MiR-218 sensitizes glioma cells to apoptosis and inhibits tumorigenicity by regulating ECOP-mediated suppression of NF-κB activity

Malignant gliomas are the most common and deadly primary brain tumors in adults. Increasing evidence has indicated that microRNAs (miRNAs) have an influence on the regulation of apoptotic cell signaling. Downregulation of miRNA 218 (miR-218) has been indicated in human glioma specimens. Here, we investigate the function of miR-218 in apoptosis and tumor growth of glioma cells. The expression of miR-218 was detected by real-time quantitative reverse transcriptase PCR. The effects of miR-218 on glioma cell proliferation and tumorigenicity were investigated by in vitro clonogenicity and in vivo xenograft assay. Apoptosis was evaluated by flow cytometric analysis and assay by terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling. The downstream targets of miR-218 were identified by bioinformatics analysis and further validated by Western blot and luciferase reporter assay. Overexpression of miR-218 induces glioma cell apoptosis and inhibits glioma cell viability, proliferation, and tumorigenicity. Epidermal growth factor receptorcoamplified and overexpressed protein (ECOP) was identified as a functional downstream target of miR-218, which can regulate transcriptional activity of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-B) and associated with apoptotic response. Ectopic expression of ECOP rescued the glioma cells from miR-218induced apoptosis and increased NF-B activity. These results suggest that miR-218 sensitizes glioma cells to apoptosis by regulating ECOP-mediated suppression of NF-B activity, which may provide novel opportunities for glioma therapy.