Synergistic Growth-Suppressive Effects of Quercetin and Cisplatin on HepG2 Human Hepatocellular Carcinoma Cells

Quercetin, a natural flavonoid, exhibits anticancer effects. The aim of this study is to determine whether the combination of quercetin with cisplatin, a conventional chemotherapeutic drug, would have synergistic suppressive effects on hepatocellular carcinoma (HCC) cells. To this end, HepG2 cells were exposed to quercetin (50 mu M) or cisplatin (10 mu M) alone or combination of both and cell proliferation and apoptosis were investigated. Our data revealed that the combination of quercetin and cisplatin was significantly (P<0.05) effective in inducing growth suppression and apoptosis in HepG2 cells, when compared with single agent treatment. Quercetin combined with cisplatin modulated the expression of numerous genes involved in cell cycle progression and apoptosis. Treatment with quercetin rather than cisplatin resulted in a marked elevation of p16 expression in HepG2 cells. Targeted reduction of p16 using RNA interference technology partially reversed quercetin-induced cell cycle G1 arrest and apoptosis in HepG2 cells. In conclusion, quercetin has suppressive activity against HCC cells through p16-mediated cell cycle arrest and apoptosis and its combination with cisplatin yielded synergistic inhibitory effects in suppressing cell growth and inducing apoptosis.