人新型CD73+γδTreg 细胞在促进乳腺癌免疫抑制微环境形成中的作用及机制研究

Tumor microenvironment is closely linked to initiation, promotion and progression of breast cancer. Inflammatory immune cells are one of the key components in breast cancer to facilitate tumor progression and immune evasion. However, the composition and the underlying mechanism of tumor promoting immune cells in the breast cancer still remain largely unknown. Tumor-infiltrating γδT cells have been shown to be positively correlated with progression of human breast cancer. Our previous study has found that the majority of γδT cells (60%) express CD73. Human CD73+γδT cells exhibited more potent immunosuppressive activity than conventional CD4+ regulatory T cells (CD4+Tregs), could produce exogenous adenosine to establish an immunosuppressive microenvironment. These cells are therefore named as novel CD73+γδTregs. Thus, based on these findings, we aim to investigate the characteristics, function, and polarization of CD73+γδTreg cells in the breast cancer microenvironment by using human breast cancer tissues and several research techniques including fluorescence-activated cell sorting and in vitro multiple-cell co-cuture experiments etal. Furthermore, we will uncover the correlation between the polarization of human CD73+γδTregs and tumor microenvironment, metabolism and immune evasion in breast cancer. This study will be the first to clarify the interconnectedness of ‘tumor cells, immune cells, metabolism and immune evasion’ in breast cancer. And furthermore it will elucidate the roles and mechanisms of such new γδT cell subset in breast cancer and will also shed lights on the understanding of tumor immune evasion and may help identify new potential target for effective immunotherapy for human breast cancer.

乳腺癌发生发展与肿瘤微环境密切相关，免疫炎症细胞是肿瘤微环境中促进免疫逃逸的关键因素之一，然其主导细胞及机制不明。人肿瘤浸润γδT细胞被认为与乳腺癌进展呈正相关，我们前期研究显示其中60%为CD73阳性，还发现CD73+γδT细胞比传统的CD4+Treg细胞具有更强的免疫抑制作用，可通过代谢产物腺苷形成免疫抑制微环境，故命名为人新型CD73+γδTreg细胞。为此，本项目拟以人乳腺癌生物样本、流式分选及体外多细胞共培养等为研究手段，阐明CD73+γδTreg细胞的特征、功能及极化机制，探明CD73+γδTreg细胞及其相关代谢产物与肿瘤微环境、代谢、免疫逃逸的关联及机制。该项目的完成将首次阐明“肿瘤细胞-免疫细胞-代谢-免疫逃逸”在乳腺癌微环境中的相互关联性，明确该γδT新亚群在乳腺癌免疫调控中的关键作用及机制，为靶向干预乳腺癌免疫抑制关键细胞（分子）进而防治乳腺癌提供新的思路和潜在靶标。

背景：乳腺癌发生发展与肿瘤微环境密切相关，免疫炎症细胞是肿瘤微环境中促进免疫逃逸的关键因素之一，然其主导细胞及机制不明。.方法：我们利用人乳腺癌生物样本、流式细胞检测、流式分选、体外多细胞共培养、RT-PCR、siRNA沉默、免疫荧光染色等技术，来阐明CD73+γδTreg细胞的特征、功能及极化机制，探明CD73+γδTreg细胞及其相关代谢产物与肿瘤微环境、代谢、免疫逃逸的关联及机制。.结果：在本研究中，我们发现γδT细胞在肿瘤组织中高表达CD73（约60％）。肿瘤浸润的CD73+ γδT细胞是人乳腺癌中主导的抑制性T细胞，对CD4+和CD8+ T细胞（CD73+ γδTregs）展现出强有力的、直接的免疫抑制功能。CD73+ γδTreg细胞被肿瘤相关成纤维细胞（CAFs）来源的IL6而非TGFβ1通过IL6/STAT3信号通路进行诱导分化，从而产生更多的外源性腺苷并发挥免疫抑制作用。更重要的是，活化的CD73+ γδTreg细胞又反过来通过腺苷/A2BR/p38MAPK信号促进CAFs分泌IL6，从而形成IL6-腺苷正反馈回路。而且，CD73+ γδTreg细胞的浸润损害了CD8+ T细胞的杀肿瘤功能，并且与不良临床结局如总生存期（OS）和无病生存期（DFS）显著相关。.结论：我们揭示了人乳腺癌微环境中主导的抑制性γδT细胞亚群和CD73+ γδTreg细胞与CAFs之间的正反馈回路在促进免疫抑制和肿瘤进展中的重要作用。明确该γδT新亚群在乳腺癌免疫调控中的关键作用及机制，为靶向干预乳腺癌免疫抑制关键细胞（分子）进而防治乳腺癌提供新的思路和潜在靶标。