Tissue-reactive zonation of mesenchymal-like phenotypes in human glioblastoma.
BACKGROUND Glioblastoma is the deadliest brain cancer, characterized by large cellular diversity. Both neurodevelopment-like and mesenchymal-like cell states have been described, with the latter being strongly implicated in malignancy and disease progression. However, the spatial organization of these mesenchymal-like cell states has not been systematically described outside the tumor bulk. METHODS We performed deep single-cell RNA sequencing of rare glioblastoma cases where tissue could be sampled from tumor core to macroscopically normal cortex and 888-plex enhanced electric single-molecule fluorescence in situ hybridization (EEL-FISH) spatial transcriptomics on a large cohort of standard resections. We also established four glioblastoma organoid lines to test in vitro inducibility of mesenchymal-like cell states under hypoxia and blood plasma exposure. FINDINGS We discovered that previously defined mesenchymal-like tumor cell states were shared across both malignant and non-malignant cell types and spatially confined to the tumor bulk. Peripheral regions were instead dominated by neurodevelopment-like tumor states and endogenous microglia. In patient-derived organoids and non-malignant astrocytes, the mesenchymal transcriptional state could be reversibly induced in vitro by hypoxia and human plasma, indicative of a wound response. Multiplex single-molecule spatial transcriptomics revealed that the activation of mesenchymal-like states was associated with hypoxia and organized by distance to perivascular niches. CONCLUSIONS Our findings clarify the cellular landscape and biology of glioblastoma, wherein the mesenchymal state arises at least partly as a reactive tissue state shared by all cells in the tumor bulk. FUNDING This work was supported by Region Stockholm, Erling-Persson Family Foundation (Atlas of Childhood Disease), Hjärnfonden (FO2023-0309), Swedish Research Council (2022-01248), and Torsten Söderberg Foundation.