Zerumbone Induced ROS-Mediated Autophagic Cell Death in Human Melanoma Cells: An In Vitro and In Vivo Study

Abstract

Zerumbone (Zer), a natural sesquiterpene of Zingiber zerumbet, exerts apoptosis in human melanoma cells. We evaluated the anticancer efficacies and the underlying molecular mechanisms of Zer through autophagic cell death in both in vitro melanoma (A375 and/or A2058) cells and in vivo xenografted athymic nude mice. We found that Zer inhibited cell growth and EGFR/BRAF expression in A375 and A2058 cells. Additionally, Zer-induced autophagy was apparent from enhanced LC3-II accumulation, p62 expression, ATG4B reduction, Beclin-1/Bcl-2 ratio, AKT/mTOR suppression, and AVO production in A375 and A2058 cells. Surprisingly, Zer-triggered cell death was prevented by autophagic inhibitors 3-MA and CQ, suggesting the contribution of autophagy as a death mechanism. TEM data displayed that Zer provoked autophagosome generation in A375 and A2058 cells. However, obstruction of autophagy by 3-MA or CQ, and LC3 silencing curbed Zer-incited apoptosis in A375 cells, which suggests autophagy induction enhanced apoptosis in Zer-treated A375 cells. Interestingly, reduction of apoptosis by caspase blocker Z-VAD-FMK enhanced Zer-provoked autophagy in A375 cells, indicating induction of apoptosis inhibited autophagy in Zer-treated A375 cells. Moreover, Zer instigated intracellular ROS generation, whereas antioxidant NAC or Mito-Tempo reversed autophagic or apoptotic cell death in A375 and/or A2058 cells. In vivo results displayed that Zer significantly inhibited tumor development in A375 and A2058-xenografted athymic nude mice. Our findings implied that Zerumbone is a potent antitumor agent that triggered ROS-mediated autophagic cell death in human melanoma cells.