结肠癌微环境中B7-H3对γδT细胞亚群分化的调控及其机制

According to the cytokines secreting characters, gamma delta T cells are divided into three subtypes (γδT-IFN-γ，γδT-IL-4 and γδT-IL-17), which play different roles in the progression of colon cancer. However, the regulatory mechanism of the differentiation in the tumor microenvironment remains unclear. B7-H3 was identified recently to be involved in regulating the differentiation of Th1, Th2 and Th17 subsets. To explore the role of B7-H3 in the differentiation of γδT subsets, the expression and function of B7-H3 on γδT in colon cancer microenvironment was investigated. The results showed that B7-H3 was mainly expressed on γδT but not αβT cells, and promoted the secretion of Il-2 and IL-17 in vitro. Based on the previous reports and our preliminary experimental data, we speculate that B7-H3 is involved in the differentiation of gamma delta T cell subpopulation (γδT-IFN-γ，γδT-IL-4 and γδT-IL-17). Using the agonistic anti-human B7-H3 monoclonal antibody 4H7 and B7-H3 knockout mice, in the current study, we will investigate: 1) the expression and clinical significance of B7-H3 in different gamma delta T cells subsets in colon cancer microenvironment; 2) the effects and the mechanisms of B7-H3 on the differentiation of gamma delta T cell subsets; 3) the function of B7-H3 signal in gamma delta T cell-mediated tumor immune response. In conclusion, our project aims to analyze the role of B7-H3 in the differentiation of gamma delta T cells in colon cancer microenvironment, which will provide valuable clues for the further understanding of the tumor microenvironment.

γδT细胞是肠粘膜中一群重要的免疫细胞，可以分为γδT-IFN-γ、γδT-IL-4以及γδT-IL-17等多个亚群，但在肿瘤微环境中的分化调控机制尚不清楚。我们前期研究发现：B7-H3主要表达于γδT细胞而非αβT细胞，且可以体外促进IL-17和Il-2分泌。因此我们推测该分子可能参与了γδT细胞亚群分化。为了探讨该分子在诱导调控γδT细胞亚群（γδT-IFN-γ，γδT-IL-4以及γδT-IL-17）分化的作用机制，本项目拟开展如下研究：1）结肠癌微环境中B7-H3在不同γδT细胞亚群表达的临床意义；2）B7-H3调控γδT细胞亚群分化的作用和可能机制；3）B7-H3信号在γδ T细胞亚群介导的肿瘤应答中的作用。总之，本项目旨在分析B7-H3在结肠癌微环境中诱导γδT细胞亚群分化的机制，为进一步认识肿瘤免疫微环境特征提供有价值的线索。

γδT细胞在肿瘤免疫中发挥重要监视作用，但在肿瘤微环境中的分化调控机制作用尚不清楚。B7-H3是重要的B7共信号分子超家族成员之一。本项目经过研究发现，结直肠癌患者外周血和癌组织中B7H3+γδT细胞表达显著升高，并与IFN-γ+γδT细胞比例呈负相关性。本项目为明确B7-H3信号对γδT细胞亚群分化的作用机制，利用B7-H3阻断抗体MIH35、小干扰RNA和激发型抗体4H7证实B7-H3信号可以显著上调IL-4+γδT细胞；显著抑制IL-17+γδT细胞和IFN-γ+γδT细胞产生。通过体外肿瘤细胞杀伤实验及体内动物模型发现B7-H3信号可以显著抑制γδT细胞的杀伤结直肠癌细胞的能力，从而促进结直肠癌细胞的免疫逃逸。项目组还利用Tim-3配体Gal-9和阻断抗体证实Tim-3信号抑制γδT细胞产生perforin和granzyme B，从而抑制γδT细胞对结直肠癌细胞的杀伤作用。此外，项目组明确了B7-H3信号在调控结直肠癌细胞糖代谢、血管发生和放化疗抵抗中的重要作用和机制。综上，本项目阐明了结直肠癌微环境中B7-H3信号参与调控γδT细胞分化以及肿瘤发生发展的重要作用。