Spatiotemporal analysis of glioma heterogeneity reveals Col1A1 as an actionable 1 target to disrupt tumor mesenchymal differentiation, invasion and malignancy

Intra-tumoral heterogeneity and diffuse infiltration are hallmarks of glioblastoma that challenge 18 treatment efficacy. However, the mechanisms that set up both tumor heterogeneity and invasion 19 remain poorly understood. Herein, we present a comprehensive spatiotemporal study that aligns 20 distinctive intra-tumoral histopathological structures, oncostreams, with dynamic properties and 21 a unique, actionable, spatial transcriptomic signature. Oncostreams are dynamic multicellular 22 fascicles of spindle-like and aligned cells with mesenchymal properties. Their density correlates 23 with tumor aggressiveness in genetically engineered mouse glioma models, and high grade 24 human gliomas. Oncostreams facilitate the intra-tumoral distribution of tumoral and non-25 tumoral cells, and the invasion of the normal brain. These fascicles are defined by a specific 26 molecular signature that regulates their organization and function. Oncostreams structure and 27 function depend on overexpression of COL1A1. COL1A1 is a central gene in the dynamic 28 organization of glioma mesenchymal transformation, and a powerful regulator of glioma 29 malignant behavior. Inhibition of COL1A1 eliminated oncostreams, reprogramed the malignant 30 histopathological phenotype, reduced expression of the mesenchymal associated genes, and 31 prolonged animal survival. Oncostreams represent a novel pathological marker of potential value 32 for diagnosis, prognosis, and treatment.