TNFR2抗体通过抑制CD8+T细胞凋亡进而促进抗肿瘤免疫的机制研究

Induction of T cell apoptosis is an important mechanism for tumor immune escape, and is one of major factors that limit the immunotherapeutic efficacy. Therefore, it is of significant to explore new mechanism of immune escape. Tumor necrosis factor receptor 2 (TNFR2) is a key immune modulator molecule in autoimmune disease, which exert its function by promoting immune suppression of Tregs and inducing effector T cell apoptosis. However, the role of TNFR2 in tumor remains to be fully elucidated, in our study, we found TNFR2 was highly expressed on tumor-infiltrating CD8 T cells, TNFR2 antibody blockade could effectively arrest tumor growth. It was noteworthy that only increasing CD8 T cell infiltration was observed after antibody treatment, while the number of Tregs remained to be unchanged. In addition, CD8 T cell apoptosis in tumor was higher than in draining lymph node, and was decreased after TNFR2 antibody treatment. Therefore, combining with other studies, we propose that TNFR2 might promote tumor immune escape via induction of CD8 T cell apoptosis, these detailed mechanisms are still unclear. In this study, we will design a series of assays to deeply uncover the antitumor immune mechanisms of TNFR2 antibody, and to illuminate the molecular mechanism of CD8 T cell apoptosis mediated by TNFR2. We hope this study can provide a candidate target for cancer immunotherapy.

诱导T细胞凋亡是肿瘤免疫逃逸的重要机制，也是限制免疫治疗效果的主要原因之一。因此，探索免疫逃逸新的机制具有重大意义。肿瘤坏死因子受体2（TNFR2）是自身免疫疾病中重要的免疫调控分子，它的作用主要是通过增强Treg的免疫抑制和诱导效应T细胞凋亡。但它在肿瘤中的作用尚未完全明确，我们发现TNFR2高表达在肿瘤浸润CD8T细胞上，TNFR2抗体能够有效抑制肿瘤的生长，并且治疗后仅增加了CD8T细胞浸润，而对Treg无显著影响。此外，进一步分析发现肿瘤中CD8T细胞的凋亡水平要高于引流淋巴结，而TNFR2抗体治疗后降低了CD8T细胞的凋亡水平。因此，结合其他研究我们推测TNFR2可能通过诱导CD8T细胞凋亡进而促进肿瘤免疫逃逸，但详细机制不清楚。本课题将设计一系列实验深入研究TNFR2抗体的抗肿瘤免疫机理，阐明TNFR2介导CD8T细胞凋亡的分子机制，为肿瘤免疫治疗提供新的候选靶点。

经过3年的研究，我们已经完成了该课题的研究任务和目标，对TNFR2抗体在肿瘤免疫治疗中的应用以及机制进行了深入的研究，取得多个有价值的结果，主要结果已整理成论文，正在投稿。依托本课题，培养博士后1名。.在本项目中，为了深入研究TNFR2抗体的抗肿瘤作用，我们构建了小鼠结肠癌模型，综合利用流式细胞术、磁珠分选技术、免疫组化、转录组测序等技术进行研究，我们发现：1）TNFR2主要高表达在肿瘤浸润CD8+T细胞上。2）TNFR2抗体治疗能够显著抑制小鼠结肠癌CT26和MC38肿瘤的生长。3）TNFR2抗体治疗显著增加肿瘤微环境中CD8+T细胞的浸润。4）TNFR2抗体能够抑制CD8+T细胞的凋亡，从而改善肿瘤免疫抑制微环境，有利于抗肿瘤免疫反应。5）TNFR2抗体治疗进一步激活了肿瘤微环境中PD-1/PD-L1信号通路；TNFR2抗体联合PD-1抗体治疗能够很好地发挥协同作用，治疗后部分小鼠的肿瘤完全消退。6）TNFR2抗体与PD-1抗体单独治疗和联合治疗能够诱导产生持久、肿瘤特异的保护作用。以上研究表明抗体阻断TNFR2能够有效地抑制小鼠结肠癌肿瘤生长，且能够与PD-1抗体发挥协同抗肿瘤作用，具有潜在的临床应用价值。

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