Abstract 3950: Spatiotemporal analysis of gliomas: Dynamics of mesenchymal multicellular structures as novel target for tumor treatment
Authors: Comba Andrea , Dunn Patrick , Argento Anna E. , Kadiyala Padma , Motsch Sebastien , Zamler Daniel , Kahana Alon , Kish Phillips E. , Castro Maria G. , Lowenstein Pedro R. 
Published: September 2020

Abstract
Glioblastoma multiforme (GBM) is the most frequent and lethal tumor of the central nervous system. GBM are characterized by diffuse invasion and cellular heterogeneity which challenges treatment efficacy. Tumors with mesenchymal properties display the most aggressive phenotype. However, the biological function and molecular mechanisms underlying GBM mesenchymal transformation remain unknown. Analysis of mouse and human malignant gliomas revealed the presence of organized multicellular structures formed by elongated and aligned cells. These structures resemble areas of GBM mesenchymal transformation that we named Oncostreams. We determined the molecular signature underlying oncostreams function by performing laser capture microdissection followed by transcriptomic analysis. We found that oncostreams overexpressed Col1a1, ACTA2, MMP9, MMP10 and ADAMTS2 genes, all of them associated with regulation of extracellular matrix organization, collagen catabolic process and cellular migration pathways. Functional network analysis indicated that Col1a1 was a primary regulator gene. To analyze whether these structures display migratory properties we used time lapse imagining in a 3D organotypic glioma model. Morphological and statistical analysis revealed that oncostreams displayed a collective motion pattern, organized as streams or flocks. This dynamic patterns participate in local invasion and function as tumoral highways to facilitate the spread of several cells as intra-. Further analysis showed that oncostreams presence correlates with increased collagen expression and decreased animal survival. Patient's glioma biopsies also evidenced that these areas of Col1a1 overexpression were present in high grade but no in low-grade gliomas. We corroborated by immune-hystochemistry that Col1a1 were overexpressed and co-localized within GFP positive tumoral cells. Further, to analyze the origin and role of Col1a1 in glioma malignancy we generated genetically engineered mouse glioma models (GEMM) with Col1a1 downregulation. Interestingly, Col1a1 was retained only surrounding the blood vessel but was completed absent within the tumor parenchyma. We demonstrated that Col1a1 downregulation ablates oncostreams structures, reversed the malignant phenotype resembling low grade glioma histopathology and prolonged animal survival. This study reveals that oncostreams are organized dynamic structures that regulate glioma growth and invasion. They are areas of mesenchymal transformation defined by a molecular signature associated to extracellular matrix proteins expressed as Col1a1. Oncostreams with high expression of Col1a1 within glioma cells represent a novel potential targets for future translational development. Disruption of oncostreams will provide a new avenue to treat GBM.
Citation Format: Andrea Comba, Patrick Dunn, Anna E. Argento, Padma Kadiyala, Sebastien Motsch, Daniel Zamler, Alon Kahana, Phillips E. Kish, Maria G. Castro, Pedro R. Lowenstein. Spatiotemporal analysis of gliomas: Dynamics of mesenchymal multicellular structures as novel target for tumor treatment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3950.