IL-6家族与miR-340交互负反馈调控胶质瘤免疫抑制的功能与机制研究

The symbiosis and interplay between glioma cells and glioma associated microglia/macrophage (GAM) within the tumor microenvironment leads to tumor immunosuppressant with the mechanisms unelaborated. Our previous work demonstrates that miR-340 plays a vital role in glioma. Further studies show that genes related with miR-340 are found to mainly implicate in immune response, and moreover, overexpression of miR-340 in glioma cells is capable to improve phagocytosis of GAM cells. Our preliminary work shows that overexpression of miR-340 results in inhibition of cytokine IL-6 family in glioma cells, while IL-6 treatment induces up-regulation of miR-340. The analysis of genome locus using UCSC genome browser shows that EZH2 is likely to suppress miR-340 expression through methylation of H3K27 histone within the promoter of miR-340. Collectively, we come up with the hypothesis that down-regulation of miR-340 in glioma contributes to disinhibition of IL-6 family synthesis, resulting in the transformation of GAM cell to the tumor-promoting form; whereas GAM cells in turn blocks miR-340 expression through IL-6/EZH2 pathway in glioma, eventually coming to a vicious circle between glioma and GAM cells promoting the tumor immunosuppression. The expected outcome of this project will help to unravel the molecular mechanism involved in the immunosuppression of glioma, and suggest potential intervention targets of immunal therapies against glioma.

肿瘤微环境中，胶质瘤细胞与胶质瘤相关小胶质细胞（GAM）共生存在和相互作用导致胶质瘤免疫抑制，机制仍不明确。我们前期研究证明，miR-340在胶质瘤中发挥重要作用。进一步研究发现，与miR-340表达显著相关的基因主要参与免疫应答，且高表达miR-340可提高GAM细胞吞噬功能。初步研究结果发现，过表达miR-340可抑制胶质瘤细胞细胞因子IL-6家族表达；而IL-6可诱导胶质瘤EZH2表达升高。生物信息学分析显示，EZH2可能通过调控miR-340启动子区的甲基化而抑制其表达。综上，我们提出假设，胶质瘤细胞miR-340表达降低，导致靶基因IL-6家族合成脱抑制，促进GAM细胞转化为促癌型，后者再通过IL-6/EZH2通路阻遏胶质瘤miR-340表达，形成恶性循环导致肿瘤免疫抑制。本项目的研究结果有助于揭示胶质瘤免疫抑制的分子机制，为胶质瘤免疫治疗提供潜在的干预靶点。

肿瘤微环境中，胶质瘤(GBM)细胞与胶质瘤相关小胶质细胞（GAM）共生存在和相互作用导致胶质瘤免疫抑制，但具体机制仍不明确。我们通过临床胶质瘤标本及TCGA数据库发现miR-340 在胶质瘤中表达下调，且其表达水平与胶质瘤患者总生存时间与无进展生存时间具有显著相关性。过表达miR-340可抑制胶质瘤细胞细胞因子IL-6家族表达；而IL-6可诱导胶质瘤EZH2表达升高；而抑制胶质瘤的EZH2表达可使肿瘤微环境中的巨噬细胞向M1型极化。我们还发现miR-340-5p表达的高低，接受化疗与否，肿瘤是否复发为GBM患者DFS的独立影响因素。miR-340-5p直接靶向POSTN和LTBP-1，下调miR-340-5p通过POSTN介导的αVβ3募集巨噬细胞，并通过LTBP-1介导TGF-β1调节M2-巨噬细胞极化。过表达miR-340-5p抑制胶质瘤生长以及巨噬细胞募集和M2转化。M2-TAMs通过调节TGFβ-1/HMGA2途径抑制GBM细胞中miR-340-5p的表达。TCGA验证发现miR-340-5p-巨噬细胞环路中基因在GBM组织与正常脑组织之间的表达显示出显著的差异，并且证实miR-340-5p-巨噬细胞环路中的基因对于胶质瘤患者具有临床预后价值。以上这些发现提示miRNA与巨噬细胞环路调节胶质瘤的进展和肿瘤微环境，可能是胶质瘤的预后生物标志物和新的治疗靶标。