Fig. 6. (a) Nuclear DNA fragmentation. MCF-7 cells were treated for 12 or 24 h with IC₅₀ of I, VI or cisplatin (CDDP). Quantitative estimation of DNA fragmentation was obtained with an ELISA test. Data are the means of five independent experiments. Error bars indicate SD. (b) MCF-7 cells were treated with IC₅₀ of I and VI for 72 h and stained with the fluorescent dye Hoechst 33258. (c) Caspase activity. MCF-7 cells incubated for 24 h with IC₅₀ of I, VI or staurosporine ± broad-spectrum caspase inhibitor zVAD, and processed for caspase-3/-7, -6, -8, -9 activity. Data are the means of at least three independent experiments. Error bars indicate SD.