Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Keywords: CANCER ; DISTINCT ; prognosis ; PROGRESSION ; chemotherapy ; ABERRATIONS ; MUTATIONS ; CHILDREN ; ADOLESCENTS ; INTRATUMOR HETEROGENEITY
    Abstract: BACKGROUND: Recurrent medulloblastoma is a therapeutic challenge because it is almost always fatal. Studies have confirmed that medulloblastoma consists of at least four distinct subgroups. We sought to delineate subgroup-specific differences in medulloblastoma recurrence patterns. METHODS: We retrospectively identified a discovery cohort of all recurrent medulloblastomas at the Hospital for Sick Children (Toronto, ON, Canada) from 1994 to 2012 (cohort 1), and established molecular subgroups using a nanoString-based assay on formalin-fixed paraffin-embedded tissues or frozen tissue. The anatomical site of recurrence (local tumour bed or leptomeningeal metastasis), time to recurrence, and survival after recurrence were assessed in a subgroup-specific manner. Two independent, non-overlapping cohorts (cohort 2: samples from patients with recurrent medulloblastomas from 13 centres worldwide, obtained between 1991 and 2012; cohort 3: samples from patients with recurrent medulloblastoma obtained at the NN Burdenko Neurosurgical Institute [Moscow, Russia] between 1994 and 2011) were analysed to confirm and validate observations. When possible, molecular subgrouping was done on tissue obtained from both the initial surgery and at recurrence. RESULTS: Cohort 1 consisted of 30 patients with recurrent medulloblastomas; nine with local recurrences, and 21 with metastatic recurrences. Cohort 2 consisted of 77 patients and cohort 3 of 96 patients with recurrent medulloblastoma. Subgroup affiliation remained stable at recurrence in all 34 cases with available matched primary and recurrent pairs (five pairs from cohort 1 and 29 pairs from cohort 2 [15 SHH, five group 3, 14 group 4]). This finding was validated in 17 pairs from cohort 3. When analysed in a subgroup-specific manner, local recurrences in cohort 1 were more frequent in SHH tumours (eight of nine [89%]) and metastatic recurrences were more common in group 3 and group 4 tumours (17 of 20 [85%] with one WNT, p=0.0014, local vs metastatic recurrence, SHH vs group 3 vs group 4). The subgroup-specific location of recurrence was confirmed in cohort 2 (p=0.0013 for local vs metastatic recurrence, SHH vs group 3 vs group 4,), and cohort 3 (p〈0.0001). Treatment with craniospinal irradiation at diagnosis was not significantly associated with the anatomical pattern of recurrence. Survival after recurrence was significantly longer in patients with group 4 tumours in cohort 1 (p=0.013) than with other subgroups, which was confirmed in cohort 2 (p=0.0075), but not cohort 3 (p=0.70). INTERPRETATION: Medulloblastoma does not change subgroup at the time of recurrence, reinforcing the stability of the four main medulloblastoma subgroups. Significant differences in the location and timing of recurrence across medulloblastoma subgroups have potential treatment ramifications. Specifically, intensified local (posterior fossa) therapy should be tested in the initial treatment of patients with SHH tumours. Refinement of therapy for patients with group 3 or group 4 tumours should focus on metastases. FUNDING: Canadian Institutes of Health Research, National Institutes of Health, Pediatric Brain Tumor Foundation, Garron Family Chair in Childhood Cancer Research at The Hospital for Sick Children and The University of Toronto.
    Type of Publication: Journal article published
    PubMed ID: 24140199
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    Keywords: CANCER ; CELLS ; DISTINCT ; CENTRAL-NERVOUS-SYSTEM ; METHYLATION ; ADULT ; BRAIN-TUMORS ; TELOMERASE ACTIVITY ; RISK STRATIFICATION ; SELF-RENEWAL
    Abstract: Telomerase reverse transcriptase (TERT) promoter mutations were recently shown to drive telomerase activity in various cancer types, including medulloblastoma. However, the clinical and biological implications of TERT mutations in medulloblastoma have not been described. Hence, we sought to describe these mutations and their impact in a subgroup-specific manner. We analyzed the TERT promoter by direct sequencing and genotyping in 466 medulloblastomas. The mutational distributions were determined according to subgroup affiliation, demographics, and clinical, prognostic, and molecular features. Integrated genomics approaches were used to identify specific somatic copy number alterations in TERT promoter-mutated and wild-type tumors. Overall, TERT promoter mutations were identified in 21 % of medulloblastomas. Strikingly, the highest frequencies of TERT mutations were observed in SHH (83 %; 55/66) and WNT (31 %; 4/13) medulloblastomas derived from adult patients. Group 3 and Group 4 harbored this alteration in 〈5 % of cases and showed no association with increased patient age. The prognostic implications of these mutations were highly subgroup-specific. TERT mutations identified a subset with good and poor prognosis in SHH and Group 4 tumors, respectively. Monosomy 6 was mostly restricted to WNT tumors without TERT mutations. Hallmark SHH focal copy number aberrations and chromosome 10q deletion were mutually exclusive with TERT mutations within SHH tumors. TERT promoter mutations are the most common recurrent somatic point mutation in medulloblastoma, and are very highly enriched in adult SHH and WNT tumors. TERT mutations define a subset of SHH medulloblastoma with distinct demographics, cytogenetics, and outcomes.
    Type of Publication: Journal article published
    PubMed ID: 24174164
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    Keywords: RECEPTOR ; CANCER ; EXPRESSION ; INHIBITION ; PATHWAY ; MIGRATION ; HEPATOCYTE GROWTH-FACTOR ; C-MET ; PEDIATRIC MEDULLOBLASTOMA ; GENETIC PROFILES
    Abstract: Medulloblastoma is the most common malignant pediatric brain tumor, with metastases present at diagnosis conferring a poor prognosis. Mechanisms of dissemination are poorly understood and metastatic lesions are genetically divergent from the matched primary tumor. Effective and less toxic therapies that target both compartments have yet to be identified. Here we report that the analysis of several large non-overlapping cohorts of medulloblastoma patients reveal MET kinase as a marker of sonic hedgehog (SHH) driven medulloblastoma. Immunohistochemical analysis of phosphorylated, active MET kinase in an independent patient cohort confirmed its correlation with increased tumor relapse and poor survival, suggesting that SHH medulloblastoma patients may benefit from MET-targeted therapy. In support of this hypothesis, we found that the approved MET inhibitor foretinib could suppress MET activation, decrease tumor cell proliferation and induce apoptosis in SHH medulloblastomas in vitro and in vivo. Foretinib penetrated the blood-brain barrier and was effective in both the primary and metastatic tumor compartments. In established mouse xenograft or transgenic models of metastatic SHH medulloblastoma, foretinib administration reduced the growth of the primary tumor, decreased the incidence of metastases and increased host survival. Taken together, our results provide a strong rationale to clinically evaluate foretinib as an effective therapy for patients with SHH-driven medulloblastoma.
    Type of Publication: Journal article published
    PubMed ID: 25391241
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    Keywords: GROWTH ; TUMORS ; MUTATIONS ; CENTRAL-NERVOUS-SYSTEM ; PYRUVATE-KINASE
    Abstract: PURPOSE: Myxopapillary ependymoma (MPE) is a distinct histologic variant of ependymoma arising commonly in the spinal cord. Despite an overall favorable prognosis, distant metastases, subarachnoid dissemination, and late recurrences have been reported. Currently, the only effective treatment for MPE is gross-total resection. We characterized the genomic and transcriptional landscape of spinal ependymomas in an effort to delineate the genetic basis of this disease and identify new leads for therapy. EXPERIMENTAL DESIGN: Gene expression profiling was performed on 35 spinal ependymomas, and copy number profiling was done on an overlapping cohort of 46 spinal ependymomas. Functional validation experiments were performed on tumor lysates consisting of assays measuring pyruvate kinase M activity (PKM), hexokinase activity (HK), and lactate production. RESULTS: At a gene expression level, we demonstrate that spinal grade II and MPE are molecularly and biologically distinct. These are supported by specific copy number alterations occurring in each histologic variant. Pathway analysis revealed that MPE are characterized by increased cellular metabolism, associated with upregulation of HIF1alpha. These findings were validated by Western blot analysis demonstrating increased protein expression of HIF1alpha, HK2, PDK1, and phosphorylation of PDHE1A. Functional assays were performed on MPE lysates, which demonstrated decreased PKM activity, increased HK activity, and elevated lactate production. CONCLUSIONS: Our findings suggest that MPE may be driven by a Warburg metabolic phenotype. The key enzymes promoting the Warburg phenotype: HK2, PKM2, and PDK are targetable by small-molecule inhibitors/activators, and should be considered for evaluation in future clinical trials for MPE. Clin Cancer Res; 21(16); 3750-8. (c)2015 AACR.
    Type of Publication: Journal article published
    PubMed ID: 25957288
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    Abstract: The development of targeted anti-cancer therapies through the study of cancer genomes is intended to increase survival rates and decrease treatment-related toxicity. We treated a transposon-driven, functional genomic mouse model of medulloblastoma with 'humanized' in vivo therapy (microneurosurgical tumour resection followed by multi-fractionated, image-guided radiotherapy). Genetic events in recurrent murine medulloblastoma exhibit a very poor overlap with those in matched murine diagnostic samples (〈5%). Whole-genome sequencing of 33 pairs of human diagnostic and post-therapy medulloblastomas demonstrated substantial genetic divergence of the dominant clone after therapy (〈12% diagnostic events were retained at recurrence). In both mice and humans, the dominant clone at recurrence arose through clonal selection of a pre-existing minor clone present at diagnosis. Targeted therapy is unlikely to be effective in the absence of the target, therefore our results offer a simple, proximal, and remediable explanation for the failure of prior clinical trials of targeted therapy.
    Type of Publication: Journal article published
    PubMed ID: 26760213
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    Keywords: CANCER ; radiation ; leukemia ; MUTATIONS ; FREQUENT ; CHILDREN ; METHYLATION ; DECITABINE ; MULTIPLE ; PROTOCADHERIN PCDH10
    Abstract: PURPOSE: The aim of this study was to investigate the genetic and epigenetic mechanisms contributing to PCDH10 down-regulation in medulloblastoma. We examined the role of PCDH10 as a mediator of medulloblastoma cell proliferation, cell cycle progression, and cell migration. METHODS: We identified a focal homozygous deletion of PCDH10 in medulloblastoma by surveying a cohort of 212 tumours by Affymetrix SNP array analysis. PCDH10 expression was assessed by quantitative reverse transcriptase PCR in a series of 26 tumours. The promoter methylation status of PCDH10 was determined using methylation specific PCR and Sequenom MassCLEAVE analysis. Functional studies examining the role of PCDH10 in medulloblastoma development were performed by re-expression of PCDH10 in the DAOY medulloblastoma cell line, and then, cell proliferation, cell cycle distribution, and cell migration assays were performed. RESULTS: We report a very focal homozygous deletion on chromosome 4q28.3 harbouring the PCDH10 gene. We demonstrate that PCDH10 transcription is down-regulated in 19/26 (73%) of medulloblastomas suggesting that other mechanisms also could be involved in gene repression. We found that DNA hypermethylation contributed to the deregulation of PCDH10 in 11/44 (25%) of medulloblastoma cell lines and primary tumours. Using a stable cell line (DAOY) re-expressing PCDH10, we observed that cell migration was impaired upon restoration of PCDH10 expression. CONCLUSIONS: Our findings suggest that genetic and epigenetic deregulation of PCDH10 occurs in a significant portion of medulloblastoma patients. Failure to express PCDH10 may result in loss of inhibition of cell migration, thereby contributing to medulloblastoma progression.
    Type of Publication: Journal article published
    PubMed ID: 21597995
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    Keywords: CANCER ; CELLS ; DISEASE ; DISTINCT ; GENE-EXPRESSION ; MESSENGER-RNA ; alternative splicing ; WNT ; BRAIN-TUMORS ; medulloblastoma ; molecular diagnostics ; SUBGROUPS ; pediatric cancer ; BIOLOGICAL NETWORKS ; SHH ; Molecular subgroup ; Group 3 ; Group 4 ; BETA-2-CHIMAERIN ; Neuronal development
    Abstract: Medulloblastoma comprises four distinct molecular variants: WNT, SHH, Group 3, and Group 4. We analyzed alternative splicing usage in 14 normal cerebellar samples and 103 medulloblastomas of known subgroup. Medulloblastoma samples have a statistically significant increase in alternative splicing as compared to normal fetal cerebella (2.3-times; P 〈 6.47E-8). Splicing patterns are distinct and specific between molecular subgroups. Unsupervised hierarchical clustering of alternative splicing events accurately assigns medulloblastomas to their correct subgroup. Subgroup-specific splicing and alternative promoter usage was most prevalent in Group 3 (19.4%) and SHH (16.2%) medulloblastomas, while observed less frequently in WNT (3.2%), and Group 4 (9.3%) tumors. Functional annotation of alternatively spliced genes reveals overrepresentation of genes important for neuronal development. Alternative splicing events in medulloblastoma may be regulated in part by the correlative expression of antisense transcripts, suggesting a possible mechanism affecting subgroup-specific alternative splicing. Our results identify additional candidate markers for medulloblastoma subgroup affiliation, further support the existence of distinct subgroups of the disease, and demonstrate an additional level of transcriptional heterogeneity between medulloblastoma subgroups.
    Type of Publication: Journal article published
    PubMed ID: 22358458
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    Keywords: EXPRESSION ; tumor ; DISTINCT ; GENE-EXPRESSION ; TUMORS ; FEATURES ; clinical trials ; medulloblastoma ; MOLECULAR CLASSIFICATION ; SUBGROUPS ; MYC ; Molecular subgroup ; NanoString
    Abstract: The diagnosis of medulloblastoma likely encompasses several distinct entities, with recent evidence for the existence of at least four unique molecular subgroups that exhibit distinct genetic, transcriptional, demographic, and clinical features. Assignment of molecular subgroup through routine profiling of high-quality RNA on expression microarrays is likely impractical in the clinical setting. The planning and execution of medulloblastoma clinical trials that stratify by subgroup, or which are targeted to a specific subgroup requires technologies that can be economically, rapidly, reliably, and reproducibly applied to formalin-fixed paraffin embedded (FFPE) specimens. In the current study, we have developed an assay that accurately measures the expression level of 22 medulloblastoma subgroup-specific signature genes (CodeSet) using nanoString nCounter Technology. Comparison of the nanoString assay with Affymetrix expression array data on a training series of 101 medulloblastomas of known subgroup demonstrated a high concordance (Pearson correlation r = 0.86). The assay was validated on a second set of 130 non-overlapping medulloblastomas of known subgroup, correctly assigning 98% (127/130) of tumors to the appropriate subgroup. Reproducibility was demonstrated by repeating the assay in three independent laboratories in Canada, the United States, and Switzerland. Finally, the nanoString assay could confidently predict subgroup in 88% of recent FFPE cases, of which 100% had accurate subgroup assignment. We present an assay based on nanoString technology that is capable of rapidly, reliably, and reproducibly assigning clinical FFPE medulloblastoma samples to their molecular subgroup, and which is highly suited for future medulloblastoma clinical trials.
    Type of Publication: Journal article published
    PubMed ID: 22057785
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    Keywords: POOR-PROGNOSIS ; BRAIN-TUMORS ; CHILDHOOD MEDULLOBLASTOMA ; RISK STRATIFICATION ; outcome prediction ; TP53 MUTATIONS ; PATHWAY ACTIVATION ; MOLECULAR SUBGROUPS ; NEUROTROPHIN RECEPTOR TRKC ; MYCN AMPLIFICATION
    Abstract: Purpose Medulloblastoma comprises four distinct molecular subgroups: WNT, SHH, Group 3, and Group 4. Current medulloblastoma protocols stratify patients based on clinical features: patient age, metastatic stage, extent of resection, and histologic variant. Stark prognostic and genetic differences among the four subgroups suggest that subgroup-specific molecular biomarkers could improve patient prognostication. Patients and Methods Molecular biomarkers were identified from a discovery set of 673 medulloblastomas from 43 cities around the world. Combined risk stratification models were designed based on clinical and cytogenetic biomarkers identified by multivariable Cox proportional hazards analyses. Identified biomarkers were tested using fluorescent in situ hybridization (FISH) on a nonoverlapping medulloblastoma tissue microarray (n = 453), with subsequent validation of the risk stratification models. Results Subgroup information improves the predictive accuracy of a multivariable survival model compared with clinical biomarkers alone. Most previously published cytogenetic biomarkers are only prognostic within a single medulloblastoma subgroup. Profiling six FISH biomarkers (GLI2, MYC, chromosome 11 [chr11], chr14, 17p, and 17q) on formalin-fixed paraffin-embedded tissues, we can reliably and reproducibly identify very low-risk and very high-risk patients within SHH, Group 3, and Group 4 medulloblastomas. Conclusion Combining subgroup and cytogenetic biomarkers with established clinical biomarkers substantially improves patient prognostication, even in the context of heterogeneous clinical therapies. The prognostic significance of most molecular biomarkers is restricted to a specific subgroup. We have identified a small panel of cytogenetic biomarkers that reliably identifies very high-risk and very low-risk groups of patients, making it an excellent tool for selecting patients for therapy intensification and therapy de-escalation in future clinical trials.
    Type of Publication: Journal article published
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    Keywords: MODEL ; chemotherapy ; CHILDREN ; SUBTYPES ; GLIOBLASTOMA ; INTRATUMORAL HETEROGENEITY ; RISK MEDULLOBLASTOMA
    Abstract: Medulloblastoma comprises four distinct molecular variants with distinct genetics, transcriptomes, and outcomes. Subgroup affiliation has been previously shown to remain stable at the time of recurrence, which likely reflects their distinct cells of origin. However, a therapeutically relevant question that remains unanswered is subgroup stability in the metastatic compartment. We assembled a cohort of 12-paired primary-metastatic tumors collected in the MAGIC consortium, and established their molecular subgroup affiliation by performing integrative gene expression and DNA methylation analysis. Frozen tissues were collected and profiled using Affymetrix gene expression arrays and Illumina methylation arrays. Class prediction and hierarchical clustering were performed using existing published datasets. Our molecular analysis, using consensus integrative genomic data, establishes the unequivocal maintenance of molecular subgroup affiliation in metastatic medulloblastoma. We further validated these findings by interrogating a non-overlapping cohort of 19 pairs of primary-metastatic tumors from the Burdenko Neurosurgical Institute using an orthogonal technique of immunohistochemical staining. This investigation represents the largest reported primary-metastatic paired cohort profiled to date and provides a unique opportunity to evaluate subgroup-specific molecular aberrations within the metastatic compartment. Our findings further support the hypothesis that medulloblastoma subgroups arise from distinct cells of origin, which are carried forward from ontogeny to oncology.
    Type of Publication: Journal article published
    PubMed ID: 25689980
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...