Induction of G1/S phase arrest and apoptosis by quercetin in human osteosarcoma cells

Quercetin (3,3′,4′,5,7-pentahydroxyflavone) is a polyphenolic flavonoid compound and is found in a variety of plants. Potential biological activities including antioxidant and anticarcinogenesis have been reported. The antiproliferative effect and apoptosis inducing effect of quercetin in human osteosarcoma cells was evaluated in this study. The IC50 values were 290 μM and 160 μM at 24 h and 48 h incubation, respectively. Antiproliferative action of quercetin appeared to be linked to apoptotic cell death based on increase in the sub-G1 apoptotic cell population analyzed by flow cytometric analysis. Prior to apoptosis induction, quercetin caused cell cycle arrest at G1/S phase. The G1/S phase arrest was accompanied by down regulation of cyclin D1, one of the cyclins required for advance from G1 to S. Subsequent apoptosis was induced by the gradual activation of caspase-3 and the cleavage of PARP.