Increased anticancer efficacy by the combined administration of quercetin in multidrug resistantbreast cancer cells

Abstract

Quercetin is one of the bioactive flavonoid isolated from the leaves of Euphorbia hirta (Euphorbiaceae). The isolated quercetin was investigated for its antiproliferative activity in human breast adenocarcinoma MCF-7 cells. Furthermore, the combined efficacy of quercetin with standard chemotherapeutic drug tamoxifen also studied. The results showed greater reduction in the cell viability from the QuerTam group (quercetin with tamoxifen) than tamoxifen and quercetin alone group. The IC50 values of test compounds were determined as 2μM, 0.5μM and 1.8μM for quercetin, Quertam and tamoxifen respectively. An elevated induction of apoptosis was found in QuerTam treatment when compared to quercetin and tamoxifen alone. The combined efficacy of QuerTam showed significant inhibition of cell viability by decreasing Bcl-2 protein expression and inducing apoptosis. Flow cytometry revealed a decrease in normal cells and increasing pro and late apoptotic cells indicative of apoptosis induction, while fluorescence microscopy showed evidence of the induction of apoptosis and nuclear fragmentation. To summarize these results showed that quercetin enhances the MCF-7 cell sensitivity to tamoxifen, as demonstrated by the improvement in the anticancer therapy.