MiR-136 modulates glioma cell sensitivity to temozolomide by targeting astrocyte elevated gene-1

BACKGROUND Recent studies have linked chemotherapy resistance to the altered expression of microRNAs (miRNAs). Thus, miRNA-based approaches to modulating sensitivity to temozolomide (TMZ) may overcome chemoresistance. The aim of the present study was to investigate whether miR-136 could modulates glioma cell sensitivity to TMZ. METHODS The proliferation of glioma U251 cell line was evaluated by MTT assay. The expression of astrocyte elevated gene-1 (AEG-1)was detected by real‑time polymerase chain reaction (RT-PCR)and Western blot. The luciferase reporter gene was used to test whether AEG-1 was the target of the miR-136. RESULTS The MTT assay showed that U251 cells with miR-136 overexpression were significantly more sensitive to the therapy of TMZ than control cells. Luciferase assays revealed that miR-136 directly targeted the 3'UTR of AEG-1. qRT-PCR and western blotting analysis found that AEG-1 expression at the mRNA and protein levels decreased in the miR-136 mimic-treatment group relative to control group. Downregulation of AEG-1 expression by siRNAs, U251 cells became more sensitive to the therapy of TMZ. In addition, the enhanced growth-inhibitory effect by the miR-136 mimics transfection was enhanced after the addition of AEG-1 siRNA. CONCLUSIONS The present study provides the first evidence that miR-136 plays a key role in TMZ resistance by targeting the AEG-1 protein in glioma cell line, suggesting that miR-136 can be used to predict a patient's response to TMZ therapy as well as serve as a novel potential maker for glioma therapy. VIRTUAL SLIDES The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_173.