Gene rearrangement in the form of an intragenic deletion is the primary mechanism of oncogenic mutation of the epidermal growth factor receptor (EGFR) gene in gliomas. However, the incidence of platelet-derived growth factor receptor-a (PDGFRA) gene rearrangement in these tumors is unknown. We investigated the PDGFRA locus in PDGFRA-amplified gliomas and identified two rearrangements, including the first case of a gene fusion between kinase insert domain receptor (KDR) (VEGFRII) and the PDGFRA gene, and six cases of PDGFRA D8, 9 , an intragenic deletion rearrangement. The PDGFRA D8, 9 mutant was common, being present in 40% of the glioblastoma multiformes (GBMs) with PDGFRA amplification. Tumors with these two types of PDGFRA rearrangement displayed histologic features of oligodendroglioma, and the gene products of both rearrangements showed constitutively elevated tyrosine kinase activity and transforming potential that was reversed by PDGFR blockade. These results suggest the possibility that these PDGFRA mutants behave as oncogenes in this subset of gliomas, and that the prevalence of such rearrangements may have been considerably underestimated.[Keywords: Copy number alteration; glioma; PDGFRA gene rearrangement; receptor tyrosine kinase] Supplemental material is available at http://www.genesdev.org.

The majority of supratentorial ependymomas (ST-ependymomas) have few mutations but frequently display chromothripsis of chromosome 11q that generates a fusion between C11orf95 and RELA (RELA). Neural stem cells transduced with RELAex vivo form ependymomas when implanted in the brain. These tumors display enhanced NF-κB signaling, suggesting that this aberrant signal is the principal mechanism of oncogenesis. However, it is not known whether RELA is sufficient to drive de novo ependymoma tumorigenesis in the brain and, if so, whether these tumors also arise from neural stem cells. We show that RELA drives ST-ependymoma formation from periventricular neural stem cells in mice and that RELA-induced tumorigenesis is likely dependent on a series of cell signaling pathways in addition to NF-κB.

This study is a histological and clinical investigation of four cases of cerebellar glioblastoma, a rare tumor. The cases included three males and one female, from 33 to 67 years in age (mean 49 years). Tumor resection, postoperative irradiation and chemotherapy were performed in all cases. Two patients died of local tumor recurrence after 14 and 27 months. Another patient relapsed after 10 months; however, after additional tumor resection and second line chemotherapy, she remains disease-free 41 months after the initial treatment. The fourth patient has not relapsed in the 6 months since initial treatment. The histopathology of all cases was glioblastoma with pseudopalisading necrosis. However, low-grade glioma histopathology was found in three patients. All glioblastomas were immunopositive for p53 and immunonegative for epidermal growth factor receptor (EGFR) and isocitrate dehydrogenase 1 (IDH1). These adult cerebellar glioblastoma cases had similar clinical and pathological characteristics, and had different characteristics compared with supratentorial glioblastomas.

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