联合cDC细胞疫苗和PD-1抗体对前列腺癌的治疗及机制研究

Tumor immunotherapy shows powerful on several types of cancer lately, and the first therapeutic tumor vaccine approved by American FDA is for prostate cancer, suggesting that immunotherapy may be an important breakthrough for conquering prostate cancer. This project will explore feasible immunotherapies in spontaneous prostate cancer mouse models. Based on the fact that combination therapy with traditional DC tumor vaccine and PD-1 Ab had no effect on treatment of prostate cancer, we modified the preparation method of DC vaccine and developed the conventional dendritic cell (cDC) tumor vaccine. The preliminary data showed that cDC tumor vaccine combined with PD-1 Ab dramatically inhibited the progression of prostate cancer. This project will confirm the effect of the combination in multiple prostate mouse model and figure out the range of application. At the same time, we will try to modify the induction method of cDC in vitro to satisfy the needs of cDC cells in future clinical application. For the study on mechanism, we found that treatment of PD-1 Ab can increase the expression of ICOS on T cells, and the addition of cDC tumor vaccine can enhance the proliferation of ICOS+ T cells and their migration into tumor site. We will further explore the role of ICOS-ICOSL pathway on the combination therapy. This project will promote the immunotherapy of prostate cancer to translate into clinic, and benefit prostate cancer patient as early as possible.

肿瘤免疫治疗近来展现了强大的威力，美国FDA批准的第一个治疗型肿瘤疫苗就是针对前列腺癌，提示免疫治疗可能是攻克前列腺癌的重要突破口。本课题将在自发前列腺癌模型中，探索可行的免疫治疗方法。在证实传统树突细胞疫苗与PD-1抗体联合治疗无效的基础上，我们创新疫苗制备方法，研发了前列腺癌的经典树突细胞（cDC）疫苗，其与PD-1抗体联合后显著抑制前列腺癌的进展。本课题将在多种前列腺癌模型中验证此方法的有效性及在不同类型前列腺癌中的适用情况。同时我们探索优化鼠（人）cDC细胞的诱导方法，解决将来临床应用中细胞来源的问题。机制研究中我们发现，PD-1抗体会增加T细胞共激活分子ICOS的表达，cDC细胞疫苗加入后则可显著增加ICOS+ T细胞的增殖和肿瘤部位浸润。我们将进一步探讨ICOS-ICOSL信号通路在联合治疗中发挥的作用。本课题将促进前列腺癌新型免疫治疗方法的转化，以期使前列腺癌患者尽早受益。

树突状细胞（DCs）做为肿瘤疫苗回输患者体内，常受到瘤内免疫抑制环境的影响，难以发挥正常功能。本课题我们通过对DCs进行基因改造以提升其抗肿瘤活性。实验设计：肿瘤DCs疫苗需从患者外周血髓系细胞中诱导获得，晚期肿瘤患者的髓系细胞主要是MDSCs为主，本课题着重研究此阶段的DCs的诱导，故将其定义为MDSC-DCs细胞。我们对来源于野生型（CCL5+/+）和CCL5基因缺失（CCL5-/-）荷瘤小鼠的富含MDSCs的脾脏细胞进行体外诱导并优化培养体系，获得CCL5+/+和CCL5-/-的MDSC-DCs细胞，然后荷载肿瘤抗原对野生型荷瘤小鼠进行治疗，观察对肿瘤生长的影响。并通过流式细胞、中和抗体阻断、RNA测序和体外共培养等方法，探索CCL5-/- MDSC-DCs的作用机制。为实现临床转化的可能，我们分别在小鼠和人MDSC-DCs的体外诱导中，通过慢病毒载体敲低CCL5的表达，并检测其抗肿瘤活性。实验结果：CCL5-/-可获得一种CD24高表达MDSC-DCs（CD24+ MDSC-DCs），相对对照细胞，其可以显著抑制肿瘤的生长，机制研究发现CD24+ MDSC-DCs通过抑制微环境中CD4+ T细胞向Treg的极化来发挥作用。此外，体外敲低鼠和人MDSC-DCs中的CCL5表达可得到与CD24+ MDSC-DCs相似功能的细胞。结论：本研究发现CCL5-/- 生成的CD24+ MDSC-DCs通过抑制Treg的极化，减少瘤内免疫抑制环境的影响，增强DCs疫苗的抗肿瘤活性，为新型DCs疫苗开发提供了理论依据。