A New Strategy for Adult T‐Cell Leukemia Treatment Targeting Glycogen Synthase Kinase‐3β

ABSTRACT Objectives The role of glycogen synthase kinase (GSK)‐3β in adult T‐cell leukemia (ATL) caused by human T‐cell leukemia virus type 1 (HTLV‐1) is paradoxical and enigmatic. Here, we investigated the role of GSK‐3β and its potential as a therapeutic target for ATL. Methods Cell proliferation/survival, cell cycle, apoptosis, and reactive oxygen species (ROS) generation were examined using the WST‐8 assay, flow cytometry, and Hoechst 33342 staining, respectively. Expression of GSK‐3β and cell cycle/death‐related proteins, and survival signals was analyzed using RT‐PCR, immunofluorescence staining, and immunoblotting. Results HTLV‐1‐infected T‐cell lines showed nuclear accumulation of GSK‐3β. GSK‐3β knockdown and its inhibition with 9‐ING‐41 and LY2090314 suppressed cell proliferation/survival. 9‐ING‐41 induced G2/M arrest by enhancing the expression of γH2AX, p53, p21, and p27, and suppressing the expression of CDK1, cyclin A/B, and c‐Myc. It induced caspase‐mediated apoptosis by decreasing the expression of Bcl‐xL, Mcl‐1, XIAP, c‐IAP1/2, and survivin, and increasing the expression of Bak and Bax. 9‐ING‐41 also induced ferroptosis and necroptosis, promoted JNK phosphorylation, and suppressed IKKγ and JunB expression. It inhibited the phosphorylation of IκBα, Akt, and STAT3/5, induced ROS production, and reduced glycolysis‐derived lactate levels. Conclusion GSK‐3β functions as an oncogene in ATL and could be a potential therapeutic target.