肿瘤相关成纤维细胞来源的IL-33调控髓系抑制性细胞扩增和功能促进肿瘤免疫逃逸的机制研究

Myeloid-derived suppressor cells (MDSC) are a tolerogenic and immune-suppressive population of myeloid cells that are significantly expanded in cancer patients. However, the molecular mechanisms governing the accumulation and activation of MDSC remain unclear. Our previous study found that high expression of IL-33 was significantly associated with high MDSC numbers in gastric cancer tissues, and cancer associated fibroblasts (CAFs) was a potential source of IL-33 within the tumor microenvironment of gastric cancer. The supernatant from CAFs induced MDSC expansion, which could be inhibited by IL-33 neutralizing antibody. Thus, we hypotheized that CAFs regulate the immune escape of gastric cancer cells through expanding MDSC via secretion of IL-33. In this study, we aim to: 1. demonstrate the association of IL-33 expression and MDSC in gastric cancer patients; 2. define the expression and regulation of IL-33 in CAFs in tumor microenvironment of gastric cancer; 3. expolre the molecular mechanism of CAFs in the regualtion of MDSC expansion and activation via secretion of IL-33. Thus, our study identified the critical role of CAFs-IL-33 pathway in the regulation of MDSC through the cross-talk between tumor stromal cells, and these findings should thereby ultimately contribute to the broaden understanding of MDSC expansion and activation, and provide the new evidences for the crosstalk between CAFs and MDSC, and as well as make new explanation for the mechanisms of tumor immune escape.

髓系抑制性细胞（MDSC）是近年来发现的一群骨髓来源的免疫抑制细胞，在荷瘤宿主体内及肿瘤局部大量聚集，但其扩增和功能的调控机制尚未完全阐明。我们前期发现胃癌组织中IL-33高表达与MDSC密切相关，肿瘤相关成纤维细胞（CAFs）是IL-33的主要细胞来源；CAFs上清可有效扩增MDSC，但这种扩增能被IL-33中和抗体阻断。我们推测CAFs来源的IL-33能调控MDSC扩增和功能促进肿瘤免疫逃逸。本课题拟从胃癌临床样本，进一步证实CAFs中IL-33高表达与MDSC的相关性；建立CAFs依赖的肿瘤微环境和小鼠荷瘤模型，研究CAFs来源的IL-33调控MDSC病理性扩增和功能活化的机理，并揭示CAFs中IL-33的表达调控机制。本研究结果不仅进一步拓宽了MDSC扩增和功能的调控机制，而且对肿瘤微环境中CAFs和MDSC相互对话提供新的证据，同时也对肿瘤免疫逃逸机制的阐明提供新的解释。

髓系抑制性细胞（MDSC）是近年来发现的一群骨髓来源的免疫抑制细胞，在荷瘤宿主体内及肿瘤局部大量聚集，但其扩增和功能的调控机制尚未完全阐明。肿瘤细胞-基质细胞-免疫细胞的相互作用形成利于肿瘤生长的免疫抑制微环境，促进了肿瘤的免疫逃逸和侵袭转移。本课题组研究工作发现：1）胃癌组织中IL-33高表达，其表达水平与胃癌的病理特征如肿瘤浸润、TNM分期密切相关，并提示了胃癌患者较差的临床预后。2）我们以HLA-DR-CD11b+CD33+作为胃癌患者MDSC标志，发现胃癌组织中MDSC比例明显升高，通过相关性分析发现胃癌组织中MDSC比例与IL-33表达水平密切正相关。3）肿瘤相关成纤维细胞（CAFs）是IL-33的主要细胞来源，胃癌细胞来源的TNF-α通过TNFR2-NF-kB-IRF1通路促进CAFs中IL-33表达。4）我们将健康人PBMC与胃癌CAFs进行共培养发现，CAFs可有效扩增MDSC，但这种扩增作用能被IL-33中和抗体阻断。5）CAFs来源的IL-33可以诱导MDSC内p38MAPK、c-Kit和STAT3发生磷酸化，而IL-33中和抗体组细胞p38MAPK和c-Kit磷酸化不明显；在共培养体系中加入c-Kit抑制剂Imatinib后，CD11b+CD33+HLA-DR-细胞的比例升高不明显。6）CAFs来源的IL-33通过ST2L直接促进胃癌细胞的侵袭、迁移和EMT，这种促肿瘤作用依赖于胃癌细胞内ST2L-ERK1/2-SP1-ZEB2通路的活化；下调CAFs内IL-33 或胃癌细胞内ST2L表达抑制了胃癌细胞在裸鼠腹腔内播散转移的能力。本研究结果不仅从基础研究中进一步拓宽了MDSC扩增和功能的调控机制，而且对肿瘤微环境中胃癌细胞、CAFs、MDSC相互对话提供新的证据，同时也对肿瘤复发转移和免疫逃逸机制的阐明提供新的解释，为靶向肿瘤基质干预胃癌的复发转移提供了实验依据。