Fig. 4. Caspase-2 and caspase-9 function as upstream caspases during anoikis. IEC cytosol was extracted at the indicated times during anoikis and analyzed by Western blot for activation of caspases. Caspase-2 (p48) is activated almost instantly by deletion of the prodomain (yielding the p33 intermediate) as the active p16 becomes detectable before 15 min of detachment. Caspase-9 is processed within 15 min as the prodomain is lost, yielding the p37 intermediate, and further rapid processed to yield the p10 subunit within 1530 min. The protein at Mr 35,000 represents another intermediate of caspase-9 activation.