Ionizing radiation-inducible miR-30e promotes glioma cell invasion through EGFR stabilization by directly targeting CBL-B

MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression at the transcriptional and post-transcriptional levels. Here we show that miR-30e, which was previously identified as an ionizing radiation-inducible miRNA, enhances cellular invasion by promoting secretion of the matrix metalloproteinase MMP-2. The enhancement of cellular invasion by miR-30e involved up-regulation of the epidermal growth factor receptor (EGFR) and subsequent activation of its downstream signaling mediators, AKT and extracellular signal-regulated kinase. EGFR up-regulation by miR-30e occurred due to stabilization of the EGFR protein. The E3 ubiquitin ligase casitas B-lineage lymphomaB (CBL-B) was down-regulated by miR-30e, and this led to increased EGFR abundance. A 3 UTR reporter assay confirmed that CBL-B is a direct target of miR-30e. Knocking down CBL-B expression phenocopied the effects of miR-30e, whereas ectopic expression of CBL-B suppressed miR-30e-induced EGFR up-regulation and invasion. Collectively, our results suggest that targeting miR-30e may limit the invasiveness induced during glioma radiotherapy.