Unknown,Transcriptomics,Genomics,Proteomics

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Clonal Selection Drives Genetic Divergence of Metastatic Medulloblastoma [Illumina Infinium HumanMethylation27 Beadchip v1.2]

ABSTRACT: Medulloblastoma, the most common malignant pediatric brain tumour, disseminates by shedding cells into the cerebrospinal fluid, which then re-implant to cover the surface of the brain and spinal cord. Metastases are a very poor prognostic sign at presentation and are usually lethal at recurrence. Mechanisms driving dissemination have been described in the bulk primary tumour, with the underlying assumption that primary tumour and metastases are biologically similar. Here we show that in both mouse and human medulloblastoma, multiple metastases from a single animal are extremely similar, but are genetically highly divergent from the primary tumour. Clonal genetic events in the metastases can be demonstrated in a restricted sub-clone 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 primary and metastatic medulloblastoma represents a major barrier to the development of effective targeted therapies. DNA methylation analysis of 15 pediatric medulloblastoma samples consisting of 6 primary-metastatic pairs and 4 normal cerebella samples profiled in Illumina Infinium HumanMethylation27 Beadchip v1.2

ORGANISM(S): Homo sapiens

SUBMITTER: Paul Northcott

PROVIDER: E-GEOD-34355 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Medulloblastoma is a highly aggressive pediatric brain tumor, in which expression of the pluripotency factor OCT4 has been recently correlated with poor patient survival. However, the contribution of OCT4 transcript variants to tumor aggressiveness is still poorly understood. In this study, we found that transcripts encoding OCT4A, but not OCT4B or OCT4B1, were significantly correlated with LIN28A expression, which encodes another well-known pluripotency factor. LIN28A was found to specifically bind OCT4A transcripts and interact with poly(A) binding protein and RNA helicase A in polysomal fractions of medulloblastoma cells, favoring increased OCT4A protein levels in these cells. Medulloblastoma cells stably overexpressing OCT4A displayed significantly enhanced clonogenic activity, tumorsphere generation and invasion capability, as well as increased tumorigenicity. In an orthotopic metastatic model of medulloblastoma, OCT4A overexpressing cells generated more developed, aggressive and infiltrative tumors, with tumor-bearing mice attaining advanced metastatic disease and shorter survival rates. Pro-oncogenic effects of OCT4A were found to be expression-level dependent and accompanied by distinct subchromosomal aberrations and differential expression of newly discovered, still poorly characterized, non-coding RNAs. Altogether, our findings support the relevance of pluripotency-related factors in the aggravation of medulloblastoma traits classically associated with poor clinical outcome, and underscore the prognostic and therapeutic value of OCT4A in this challenging type of pediatric brain cancer. Total RNA of 2-3 clones of each cell line (Control and OCT4A overexpression) was extracted with the RNeasy Mini kit (Qiagen), following the manufacturerâs protocol. Gene expression profiling was carried out independently for each sample using Affymetrix GeneChipÂ® Human Gene 2.0 ST whole-transcript arrays (Affymetrix, Santa Clara, CA, USA). The quality control and normalization of data were processed by AffymetrixÂ® Expression Console Software (Affymetrix). Differentially expressed genes were identified with the One-Way ANOVA, with a p-value cutoff of 0.05, using Transcriptome Analysis Console v3.0 (Affymetrix).

Dataset Information

Clonal Selection Drives Genetic Divergence of Metastatic Medulloblastoma [Illumina Infinium HumanMethylation27 Beadchip v1.2]

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