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Genomic Aberrations in Paediatric Gliomas and Embryonal Tumours

ABSTRACT: The pathogenesis of paediatric central nervous system tumours is still poorly understood. In an attempt to increase the knowledge of the genetic mechanisms underlying these tumours, we performed genome-wide screening of 17 paediatric gliomas and embryonal tumours using a combination of G-band karyotyping and array comparative genomic hybridisation (aCGH). G-banding revealed abnormal karyotypes in 56% of tumour samples (9 of 16; one failed in culture), whereas aCGH analysis found copy number aberrations in all 13 tumours that could be examined. Pilocytic astrocytomas (n=3) showed normal karyotypes or simple non-recurrent translocations by karyotyping, but revealed the now well-established recurrent gain of 7q34 by aCGH. Our series included one anaplastic oligoastrocytoma, tumours that have not previously been characterised genomically in children, and an anaplastic neuroepithelial tumour (probably an oligoastrocytoma); both tumours showed losses of chromosomes 14 by G-banding as well as structural aberrations of the long arm of chromosome 6, and loss of 14q, 17p, and 22q by aCGH. Three supratentorial primitive neuroectodermal tumours (n=5) showed aberrant karyotypes; two near-diploid with mainly structural changes and one near-triploid with several trisomies including gains of one copy of chromosomes 1, 2, and 7. aCGH confirmed these findings and revealed additional recurrent gains of 1q21-44, 3p21, and 3q29. We also describe cytogenetically for the first time a cribriform neuroepithelial tumour, a recently identified variant of atypical teratoid/rhabdoid tumour with a favourable prognosis, which showed loss of 1p33, 4q13.2, 10p12.31, 10q11.22, and 22q by aCGH.

ORGANISM(S): Homo sapiens

PROVIDER: GSE27671 | GEO | 2011/07/01

SECONDARY ACCESSION(S): PRJNA138183

REPOSITORIES: GEO

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Project description:Recurrent non-medullary thyroid carcinoma (NMTC) is a rare disease. We initially characterized 27 recurrent NMTC: 13 papillary thyroid cancers (PTC), 10 oncocytic follicular carcinomas (FTC-OV), and 4 non-oncocytic follicular carcinomas (FTC). A validation cohort composed of benign and malignant (both recurrent and non-recurrent) thyroid tumours was subsequently analysed (n = 20). Methods Data from genome-wide SNP arrays and flow cytometry were combined to determine the chromosomal dosage (allelic state) in these tumours, including mutation analysis of components of PIK3CA/AKT and MAPK pathways. Results All FTC-OVs showed a very distinct pattern of genomic alterations. Ten out of 10 FTC-OV cases showed near-haploidisation with or without subsequent genome endoreduplication. Near-haploidisation was seen in 5/10 as extensive chromosome-wide monosomy (allelic state [A]) with near-haploid DNA indices and retention of especially chromosome 7 (seen as a heterozygous allelic state [AB]). In the remaining 5/10 chromosomal allelic states AA with near diploid DNA indices were seen with allelic state AABB of chromosome 7, suggesting endoreduplication after preceding haploidisation. The latter was supported by the presence of both near-haploid and endoreduplicated tumour fractions in some of the cases. Results were confirmed using FISH analysis. Relatively to FTC-OV limited numbers of genomic alterations were identified in other types of recurrent NMTC studied, except for chromosome 22q which showed alterations in 6 of 13 PTCs. Only two HRAS, but no mutations of EGFR or BRAF were found in FTC-OV. The validation cohort showed two additional tumours with the distinct pattern of genomic alterations (both with oncocytic features and recurrent). Conclusions We demonstrate that recurrent FTC-OV is frequently characterised by genome-wide DNA haploidisation, heterozygous retention of chromosome 7, and endoreduplication of a near-haploid genome. Whether normal gene dosage on especially chromosome 7 (containing EGFR, BRAF, cMET) is crucial for FTC-OV tumour survival is an important topic for future research. 28 thyroid tumors from 27 patients were profiled by SNP array. Comparisons between different types were made.

Project description:Background: The high incidence of recurrence and unpredictable clinical outcome for paediatric ependymoma reflect the imprecision of current therapeutic staging and need for novel risk stratification markers. Gain of chromosome 1q has been reported as a frequent aberration and correlate of adverse outcome in ependymoma. We therefore evaluated a prognostic role for 1q25 gain across three age-defined European clinical trial cohorts of paediatric intracranial ependymoma. Methods: The frequency of 1q gain in paediatric ependymoma was assessed across 51 tumours (42 primary, 9 recurrent) using Affymetrix® 500K SNP arrays. Gain of 1q25 was evaluated by interphase FISH (iFISH) across 189 primary intracranial ependymomas from children treated on the CCLG/SIOP CNS9204 (n = 60) and BBSFOP (n = 65) adjuvant chemotherapy trials, or with primary post-operative radiotherapy (SIOP CNS9904/RT group, n = 64). Results were correlated with clinical, histological and survival data. Findings: Gain of 1q was the most frequent imbalance in primary (7/42, 17 %) and recurrent ependymomas (3/9, 33 %). Gain of 1q25 was the strongest independent predictor of tumour progression in both CNS9204 (HR 3·36, p = 0·0009) and BBSFOP (HR 4·10, p = 0·0009) trial cohorts. In contrast, 1q25 gain was not prognostic for the older CNS9904/RT only group (PFS: p = 0·37, OS: p = 0·95). Clinical variables implicated in adverse outcome amongst cohorts included incomplete tumour resection and posterior fossa location. Interpretation: This is the first study to prospectively identify then validate a prognostic genomic marker for childhood ependymoma across independent prospective trial groups. 1q25 gain predicts progression in primary chemotherapy cohorts but not those treated by post-operative radiotherapy. We propose 1q25 gain is incorporated as an adverse marker into future European chemotherapeutic clinical trial design. Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from flash frozen tumour specimens and patient-matched peripheral blood Copy number analysis of Affymetrix 500K SNP arrays was performed for DNA from 51 ependymomas and 40 constitutional DNA samples. Analysing broad genomic aberrations in 51 paediatric ependymomas, looking particularly at 1q gain.

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Genomic Aberrations in Paediatric Gliomas and Embryonal Tumours

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