Coenzyme Q0 (CoQ0, 2,3-dimethoxy-5-methyl-1,4-benzoquinone) has been reported to exert anticancer properties against human breast/lung cancer cells. This study investigated the in vitro and in vivo anticancer properties of CoQ0 on human ovarian carcinoma (SKOV-3) cells and xenografted nude mice, and revealed the underlying molecular mechanism. CoQ0 induced G2/M arrest through downregulation of cyclin B1/A and CDK1/K2 expressions. CoQ0-induced autophagy as a survival mechanism was evidenced by increased accumulation of LC3-II, GFP-LC3 puncta, AVOs formation and Beclin-1/Bcl-2 dysregulation. Increased TUNEL-positive cells and Annexin-V/PI stained cells indicated CoQ0-induced late apoptosis. Both mitochondrial (caspase-3, PARP and Bax/Bcl-2 dysregulation) and ER stress (caspase-12 and Hsp70) signals are involved in execution of apoptosis. Interestingly, CoQ0-induced apoptosis/autophagy is associated with suppression of HER-2/neu and PI3K/AKT signalling cascades. CoQ0 triggered intracellular ROS production, whereas antioxidant N-acetylcysteine prevented CoQ0-induced apoptosis, but not autophagy. Inhibition of apoptosis by Z-VAD-FMK suppressed CoQ0-induced autophagy (diminished LC3-II/AVOs), indicates CoQ0-induced apoptosis led to evoke autophagy. Contrary, inhibition of autophagy by 3-MA/CQ potentiated CoQ0-induced apoptosis (increased DNA fragmentation/PARP cleavage). Furthermore, CoQ0 treatment to SKOV-3 xenografted nude mice reduced tumor incidence and burden. Histopathological analyses confirmed that CoQ0 modulated xenografted tumor progression by apoptosis induction. Our findings emphasize that CoQ0 triggered ROS-mediated apoptosis and cytoprotective autophagy.
