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. Single cell RNA sequencing of mice brain bearing intracranial KR158 GBM transplants. Tamoxifen was injected every other day (i.p., 100 mg kg−1) from 3 days before KR158 transplantation until 8 weeks after. Cells from KR158 GBM bearing brains from Control or Plexin-B2 cKO hosts (C57BL/6 background) were prepared and ran with 10x genomics pipeline.