Caspase-8 and caspase-3 are not activated in Fas-stimulated BL cells. Cytosolic extracts made from untreated (0) and Fas-induced (1 and 2 hours) SKW6.4 and Mutu-BL III cells.³⁵S-labeled caspases were generated by coupled in vitro transcription/translation driven by the T7 promoter of the pcDNA3 expression construct. Cleavage reactions were initiated by combining labeled (A) caspase-8 or (B) caspase-3 with the cytosolic extracts (25 μg) and incubated at 37°C for 2 hours. Reactions were terminated by the addition of Laemmli sample buffer and subjected to 15% SDS-PAGE and autoradiography.