ABSTRACT
BACKGROUND: miR-15b plays an important role in the initiation and development of tumors, based on which, we speculate that miR-15b may be involved in the migration and invasion of glioma stem cells (GSCs). However, there is no relevant report and the mechanism of action is also unclear. OBJECTIVE: To identify the effects of miR-15b on the migration and invasion of GSCs and the mechanisms involved in this process. METHODS: Quantitative PCR was performed to evaluate the expression of miR-15b in the gliomas tissues, normal brain tissues, GSCs and non-GSCs. After knockdown of ATP-binding cassette superfamily G member 2 (ABCG2) by ABCG2 specific siRNA, Transwell assay was performed to determine the effect of ABCG2 on GSCs migration and invasion. Additionally, the GSCs were transfected with miR-15b mimics or inhibitor to up-regulate or down-regulate the expression of miR-15b. At 48 hours after transfection, Transwell assay was used to detect the effect of miR-15b on GSCs migration and invasion; ELISA and gelatin zymography assays were performed to determine the matrix metalloproteinase-2/-9 (MMP-2/-9) expression and activity after treatment with miR-15b. CD133-positive or non-CD133-positive cells were directly injected subcutaneously into nude mice. Tumor formation was observed within 30 days after injection. RESULTS AND CONCLUSION: miR-15b was significantly down-regulated in gliomas tissues compared with normal brain tissues, which was negatively correlated with the stage of gliomas. In addition, miR-15b was significantly down-regulated in GSCs compared with non-GSCs. Up-regulation of miR-15b significantly reduced the migration and invasion ability of GSCs (P < 0.01), and down-regulation of miR-15b significantly enhanced the cell migration and invasion of GSCs (P < 0.01). By target prediction analysis, we obtained that ABCG2 was a potential target gene of miR-15b. Luciferase assay confirmed that miR-15b targeted ABCG2 directly, and migration and invasion of GSCs were dramatically reduced by ABCG2 siRNA (P < 0.01). ELISA results showed that up-regulation miR-15b significantly inhibited MMP-2/-9 expression. ELISA and gelatin zymography assay results showed that ABCG2 siRNA did not affect MMP-2/-9 expression, but significantly inhibited the activity of MMP-2/-9. In the in vivo tumor model, GSCs were more tumorigenic as compared with non-GSCs from the same tumor in vivo. To conclude, miR-15b regulates the migration and invasion of GSCs by targeting the ABCG2 signaling pathway, and up-regulation of miR-15b can suppress the migration and invasion of GSCs.