Identification of a Druggable Pathway Controlling Glioblastoma Invasiveness

Abstract

Diffuse and uncontrollable brain invasion is a hallmark of glioblastoma (GBM), but its mechanism is understood poorly. We developed a 3D ex vivo organotypic model to study GBM invasion. We demonstrate that invading GBM cells upregulate a network of extracellular matrix (ECM) components, including multiple collagens, whose expression correlates strongly with grade and clinical outcome. We identify interferon regulatory factor 3 (IRF3) as a transcriptional repressor of ECM factors and show that IRF3 acts as a suppressor of GBM invasion. Therapeutic activation of IRF3 by inhibiting casein kinase 2 (CK2)-a negative regulator of IRF3-downregulated the expression of ECM factors and suppressed GBM invasion in ex vivo and in vivo models across a panel of patient-derived GBM cell lines representative of the main molecular GBM subtypes. Our data provide mechanistic insight into the invasive capacity of GBM tumors and identify a potential therapy to inhibit GBM invasion.

Dissecting Glioma Invasiveness in a 3D-Organotypic Model

“…Robust testing is also needed to dissect how the collagens identified in this study, such as collagen I and collagen V, promote glioma invasiveness. The observation that CX4945 did not reduce tumor growth in the current study (7) supports the notion that glioma invasion and glioma proliferation are driven by different pathways (3). In an attempt to improve glioma patient outcomes, oncological research should place its efforts into revealing strategies and mechanisms that can simultaneously combine the blockade of glioma invasion and cell proliferation pathways.…”

“…The invasive subclones showed an enrichment of several ECM components, including multiple collagens, collagen-interacting proteins, and collagen-processing enzymes. These same genes were upregulated in GBM cell lines belonging to the more invasive mesenchymal subtype (7). The authors then identified interferon regulatory factor 3 (IRF3) as the transcriptional repressor of these “pro-invasive” genes and showed that IRF3 knock-down increased expression of all 17 ECM-signature genes.…”

“…Recent advances in bioengineering and cancer biology provide opportunities to study tumor cell invasion within three-dimensional (3D) extracellular environments, including organoids, spheroid cultures embedded into chemically inert scaffolds, and primary cells grafted directly into biologically relevant matrix preparations (6). A new study by Pencheva et al published in Cell Reports , describes a new method of quantifying glioma invasion in 3D and determining the contribution of specific signaling pathways in this process (7). In brief, the authors seeded patient-derived GBM cell lines – expressing green-fluorescent protein - onto the center of a 300µm-thick organotypic mouse brain slice and quantified their invasion into the brain tissue in 11 consecutive confocal imaging z-planes at 20µm increments, ultimately resulting in a 3D score for tumor cell invasion.…”

“…This was indeed the case in multiple models; moreover, CK2 inhibition was associated with downregulation of these ‘proinvasive’ ECM genes, increasing IRF3 recruitment to their promoters. Conversely, genetic silencing of IRF3 increased glioma invasiveness (7). …”

Spontaneous Glioblastoma Spheroid Infiltration of Early-Stage Cerebral Organoids Models Brain Tumor Invasion

“…Additional studies are required in terms of comparing stem cell-based organoids with other ex vivo glioma migration methodologies, including organotypic slice culture models. [13][14][15] However, eCO/GBM hybrid organoids (and their non-cancerous controls) provide the foundation for the future development of high-throughput assays to investigate the underlying molecular mechanisms of invasion and screen for drugs that abrogate this phenotype. Future modifications of the assay may be based on the replacement of R1 mESCs with other (e.g., human) ESCs, and/or the replacement of the GBM1 stem cell-like model with other brain tumor cell models and/or freshly-isolated primary cells.…”