Uptake, metabolism, and cytotoxicity of doxorubicin in human Ewing's sarcoma and rhabdomyosarcoma cells

Uptake, metabolism, and cytotoxicity of doxorubicin (DOX) in human Ewing's sarcoma (ES) and rhabdomyosarcoma (RS) cells were examined. Cellular uptake of DOX was determined by liquid scintillation spectrometry, and intracellular metabolism was examined by high performance liquid chromatography. The cytotoxicity of DOX was assessed by two different methods: an extracellular matrix detachment assay (ECM-D) and 3H-thymidine incorporation. The uptake of DOX by ES cells was 1.5-3.0 times greater than RS cells, even though both cell types achieved intracellular steady-state though both cell types achieved intracellular steady-state concentrations between 6-8 h. No significant intracellular metabolism ( less than 5%) was seen after 8-h incubations with the drug. The cytotoxic effects of DOX in both cell lines were concentration-dependent, with the RS cells being more sensitive. Measurement of 14C-DOX appears to be a reliable method for quantitating intracellular DOX. In addition, the ECM-D and 3H-thymidine assays used for assessing cytotoxicity produced similar results, showing that the ECM-D can be reliable and easily performed test of cell death.