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CaArray_golub-00460: Prediction of central nervous system embryonal tumour outcome based on gene expression

ABSTRACT: Embryonal tumours of the central nervous system (CNS) represent a heterogeneous group of tumours about which little is known biologically, and whose diagnosis, on the basis of morphologic appearance alone, is controversial. Medulloblastomas, for example, are the most common malignant brain tumour of childhood, but their pathogenesis is unknown, their relationship to other embryonal CNS tumours is debated, and patients' response to therapy is difficult to predict. We approached these problems by developing a classification system based on DNA microarray gene expression data derived from 99 patient samples. Here we demonstrate that medulloblastomas are molecularly distinct from other brain tumours including primitive neuroectodermal tumours (PNETs), atypical teratoid/rhabdoid tumours (AT/RTs) and malignant gliomas. Previously unrecognized evidence supporting the derivation of medulloblastomas from cerebellar granule cells through activation of the Sonic Hedgehog (SHH) pathway was also revealed. We show further that the clinical outcome of children with medulloblastomas is highly predictable on the basis of the gene expression profiles of their tumours at diagnosis.

ORGANISM(S): Homo sapiens

PROVIDER: GSE68956 | GEO | 2015/05/16

SECONDARY ACCESSION(S): PRJNA284157

REPOSITORIES: GEO

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Project description:Pediatric embryonal brain tumor (PEBT), which includes medulloblastoma (MB), primitive neuroectodermal tumor (PNET) and atypical teratoid/rhabdoid tumor (AT/RT), is the second most prevalent pediatric tumor type among brain tumors of childhood. AT/RT is highly malignant and is often misdiagnosed as MB and PNET. Distinguishing AT/RT from PNET/MB is of clinical significance since the survival rate of AT/RT patients is much lower. The diagnosis of AT/RT relies primarily on the morphologic assessment and immunohistochemistry (IHC) staining on a few known markers such as the lack of INI1 protein expression. However, in our clinical practice we observed several AT/RT-like tumors, which fulfilled histopathologic and all other biomarker criteria for AT/RT diagnosis, still showed retained INI1 immunoreactivity. Recent studies also reported retained INI1 immunoreactivity among certain diagnosed AT/RTs. It is therefore necessary to re-evaluate INI1(+), AT/RT-like cases. Sanger sequencing, array CGH and mRNA microarray analyses were performed on PEBT samples for studying their genomics landscapes. AT/RT and INI(+) AT/RT-like patients had similar survival rate, and global array CGH analysis and INI1 gene sequencing showed there is no differential chromosomal aberration marker between INI1(-) AT/RT and INI(+) AT/RT-like cases. We did not misdiagnose MB or PNET as AT/RT-like cases since transcriptome profiling revealed that not only AT/RT and INI(+) AT/RT-like cases expressed distinct mRNA and microRNA profiles, and their gene expression patterns were different from those of MBs and PNETs. AT/RTs shared the closest transcriptome profile to embryonic stem cells, INI1(+) AT/RT-like tumors were more similar to somatic neural stem cell, while MBs were closer to fetal brain. Novel biomarkers were identified to distinguish INI1(-) AT/RTs, INI1(+) AT/RT-like cases and MBs. Our studies disclosed a novel INI1(+) ATRT-like subtype among Taiwanese pediatric cases. New diagnostic biomarkers, as well as new therapeutic tactics, can be developed according to the transcriptome information unveiled in this work. 2 AT/RT-like cases and 7 AT/RT cases are subjected to transcriptome analysis.

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CaArray_golub-00460: Prediction of central nervous system embryonal tumour outcome based on gene expression

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