Uptake of free and DNA-bound daunorubicin and doxorubicin into human leukemic cells.

Leukemic cells from seven patients with acute nonlymphoblastic leukemia and granulocytes, and mononuclear cells from three healthy controls were isolated by centrifugation on metrozoate-dextran. The intracellular accumulation of both the free and DNA-bound forms of daunorubicin and doxorubicin was studied in vitro. The uptake of unbound daunorubicin was higher than that of doxorubicin. At drug concentrations of 1.75 microM and higher the uptake of the free drugs was greater than that of the bound forms, but at lower drug concentrations the uptake was about the same. This could at least partly be explained by a greater dissociation of the DNA-drug complexes at lower drug concentrations. The uptake into normal leukocytes was of the same order of magnitude as that into leukemic cells. There was a great interindividual variation in the accumulation of both free and DNA-bound drugs in the cells from leukemic patients. This variation might be of importance for the prediction of individual sensitivity to the different drugs.