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In order to investigate pathways that may influence on tumour development in meningiomas, we performed high throughput microarray analysis of the RNA expression and DNA copy number of 22 WHO grade I and five WHO grade II meningiomas. Since meningiomas derive from arachnoid cap cells, we used samples from four patients operated for arachnoid cysts as control tissue.The expression of the tumour suppressor gene WW containing oxidoreductase (WWOX) was down-regulated, and the thymidylate synthase (TYMS) oncogene was up-regulated in all meningiomas as compared to arachnoid cysts. Unsupervised RNA cluster analysis showed that fibrous meningiomas gathered in two clusters, and thus were more homogeneous than the other meningiomas. The other histological subgroups could not be linked to any uniform gene expression signatures. Rearrangements were most abundant on chromosomes 1 and 22, but were identified on all except chromosome 16. The fibrous and mixed meningiomas generally had chromosomal deletions. Duplications were more frequent in the meningothelial meningiomas. WHO grade II meningiomas had increased chromosomal instability.Decreased expression of the WWOX tumour suppressor gene and increased expression of the TYMS oncogene may be of importance for the development of human intracranial meningiomas. We have identified several genes (BMPR1B, DMD, RAMP1) with expression signatures specific for fibrous meningiomas. CGH analysis revealed distinct chromosomal patterns in relation to the histological subtypes of the meningiomas.