Pathogenesis of peritumoral hyperexcitability in an immunocompetent CRISPR-based glioblastoma model
Asante Hatcher, … , Benjamin Deneen, Jeffrey L. Noebels
Asante Hatcher, … , Benjamin Deneen, Jeffrey L. Noebels
Published April 6, 2020
Citation Information: J Clin Invest. 2020;130(5):2286-2300. https://doi.org/10.1172/JCI133316.
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Research Article Oncology

Pathogenesis of peritumoral hyperexcitability in an immunocompetent CRISPR-based glioblastoma model

Abstract

Seizures often herald the clinical appearance of gliomas or appear at later stages. Dissecting their precise evolution and cellular pathogenesis in brain malignancies could inform the development of staged therapies for these highly pharmaco-resistant epilepsies. Studies in immunodeficient xenograft models have identified local interneuron loss and excess glial glutamate release as chief contributors to network disinhibition, but how hyperexcitability in the peritumoral microenvironment evolves in an immunocompetent brain is unclear. We generated gliomas in WT mice via in utero deletion of key tumor suppressor genes and serially monitored cortical epileptogenesis during tumor infiltration with in vivo electrophysiology and GCAMP7 calcium imaging, revealing a reproducible progression from hyperexcitability to convulsive seizures. Long before seizures, coincident with loss of inhibitory cells and their protective scaffolding, gain of glial glutamate antiporter xCT expression, and reactive astrocytosis, we detected local Iba1+ microglial inflammation that intensified and later extended far beyond tumor boundaries. Hitherto unrecognized episodes of cortical spreading depolarization that arose frequently from the peritumoral region may provide a mechanism for transient neurological deficits. Early blockade of glial xCT activity inhibited later seizures, and genomic reduction of host brain excitability by deleting MapT suppressed molecular markers of epileptogenesis and seizures. Our studies confirmed xenograft tumor–driven pathobiology and revealed early and late components of tumor-related epileptogenesis in a genetically tractable, immunocompetent mouse model of glioma, allowing the complex dissection of tumor versus host pathogenic seizure mechanisms.

Authors

Asante Hatcher, Kwanha Yu, Jochen Meyer, Isamu Aiba, Benjamin Deneen, Jeffrey L. Noebels

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Figure 7

Histopathological analysis of tumoral and peritumoral regions in tau-WT- and tau-KO-tumor animals.

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Histopathological analysis of tumoral and peritumoral regions in tau-WT-...
Representative images of (A) NeuN, (B) PV, and (C) Iba1 expression in tumor-burdened cortex of tau-WT and -KO mice. The lower images are the same as the upper, but the tumor GFP channel has been removed so that changes in expression within the tumor burden can be more easily seen. The dotted white line demarcates the tumor margin. (D) Compared with control brain, NeuN+ cell number was significantly reduced in GFP+ tumor regions of WT (P = 0.0236) but not KO animals. (E) Relative to control brain, PV+ cells were significantly reduced in peritumoral margin (WT P = 0.0014, KO P = 0.0385) and GFP+ tumor regions (WT P = 0.012, KO P = 0.0385). (F) Increase in Iba1+ cell number was significantly larger in tau-WT-tumor animals compared with tau-KO-tumor animals in both peritumoral margin (P = 0.0038) and GFP+ tumor regions (P < 0.0001). NeuN (WT and KO), control n = 3, tumor n = 4. PV (WT and KO) control and tumor n = 4. Iba1 (WT and KO) control and tumor n = 3. Data are presented as mean ± SEM. *P < 0.05; **P < 0.01; ****P < 0.0001 by 2-way ANOVA with Tukey’s multiple-comparisons test. Scale bars: 100 μm.