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Chromosomal Instability and Phosphoinositide Pathway Gene Signatures in Glioblastoma Multiforme
1Lipid and Membrane Biology Group, Institute for Liver and Digestive Health, UCL, Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK. m.waugh@ucl.ac.uk.
Abstract:
Structural rearrangements of chromosome 10 are frequently observed in glioblastoma multiforme and over 80 % of tumour samples archived in the catalogue of somatic mutations in cancer database had gene copy number loss for PI4K2A which encodes phosphatidylinositol 4-kinase type IIalpha. PI4K2A loss of heterozygosity mirrored that of PTEN, another enzyme that regulates phosphoinositide levels and also PIK3AP1, MINPP1, INPP5A and INPP5F. These results indicated a reduction in copy number for a set of phosphoinositide signalling genes that co-localise to chromosome 10q. This analysis was extended to a panel of phosphoinositide pathway genes on other chromosomes and revealed a number of previously unreported associations with glioblastoma multiforme. Of particular note were highly penetrant copy number losses for a group of X-linked phosphoinositide phosphatase genes OCRL, MTM1 and MTMR8; copy number amplifications for the chromosome 19 genes PIP5K1C, AKT2 and PIK3R2, and also for the phospholipase C genes PLCB1, PLCB4 and PLCG1 on chromosome 20. These mutations are likely to affect signalling and trafficking functions dependent on the PI(4,5)P2, PI(3,4,5)P3 and PI(3,5)P2 lipids as well as the inositol phosphates IP3, IP5 and IP6. Analysis of flanking genes with functionally unrelated products indicated that chromosomal instability as opposed to a phosphoinositide-specific process underlay this pattern of copy number variation. This in silico study suggests that in glioblastoma multiforme, karyotypic changes have the potential to cause multiple abnormalities in sets of genes involved in phosphoinositide metabolism and this may be important for understanding drug resistance and phosphoinositide pathway redundancy in the advanced disease state.
Insights
Glioblastoma multiforme frequently shows chromosome 10 rearrangements, impacting phosphoinositide pathway genes. Chromosomal instability, not specific mutations, drives these copy number variations, potentially affecting drug resistance.
Area of Science:
- Genomics
- Cancer Biology
- Molecular Oncology
Background:
- Glioblastoma multiforme (GBM) frequently exhibits structural chromosomal rearrangements.
- Gene copy number alterations in phosphoinositide signaling pathways are implicated in GBM pathogenesis.
- Specific genes on chromosome 10, like PI4K2A, show frequent copy number loss in GBM.
Purpose of the Study:
- To investigate the association of phosphoinositide pathway gene copy number variations with glioblastoma multiforme.
- To identify specific genes and chromosomal locations affected by copy number alterations in GBM.
- To understand the underlying mechanisms driving these genetic changes in GBM.
Main Methods:
- In silico analysis of tumor sample data from the Catalogue of Somatic Mutations in Cancer database.
- Examination of gene copy number status for phosphoinositide pathway genes across multiple chromosomes.
- Analysis of flanking genes to differentiate between chromosomal instability and pathway-specific alterations.
Main Results:
- Frequent copy number losses were observed for phosphoinositide signaling genes on chromosome 10q, including PI4K2A, PTEN, PIK3AP1, MINPP1, INPP5A, and INPP5F.
- Significant copy number losses were found for X-linked phosphoinositide phosphatase genes (OCRL, MTM1, MTMR8).
- Copy number amplifications were identified for genes on chromosomes 19 (PIP5K1C, AKT2, PIK3R2) and 20 (PLCB1, PLCB4, PLCG1).
- Analysis suggested chromosomal instability as the primary driver of these copy number variations, rather than a phosphoinositide-specific process.
Conclusions:
- Karyotypic changes in GBM can lead to widespread abnormalities in genes regulating phosphoinositide metabolism.
- These genetic alterations may contribute to drug resistance and pathway redundancy in advanced GBM.
- Understanding these genomic changes is crucial for developing targeted therapies for glioblastoma.
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