SIRPα在肿瘤相关巨噬细胞介导的T细胞分化与功能调节中的作用及机制

Hepatocellular carcinoma (HCC) is usually present in inflamed fibrotic and/or cirrhotic liver with extensive leukocyte infiltration, indicating a relationship between inflammation and HCC. Macrophages within the tumor microenvironment, which is called tumor-associated macrophages (TAM), are the key regulators of tumor-associated inflammation. It has been reported that TAM facilitate angiogenesis and extracellularmatrix breakdown and remodeling and promote tumor cell motility. Moreover, recent studies reveal that TAM also play a pivotal role in modulating anti-tumor adaptive immunity. TAM existing in HCC promote IL-17-producing Th17 cells expansion, and increased intratumoral Treg cells are related to intratumoral TAM and poor prognosis in HCC patients. In addition, TAM deletion in tumor improves adoptive anti-tumor CD8+ T cell therapy. These results above indicate that TAM may be an important regulator in T cell differentiation and function. It will be worthful to look for how TAM direct T cell differentiation and which molecule or pathway in TAM is the major driver. Signal regulatory protein α (SIRPα) is a cell-surface protein mainly expressed on myeloid cells, including macrophages. Recently, we have found that SIRPα could be crucial in TAM function modulation. SIRPα expression is reduced on TAM obtained from HCC tissues. Down-regulation of SIRPα expression promotes TAM migration, survival and phenotype switch. What’s more, SIRPα-knockdown in TAM enhance IL-6, IL-1β, and TGF-β secretion, which is involved in Th17 and Treg cells maturation, suggesting that SIRPα expression on TAM may play a role in regulating T cell differentiation. To testify this hypothesis, we plan to assay the relationship between SIRPα expression on TAM and T cell subpopulation distribution in HCC samples. Meanwhile, we will use the in vitro and in vivo experiments to investigate whether SIRPα expression on macrophages is involved in T cell differentiation and how this occurred. At last, we try to find out whether anti-SIRPα blocking antibodies could improve the adoptive CD8+ T cells therapy in HCC. Thereby, this study is expected to deep our understanding about the inflammation and cancer, and to provide a new target and a new strategy for HCC prevention and treatment.

肝癌发生发展与慢性炎症密切相关。肿瘤相关巨噬细胞（TAM）作为肝癌微环境中最为丰富的免疫细胞，是联系慢性炎症与肿瘤的桥梁。研究发现TAM参与肿瘤免疫抑制微环境形成，抑制CTL细胞抗肿瘤功能，诱导Th17/Treg细胞分化成熟，促进肿瘤发生发展。因此深入研究TAM调控T细胞分化与功能的作用方式，寻找TAM的关键效应分子成为亟待解决的问题。前期研究中我们发现信号调节蛋白α（SIRPα）是调控TAM功能的关键分子，SIRPα参与调节TAM释放诱导T细胞分化相关因子，提示TAM中SIRPα可能参与调节T细胞分化与功能。因此本课题拟利用临床样本分析肝癌TAM中SIRPα的表达水平与T细胞各亚群的关联；利用体内外实验探讨差异表达SIRPα的巨噬细胞对T细胞各亚群分化的调节作用及分子机制；探讨针对SIRPα的干预手段对肝癌的治疗效果。希望这一工作能加深肝癌发生发展机制的理解，为肝癌的防治提供新的策略。

肝癌发生发展与慢性炎症密切相关。肿瘤相关巨噬细胞（TAM）作为肝癌微环境中最为丰富的免疫细胞，是联系慢性炎症与肿瘤的桥梁。研究发现TAM参与肿瘤免疫抑制微环境形成，抑制CTL细胞抗肿瘤功能，诱导Th17/Treg细胞分化成熟，促进肿瘤发生发展。因此深入研究TAM调控T细胞分化与功能的作用方式，寻找TAM的关键效应分子成为亟待解决的问题。本课题利用临床样本分析肝癌TAM中SIRPα的表达水平与肿瘤临床资料的相关性；利用体内外实验探讨巨噬细胞SIRPα对生理条件与肿瘤微环境中固有免疫与T细胞稳态的调节作用及分子机制；探讨体内SIRPα-CD47信号轴的快速检测方法，旨在探讨SIRPα在肿瘤相关巨噬细胞介导的微环境重塑中的作用。我们发现肝癌巨噬细胞SIRPα表达与肿瘤大小呈负相关，提示SIRPα是肿瘤治疗的新靶点。利用SIRPα基因敲除小鼠，我们发现SIRPα敲除促进化学诱导小鼠肝癌的发生与肝癌、黑色素瘤、肺癌等多种肿瘤细胞的皮下生长。但是SIRPα敲除抑制黑色素瘤与肺癌细胞的肺转移过程，表明SIRPα对肿瘤的生长与转移具有不同的调节作用。本项目发现SIRPα敲除对小鼠本底与荷瘤条件下的免疫状态具有重要调节作用。SIRPα敲除引起体内DC细胞稳态失衡，特别是CD4+ DC细胞亚群的发育受到显著影响，而巨噬细胞的含量无显著变化。此外SIRPα敲除影响脾脏与淋巴结中CD4+ T细胞的数量，提示SIRPα对机体免疫反应具有复杂而广泛的调节作用。本项目建立了一种新型快速检测肿瘤组织中CD47分子（SIRPα天然配体）表达水平的技术。我们利用二维硫化钼材料与识别CD47的多肽制备新型二维多肽材料复合物，实现对临床肿瘤冰冻样本CD47的30分钟内快速检测。综合以上结果，我们发现信号调节蛋白α（SIRPα）是调控TAM功能的关键分子。希望这一工作能加深肝癌发生发展机制的理解，为肝癌的防治提供新的策略。