GSK3B and neuroblastoma: Valproate was shown to inhibit GSK3 through a variety of mechanisms, such as serine phosphorylation [66,68,139], tau protein phosphorylation-mediated GSK3 inhibition in human neuroblastoma cell lines overexpressing GSK3β [144], or through the action of metabolites that potently inhibit GSK3 activity in vivo [138].