👤 Reno Hrašćan

Postreplicative mismatch repair safeguards the stability of our genome. The defects in its functioning will give rise to microsatellite instability. In this study, 50 meningiomas were investigated for microsatellite instability. Two major mismatch repair genes, MLH1 and MSH2, were analyzed using microsatellite markers D1S1611 and BAT26 amplified by polymerase chain reaction and visualized by gel electrophoresis on high-resolution gels. Furthermore, genes DVL3 (D3S1262), AXIN1 (D16S3399), and CDH1 (D16S752) were also investigated for microsatellite instability. Our study revealed constant presence of microsatellite instability in meningioma patients when compared to their autologous blood DNA. Altogether 38% of meningiomas showed microsatellite instability at one microsatellite locus, 16% on two, and 13.3% on three loci. The percent of detected microsatellite instability for MSH2 gene was 14%, and for MLH1, it was 26%, for DVL3 22.9%, for AXIN1 17.8%, and for CDH1 8.3%. Since markers also allowed for the detection of loss of heterozygosity, gross deletions of MLH1 gene were found in 24% of meningiomas. Genetic changes between MLH1 and MSH2 were significantly positively correlated (p = 0.032). We also noted a positive correlation between genetic changes of MSH2 and DVL3 genes (p = 0.034). No significant associations were observed when MLH1 or MSH2 was tested against specific histopathological meningioma subtype or World Health Organization grade. However, genetic changes in DVL3 were strongly associated with anaplastic histology of meningioma (χ Show less

Tumor suppressor gene AXIN1 is an inhibitor of Wnt signaling pathway. It down-regulates the pathway's main signaling effector molecule, beta-catenin, in an AXIN-based destruction complex. In the present study we investigated the involvement of AXIN1 in intracranial meningioma. Loss of heterozygosity and microsatellite instability analyses were performed. The consequences of genetic changes on protein expression levels were studied in the same patients by immunohistochemistry. Allelic deletions of AXIN1 gene were found in 21.1% of meningiomas. Microsatellite instability was also observed in 5.3% of cases. Weak or lack of AXIN1 expression was found in 21.9% of meningiomas. We found strong statistical correlations between cytoplasmic localization of AXIN1 and its weak expression and also between the simultaneous cytoplasmic and nuclear localizations and moderate and strong expression levels (p<0.000). The findings on AXIN1 were compared to concomitant expression of APC, beta-catenin and E-cadherin in the same patients by Chi-Square tests and Pearson's correlations. Analysis revealed that AXIN1 genetic changes were significantly associated to lack of the expression of APC and presence of mutant APC proteins (p<0.018). Moderate and strong cytoplasmic and nuclear AXIN1 expressions were positively correlated to strong expression of E-cadherin (p<0.05). Our findings on genetic changes and expression levels of AXIN1 bring novel data on its involvement in meningeal brain tumors and reveal AXIN1's relation to specific Wnt molecules. Show less