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 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.