Efflux of daunorubicin and mitoxantrone from leukemic SP cells in bone marrow samples from 3 patients with AML.

After incubation of the cells with Hoechst 33342 and daunorubicin (panels A, C, E) or mitoxantrone (panels B, D, F), the fluorescence emitted by the drugs was plotted for 3 gated cell populations: SP (solid line, shaded); non-SP (dashed line); and negative control, SP cells stained with Hoechst 33342 alone (dotted line).