Regulation of mTOR by miR-107 to facilitate glioma cell apoptosis and to enhance cisplatin sensitivity.

OBJECTIVE

The aberrant increasing expression of mammalian target of rapamycin (mTOR) participates in tumor occurrence and drug resistance. It has been found elevation of mTOR expression but reducing miR-107 expression in glioma tissues. Thus, we investigated the regulatory role of miR-107 on mTOR expression as well as glioma cell proliferation, apoptosis and cisplatin (DDP) resistance.

PATIENTS AND METHODS

Dual luciferase reporter gene assay was applied to confirm targeted regulation between miR-107 and mTOR. Tumor tissues were collected from glioma patients, in parallel with normal tissues after brain contusion surgery. Expressions of miR-107, mTOR and p-mTOR were compared. DDP-resistant cell line U251/DPP was generated. U251/DPP cells were further treated with miR-107 mimic or si-mTOR to examine the change of miR-107, mTOR, p-mTOR and survivin levels. Flow cytometry was used to quantify the effect of DDP treatment on cell proliferation or apoptosis.

RESULTS

Bioinformatics analysis revealed complementary binding sites between miR-107 and 3'-UTR of mTOR mRNA. Dual luciferase assay confirmed targeted regulation between miR-107 and mTOR. Compared to control group, in glioma tissues, mTOR and p-mTOR expressions were significantly elevated, while the level of miR-107 expression was markedly decreased. Of note, U251/DDP cells presented weakened apoptosis compared to U251 cells, with high levels of mTOR, p-mTOR and survivin and reduction of miR-107 expression. However, the transfection of miR-107 mimic and/or si-mTOR remarkably suppressed expressions of mTOR, p-mTOR and survivin in U251/DPP cells, weakened cell proliferation and enhanced apoptosis.

CONCLUSIONS

We demonstrated that the level of miR-107 was correlated with DDP resistance in glioma cells. Over-expression of miR-107 decreased DPP resistance of glioma cells via inhibition of mTOR, which provides academic basis for the future anti-glioma therapy.