LGG-49. EVALUATING THE EFFECTS OF MIRDAMETINIB IN NF1-MUTANT LOW-GRADE GLIOMAS USING BOTH CULTURED CELLS AND A NOVEL ZEBRAFISH XENOGRAFT MODEL

Abstract

Abstract BACKGROUND Pediatric low-grade gliomas (LGGs) with NF1 mutations represent a significant portion of childhood brain tumors. NF1 mutations lead to the dysregulation of the MAPK kinase and mTOR pathways, contributing to tumor growth. However, obtaining cell lines and xenograft animal models for NF1-mutated LGGs remains challenging due to their slow growth and less aggressive nature. Methods and RESULTS We examined the therapeutic efficacy of a novel MEK inhibitor mirdametinib in targeting the MAPK pathway within JHH-NF1-PA1 cells, a cell line derived from a low-grade optic pathway glioma originating from a patient with type 1 neurofibromatosis. Mirdametinib decreased p-ERK protein expression levels on western blot within four hours. We confirmed that mirdametinib significantly suppressed tumor cell proliferation by approximately 60% (BrdU staining (P<0.05), CellTiter Blue assay). β-galactosidase staining revealed approximately a 50% induction of cellular senescence in JHH-NF1-PA1 cells following mirdametinib treatment (P<0.05). We confirmed our findings using murine Nf1-null low grade glioma cell lines 1861 and 1491. To establish an in vivo model for drug testing, we utilized zebrafish due to their transparency, rapid reproduction, and short development time. Injecting RFP-labeled JHH-NF1-PA1 cells into the zebrafish at the 1000-cell stage, we monitored tumor growth using TECAN fluorescence detection from the third to eighth days post-injection. The fluorescence signals obtained from TECAN were validated by fluorescence microscopy. Western blot analysis confirmed a decrease in p-ERK levels within the zebrafish following mirdametinib treatment. We are evaluating the effect of mirdametinib on NF1 low grade glioma cell survival, migration and senescence in the zebrafish brain. CONCLUSION Our findings show that mirdametinib inhibits cell proliferation and induces senescence in NF1-mutated LGGs. Moreover, our zebrafish model provides a valuable tool for evaluating the efficacy of MEK inhibitors in vivo, particularly in cases where traditional xenograft models are difficult to establish.