Uptake and Intracellular Distribution of Doxorubicin Metabolites in B-Lymphocytes of Chronic Lymphocytic Leukemia¹

The toxicity of doxorubicin metabolites was evaluated on lymphocytes of B-cell chronic lymphocytic leukemia. Only doxorubicinol was found to be cytotoxic for these lymphocytes, whereas exposure to aglycones at concentrations as high as 5 µm for 1 h had no effect on the proliferative capacity of these cells. After exposure of cells to isomolar concentrations of doxorubicin or its metabolites, uptake/retention of doxorubicinol was 23% of doxorubicin, and uptake/retention of aglycones was 5 to 13% of doxorubicin. Seventy to 90% of doxorubicin and 60 to 90% of doxorubicinol taken up/retained by the cells were detected in the cell nuclear fraction, whereas only 20 to 40% of the aglycones were localized in the cell nucleus. Cytotoxicity of metabolites was generally related to the proportion of drug taken up/retained by the cells and localized to the nuclei. The low uptake and nuclear localization may be at least partially responsible for the lack of cytotoxicity of aglycones on B-lymphocytes from chronic lymphocytic leukemia.