Flavokawain B induces apoptosis of human oral adenoid cystic cancer ACC-2 cells via up-regulation of Bim and down-regulation of Bcl-2 expression

Abstract

Novel effective drugs are still urgently needed in the prevention and treatment of oral adenoid cystic carcinoma (ACC). In this study, we have assessed the antitumor potential and molecular mechanisms of flavokawain B (FKB) as a kava chalcone on the ACC-2 cell line in vitro. The results demonstrated that FKB could significantly inhibit the cell proliferation of ACC-2 in a dose-dependent manner that was associated with induced apoptosis and cell cycle G2-M arrest, and the half maximal inhibitory concentration (IC50) of flavokawain-B treatment for 48 h was estimated to be 4.69 ± 0.43 µmol/L. Mechanistically, FKB could induce the release of cytochrome c from mitochondria into the cytosol, and activate the cleavage of caspase-3 and, eventually, the poly(ADP-ribose) polymerase (PARP), in a dose-dependent manner, leading to marked apoptotic effect of ACC-2 cells. The apoptotic action of FKB was associated with the increased expression of proapoptotic proteins: Bim, Bax, Bak and a decreased expression of antiapoptotic Bcl-2. Among them, Bim expression was significantly induced by FKB, and knockdown of Bim expression by short-hairpin RNAs attenuated the inhibitory effect induced by FKB on ACC-2 cells. These results suggest Bim may be one of the potential transcriptional targets, and suggests the potential usefulness of FKB for the prevention and treatment of ACC.Key words: flavokawain B (FKB), apoptosis, Bcl-2, Bim, ACC-2.Résumé : Il existe toujours un besoin urgent de nouveaux médicaments efficaces pour la prévention et le traitement du carcinome adénoïde kystique (CAK). Dans la présente étude, nous avons évalué le potentiel antitumoral et les mécanismes moléculaires du flavokawain B (FKB), une chalcone issue du kava, sur les cellules CAK-2 in vitro. Les résultats ont montré que FKB a pu inhiber considérablement la prolifération des cellules CAK-2 en fonction de la dose administrée, ce qui été associé à l'arrêt du cycle cellulaire en G2-M et à l'induction de l'apoptose, et que la valeur CI 50 après le traitement au flavokawain B pendant 48 heures a été de 4,69 ± 0,43 µmol/L. Du point de vue des mécanismes, FKB a pu induire la libération du cytochrome c des mitochondries dans le cytosol, et activer le clivage de la caspase-3 et de la poly(ADP-ribose) polymé-rase (PARP) de manière dose dépendante, ce qui a eu un effet apoptotique marqué sur les cellules CAK-2. L'action apoptotique de FKB a été associée à la surexpression des protéines pro-apoptotiques Bim, Bax, Bak et à la sous-expression de la Bcl-2 antiapoptotique. FKB a particulièrement augmenté l'expression de Bim, et l'inhibition de cette expression par les petits ARN en épingle à cheveux a atténué l'effet inhibiteur induit par FKB sur les cellules CAK-2. Ces résultats donnent à penser que Bim pourrait être une cible de transcription potentielle et que FKB pourrait être utile pour la prévention et le traitement du CAK.

Flavokawain B, a kava chalcone, inhibits growth of human osteosarcoma cells through G2/M cell cycle arrest and apoptosis

“…Bcl-2 inhibits the realease of cytochrome c against Bax. The disturbance of Bcl-2/Bax protein ratio has been recognized as a factor contributing to the FKB-induced apoptosis [6,20]. In the present study, the increase in Bax and decrease in Bcl-2 was observed in both OS cell lines.…”

“…The consumption of kava root extracts in the Pacific Islands has been associated with a lower incidence of cancer [4]. Extracts of kava are classified into two main classes of compounds: kavalactone and chalcone [5,6]. Chalcones have shown anticancer activity via inhibition of cell proliferation, carcinogenesis and metastasis [4,7,8].…”

Discovery of 2′,4′-dimethoxychalcone as a Hsp90 inhibitor and its effect on iressa-resistant non-small cell lung cancer (NSCLC)

“…Interestingly, epidemiological studies illustrated that populations that consume the kava beverage have low incidences of cancer, compared to non-kava-drinking populations (Steiner 2000;Agarwal and Deep 2008). Extracts of kava are classified into two main classes of compounds kavalactone and chalcone, and flavokawain B belongs to chalcone compounds (Warmka et al 2012;Zhao et al 2011).…”

Inhibition of c-Met promoted apoptosis, autophagy and loss of the mitochondrial transmembrane potential in oridonin-induced A549 lung cancer cells

“…The relationship between autophagy and apoptosis is complex and varies with cell category, cell condition and stimulation . Accumulating evidences suggest that there is a mechanistic overlap between apoptosis and autophagy . Thus, researchers are interested in signalling pathways that regulate both autophagy and apoptosis.…”