gms | German Medical Science

Objective: miRNAs are small, non-coding RNA segments that influence gene expression. To do this, they bind to corresponding mRNA segments and inhibit the subsequent translation of the proteins. It is currently assumed that about 30% of our genes are regulated by miRNAs. Dysregulated miRNAs can act as tumour promoters as well as tumour suppressors. The aim of this study was to verify let-7a,-7b and miRNA-92a as a signature for the detection of glioma recurrence by analysing their expression in glioma tissue.

Methods: Samples: Tissue was obtained during neurosurgery and shock frozen in liquid nitrogen. Only glioma patients (n=25) with two or more relapses were included in the study (tissue samples n=89). RT qPCR: Performed with miRCURY LNA SYBR Green PCR Kit (Qiagen). The primers of let-7a, let-7b and miRNA-92a were purchased from Qiagen. miRNA-151a was used as internal reference.

Results: The expression of let-7a shows a tendency of lower expression in first relapse compared to primary glioma. The expression level of let-7b was significantly lower in first relapse compared to primary glioma (p<0,005). miRNA-92a shows a tendency of lower expression in first recurrent compared to primary. In relation to tumour grade there’s a significant lower expression of let-7a and 7b with increasing tumour grade (p<0,0001). miR92a presents a significant higher expression in high-grade glioma than in low-grade glioma (p<0,01).

Conclusion: The results of this study suggest that let-7a and -7b acts tumour suppressive and miRNA-92a is oncogenic. Furthermore, let-7b is constantly expressed at a lower level in the first relapse compared to the primary tumour, regardless of tumour grade. To assess the role of let-7a and miRNA-92a as relapse markers, more comprehensive analyses of expression in first relapse and primary tumour tissue are required.