Suppression of reactive oxygen species-mediated ERK and JNK activation sensitizes dihydromyricetin-induced mitochondrial apoptosis in human non-small cell lung cancer

Nonsmall cell lung cancer (NSCLC) is the most common type of lung cancer with a high mortality rate and still remains a therapeutic challenge. A strategy for targeting NSCLC is to identify agents that are effective against NSCLC cells while sparing normal cells. Dihydromyricetin (DHM) is the major flavonoid component derived from Ampelopsis grossedentata, which has a long history of use in medicine. Herein, the molecular mechanisms by which DHM exerts its anticancer effects against NSCLC cells were investigated. Results from MTS, colony formation, Western blot, flow cytometric, and JC-1 mitochondrial membrane potential assays revealed that DHM showed a selective cytotoxic effect against NSCLC cells (A549 and H1975), but not against normal lung (WI-38) fibroblasts, by inducing apoptosis. DHM-induced cell apoptosis occurred through Bcl-w suppression-mediated mitochondrial membrane depolarization, caspase-9/-7/-3 activation, and poly(ADP-ribose) polymerase (PARP) cleavage in A549 and H1975 cells. Moreover, treatment of A549 and H1975 cells with DHM induced increase of intracellular peroxide and sustained activation of extracellular signal-regulated kinase (ERK)1/2 and c-Jun N-terminal kinase (JNK)1/2, and the reactive oxygen species scavenger, N-acetylcysteine (NAC), reversed DHM-induced ERK and JNK activation. Furthermore, treatment of cells with specific inhibitors of ERK and JNK or NAC significantly promoted the DHM-induced activation of caspase-9/-7/-3 and PARP cleavage and also sensitized the antitumorigenic effect of DHM on NSCLC cells. These findings define and support a novel function of DHM of inducing mitochondrion-derived apoptosis in human NSCLC cells, and a combination of DHM with ERK and JNK inhibitors should be a good strategy for preventing NSCLC proliferation.