Valproic Acid Promotes Human Glioma U87 Cells Apoptosis and Inhibits Glycogen Synthase Kinase-3β Through ERK/Akt Signaling
Background: Valproic acid (VPA), an established antiepileptic drug, was assessed for antitumor activity, including its effects on glioblastoma, but its role has not been determined. Methods: In the present study, we investigated VPA-induced apoptosis effects on human U87 cells by cell viability, lactate dehydrogenase (LDH) release, TUNEL/Hoechst staining and flow cytometric in vitro, then we further explored the underlying molecular mechanisms using the selective antagonists PD98059, LY294002 and SB216763. Results: The data showed that VPA dose-dependent induction of glioma U87 cells to undergo apoptosis through the mitochondria-dependent pathway in vitro. VPA activated the ERK/Akt pathways by increasing their protein phosphorylation and in turn inhibited GKS3β activation by the induction of GKS3β phosphorylation. However, the MAPK inhibitor PD98059 and/or PI3K inhibitor LY294002 were able to antagonize the effects of VPA by abolishing ERK/Akt activations and cancelling GSK3β suppression, thus it impaired VPA apoptosis-inducing effects on glioma cells. Furthermore, the GSK3β inhibitor SB216763 caused a strong suppression of GSK3β activity, which showed similar effects of VPA on regulation of protein expression and apoptosis. Conclusion: These findings suggest that GSK3β may be the central hub for VPA-induced apoptosis and VPA can be further evaluated as a novel agent for glioma therapy.