The Effects And Mechanism Of MiR-26a On The Radiosensitivity Of Glioblastoma Multiforme

PURPOSE: to study the effects and mechanism of miR-26a onglioblastoma multiforme (GBM) radiosensitivity; to investigate the potentialsignificance and afford more evidence for the individual therapy of GBMpatients.METHODS: to check the miR-26a expression level of U251, A172,T98g cell lines using Real-time PCR; construct stable miR-26aoverexpression and knockdown GBM cell lines; Flow cytometry techniqueswere used to investigate the cell cycle of miR-26a overexpression GBM cells;BrdU assays were performed to detect the effect of miR-26a on the GBM cellproliferation; the effects of miR-26a on the cell apoptosis were checked byFlow cytometry after radiation; the impact of miR-26a on DNA repair ofGBM cells were investigated by the γH2AX foci assay and the comet assay;using miRanda, we predicted the theoretic targets of miR-26a, and then verified by the luciferase assay; using Western Blot, the expression of ATM,p-CHK2and P53were checked after changing the miR-26a expression level;orthotopic glioma model were built; evaluating the tumor volume usingmagnetic resonance imaging, and then the survival analysis was taken todetermine the effect of miR-26a on radiosensitivity in vivo.RESULTS: the miR-26a expression level were consistent with theradiosensitivity in U251, A172and T98g GBM cell lines; compared with thecontrol group cells, more clones contained in the miR-26a knockdown U87and U251cells (P<0.05), however, the fewer clones in the miR-26aoverexpression U87and U251cells (P<0.05); compared with the controlgroup cells, the miR-26a overexpression U87cells have shorter S phase andstronger cell proliferation ability (P<0.05), and more apoptosis rate afterradiation (P<0.001); there were fewerγH2AX foci numbers and shorterOTMs in the miR-26a knockdown U87cells than the control group cells(P<0.05), however, the miR-26a overexpresson U87cells played the oppositeside (P<0.05); miR-26a could directly target ATM, and downregulate theexpression of its downstream factors p-CHK2and P53; in vivo, afterradiation, the miR-26a overexpression group of mice had significantlysmaller tumors and longer survival time than the control group (P<0.05).CONCLUSION: miR-26a could directly target ATM, and then decrease the DNA repair ability and ultimately enhance the radiosensitivity of GBMcells.