MODL-33. AN ANIMAL MODEL OF GLI2-AMPLIFIED MEDULLOBLASTOMA

Abstract

Abstract Medulloblastoma (MB) is the most common malignant brain tumor affecting children. Among the known subtypes of MB, GLI2-amplified SHH-MB associated with P53 mutations has the worst prognosis, and a 5-year survival rate of less than 30%. Moreover, GLI2-amplified MBs are non-responsive to SMO inhibitors, the only targeted treatment option available for SHH-MB. To address this treatment gap, there is an urgent need to identify novel potential therapeutic targets, an effort that requires better understanding of key cellular and molecular mechanisms underlying GLI2-amplified MB. To that end, we generated a mouse model of GLI2-amplified MB and identified GL12 as the critical driver of tumorigenesis, and granule cell progenitors (GCPs) as the cells of tumor origin. We further found that GLI2 specifically drives embryonic, but not neonatal, Math1+ GCPs to form SHH-MB tumors. An scRNA-seq analysis revealed MAPK pathway activation specifically in embryonic Math1+ GCPs. The MAPK pathway was activated in mouse and human GLI2-driven MB tumors, and a MEK/ERK inhibitor significantly inhibited GLI2-driven MB in vivo. Based on these findings, we hypothesize that GLI2-driven MB originates from a specific population of Math1+ GCPs during a discrete temporal interval in cerebellar development, and that targeting MAPK/MEK/ERK pathway components represents a novel approach to treatment of GLI2-amplified MB.