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Low-level microsatellite instability phenotype in sporadic glioblastoma multiforme
R Martinez1, H K Schackert, H Appelt
1Department of Neurosurgery, Klinikum Fulda, Academic Hospital University of Marburg, Pacelliallee 4, 36043 Fulda, Germany. voelter.martinez@t-online.de
Journal of Cancer Research and Clinical Oncology
|January 27, 2005
Summary
Microsatellite instability (MSI) occurs in 5.5% of glioblastoma multiforme (GBM) and may not be a major factor in its development. Further research is needed to understand the role of minor mismatch repair genes in GBM.
Area of Science:
- Oncology
- Genetics
- Molecular Biology
Background:
- Genetic instability is a key characteristic of glioblastoma multiforme (GBM).
- Microsatellite instability (MSI) is implicated in the tumorigenesis of various sporadic cancers.
Purpose of the Study:
- To investigate the prevalence and characteristics of microsatellite instability (MSI) in newly diagnosed glioblastomas (GBMs).
Main Methods:
- Analyzed MSI in 109 GBMs using 15 microsatellite markers.
- Performed immunohistochemistry for mismatch repair (MMR) proteins (hMLH1, hMSH2, hPMS2, hMSH6).
- Investigated hMLH1 sequence and promoter methylation, LOH, EGFR amplification, and p53/PTEN mutations in MSI-positive cases.
Main Results:
- MSI was detected in 5.5% of GBMs, with higher frequency in those with prior lower-grade astrocytoma (18.8%).
- One MSI-positive GBM showed aberrant hMLH1 and hPMS2 expression without hMLH1 inactivation.
- MSI-positive GBMs often presented with wild-type p53 and PTEN and no EGFR amplification, occurring across different molecular subtypes.
Conclusions:
- MSI in GBM may result from minor MMR gene inactivation rather than hMLH1/hMSH2 deficiency.
- MSI does not appear to be a primary driver in glioblastoma pathogenesis.
- MSI-positive GBMs exhibit specific molecular profiles, including wild-type p53/PTEN and absence of EGFR amplification.