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  • 1
    Keywords: EXPRESSION ; tumor ; IDENTIFICATION ; PROGRESSION ; OVARIAN-CANCER ; PROGNOSTIC-FACTORS ; CHILDHOOD MEDULLOBLASTOMA ; STEM-CELL ; BREAST-CANCER CELLS ; INFLUENCES ZYXIN LOCALIZATION
    Abstract: Medulloblastoma is the most common malignant pediatric brain tumor and is one of the leading causes of cancer-related mortality in children. Treatment failure mainly occurs in children harboring metastatic tumors, which typically carry an isochromosome 17 or gain of 17q, a common hallmark of intermediate and high-risk medulloblastoma. Through mRNA expression profiling, we identified LIM and SH3 protein 1 (LASP1) as one of the most upregulated genes on chromosome 17q in tumors with 17q gain. In an independent validation cohort of 101 medulloblastoma samples, the abundance of LASP1 mRNA was significantly associated with 17q gain, metastatic dissemination, and unfavorable outcome. LASP1 protein expression was analyzed by immunohistochemistry in a large cohort of patients (n = 207), and high protein expression levels were found to be strongly correlated with 17q gain, metastatic dissemination, and inferior overall and progression-free survival. In vitro experiments in medulloblastoma cell lines showed a strong reduction of cell migration, increased adhesion, and decreased proliferation upon LASP1 knockdown by small interfering RNA-mediated silencing, further indicating a functional role for LASP1 in the progression and metastatic dissemination of medulloblastoma.
    Type of Publication: Journal article published
    PubMed ID: 20924110
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  • 2
    Keywords: CANCER ; EXPRESSION ; SURVIVAL ; GENES ; PROTEIN ; transcription ; TRANSCRIPTION FACTOR ; IDENTIFICATION ; PROMOTER ; chemotherapy ; MUTATIONS ; LOCALIZATION ; METHYLATION ; BRAIN-TUMORS ; ACUTE MYELOID-LEUKEMIA ; INTRACRANIAL EPENDYMOMAS ; MDS1/EVI1
    Abstract: Purpose: 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. Experimental Design: 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). Results: 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. Conclusions: To conclude, the transcription factor Evi-1 is overexpressed in infratentorial ependymomas, promotes proliferation of ependymal tumor cells, and is prognostically unfavorable.
    Type of Publication: Journal article published
    PubMed ID: 21493867
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  • 3
    Keywords: DISTINCT ; GENE ; BREAST-CANCER ; COPY-NUMBER ; SONIC HEDGEHOG ; GERMLINE ; LI-FRAUMENI-SYNDROME ; ACUTE MYELOID-LEUKEMIA ; telomere length ; FAMILIAL SYNDROME
    Abstract: Genomic rearrangements are thought to occur progressively during tumor development. Recent findings, however, suggest an alternative mechanism, involving massive chromosome rearrangements in a one-step catastrophic event termed chromothripsis. We report the whole-genome sequencing-based analysis of a Sonic-Hedgehog medulloblastoma (SHH-MB) brain tumor from a patient with a germline TP53 mutation (Li-Fraumeni syndrome), uncovering massive, complex chromosome rearrangements. Integrating TP53 status with microarray and deep sequencing-based DNA rearrangement data in additional patients reveals a striking association between TP53 mutation and chromothripsis in SHH-MBs. Analysis of additional tumor entities substantiates a link between TP53 mutation and chromothripsis, and indicates a context-specific role for p53 in catastrophic DNA rearrangements. Among these, we observed a strong association between somatic TP53 mutations and chromothripsis in acutemyeloid leukemia. These findings connect p53 status and chr
    Type of Publication: Journal article published
    PubMed ID: 22265402
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  • 4
    Keywords: CANCER ; PATHWAY ; GENES ; ACTIVATION ; MUTATIONS ; SUBGROUPS ; LANDSCAPE ; TETRAPLOID TUMOR-CELLS ; TBR1
    Abstract: Medulloblastoma is an aggressively growing tumour, arising in the cerebellum or medulla/brain stem. It is the most common malignant brain tumour in children, and shows tremendous biological and clinical heterogeneity. Despite recent treatment advances, approximately 40% of children experience tumour recurrence, and 30% will die from their disease. Those who survive often have a significantly reduced quality of life. Four tumour subgroups with distinct clinical, biological and genetic profiles are currently identified. WNT tumours, showing activated wingless pathway signalling, carry a favourable prognosis under current treatment regimens. SHH tumours show hedgehog pathway activation, and have an intermediate prognosis. Group 3 and 4 tumours are molecularly less well characterized, and also present the greatest clinical challenges. The full repertoire of genetic events driving this distinction, however, remains unclear. Here we describe an integrative deep-sequencing analysis of 125 tumour-normal pairs, conducted as part of the International Cancer Genome Consortium (ICGC) PedBrain Tumor Project. Tetraploidy was identified as a frequent early event in Group 3 and 4 tumours, and a positive correlation between patient age and mutation rate was observed. Several recurrent mutations were identified, both in known medulloblastoma-related genes (CTNNB1, PTCH1, MLL2, SMARCA4) and in genes not previously linked to this tumour (DDX3X, CTDNEP1, KDM6A, TBR1), often in subgroup-specific patterns. RNA sequencing confirmed these alterations, and revealed the expression of what are, to our knowledge, the first medulloblastoma fusion genes identified. Chromatin modifiers were frequently altered across all subgroups. These findings enhance our understanding of the genomic complexity and heterogeneity underlying medulloblastoma, and provide several potential targets for new therapeutics, especially for Group 3 and 4 patients.
    Type of Publication: Journal article published
    PubMed ID: 22832583
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  • 5
    Keywords: CANCER ; GROWTH ; TUMORS ; NERVOUS-SYSTEM ; ADULT ; MOUSE MODELS ; PEDIATRIC MEDULLOBLASTOMA ; HEDGEHOG PATHWAY INHIBITOR ; TERT PROMOTER MUTATIONS ; ITRACONAZOLE
    Abstract: Smoothened (SMO) inhibitors recently entered clinical trials for sonic-hedgehog-driven medulloblastoma (SHH-MB). Clinical response is highly variable. To understand the mechanism(s) of primary resistance and identify pathways cooperating with aberrant SHH signaling, we sequenced and profiled a large cohort of SHH-MBs (n = 133). SHH pathway mutations involved PTCH1 (across all age groups), SUFU (infants, including germline), and SMO (adults). Children 〉3 years old harbored an excess of downstream MYCN and GLI2 amplifications and frequent TP53 mutations, often in the germline, all of which were rare in infants and adults. Functional assays in different SHH-MB xenograft models demonstrated that SHH-MBs harboring a PTCH1 mutation were responsive to SMO inhibition, whereas tumors harboring an SUFU mutation or MYCN amplification were primarily resistant.
    Type of Publication: Journal article published
    PubMed ID: 24651015
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  • 6
    Keywords: APOPTOSIS ; PATHWAY ; GENES ; POOR-PROGNOSIS ; INCREASED EXPRESSION ; MICE LACKING ; high-throughput analysis ; ISLAND METHYLATOR PHENOTYPE ; D-DEPENDENT KINASES ; INK4 FAMILY
    Abstract: Uncontrolled cell cycle entry, resulting from deregulated CDK-RB1-E2F pathway activity, is a crucial determinant of neuroblastoma cell malignancy. Here we identify neuroblastoma-suppressive functions of the p19-INK4d CDK inhibitor and uncover mechanisms of its repression in high-risk neuroblastomas. Reduced p19-INK4d expression was associated with poor event-free and overall survival and neuroblastoma risk factors including amplified MYCN in a set of 478 primary neuroblastomas. High MYCN expression repressed p19-INK4d mRNA and protein levels in different neuroblastoma cell models with conditional MYCN expression. MassARRAY and 450K methylation analyses of 105 primary neuroblastomas uncovered a differentially methylated region within p19-INK4d. Hypermethylation of this region was associated with reduced p19-INK4d expression. In accordance, p19-INK4d expression was activated upon treatment with the demethylating agent, 2'-deoxy-5-azacytidine, in neuroblastoma cell lines. Ectopic p19-INK4d expression decreased viability, clonogenicity and the capacity for anchorage-independent growth of neuroblastoma cells, and shifted the cell cycle towards the G1/0 phase. p19-INK4d also induced neurite-like processes and markers of neuronal differentiation. Moreover, neuroblastoma cell differentiation, induced by all-trans retinoic acid or NGF-NTRK1-signaling, activated p19-/NK4dexpression. Our findings pinpoint p19-INK4d as a neuroblastoma suppressor and provide evidence for MYCN-mediated repression and for epigenetic silencing of p19-INK4d by DNA hypermethylation in high-risk neuroblastomas.
    Type of Publication: Journal article published
    PubMed ID: 25104850
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  • 7
    Keywords: GENE ; INFECTION ; HEPATOMA-CELLS ; RIG-I ; RNA REPLICATION ; MDA5 ; NS5A PROTEIN ; WEST NILE VIRUS ; REGULATORY FACTOR-3 ; ANTIVIRAL RESPONSE
    Abstract: BACKGROUND & AIMS: Hepatitis C virus (HCV) nonstructural protein 5A (NS5A) is a multifunctional protein playing a crucial role in diverse steps of the viral replication cycle and perturbing multiple host cell pathways. We showed previously that removal of a region in domain 2 (D2) of NS5A (mutant NS5A(D2Delta)) is dispensable for viral replication in hepatoma cell lines. By using a mouse model and immune-competent cell systems, we studied the role of D2 in controlling the innate immune response. METHODS: In vivo replication competence of NS5A(D2Delta) was studied in transgenic mice with human liver xenografts. Results were validated using primary human hepatocytes (PHHs) and mechanistic analyses were conducted in engineered Huh7 hepatoma cells with reconstituted innate signaling pathways. RESULTS: Although the deletion in NS5A removed most of the interferon (IFN) sensitivity determining-region, mutant NS5A(D2Delta) was as sensitive as the wild type to IFN-alpha and IFN-lambda in vitro, but severely attenuated in vivo. This attenuation could be recapitulated in PHHs and was linked to higher activation of the IFN response, concomitant with reduced viral replication and virus production. Importantly, immune-reconstituted Huh7-derived cell lines revealed a sequential activation of the IFN-response via RIG-I (retinoic acid-inducible gene I) and MDA5 (Myeloma differentiation associated factor 5), respectively, that was significantly higher in the case of the mutant lacking most of NS5A D2. CONCLUSIONS: Our study reveals an important role of NS5A D2 for suppression of the IFN response that is activated by HCV via RIG-I and MDA5 in a sequential manner.
    Type of Publication: Journal article published
    PubMed ID: 25908268
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  • 8
    Abstract: Chromothripsis is a recently discovered form of genomic instability, characterized by tens to hundreds of clustered DNA rearrangements resulting from a single dramatic event. Telomere dysfunction has been suggested to play a role in the initiation of this phenomenon, which occurs in a large number of tumor entities. Here, we show that telomere attrition can indeed lead to catastrophic genomic events, and that telomere patterns differ between cells analyzed before and after such genomic catastrophes. Telomere length and telomere stabilization mechanisms diverge between samples with and without chromothripsis in a given tumor subtype. Longitudinal analyses of the evolution of chromothriptic patterns identify either stable patterns between matched primary and relapsed tumors, or loss of the chromothriptic clone in the relapsed specimen. The absence of additional chromothriptic events occurring between the initial tumor and the relapsed tumor sample points to telomere stabilization after the initial chromothriptic event which prevents further shattering of the genome.
    Type of Publication: Journal article published
    PubMed ID: 26856307
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  • 9
    Abstract: Ependymomas in children can arise throughout all compartments of the central nervous system (CNS). Highly malignant paediatric ependymoma subtypes are Group A tumours of the posterior fossa (PF-EPN-A) and RELA-fusion positive (ST-EPN-RELA) tumours in the supratentorial compartment. It was repeatedly reported in smaller series that accumulation of p53 is frequently observed in ependymomas and that immunohistochemical staining correlates with poor clinical outcome, while TP53 mutations are rare. Our TP53 mutation analysis of 130 primary ependymomas identified a mutation rate of only 3%. Immunohistochemical analysis of 398 ependymomas confirmed previous results correlating the accumulation of p53 with inferior outcome. Among the p53-positive ependymomas, the vast majority exhibited a RELA fusion leading to the hypothesis that p53 inactivation might be linked to RELA positivity.In order to assess the potential of p53 reactivation through MDM2 inhibition in ependymoma, we evaluated the effects of Actinomycin-D and Nutlin-3 treatment in two preclinical ependymoma models representing the high-risk subtypes PF-EPN-A and ST-EPN-RELA. The IC-50 of the agent as determined by metabolic activity assays was in the lower nano-molar range (0.2-0.7 nM). Transcriptome analyses of high-dose (100 nM), low-dose (5 nM) and non-treated cells revealed re-expression of p53 dependent genes including p53 upregulated modulator of apoptosis (PUMA) after low-dose treatment. At the protein level, we validated the Actinomycin-D induced upregulation of PUMA, and of p53 interaction partners MDM2 and p21. Proapoptotic effects of low-dose application of the agent were confirmed by flow cytometry. Thus, Actinomycin-D could constitute a promising therapeutic option for ST-EPN-RELA ependymoma patients, whose tumours frequently exhibit p53 inactivation.
    Type of Publication: Journal article published
    PubMed ID: 27556362
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  • 10
    Keywords: EXPRESSION ; SURVIVAL ; IDENTIFICATION ; PROGRESSION ; COMPARATIVE GENOMIC HYBRIDIZATION ; ABERRATIONS ; PROGNOSTIC-FACTORS ; CHROMOSOMAL IMBALANCES ; CANDIDATE GENES ; PEDIATRIC EPENDYMOMA
    Abstract: PURPOSE: The biologic behavior of intracranial ependymoma is unpredictable on the basis of current staging approaches. We aimed at the identification of recurrent genetic aberrations in ependymoma and evaluated their prognostic significance to develop a molecular staging system that could complement current classification criteria. PATIENTS AND METHODS: As a screening cohort, we studied a cohort of 122 patients with ependymoma before standardized therapy by using array-based comparative genomic hybridization. DNA copy-number aberrations identified as possible prognostic markers were validated in an independent cohort of 170 patients with ependymoma by fluorescence in situ hybridization analysis. Copy-number aberrations were correlated with clinical, histopathologic, and survival data. RESULTS: In the screening cohort, age at diagnosis, gain of 1q, and homozygous deletion of CDKN2A comprised the most powerful independent indicators of unfavorable prognosis. In contrast, gains of chromosomes 9, 15q, and 18 and loss of chromosome 6 were associated with excellent survival. On the basis of these findings, we developed a molecular staging system comprised of three genetic risk groups, which was then confirmed in the validation cohort. Likelihood ratio tests and multivariate Cox regression also demonstrated the clear improvement in predictive accuracy after the addition of these novel genetic markers. CONCLUSION: Genomic aberrations in ependymomas are powerful independent markers of disease progression and survival. By adding genetic markers to established clinical and histopathologic variables, outcome prediction can potentially be improved. Because the analyses can be conducted on routine paraffin-embedded material, it will now be possible to prospectively validate these markers in multicenter clinical trials on population-based cohorts.
    Type of Publication: Journal article published
    PubMed ID: 20516456
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