c-Jun NH2-terminal kinase signaling axis regulates diallyl trisulfide-induced generation of reactive oxygen species and cell cycle arrest in human prostate cancer cells

We have shown previously that generation of reactive oxygen species (ROS) is a critical event in G2-M phase cell cycle arrest caused by diallyl trisulfide (DATS), which is a highly promising anticancer constituent of processed garlic. Using DU145 and PC-3 human prostate cancer cells as a model, we now report a novel mechanism involving c-Jun NH2-terminal kinase (JNK) signaling axis, which is known for its role in regulation of cell survival and apoptosis, in DATS-induced ROS production. The DATS-induced ROS generation, G2-M phase cell cycle arrest and degradation, and hyperphosphorylation of Cdc25C were significantly attenuated in the presence of EUK134, a combined mimetic of superoxide dismutase and catalase. Interestingly, the DATS-induced ROS generation and G2-M phase cell cycle arrest were also inhibited significantly in the presence of desferrioxamine, an iron chelator, but this protection was not observed with iron-saturated desferrioxamine. DATS treatment caused a marked increase in the level of labile iron that was accompanied by degradation of light chain of iron storage protein ferritin. Interestingly, DATS-mediated degradation of ferritin, increase in labile iron pool, ROS generation, and/or cell cycle arrest were significantly attenuated by ectopic expression of a catalytically inactive mutant of JNK kinase 2 and RNA interference of stress-activated protein kinase/extracellular signal-regulated kinase 1 (SEK1), upstream kinases in JNK signal transduction pathway. In conclusion, the present study provides experimental evidence to indicate existence of a novel pathway involving JNK signaling axis in regulation of DATS-induced ROS generation.