用抗PSCA和VEGF的双特异抗体干扰免疫抑制性肿瘤微环境，改善DCs的免疫学功能，基于Fascin1特异抗体与前列腺癌特异性多肽PSA146-154融合表达的前列腺癌疫苗将直接靶向体内DCs，从而诱导抗前列腺癌的特异性免疫应答，以期实现通过被动免疫治疗的协同作用来增强靶向体内DCs的前列腺癌疫苗的免疫效果，为肿瘤的免疫治疗提供新的思路，具有重要的基础研究和临床意义。

树突状细胞（dendritic cells, DCs）是机体内功能最强大的抗原提呈细胞，在肿瘤免疫调节过程中发挥着关键作用，基于DCs的肿瘤疫苗在肿瘤的免疫治疗方面有望提供一种有效的解决途径。但是，由于免疫抑制性肿瘤微环境对DCs运动能力和免疫学功能的影响，基于DCs的肿瘤疫苗还存在疗效不理想等许多问题，本项目期望利用DCs的超强抗原呈递能力和重组抗体的特性，研制靶向体内DCs的前列腺癌疫苗来探索肿瘤免疫治疗的新思路。本项目在研究血管内皮生长因子（vascular endothelial growth factor, VEGF）等肿瘤微环境中高表达细胞因子对DCs迁移能力和免疫功能影响的基础上，克隆表达Fascin1、前列腺干细胞抗原（prostate stem cell antigen, PSCA）和VEGF重组蛋白，利用杂交瘤技术和噬菌体展示技术制备抗Fascin1、PSCA和VEGF的特异重组抗体，基于抗Fascin1抗体与3个重复的前列腺癌特异性多肽PSA146-154融合表达制备前列腺癌疫苗并分析其活性，同时构建抗PSCA-抗VEGF双特异抗体以及抗PSCA抗体-碱性磷酸酶融合蛋白，分析其作为被动免疫治疗和快速免疫检测的可行性，其结果显示在优化真核表达系统获得大量高纯度重组蛋白后，体内靶向DCs肿瘤疫苗和双特异抗体具有良好的临床应用前景。