Cross-inhibition of protease expression by antisense constructs. Cells were electroporated with the respective constructs and enriched for transfection by G418 treatment as indicated in the Materials and Methods. Protein extracts were subjected to Western blot analysis as described. In addition, films were evaluated by densitometry using HEROLAB system (Herolab Molekulare Trenntechnik, Wiesloch, Germany) equiped with EASY software (data not shown). The level of protease expression in empty vector-transfected cells was given as 100%. In SHEP cells, pCDNA-3-α300h.ICE decreased caspase-1 expression to 23% and caspase-3 expression to 26%. In CEM cells, pCDNA-3-α300h.ICE inhibited caspase-1 expression to 21% and caspase-3 expression to 25%. pCDNA-3-α300h.CPP32 inhibited caspase-3 expression to 24% in SHEP and to 21% in CEM cells, but there was no cross-inhibition of caspase-1 expression by this construct. Experiments have been performed twice, with differences between experiments of less than 12%.