Adriamycin and paclitaxel are simultaneously used for cancer treatment in some cases. The formula of paclitaxel contains cremophor EL as a solvent. Since this solvent exerts diverse biological actions, the modification of adriamycin action by cremophor EL has been studied on human leukemia K562 cells. Cremophor EL did not significantly affect the concentration-response relation for antiproliferative action of adriamycin and the cell cycle changed by adriamycin. However, the induction of morphological change by adriamycin was significantly augmented by cremophor EL. The simultaneous application of cremophor EL increased the intensity of fluorescence from adriamycin trapped inside the cells in a concentration-dependent manner, suggesting an increase in intracellular concentration of adriamycin by cremophor EL. Adriamycin alone at concentrations higher than those to completely inhibit the growth induced morphological change in K562 cells. Therefore, cremophor EL may potentiate some of actions induced by adriamycin when adriamycin and paclitaxel are simultaneously applied
