A syngeneic spontaneous zebrafish model of tp53-deficient, EGFRviii, and PI3KCAH1047R-driven glioblastoma reveals inhibitory roles for inflammation during tumor initiation and relapse in vivo

Abstract

To build a patient-relevant in vivo model of human glioblastoma, we expressed common oncogenic variants including activated human EGFR viii and PI3KCA H1047R under the control of the radial glial-specific promoter her4.1 in syngeneic tp53 loss-of-function mutant zebrafish. Robust tumor formation was observed prior to 45 days of life, with a gene expression signature similar to human glioblastoma of the mesenchymal subtype, along with a strong inflammatory component. Within early stage tumor lesions, and in an intact and endogenous tumor microenvironment, we visualized infiltration of phagocytic cells, as well as internalization of tumor cells by mpeg1.1 :GFP+ microglia/macrophages, suggesting negative regulatory pressure by pro-inflammatory cell types on tumor growth at early stages of glioblastoma initiation in vivo . Furthermore, CRISPR/Cas9-mediated gene targeting of master inflammatory transcription factors irf7 and irf8 led to increased tumor formation in the primary context, while suppression of microglial/macrophage activity led to enhanced tumor cell engraftment following transplantation into otherwise immune competent zebrafish hosts. Altogether, we developed a genetically-relevant model of aggressive human glioblastoma and harnessed the unique advantages of zebrafish including live imaging, high-throughput genetic and chemical manipulations to highlight important tumor suppressive roles for the innate immune system on glioblastoma initiation, with important future significance for therapeutic discovery and optimizations.