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  • 1
    Language: English
    In: The Journal of clinical investigation, April 2011, Vol.121(4), pp.1344-8
    Description: Pilocytic astrocytoma (PA) is the most common type of primary brain tumor in children and the second most frequent cancer in childhood. Children with incompletely resected PA represent a clinically challenging patient cohort for whom conventional adjuvant therapies are only moderately effective. This has produced high clinical demand for testing of new molecularly targeted treatments. However, the development of new therapeutics for PA has been hampered by the lack of an adequate in vivo tumor model. Recent studies have identified activation of MAPK signaling, mainly by oncogenic BRAF activation, as a hallmark genetic event in the pathogenesis of human PA. Using in vivo retroviral somatic gene transfer into mouse neural progenitor cells, we have shown here that ectopic expression of the activated BRAF kinase domain is sufficient to induce PA in mice. Further in vitro analyses demonstrated that overexpression of activated BRAF led to increased proliferation of primary mouse astrocytes that could be inhibited by treatment with the kinase inhibitor sorafenib. Our in vivo model for PA shows that the activated BRAF kinase domain is sufficient to induce PA and highlights its role as a potential therapeutic target.
    Keywords: Astrocytoma -- Etiology ; Brain Neoplasms -- Etiology ; Proto-Oncogene Proteins B-Raf -- Genetics
    ISSN: 00219738
    E-ISSN: 1558-8238
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  • 2
    In: International Journal of Cancer, 01 February 2014, Vol.134(3), pp.703-716
    Description: Based on extensive pre‐clinical studies, the oncolytic parvovirus H‐1 (H‐1PV) is currently applied to patients with recurrent glioblastoma in a phase I/IIa clinical trial (ParvOryx01, NCT01301430). Cure rates of about 40% in pediatric high‐risk medulloblastoma (MB) patients also indicate the need of new therapeutic approaches. In order to prepare a future application of oncolytic parvovirotherapy to MB, the present study preclinically evaluates the cytotoxic efficacy of H‐1PV on MB cells and characterizes cellular target genes involved in this effect. Six MB cell lines were analyzed by whole genome oligonucleotide microarrays after treatment and the results were matched to known molecular and cytogenetic risk factors. In contrast to non‐transformed infant astrocytes and neurons, in five out of six MB cell lines lytic H‐1PV infection and efficient viral replication could be demonstrated. The cytotoxic effects induced by H‐1PV were observed at LD50s below 0.05 p. f. u. per cell indicating high susceptibility. Gene expression patterns in the responsive MB cell lines allowed the identification of candidate target genes mediating the cytotoxic effects of H‐1PV. H‐1PV induced down‐regulation of key regulators of early neurogenesis shown to confer poor prognosis in MB such as ZIC1, FOXG1B, MYC, and NFIA. In MB cell lines with genomic amplification of MYC, expression of MYC was the single gene most significantly repressed after H‐1PV infection. H‐1PV virotherapy may be a promising treatment approach for MB since it targets genes of functional relevance and induces cell death at very low titers of input virus. What's new? Medulloblastoma, the most frequent pediatric brain cancer, causes death in about 60 percent of high‐risk patients, and so there is a major need for novel, highly effective therapies. One therapy of interest is parvovirus H‐1 (H‐1PV), which was found in this study to produce marked cytotoxic effects in six medulloblastoma cell lines. Gene expression profiling revealed that H‐1PV infection causes down‐regulation of key regulatory genes involved in early neurogenesis, with significant repression of . The master regulators affected may represent putative direct or indirect H‐1PV target genes.
    Keywords: Medulloblastoma ; Oncolytic Virus ; Parvovirus H‐1pv ; Cellular Targets ; Myc ; Master Regulators Of Neurogenesis
    ISSN: 0020-7136
    E-ISSN: 1097-0215
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  • 3
    Language: English
    In: Cancer Research, 10/01/2014, Vol.74(19 Supplement), pp.LB-198-LB-198
    ISSN: 0008-5472
    E-ISSN: 1538-7445
    Source: CrossRef
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  • 4
    Language: English
    In: Cancer Research, 04/15/2011, Vol.71(8 Supplement), pp.4724-4724
    ISSN: 0008-5472
    E-ISSN: 1538-7445
    Source: CrossRef
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  • 5
  • 6
    In: Nature, 2012, Vol.482(7386), p.529
    Description: Medulloblastoma, the most common malignant paediatric brain tumour, arises in the cerebellum and disseminates through the cerebrospinal fluid in the leptomeningeal space to coat the brain and spinal cord (1). Dissemination, a marker of poor prognosis, is found in up to 40% of children at diagnosis and in most children at the time of recurrence. Affected children therefore are treated with radiation to the entire developing brain and spinal cord, followed by high-dose chemotherapy, with the ensuing deleterious effects on the developing nervous system (2). The mechanisms of dissemination through the cerebrospinal fluid are poorly studied, and medulloblastoma metastases have been assumed to be biologically similar to the primary tumour (3,4). Here we show that in both mouse and human medulloblastoma, the metastases from an individual are extremely similar to each other but are divergent from the matched primary tumour. Clonal genetic events in the metastases can be demonstrated in a restricted subclone of the primary tumour, suggesting that only rare cells within the primary tumour have the ability to metastasize. Failure to account for the bicompartmental nature of metastatic medulloblastoma could be a major barrier to the development of effective targeted therapies.
    Keywords: Gene Mutation -- Health Aspects ; Gene Mutation -- Research ; Medulloblastoma -- Development And Progression ; Medulloblastoma -- Genetic Aspects ; Medulloblastoma -- Risk Factors ; Medulloblastoma -- Research;
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 7
    Language: English
    In: Clinical cancer research : an official journal of the American Association for Cancer Research, 01 June 2011, Vol.17(11), pp.3631-7
    Description: Ependymomas are glial tumors of presumably radial glial origin that share morphologic similarities with ependymal cells. The molecular genetics of ependymomas of supratentorial, infratentorial, and spinal location is heterogeneous. We aimed at identifying pathways operative in the development of infratentorial ependymomas. To do so, gene expression profiles of tumor cells laser microdissected from infratentorial ependymomas (n = 15) were compared with that of nonneoplastic ependymal cells laser microdissected from autopsy tissue (n = 7). Among 31 genes significantly overexpressed (〉5-fold) in ependymomas, transcription factor EVI1 (ecotropic viral integration site 1) showed the highest overexpression (35-fold). Evi-1 protein expression could be confirmed in formalin-fixed, paraffin-embedded samples of 26 of 28 infratentorial ependymomas but only in 7 of 47 nonependymal glial tumors (P 〈 0.001). Furthermore, MDS1/EVI1 fusion transcripts were detectable in 17 of 28 infratentorial ependymomas and significantly correlated with MGMT (O6-methylguanine-DNA-methyltransferase) promoter hypermethylation (P 〈 0.05). In primary infratentorial ependymoma cells, transfection with EVI1-specific siRNAs resulted in significant growth inhibition [48 hours: 87% ± 2% and 74% ± 10% as compared with control (mean ± SD; P 〈 0.001)]. The prognostic role of EVI1 could further be validated in an independent cohort of 39 infratentorial and 26 supratentorial ependymomas on the basis of mRNA expression profiling. Although in supratentorial ependymomas EVI1 expression status had no prognostic impact, in infratentorial ependymomas, high EVI1 expression was associated with shorter overall survival and progression-free survival. To conclude, the transcription factor Evi-1 is overexpressed in infratentorial ependymomas, promotes proliferation of ependymal tumor cells, and is prognostically unfavorable.
    Keywords: Cell Proliferation ; DNA-Binding Proteins -- Biosynthesis ; Ependymoma -- Metabolism ; Infratentorial Neoplasms -- Metabolism ; Transcription Factors -- Biosynthesis
    ISSN: 1078-0432
    E-ISSN: 15573265
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  • 8
  • 9
    In: Nature, 2012, Vol.482(7384), p.226
    Description: Glioblastoma multiforme (GBM) is a lethal brain tumour in adults and children. However, DNA copy number and gene expression signatures indicate differences between adult and paediatric cases (1-4). To explore the genetic events underlying this distinction, we sequenced the exomes of 48 paediatric GBM samples. Somatic mutations in the H3.3-ATRX-DAXX chromatin remodelling pathway were identified in 44% of tumours (21/48). Recurrent mutations in H3F3A, which encodes the replication-independent histone 3 variant H3.3, were observed in 31% of tumours, and led to amino acid substitutions at two critical positions within the histone tail (K27M, G34R/G34V) involved in key regulatory post-translational modifications. Mutations in ATRX([alpha]-thalassaemia/mental retardation syndrome X-linked) (5) and DAXX (death-domain associated protein), encoding two subunits of a chromatin remodelling complex required for H3.3 incorporation at pericentric heterochromatin and telomeres (6,7), were identified in 31% of samples overall, and in 100% of tumours harbouring a G34R or G34V H3.3 mutation. Somatic TP53 mutations were identified in 54% of all cases, and in 86% of samples with H3F3A and/or ATRX mutations. Screening of a large cohort of gliomas of various grades and histologies (n = 784) showed H3F3A mutations to be specific to GBM and highly prevalent in children and young adults. Furthermore, the presence of H3F3A/ATRX-DAXX/TP53 mutations was strongly associated with alternative lengthening of telomeres and specific gene expression profiles. This is, to our knowledge, the first report to highlight recurrent mutations in a regulatory histone in humans, and our data suggest that defects of the chromatin architecture underlie paediatric and young adult GBM pathogenesis.
    Keywords: Gene Mutation -- Research ; Dna -- Research ; Dna -- Physiological Aspects ; Glioblastomas -- Genetic Aspects ; Glioblastomas -- Research ; Tumor Proteins -- Physiological Aspects ; Tumor Proteins -- Research;
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 10
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