Effects of quercetin on the cell growth and the intracellular accumulation and retention of adriamycin.

In this study, we examined the inhibitory effects on cell growth and the effects of quercetin on intracellular accumulation of adriamycin (ADR) in wild type Ehrlich ascites tumor cells (wild EAT cells) and their ADR-resistant strain. Quercetin strongly inhibited growth in both strains. Cell growth reached a plateau at 3.5 days in the wild type EAT cells and at 7 days in the ADR-resistant strain. The inhibitory concentration in 50% of the ADR-resistant cells on day 7 (24 microM) was twice that of the wild type EAT cells on day 4 (12 microM) after continuous treatment with quercetin. Quercetin decreased the ADR accumulation in the wild type cells but did not affect it in the ADR-resistant cells. Further, quercetin did not affect the retention of ADR in either strain. These results indicated that quercetin decreased ADR accumulation without extruding ADR in the wild type EAT cells. ADR accumulation in the ADR-resistant cells treated with quercetin for 7 days was increased with increasing concentrations of quercetin. Moreover, ADR accumulation in the ADR-resistant cells treated with 50 microM quercetin for 7 days, increased to 186.6% and to 181.9% of that in untreated cells after 60 minutes and 120 minutes incubation, respectively, whilst it increased to 70% from 37.5% of that in the wild type EAT cells after 60 minutes incubation. These findings indicated that quercetin might reverse ADR-resistance.