TPA and S-1P inhibit cyt c and Smac/DIABLO release and cell death induced by TNF-α in U937 cells.

(A) Cytosolic extracts from U937 cells treated for 5 hours with 50 ng/mL TNF-α alone or after pretreatment with 50 nM TPA or 5 μM S-1P for 15 minutes were subjected to 15% SDS-PAGE and immunoblotted with anti-cyt c, anti-Smac/DIABLO, and anti-COX II, as described in Figure 1. (B) U937 cells were treated under the same conditions as described above. Loss of viability was assessed by the MTT assay. Samples were made in quadruplicate. Mean values with standard deviations are shown.