TAM与胶质瘤细胞融合在高侵袭性瘤细胞亚群形成中的作用及机制研究

To understand the mechanisms of malignant glioma invasion has been an important scientific issue for brain tumor research, where the origin of the highly invasive subpopulation remains elusive. We have found that M2 tumor-associated macrophages (TAMs) are closely correlated with high invasiveness of glioma cells (glioma stem cell), and peroxisome proliferator-activated receptor-gamma (PPAR-γ) is the important molecule to regulate the activities and functions of M2 TAMs. Based on the observations of TAMs and fusion of tumor cells in the malignant glioma, we propose that PPAR-γ may be the key molecule to regulate the fusion of TAMs and glioma cells in the formation of the highly invasive tumor cell subsets. In this proposal, we intend to detect the expression of PPAR-γ and fusion-associated marker in human glioma specimens and understand their clinicopathological significance. We also propose to perform in vitro cell-fusion related experiments together with zebrafish xenografted glioma invasion model and PPAR-γ macrophage conditional knock-out mice to investigate whether M2-type polarization regulate the heterotypical fusion of macrophages and glioma cells,thereby clarifying the role PPAR-γ in heterotypical fusion and the underlying mechanisms and providing the relevant and essential experimental evidence and theoretical basis for the development of a novel therapy for glioma patients by specific targeting the heterotypical fusion of macrophages and glioma cells.

恶性胶质瘤侵袭机制一直是脑肿瘤研究的重要科学问题，其中高侵袭性瘤细胞的形成机制未明。我们前期发现，M2型肿瘤相关巨噬细胞（TAMs）与高侵袭性胶质瘤细胞(具有胶质瘤干细胞特征)密切相关，而PPAR-γ是调节M2型TAM活动和功能的重要分子。基于恶性胶质瘤中存在TAMs与瘤细胞融合现象，我们推测，TAMs与胶质瘤细胞融合在高侵袭性瘤细胞亚群形成中具有重要作用，而PPAR-γ是其中关键的调节分子。本项目拟在检测人脑胶质瘤PPAR-γ和细胞融合相关标志物表达及其临床病理学意义的基础上，采用体外融合、侵袭、斑马鱼体内模型和PPAR-γ巨噬细胞定位敲除小鼠模型，观测TAMs与胶质瘤细胞融合过程、侵袭与干性表型获得以及分子通路变化，探讨TAMs极化对上述融合的调控作用，阐明PPAR-γ的作用机制，为研发针对TAMs与胶质瘤细胞融合的新型靶向治疗提供实验依据。

细胞融合学说作为肿瘤发生发展的相关机制之假设已有百年历史。然而，研究进展非常缓慢，对于巨噬细胞,尤其是不同亚群的肿瘤相关巨噬细胞（TAMs）是如何与包括恶性胶质瘤细胞在内的肿瘤细胞发生融合，仍然一无所知。本项目立项试图从研究TAMs的角度出发，以恶性胶质瘤为主要研究对象，观察病人的肿瘤病理标本，建立小动物体内形成融合细胞之模型，尝试进行多种体外融合细胞之实验，利用Microarray，RT-PCR等技术手段，检测与细胞融合相关的重要基因。取得的主要研究进展有：观察到人脑恶性胶质瘤中TAMs 与胶质瘤细胞形成的融合细胞的分布约占总细胞的2%以下；建立了小动物体内形成融合细胞之模型；发现融合细胞高表达诸如MMP家族蛋白（MMP12, MMP13和MMP14）和CXCR4等与侵袭相关的基因分子，表明融合细胞具有高侵袭性.这些主要研究进展和重要结果为本领域的进一步研究提供了理论基础，并为研发针对恶性胶质瘤等肿瘤的治疗措施的完善尤其是新型免疫治疗的提供一定实验数据和理论基础。