Figure 2

Caspase activation in DAL-1/4.1B-induced MCF-7 cells. A. Global caspase activation in cells treated with 2 μM Muristerone for 48 hours or 1 μM staurosporine (STS) for 4 hours. B. FACS analysis of the activation of Caspases 1, 2, 6, 8, 9, 10 and 13 in cells with and without the induction of DAL-1/4.1B expression by treatment with 2 μM Muristerone for 48 hours. Clear bars represent untreated cells; grey bars represent DAL-1/4.1B-expressing cells. Caspase 1, p = 0.232; Caspase 2, p = 0.64; Caspase 6, p = 0.625; Caspase 8, p = 0.007; Caspase 9, p = 0.16; Caspase 10, p = 0.10; Caspase 13, p = 0.039. C. Caspase 7 activation was investigated by Western blot analysis of PARP cleavage on proten lysates from uninduced and DAL-1/4.1B-induced MCF-7 Cl27 cells. D. Inhibition of caspase 8 activation blocks DAL-1/4.1B-associated apoptosis in a dose-dependent manner. This suggests that caspase 8 activation is critical for the induction of cell death by this tumor suppressor protein.