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Background Pyruvate kinase M2 (PKM2) is a key enzyme responsible for the final step of glycolysis. Whether and how the pyruvate kinase M2 is involved in reactive oxygen species (ROS)-mediated cytotoxicity of gastrointestinal cancer is unknown. Methods One duodenal cancer cell line AZ521, and two gastric cancer cell lines NUGC and SCM-1 and were treated with OSU-A9 which is known to induce cytotoxicity of acute myeloid leukemia through ROS generation. The in vitro cytotoxic and proapoptotic activities of OSU-A9 was evaluated by the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay and annexin V – propidium iodide staining, respectively. Overexpression experiment was performed by transfection with indicated plasmid using Lipofectamine 2000 according to the manufacturer’s protocol. Results OSU-A9 induced a dose- and time-dependent cytotoxicity and apoptosis in duodenal cancer and gastric cancer cells through ROS generation. The IC50 of OSU-A9 at 24 and 48 h for AZ-521, NUGC and SCM-1 were 2.68 and 1.83, 3.34 and 2.81, and 2.71 and 2.36 mM, respectively. Pretreatment with ROS scavenger rescued the cancer cells from apoptosis and concomitant PARP cleavage, implicating a key role of ROS in OSU-A9-induced cell death. Furthermore, OSU-A9-mediated ROS down-regulated pTyr105-PKM2 which occurred in cell nucleus rather than in cytoplasm. Ectopic overexpression of PKM-2 partially overcame the cytotoxicity of OSU-A9, which implied a role of phosphorylated PKM2 beyond glycolysis in survival of duodenal cancer and gastric cancer cells. Conclusions This study shows that ROS-mediated intranuclear PKM2 dephosphorylation, in part, contributes to the anticancer activity of OSU-A9 in duodenal cancer and gastric cancer. Differential down-regulation of phosphorylated PKM2 between nucleus and cytoplasm suggests a non-glycolytic role of PKM2 in cell survival response to ROS stress. Legal entity responsible for the study The authors. Funding The Ministry of Health and Welfare, Taiwan. Disclosure All authors have declared no conflicts of interest. |
