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Retinoblastoma-cyclin-dependent kinase pathway deregulation in vestibular schwannomas
John M Lasak1, D Bradley Welling, Elena M Akhmametyeva
1Department of Otolaryngology, The Ohio State University and Children's Hospital, Columbus, USA.
Objectives:
The purpose of the study was to identify genes of the retinoblastoma protein (pRb)-cyclin-dependent kinase (CDK) pathway that are deregulated in vestibular schwannomas when compared with normal vestibular nerve tissues.
Study Design:
Expression profiles in eight vestibular schwannomas (four sporadic tumors, one neurofibromatosis type 2 tumor, and three cystic tumors) and a paired normal vestibular nerve from one of the eight patients were chosen. Genes examined included the retinoblastoma susceptibility gene (Rb-1); cyclins D1, D2, A, and E; the CDK inhibitors p18, p19, and p27; CDK2 and CDK6; transcription factors E2F-4, E2F-5, and DP-1; and the neurofibromatosis type 2 gene.
Methods:
Total RNA samples were extracted from normal vestibular nerve and vestibular schwannoma tissues and used to generate radiolabeled complementary DNA (cDNA) samples. Labeled cDNA probes were then hybridized to cDNA microarray filters. The hybridization signal was captured and quantified. Differential gene expression profiles between the normal vestibular nerve and vestibular schwannoma were compared. Real-time polymerase chain reaction and immunohistochemistry were used to further confirm the cDNA microarray data.
Results:
Among genes in the pRb-CDK pathway, CDK2 was substantially underexpressed in seven of the eight vestibular schwannoma tumors examined. Quantitative RNA expression analysis using real-time polymerase chain reaction also showed consistent downregulation of CDK2 in the tumors. Anti-CDK2 antibody stained predominantly in the vestibular nerve and ganglion cells but only weakly in the vestibular schwannoma tissues.
Conclusions:
The pRb-CDK pathway was altered in all vestibular schwannoma tumors examined, with CDK2 significantly downregulated in seven of the eight tumors. Further investigation into the regulatory mechanisms governing CDK2 expression may lead to a better understanding of vestibular schwannoma tumorigenesis.
Insights
Vestibular schwannoma tumors show altered retinoblastoma protein (pRb)-cyclin-dependent kinase (CDK) pathways. Specifically, CDK2 is significantly downregulated in most tumors, suggesting a role in tumorigenesis.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Vestibular schwannomas are tumors affecting the cranial nerves.
- The retinoblastoma protein (pRb)-cyclin-dependent kinase (CDK) pathway regulates cell cycle progression.
- Dysregulation of this pathway is implicated in various cancers.
Purpose of the Study:
- To investigate the expression of pRb-CDK pathway genes in vestibular schwannomas.
- To compare gene expression profiles between tumors and normal vestibular nerve tissue.
- To identify specific deregulated genes in vestibular schwannoma development.
Main Methods:
- Gene expression profiling using cDNA microarrays on eight vestibular schwannomas and paired normal tissue.
- Analysis included retinoblastoma susceptibility gene (Rb-1), cyclins, CDK inhibitors, CDKs, and transcription factors.
- Validation of findings using real-time polymerase chain reaction and immunohistochemistry.
Main Results:
- Cyclin-dependent kinase 2 (CDK2) was substantially underexpressed in seven out of eight vestibular schwannoma tumors.
- Real-time polymerase chain reaction confirmed the downregulation of CDK2 mRNA expression.
- Immunohistochemistry showed significantly reduced CDK2 protein levels in tumor tissues compared to normal nerve.
Conclusions:
- The pRb-CDK pathway is altered in vestibular schwannomas, with significant CDK2 downregulation observed.
- Reduced CDK2 expression may play a crucial role in the tumorigenesis of vestibular schwannomas.
- Further research into CDK2 regulatory mechanisms could offer insights into tumor development.