Western blot analysis of caspase 3 and caspase 8 activation after doxorubicin treatment in 8226 and K562 cell lines. Cells were exposed to 5 × 10⁻⁶ mol/L doxorubicin for the indicated times, and cell lysates analyzed for caspase 3 and caspase 8 active subunits. (A) 8226/S and 8226/F4; (B) K562 untransfected, K562/pcDNA3.1 empty vector, and the CD95 high-expressing K562/fasH2. Although procaspase 8 can be detected in K562 cells, the active subunits are below the limits of detection at the time points examined. Data shown are representative of three independent experiments.