Die Auswirkung der IDH1 Regulation durch die miRNA-181a2 auf den Krankheitverlauf des Glioblastoms

Background Glioblastoma multiforme is the most frequent malignant brain tumor in adults being marked with a very poor prognosis. Therapy concept implies concomitant radio-chemotherapy and facultative implantation of carmustine-eluted wafer. Current literature suggests microRNA 26a expression in glioblastoma to interact with alkylating chemotherapy. Subsequently, the aim of this study was to investigate the correlation of miRNA-26a expression and carmustine wafer implantation and its potential usefulness as a predictive marker for therapy response. Methods In total, 229 patients with glioblastoma multiforme were included into the final analysis. Of them, 80 cases were recruited from the Saarland University Medical Center for a retrospective matched-pair analysis stratified after therapy regime: One group (carmustine wafer group; n=40) received concomitant radio-chemotherapy with carmustine wafer implantation. The other group (control group; n=40) only received concomitant radio-chemotherapy. The results were confirmed by comparing them with an independent dataset of 149 patients from the TCGA database. All tumor specimens were evaluated for miRNA-26a expression, MGMT promoter methylation, and IDH1 R132H mutation status, and the results were correlated with the clinical data. Results Twenty-three patients in the carmustine wafer group showed low expression of miRNA-26a, while 17 patients showed a high expression. In the control group, 28 patients showed low expression, while 12 patients showed a high expression. The patients with high miRNA-26a expression in the carmustine wafer group were characterized by a significantly longer overall (hazard ratio [HR] 2.750 [95% CI 1.352–5.593]; p=0.004) and progression-free survival (HR 3.091 [95% CI 1.436–6.657]; p=0.003) than patients with low miRNA-26a expression. The 17 patients in the carmustine wafer group with high miRNA-26a expression showed a significantly longer progression-free survival (p=0.013) and overall survival (p=0.007) compared with the control group. There were no such correlations identified within the control group. TCGA datasets supported these findings. Conclusions MiRNA-26a expression turned out to be a promising predictor of therapy response and clinical outcome in glioblastoma patients treated with carmustine wafer implantation. For evaluation of the role of miRNA-26a in a combined therapy setting, further studies are needed in order to translate general findings to the patient’s individual situation.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.Zusammenfassung Das Glioblastom ist der häufigste maligne Hirntumor. Die Prognose des Glioblastoms ist im Allgemeinen sehr schlecht, da unter anderem keine Therapieansätze zur Heilung existieren. Ohne Therapie liegt die mittlere Überlebenszeit bei ca. zwei Monaten. Die Standardtherapie umfasst die chirurgische Resektion des Tumors mit einer anschließenden Bestrahlung und einer adjuvanten Chemotherapie. Unter dieser Therapie liegt die mittlere Überlebenszeit bei ca. 14 Monaten. Eine entscheidende Rolle in der neuropathologischen Diagnostik des Glioblastoms stellen die molekularen Parameter dar. Die Isocitratdehydrogenase 1 ist einer der prognostisch relevantesten Marker des Glioblastoms. Patienten mit Mutationen in der Isocitratdehydrogenase 1 weisen eine längere Überlebensdauer als Patienten ohne Mutation (Isocitratdehydrogenase 1 Wildtyp) auf. MiRNAs sind kurzkettige Ribonukleinsäure Fragmente mit bis zu 23 Nukleotiden. Sie regulieren die Genexpression durch Modifikation der Translation. Es konnte gezeigt werden, dass die miRNA-181a2 im Fettgewebe die Expression der Isocitratdehydrogenase 1 reguliert. Im Hinblick auf diese Publikation stellt sich die Frage, inwieweit der Mutationsstatus der Isocitratdehydrogenase 1 die miRNA-181a2 Expression im Glioblastom beeinflusst. Weiterhin sollen die Fragen geklärt werden, inwieweit sich die miRNA-181a2 Expression auf den Verlauf einer Glioblastom-Erkrankung auswirkt und ob die miRNA-181a2 auch im Glioblastom regulatorisch auf die IDH1-Expression wirkt. Dazu werden in die vorliegende Studie 74 Patienten eingeschlossen, die neuropathologisch gesichert an einem primären Glioblastom erkrankt sind. Die Grundlage der Studie bilden Gewebeproben. Zunächst werden die Tumorproben mit Hilfe von immunhistochemischen Verfahren auf das Vorhandensein der Isocitratdehydrogenase 1 Mutation untersucht. Anschließend wird die Expression der miRNA-181a2 mittels quantitativer Realtime Polymerase-Chain-Reaction betreut. Unsere Ergebnisse zeigen bei Isocitratdehydrogenase 1 mutierten Tumoren eine signifikant höhere miRNA Expression als bei Isocitratdehydrogenase 1 Wildtyp- Tumoren. In Bezug auf die Protein-Expression des Isocitratdehydrogenase 1-Gens bei Wildtyp Tumoren kann eine inverse Korrelation zwischen der miRNA-181a2 und der Proteinexpression auf Trendniveau gezeigt werden. Des Weiteren zeigt sich, dass bei einem Glioblastom mit Isocitratdehydrogenase 1 Wildtyp eine niedrige Expression der miRNA-181a2 mit einer besseren Prognose einhergeht. Sowohl das Progression Free Survival als auch das Overall Survival sind bei einer niedrigen miRNA-181a2 Expression erhöht. In der Gruppe der Isocitratdehydrogenase 1 mutierten Tumoren hat die miRNA-181a2 Expression keinen Einfluss auf das Gesamtüberleben. Diese Aussage muss jedoch aufgrund der geringen Fallzahl mit Vorsicht interpretiert werden. Zusammenfassend konnte als Neuerung mit dieser Studie gezeigt werden, dass bei Isocitratdehydrogenase 1 Wildtyp eine niedrige miRNA-181a2 Expression mit einem längeren Überleben einhergeht. Diese Erkenntnis könnte zukünftig genutzt werden, um mit Hilfe von „liquid biopsies“ bereits zum Diagnosezeitpunkt eine Aussage bezüglich der Prognose treffen zu können. Des Weiteren könnte die miRNA-181a2 Achse genutzt werden, um mögliche Therapieoptionen zu evaluieren.Abstract Glioblastoma is the most common malignant brain tumor. The prognosis of glioblastoma is generally very poor because, among other things, there are no therapeutic approaches for healing. Without therapy, the median survival time is around two months. Standard therapy includes surgical resection of the tumor followed by radiation and adjuvant chemotherapy. The average survival time with this therapy is approximately 14 months. The molecular parameters play a decisive role in neuropathological diagnostics of glioblastoma. Isocitrate dehydrogenase 1 is one of the most relevant prognostic markers of glioblastoma. Patients with mutations in isocitrate dehydrogenase 1 have a longer survival than patients without mutation (isocitrate dehydrogenase 1 wild type). MiRNA´s are short-chain ribonucleic acid fragments with up to 23 nucleotides. They regulate gene expression through modification of translation. It could be shown that miRNA-181a2 regulates the expression of isocitrate dehydrogenase 1 in adipose tissue. With regard to this publication, the question arises to what extent the mutation status of isocitrate dehydrogenase 1 influences miRNA-181a2 expression in glioblastoma. Furthermore, the questions should be clarified, how the miRNA-181a2 expression affects the course of a glioblastoma disease and whether the miRNA-181a2 also has a regulatory effect on the IDH1 expression in glioblastoma. For this purpose, 74 patients are included in the present study who have neuropathological evidence of a primary glioblastoma. Tissue samples form the basis of the study. First, the tumor samples are examined for the presence of the isocitrate dehydrogenase 1 mutation using immunohistochemical methods. The expression of miRNA-181a2 is then monitored using quantitative real-time polymerase chain reaction. Our results show a significantly higher miRNA expression in isocitrate dehydrogenase 1 mutated tumors than in isocitrate dehydrogenase 1 wild-type tumors. With regard to the protein expression of the isocitrate dehydrogenase 1 gene in wild-type tumors, an inverse correlation between miRNA-181a2 and protein expression at trend level can be shown. Furthermore, it is shown that in a glioblastoma with isocitrate dehydrogenase 1 wild type, a low expression of the miRNA-181a2 is associated with a better prognosis. Both the progression free survival and the overall survival are increased with a low miRNA-181a2 expression. In the group of isocitrate dehydrogenase 1 mutated tumors, miRNA-181a2 expression has no influence on overall survival. However, due to the small number of cases, this statement must be interpreted with caution. In summary, as an innovation with this study it was shown that isocitrate dehydrogenase 1 wild-type low miRNA-181a2 expression goes hand in hand with longer survival. This knowledge could be used in the future to be able to make a statement regarding the prognosis at the time of diagnosis with the help of liquid biopsies. Furthermore, the miRNA-181a2 axis could be used to evaluate possible therapy options