胶质瘤微环境中miR-92对M2型巨噬细胞功能的调控及机制研究

As the most frequent primary malignant brain tumor, the invasion and progression of glioma are modulated by the tumor microenvironment. Tumor-infiltrating macrophages are the most abundant local inflammatory cells with alternatively activated M2 phenotype. These cells are capable of suppressing immune and supporting tumor, which have become a promising target for glioma immunotherapy. Our preliminary results showed that the miR-92 expression in the infiltrating M2 macrophages is significantly decreased compared to that of matching peripheral monocytes. Considering the coincidence between the downregulation of miR-92 and the immunosuppressive macrophages, we intend to confirm the correlation between the miR-92 expression and macrophage phenotype. Our goal is to systematically interpret the genetic, molecular, cellular and individual aspects of the M1/M2 macrophages transfected with miR-92 precursor and explore the regulatory role of miR-92 on the immune signaling pathway as well as macrophage functions. In addition, we plan to evaluate the influence of miR-92 on the prognosis of GL261 glioma-bearing mice. Overall, this project is to discuss the mechanism of miR-92 regulating the infiltrating M2 macrophages within the malignant glioma microenvironment and indicate a potent therapeutic for glioma immunotherapy.

恶性胶质瘤是最常见的颅内原发肿瘤，其侵袭进展受肿瘤微环境的调控。肿瘤浸润巨噬细胞是恶性胶质瘤微环境中最多见的炎性细胞，以替代活化性M2表型为主。其诱导免疫抑制并促进肿瘤生长，现已成为胶质瘤免疫治疗的研究热点。前期研究发现，相比自体外周血单核细胞，肿瘤浸润M2型巨噬细胞中miR-92a/miR-92b表达显著下调，提示miR-92可能参与对其免疫功能的调控。本课题拟在验证miR-92表达与M2型巨噬细胞表型相关性的基础上，对miR-92转染后M1/M2型巨噬细胞从基因、分子、细胞及动物模型层次研究，探索miR-92与免疫抑制信号通路及巨噬细胞功能间的相互关系，并探讨miR-92对GL261胶质瘤荷瘤小鼠生存期的影响。本课题有助于揭示胶质瘤微环境中miR-92与浸润M2型巨噬细胞介导的肿瘤免疫抑制间的相互关系，亦可为胶质瘤免疫治疗提供新的靶点。

恶性胶质瘤是最为常见的颅内原发恶性肿瘤，预后差。作为胶质瘤微环境中最常见的炎性细胞，浸润巨噬细胞介导的肿瘤相关免疫抑制在恶性胶质瘤侵袭进展中发挥了重要作用。miR-92a/b在胶质瘤等10余种肿瘤细胞中普遍表达，参与调控肿瘤细胞生长及炎性反应。本研究中，我们发现相比外周血单核细胞，miR-92a与miR-92b在胶质母细胞瘤浸润巨噬细胞中表达显著下调，分别仅为自体单核细胞表达量的20.5％与26.1％。在此基础上，我们建立了人外周血单核细胞及外周血来源单核细胞系THP-1向M1/M2型巨噬细胞诱导方案，并从形态学、表型、吞噬功能、细胞因子等角度进行了验证，证实单核细胞向巨噬细胞分化过程中miR-92a表达下调，其中免疫抑制性M2型巨噬细胞中miR-92a表达相比免疫诱导性M1型巨噬细胞下调更为明显。miR-92a模拟序列不影响单核细胞向巨噬细胞极化与M1型巨噬细胞形成，但能够选择性抑制M2型巨噬细胞表型转化并诱导M2凋亡，这种效应可能是通过TGF-β或IL-10相关信号通路实现的。因此，miR-92a参与调控胶质瘤浸润巨噬细胞免疫抑制，有望成为恶性胶质瘤免疫治疗新的靶点。