Background: Recently, miRNA-181a2 could be identified as a major regulator of IDH1 expression in fat tissue. The IDH1 gene, its mutation and expression have a major impact on overall survival in patients with glioblastoma. The presented study aimed to investigate the effect of miRNA-181a2 on IDH1 expression in glioblastoma and on the prognosis of patients suffering from, for example, a tumor. Methods: A total of 74 glioblastoma specimens were analyzed for the expression of miRNA-181a2, acquired as fold change, using qRT-PCR. IDH1 protein expression was estimated via mRNA quantification. Eight post mortal, non-glioma related brain tissue specimens served as the control group. The results were correlated with relevant demographic and clinical aspects of the cohort. A TCGA dataset was used as an independent reference. Results: MiRNA-181a2 was significantly downregulated in tumor samples compared to the control group (p < 0.001). In the glioblastoma cohort, 63/74 (85.1%) showed an IDH1 wild type, while 11/74 (14.9%) patients harbored an IDH 1 mutation. In patients with IDH1 wild type glioblastoma, low miRNA-181a2 expression correlated with a prolonged overall survival (p = 0.019), also verifiable in an independent TCGA dataset. This correlation could not be identified for patients with an IDH1 mutation. MiRNA-181a2 expression tended to correlate inversely with IDH1 protein expression (p = 0.06). Gross total resection of the tumor was an independent marker for a prolonged survival (p = 0.03). Conclusion: MiRNA-181a2 seems to be a promising prognostic marker of selective glioblastoma patients with IDH1 wild type characteristics. This effect may be mediated via direct regulation of IDH1 expression.

Objective: Epigenetic tumor characteristics are in focus for glioblastoma prognosis. This raises the question if these characteristics present with stable expression during the progression of the disease, and if potential temporal instability might influence their prognostic value. Methods: A total of 44 patients suffering from glioblastoma who were treated for their primary and relapse tumors were included in the study. Tumor specimens from the initial and recurrent tumor resection were subjected to evaluation of MGMT, p15, and p16 methylation statuses. MiRNA-21, -24, -26a, and -181d expression was evaluated as well. The stability of these epigenetic markers during the progression of the disease was correlated with further clinical data. A Cancer Genome Atlas (TCGA) dataset of 224 glioblastoma patients was used as an independent cohort to validate the results. Results: Instability was observed in all examined epigenetic markers. MGMT methylation changed in 30% of patients, p15 methylation changed in 35%, and p16 methylation changed in 37.5% of cases. MiRNA expression in corresponding initial and relapse tumor specimens varied considerably in general, individual cases presented with a stable expression. Patients with a decreased expression of miRNA-21 in their recurrence tumor showed significantly longer overall survival. These results are supported by the data from TCGA indicating similar results. Conclusions: Epigenetic characteristics may change during the course of glioblastoma disease. This may influence the prognostic value of derived molecular markers.