ID #990 Using an in utero electroporation model of thalamic diffuse midline glioma to investigate the mechanisms governing tumorigenesis, therapeutic response, and resistance
Alyssa Powell, Salvador Guerra, Santos Franco, Adam GreenAbstract
Background
Diffuse midline gliomas (DMGs) are the leading cause of cancer-related death in children. Radiotherapy is palliative, and cytotoxic and targeted chemotherapy are largely ineffective, with the exception of dordaviprone, which is most effective in thalamic DMG. We have established a state-of-the-art in utero electroporation (IUE) model that reliably produces DMG tumors in developing brains of immunocompetent mice. This strategy allows us to tailor our studies to the timeframe when the tumors are forming and growing, which is not yet possible to study in humans.
Methods
We used our IUE approach to model H3K27M-mutant thalamic DMG. The model works by electroporating the developing thalamus of mouse embryos with DNA plasmids encoding the histone 3 oncogenic driver mutation (H3K27M), dominant-negative P53 (P53-R270H), and constitutively-active PDGFRA (PDGFRA-D842V). Model validation comprised histopathologic analysis (H&E; IHC), quantification of penetrance and survival, and a pilot therapeutic efficacy study administering doraviprone or vehicle and assessing tumor burden by longitudinal bioluminescence imaging (BLI) and IHC.
Results
H&E and IHC at postnatal day (P) 21 revealed neoplastic features within the tumor compared to the unelectroporated contralateral side with no tumor. We found that many of the tumor cells co-expressed the transcription factors OLIG2 and SOX2, similar to human DMG cells. We quantified survival and tumor penetrance across 14 litters (104 embryos). We observed 80% embryo survival to birth following IUE, and 71% of surviving pups developed tumors. Finally, BLI and IHC showed that treatment with doraviprone from P21 to P42 reduced BLI signal and tumor size compared to vehicle-treated mice.
Discussion
We show that our IUE model robustly and reproducibly generates tumors that recapitulate the location, developmental timing, histopathology, and molecular profile of human thalamic DMGs. Furthermore, pilot therapeutic testing demonstrates that this system can be used to nominate promising therapies for downstream translational testing.