Article
Quantitative analysis of IDH1 mut expression level in low-grade glioma and secondary high-grade glioma by RT-PCR and Western Blot analysis
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Published: | May 13, 2014 |
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Objective: IDH1 mutations are frequent mutations in low-grade glioma (LGG) and secondary high-grade glioma (HGG). These mutations result from heterozygous missense point mutations that mainly affect codon 132. In gliomagenesis the IDH1 mutation is an early event and is associated with a better prognosis. However, its influence on gliomagenesis remains yet elusive. Recently, measuring the IDH1 mut level by quantitative real time PCR was introduced as an alternative method to immunohistochemistry (IHC) and gene sequencing. In this study we investigated the expression level of mutated IDH1 in LGG and secondary HGG.
Method: 113 tumor samples derived from 84 patients with diagnosis of WHO II grade glioma (n=21), grade III glioma (n=22), secondary GBM (sGBM; n=22) and primary glioblastoma (n=10) as well as control tissue (n=9) were analyzed for IDH1 mut and wt expression by RT-PCR. Additionally, 19 samples of LGG and their consecutive HGG were analyzed at different timepoints of disease. Corresponding IDH1 mut protein expression was measured by semiquantitative Western Blot analysis.
Results: IDH1 mut expression is upregulated in sGBM (mean±SEM: 3.52±0.55) compared to lower grade glioma (II°=1.54±0.22; III°=1.67±0.23). By contrast, IDH1 wt expression is upregulated in all glioma grades compared to control brain tissue, however, without differences between glioma grades. Western Blot analysis showed a high concordance to both, sequencing and RT-PCR results in qualitative analysis of IDH1 mut status (specificity 100% and sensitivity 100%). Moreover, semiquantitative protein expression analysis also showed higher expression levels of mutated IDH1 in sGBM.
Conclusions: In our study, Western Blot analysis was found to be a highly efficient method in detecting IDH1 mut in glioma samples. Moreover, we found an increase of IDH1 mut gene expression in sGBM compared to lower grade glioma indicating a pivotal role of IDH1 mut in glioma progression. Thus, IDH1 mut level might be a potential biomarker for disease progression.