Quercetin Enhances Chemosensitivity to Gemcitabine in Lung Cancer Cells by Inhibiting Heat Shock Protein 70 Expression

Quercetin is a bioflavonoid known for antioxidation and antiproliferation activities. We demonstrated that quercetin inhibited cancer cell growth and sensitized cancer cells to gemcitabine treatment by promoting apoptosis via inhibiting heat shock protein 70 expression. Our results suggest that quercetin might have potential to increase sensitivity to chemotherapy and that heat shock protein 70 could be a new target for lung cancer treatment.Quercetin is a bioflavonoid with antiproliferative and proapoptotic activity in various cancer cells. However, little is known about the mechanism by which quercetin inhibits cancer growth or its potential role as a chemosensitizer in lung cancer cells. We investigated whether quercetin-induced inhibition of heat shock protein 70 (HSP70) is involved in its anticancer activity and whether it could modulate the responsiveness of lung cancer cells to chemotherapy.Various concentrations of quercetin and gemcitabine, either alone or in combination, were applied to lung cancer cells (A549 and H460 cells). We evaluated cell viability with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide salt assay, apoptotic activity by determining caspase-3 and caspase-9 activities, and HSP70 expression using Western blot analysis after treatment.Quercetin reduced cell viability and suppressed HSP70 expression in both cell lines dose-dependently. Adding a fixed quercetin dose enhanced gemcitabine-induced cell death, which was related to increased caspase-3 and caspase-9 activities. Combination treatment with quercetin and gemcitabine downregulated HSP70 expression more prominently than treatment with quercetin or gemcitabine alone.Quercetin-induced HSP70 inhibition was involved in growth inhibition and sensitization to chemotreatment in lung cancer cells. Quercetin might have potential as a chemosensitizer in lung cancer treatment.