Tumor-associated myeloid cells aid GBM infiltration by organizing invasion tracks via guidance receptor Plexin-B2

Glioblastoma (GBM) is highly invasive primary brain tumor. Here, we retraced early steps of GBM invasion and interactions with tumor-associated myeloid cells (TAM) in a highly infiltrative murine GBM model in immunocompetent background. We reveal early mobilization of microglia in a wide onco-field ahead of GBM invasion, forming glial nets encircling tumor micro-infiltrates that are enmeshed with a dense network of extracellular matrix (ECM). Physical contacts with GBM cells initiate an astounding morphological, spatial, and functional transformation of microglia and monocyte-derived macrophages to form collectively organized migration streams with intertwined GBM cells, paralleled by major ECM restructuring along invasion tracks. Mechanistically, this requires upregulation of guidance receptor Plexin-B2 in TAM, which functions to resolve collisions with GBM cells by providing cell contact guidance for cell alignment and ECM restructuring. Together, our results on stage- and niche-specific mobilization of microglia/macrophages, on governing factors, and the molecular insights into pro-invasion signaling open new therapeutic opportunities to curb GBM invasion. Overall design: Single cell RNA sequencing of mice brain bearing intracranial SD3 GBM transplants. Cells from SD3 GBM bearing brain from ICR-SCID mouse were prepared and ran with 10x genomics pipeline.

胶质母细胞瘤（Glioblastoma, GBM）是一类侵袭性极强的原发性脑肿瘤。本研究以免疫健全背景下的高浸润性小鼠胶质母细胞瘤模型为对象，追溯了胶质母细胞瘤侵袭的早期进程及其与肿瘤相关髓系细胞（Tumor-associated myeloid cells, TAM）的相互作用。研究发现，在胶质母细胞瘤侵袭前的广阔癌性区域中，小胶质细胞已发生早期动员，形成环绕肿瘤微浸润灶的胶质网络，该网络与致密的细胞外基质（Extracellular matrix, ECM）网络相互交织。与胶质母细胞瘤细胞的物理接触可触发小胶质细胞与单核细胞衍生巨噬细胞发生显著的形态、空间及功能重塑，二者与相互缠绕的胶质母细胞瘤细胞共同形成有序迁移流；与此同时，侵袭通路伴随显著的细胞外基质重构。机制研究表明，该过程需要肿瘤相关髓系细胞中导向受体Plexin-B2的上调表达；该受体可通过为细胞排列提供接触导向以及介导细胞外基质重构，从而解决与胶质母细胞瘤细胞的碰撞冲突。综上，本研究关于小胶质细胞/巨噬细胞的阶段特异性及微环境特异性动员、调控因子的相关发现，以及促侵袭信号通路的分子机制解析，为抑制胶质母细胞瘤侵袭提供了全新的治疗策略。整体实验设计：对携带颅内SD3胶质母细胞瘤移植瘤的小鼠脑组织进行单细胞RNA测序。从ICR-SCID小鼠的颅内SD3胶质母细胞瘤移植瘤脑组织中分离细胞，并通过10x Genomics测序流程完成建库与测序。