Objective To investigate the effects of microRNA-15a-5p (miR-15a-5p) on the proliferation, invasion and migration of and its mechanism of sensitivity of glioma cells to temozolomide (TMZ).
Methods Glioma cell lines H4 and SHG-44, normal astrocytes HA1800 and TMZ-resistant H4 cells were selected. H4 cells were transfected with miR-NC or miR-15a-5p mimics and recorded as the miR-NC group and the miR-15a-5p group, respectively. The cells of miR-15a-5p group was further transfected with Vector or OE-RUNX1 plasmids and treated with 400 μmoL/L TMZ, and recorded as miR-15a-5p+Vector group, miR-15a-5p+RUNX1 group, TMZ+Vector group and TMZ+RUNX1 group. Additionally, the miR-NC and miR-15a-5p groups were treated with 400 μmoL/L TMZ, and recorded as TMZ+miR-NC group and TMZ+miR-15a-5p group, respectively. Untreated cells served as the Control group. Cell proliferation was assessed using the Methyl Thiazolyl Tetrazolium (MTT) assay. Invasion and migration were evaluated by Transwell assays. RUNX1 mRNA and miR-15a-5p expression levels were determined by quantitative real-time polymerase chain reaction (RT-PCR). RUNX1 protein expression was analyzed by Western blot. The binding sites between miR-15a-5p and RUNX1 were predicted using the TargetScan online database. The targeting relationship between miR-15a-5p and RUNX1 was validated by dual-luciferase reporter assays.
Results RUNX1 mRNA and its protein expression levels were significantly higher in H4 and SHG-44 cells compared to HA1800 cells, while miR-15a-5p expression was significantly lower in H4 and SHG-44 cells (P < 0.000 1). Compared with Control group, the expression level of miR-15a-5p in TMZ-resistant H4 cells was significantly lower (t=18.89, P < 0.000 1); compared with Control group, the expression level of RUNX1 mRNA and protein in TMZ-resistant H4 cells was significantly higher (t=34.11, 18.07, P < 0.000 1). Upregulation of miR-15a-5p and TMZ treatment both inhibited cell proliferation, invasion and migration, and the combination of miR-15a-5p upregulation and TMZ significantly enhanced these inhibitory effects. MiR-15a-5p negatively regulated RUNX1 expression. Overexpression of RUNX1 reversed the inhibitory effects of miR-15a-5p upregulation and TMZ on glioma cell proliferation, invasion, and migration.
Conclusion MiR-15a-5p negatively regulates RUNX1, thereby inhibiting the proliferation, invasion and migration of glioma cells and enhancing their sensitivity to TMZ.
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