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Spatiotemporal Role of GLI2 in Driving SHH-Medulloblastoma Tumorigenesis

ABSTRACT: Medulloblastoma (MB) is a malignant cerebellar tumor primarily affecting children. SHH MB with GLI2 amplification is associated with a particularly poor prognosis. Although GLI2 amplification is clinically recognized, its role in driving SHH-MB remains unclear. We generated novel mouse models of GLI2-amplified MB to investigate the role of GLI2 in driving tumorigenesis and assessed their similarity to human tumors using immunohistological and scRNA-seq analyses. Additionally, we examined the spatiotemporal window of tumor development using our mouse models and explored the mechanisms underlying the susceptibility of embryonic cerebellar granule cell progenitors (GCPs) to GLI2-induced tumorigenesis through scRNA-seq analysis. We further investigated the involvement of MAPK pathway in GLI2-driven tumorigenesis and progression by genetically disrupting the pathway. We demonstrate that GLI2 is a primary oncogenic driver in SHH-MB, with its overexpression driving embryonic Math1+ progenitor cells to form SHH-MB. The resulting GLI2-driven tumors closely resemble human GLI2-amplified SHH-MB cellularly and molecularly. Additionally, we determined that embryonic Math1+ GCPs at E13.5–E15.5 are the most susceptible to tumor initiation with GLI2 overexpression alone. In postnatal Math1+ GCPs, additional Trp53 inactivation is required for GLI2-induced tumor formation. scRNA-seq analysis reveals MAPK pathway enrichment in embryonic GCPs and GLI2-driven tumors. Functional studies show that knocking down MEK1/2 in Math1+ progenitor cells or GLI2-driven MB cells prevents tumorigenesis and tumor progression, respectively. Our studies uncover the developmental origins and molecular mechanisms underlying GLI2-amplified SHH-MB. We also reveal that the MAPK pathway plays a critical role in GLI2-driven SHH-MB tumorigenesis and progression.

ORGANISM(S): Mus musculus

PROVIDER: GSE329979 | GEO | 2026/05/10

REPOSITORIES: GEO

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Project description:BACKGROUND Focal high-level amplifications of MYC define a subset of high-risk medulloblastoma patients. However, the prognostic role of MYCN oncogene amplification remains less clear. We aimed to evaluate the prognostic value of this alteration alone and in combination with biological modifiers in a large cohort of 67 pediatric medulloblastomas with MYCN amplification (MYCN-MB). METHODS Twenty-one MYCN-MB with MYCN amplication and 56 MYCN-MB were respectively examined using either gene expression profiling and array-CGH, or immunohistochemical analysis and FISH. All 67 tumors were further subject to mutational analyses. Semi non-negative matrix factorization–based and unsupervised hierarchical clustering methods were used to identify biological groups. We compared molecular, clinical, and prognostic characteristics both within biological MYCN-MB groups and with non-amplified tumors. RESULTS Transcriptomic analysis of this large cohort of MYCN-MBs demonstrated a significant enrichment of MYCN-MB in the SHH and group D variants. Further substantiating this biological dichotomy of MYCN-MB, respective group affiliations were also accompanied by variant-specific cytogenetic aberrations including deletion of 9q in the SHH variant, and gain of 7q and isochromosome 17q/17q gain in MYCN-MBs clustering with group D tumors. Among clinically relevant variables, SHH subtype and 10q loss for Non-SHH tumors comprised the most powerful markers of favorable prognosis in MYCN-MB. CONCLUSION We demonstrate considerable heterogeneity within MYCN-MB in terms of genetics, tumor biology, and clinical outcome. Thus, assessment of disease group and 10q copy-number status may improve risk stratification of this group and may delineate MYCN-MB with the same dismal prognosis as MYC amplified tumors. Furthermore, based on the enrichment of MYCN and GLI2 amplifications in SHH-driven medulloblastoma, amplification of these downstream signaling intermediates should be excluded before a patient is enrolled into a clinical trial using a Smoothened inhibitor.

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Spatiotemporal Role of GLI2 in Driving SHH-Medulloblastoma Tumorigenesis

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