Daunorubicin uptake by leukemic cells : correlations with treatment outcome and mdr1 expression

The in vitro daunorubicin (DNR) cell uptake was investigated by flow cytometry in K562/DOX resistant cell line and in 42 patients with acute myeloid leukemia (AML). The proportion of cells able to take up DNR was higher in untreated patients (50%±30) than in previously treated patients (31%±31) (p=0.04). We noted a good correlation (p<0.001) between the drug uptake after exposure to 0.1 μM DNR and achievement of complete remission. Cyclosporin A (CsA, 1 μg/ml) and verapamil (5 μg/ml), but not cefoperazone (10 mM), completely reversed (CsA) or partially reversed (verapamil) the DNR efflux from K562/DOX mdr1(+) cell line