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  • ACUTE LYMPHOBLASTIC-LEUKEMIA  (2)
  • DIFFERENTIATION  (2)
  • 1
    Keywords: CANCER ; EXPRESSION ; GENE ; DIFFERENTIATION ; VARIANTS ; DISCOVERY ; ALPHA ; ALIGNMENT ; ESTROGEN
    Abstract: Meningiomas are among the most frequent intracranial tumors. The secretory variant of meningioma is characterized by glandular differentiation, formation of intracellular lumina and pseudopsammoma bodies, expression of a distinct pattern of cytokeratins and clinically by pronounced perifocal brain edema. Here we describe whole-exome sequencing analysis of DNA from 16 secretory meningiomas and corresponding constitutional tissues. All secretory meningiomas invariably harbored a mutation in both KLF4 and TRAF7. Validation in an independent cohort of 14 secretory meningiomas by Sanger sequencing or derived cleaved amplified polymorphic sequence (dCAPS) assay detected the same pattern, with KLF4 mutations observed in a total of 30/30 and TRAF7 mutations in 29/30 of these tumors. All KLF4 mutations were identical, affected codon 409 and resulted in a lysine to glutamine exchange (K409Q). KLF4 mutations were not found in 89 non-secretory meningiomas, 267 other intracranial tumors including gliomas, glioneuronal tumors, pituitary adenomas and metastases, 59 peripheral nerve sheath tumors and 52 pancreatic tumors. TRAF7 mutations were restricted to the WD40 domains. While KLF4 mutations were exclusively seen in secretory meningiomas, TRAF7 mutations were also observed in 7/89 (8 %) of non-secretory meningiomas. KLF4 and TRAF7 mutations were mutually exclusive with NF2 mutations. In conclusion, our findings suggest an essential contribution of combined KLF4 K409Q and TRAF7 mutations in the genesis of secretory meningioma and demonstrate a role for TRAF7 alterations in other non-NF2 meningiomas.
    Type of Publication: Journal article published
    PubMed ID: 23404370
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  • 2
    Keywords: PROSTATE-CANCER ; ACUTE LYMPHOBLASTIC-LEUKEMIA ; SQUAMOUS-CELL CARCINOMA ; LUNG ADENOCARCINOMA ; ACUTE MYELOID-LEUKEMIA ; SOMATIC MUTATIONS ; GENETIC LANDSCAPE ; 21 BREAST CANCERS ; RECURRENT MUTATIONS ; FREQUENT MUTATION
    Abstract: All cancers are caused by somatic mutations; however, understanding of the biological processes generating these mutations is limited. The catalogue of somatic mutations from a cancer genome bears the signatures of the mutational processes that have been operative. Here we analysed 4,938,362 mutations from 7,042 cancers and extracted more than 20 distinct mutational signatures. Some are present in many cancer types, notably a signature attributed to the APOBEC family of cytidine deaminases, whereas others are confined to a single cancer class. Certain signatures are associated with age of the patient at cancer diagnosis, known mutagenic exposures or defects in DNA maintenance, but many are of cryptic origin. In addition to these genome-wide mutational signatures, hypermutation localized to small genomic regions, 'kataegis', is found in many cancer types. The results reveal the diversity of mutational processes underlying the development of cancer, with potential implications for understanding of cancer aetiology, prevention and therapy.
    Type of Publication: Journal article published
    PubMed ID: 23945592
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  • 3
    Keywords: EXPRESSION ; GENE ; DIFFERENTIATION ; IDENTIFICATION ; EMBRYONIC STEM-CELLS ; HYPERMETHYLATION ; SUPPRESSOR ; methylome ; CANCER GENOME ; CPG ISLAND SHORES
    Abstract: Epigenetic alterations, that is, disruption of DNA methylation and chromatin architecture, are now acknowledged as a universal feature of tumorigenesis. Medulloblastoma, a clinically challenging, malignant childhood brain tumour, is no exception. Despite much progress from recent genomics studies, with recurrent changes identified in each of the four distinct tumour subgroups (WNT-pathway-activated, SHH-pathway-activated, and the less-well-characterized Group 3 and Group 4), many cases still lack an obvious genetic driver. Here we present whole-genome bisulphite-sequencing data from thirty-four human and five murine tumours plus eight human and three murine normal controls, augmented with matched whole-genome, RNA and chromatin immunoprecipitation sequencing data. This comprehensive data set allowed us to decipher several features underlying the interplay between the genome, epigenome and transcriptome, and its effects on medulloblastoma pathophysiology. Most notable were highly prevalent regions of hypomethylation correlating with increased gene expression, extending tens of kilobases downstream of transcription start sites. Focal regions of low methylation linked to transcription-factor-binding sites shed light on differential transcriptional networks between subgroups, whereas increased methylation due to re-normalization of repressed chromatin in DNA methylation valleys was positively correlated with gene expression. Large, partially methylated domains affecting up to one-third of the genome showed increased mutation rates and gene silencing in a subgroup-specific fashion. Epigenetic alterations also affected novel medulloblastoma candidate genes (for example, LIN28B), resulting in alternative promoter usage and/or differential messenger RNA/microRNA expression. Analysis of mouse medulloblastoma and precursor-cell methylation demonstrated a somatic origin for many alterations. Our data provide insights into the epigenetic regulation of transcription and genome organization in medulloblastoma pathogenesis, which are probably also of importance in a wider developmental and disease context.
    Type of Publication: Journal article published
    PubMed ID: 24847876
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  • 4
    Keywords: COLORECTAL-CANCER ; ACUTE LYMPHOBLASTIC-LEUKEMIA ; STEM-CELLS ; medulloblastoma ; GLIOBLASTOMA ; GENE-EXPRESSION SIGNATURE ; DISTINCT SUBGROUPS ; ISLAND METHYLATOR PHENOTYPE ; DRIVER MUTATIONS ; GENOMIC COMPLEXITY
    Abstract: Ependymomas are common childhood brain tumours that occur throughout the nervous system, but are most common in the paediatric hindbrain. Current standard therapy comprises surgery and radiation, but not cytotoxic chemotherapy as it does not further increase survival. Whole-genome and whole-exome sequencing of 47 hindbrain ependymomas reveals an extremely low mutation rate, and zero significant recurrent somatic single nucleotide variants. Although devoid of recurrent single nucleotide variants and focal copy number aberrations, poor-prognosis hindbrain ependymomas exhibit a CpG island methylator phenotype. Transcriptional silencing driven by CpG methylation converges exclusively on targets of the Polycomb repressive complex 2 which represses expression of differentiation genes through trimethylation of H3K27. CpG island methylator phenotype-positive hindbrain ependymomas are responsive to clinical drugs that target either DNA or H3K27 methylation both in vitro and in vivo. We conclude that epigenetic modifiers are the first rational therapeutic candidates for this deadly malignancy, which is epigenetically deregulated but genetically bland.
    Type of Publication: Journal article published
    PubMed ID: 24553142
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