CD71+细胞亚群经CTL/Treg途径促进肝癌免疫逃逸的机制研究

It is of great significance to study the mechanism of tumor immune escape. We have reported that immunosuppressive cells like MDSCs (Oncogene,2017) and regulatory DCs (Oncogenesis,2016) induced by carcinoma-associated fibroblasts (CAFs) could promote immune escape via STAT3 activation. We also observed that hepatic CAFs facilitated the generation of novel CD71+ immunosuppressive cells subsets, which could inhibit cytotoxic T lymphocyte proliferation and promote regulatory T cell differentiation in vitro. And we found that CD71+ cells were upregulated in peripheral blood and tumor tissue from liver cancer patients. The STAT3 pathway in CD71+ cells was also found to be significantly activated. These results suggest that after being induced by CAFs, CD71+ cells may promote tumor immune escape by regulating CTL/Treg functions. On this basis, we set out to investigate how CAFs-derived CD71+ cells orchestrate CTL/Treg function and its underlying mechanisms like STAT3 pathway through co-culture model. Moreover, we will determine the relationship between CD71+ cells and development of liver cancer by establishing animal model and analyzing clinical data. Our studies will not only help illustrate a new mechanism in tumor immune escape, but also provide theoretical basis for novel anti-cancer immunotherapy based on CD71+ cells.

深入研究肿瘤免疫逃逸的机制对肿瘤治疗有重要意义。我们前期发现肿瘤相关成纤维细胞（CAF）可通过多种途径促进免疫逃逸，如诱导MDSC（Oncogene,2017）及调节性DC（Oncogenesis,2016），该效应有赖于STAT3通路的激活。同时我们还发现CAF可诱导一类新型免疫抑制性细胞--CD71+细胞亚群，其在肝癌患者外周血及癌组织中上调表达，可抑制CTL增殖及促进Treg分化，并发现STAT3通路明显激活。提示新型CD71+细胞被CAF诱导生成后，可能经CTL/Treg途径促进肝癌免疫逃逸。以此为基础，本项目拟通过细胞共培养模型深入探讨CAF诱导的CD71+细胞对CTL/Treg的调控作用及机制，重点关注STAT3通路的活化情况；并从动物模型及临床组织水平验证CD71+细胞与肝癌发展的关系。本研究将有助于阐明肝癌免疫逃逸的新机制，并为靶向CD71+细胞的新型免疫治疗提供理论基础

本研究通过建立肝癌CAFs与单核细胞共培养模型，发现肝癌CAFs可通过分泌IL-6来抑制单核细胞向树突状细胞分化，具体表现为细胞形态、细胞表型、细胞因子分泌功能、刺激T细胞增殖等方面均无法向树突状细胞转化，而抑制IL-6可明显逆转该过程。同时发现肝癌CAFs可诱导出新型的CD71+细胞亚群，该细胞亚群具有免疫耐受型表型以及免疫调节性作用，具体表现为CD71明显上调表达，而促免疫表面分子如CD80、CD86、HLA-DR等均有明显下调。通过分析CD71+细胞亚群免疫因子分泌谱，我们发现其下调表达促免疫性细胞因子IL-12、TNF-b，而上调表达抑制性分子如IL-10、TGF-b、HGF。通过混合淋巴细胞反应进一步发现其有效抑制T细胞的增殖，且诱导更多的调节性T细胞生成。分子机制研究发现IL6-STAT3信号轴在该细胞亚群的诱导及免疫调节作用的发挥中起着关键作用，阻断该信号通路可明显逆转该细胞亚群的免疫调控作用。本项目深入研究了肝癌CAFs对新型免疫细胞亚群的诱导及树突状细胞分化的影响，将有助于阐明肝癌免疫逃逸的新机制，并为靶向CD71+细胞或CAFs的新型免疫治疗提供理论基础。