miR-126-3p sensitizes glioblastoma cells to temozolomide by inactivating Wnt/β-catenin signaling via targeting SOX2.

Objective: The acquired drug resistance has been regarded as a main barrier for the effective treatment of temozolomide (TMZ) in glioblastoma (GBM). MiR-126-3p is commonly down-regulated and exerts tumor-suppressive roles in kinds of human cancers, including GBM. This study was designed to investigate the functions and mechanisms of miR-126-3p in regulating TMZ resistance in GBM.

Methods: qRT-PCR analysis was used to measure the expressions of miR-126-3p and SOX2 mRNA in GBM tissues and cells. Cell viability, colony forming ability and apoptosis were detected to evaluate the effect of miR-126-3p or SOX2 on TMZ resistance. Luciferase reporter experiments were applied to identify the target genes of miR-126-3p. Western blot analysis was performed to determine the protein levels associated with Wnt/β-catenin signaling. TOP/FOP Flash assays were conducted to determine the effects of miR-126-3p or SOX2 on Wnt/β-catenin signaling.

Results: miR-126-3p expression was decreased in TMZ-resistant GBM tissues and cells. High levels of miR-126-3p enhanced TMZ sensitivity by inhibiting cell viability, reducing colony forming potential and inducing apoptosis. Additionally, SOX2 was identified as a downstream target of miR-126-3p. On the contrary, SOX2 overexpression conferred TMZ resistance of GBM cells. Moreover, miR-126-3p-mediated TMZ sensitivity was reversed following increased expression of SOX2. Furthermore, miR-126-3p-induced inactivation of Wnt/β-catenin signaling was greatly abrogated by SOX2 up-regulation.

Conclusions: MiR-126-3p sensitizes GBM cells to TMZ possibly by repressing SOX2 expression and blocking Wnt/β-catenin signaling. This study provides novel targets to overcome TMZ resistance in GBM chemotherapy.