Chalcones have been described to represent
cancer chemopreventive food components that are rich in fruits and vegetables. In this study, we examined the anti-
oral cancer effect of
flavokawain B (FKB), a naturally occurring
chalcone isolated from Alpinia pricei (shell gingers), and revealed its molecular mechanism of action. Treatment of human oral
carcinoma (HSC-3) cells with FKB (1.25-10 μg/mL; 4.4-35.2 μM) inhibited cell viability and caused G(2)/M arrest through reductions in
cyclin A/B1, Cdc2, and Cdc25C levels. Moreover, FKB treatment resulted in the induction of apoptosis, which was associated with DNA fragmentation,
mitochondria dysfunction,
cytochrome c and AIF release,
caspase-3 and
caspase-9 activation, and Bcl-2/Bax dysregulation. Furthermore, increased Fas activity and
procaspase-8, procaspase-4, and procaspase-12 cleavages were accompanied by
death receptor and ER-stress, indicating the involvement of mitochondria,
death-receptor, and ER-stress signaling pathways. FKB induces apoptosis through ROS generation as evidenced by the upregulation of oxidative-stress markers HO-1/Nrf2. This mechanism was further confirmed by the finding that the
antioxidant N-acetylcysteine (NAC) significantly blocked ROS generation and consequently inhibited FKB-induced apoptosis. Moreover, FKB downregulated the phosphorylation of Akt and
p38 MAPK, while their inhibitors
LY294002 and
SB203580, respectively, induced G(2)/M arrest and apoptosis. The profound reduction in cell number was observed in combination treatment with FKB and Akt/
p38 MAPK inhibitors, indicating that the disruption of Akt and
p38 MAPK cascades plays a functional role in FKB-induced G(2)/M arrest and apoptosis in HSC-3 cells.