Table 1.

Extent of DNA fragmentation induced by exposure of HL60 cells to protease inhibitors

Treatment	DNA fragmentation, %
DMSO (0.1%)	4.3  ±  1.4
PMSF (1 mM)	6.2  ±  2.0
TLCK (25 μM)	6.3  ±  2.7
E64 (50 μM)	5.6  ±  1.6
Leupeptin (25 μg/ml)	6.0  ±  1.7
LLnM (50 μM)	6.0  ±  2.5
TPCK (25 μM)	19.5  ±  4.0*
DCI (50 μM)	44.0  ±  8.7*
LLnL (50 μM)	27.4  ±  6.1*
LLnV (50 μM)	45.1  ±  8.3*
PSI (50 μM)	34.9  ±  4.9*

Cells were plated in 12-well plates in medium containing 10% fetal bovine serum, and protease inhibitors were added to the cells at the final concentrations given above. After 6 h of incubation the cells were lysed and the percentage of DNA fragmentation was assessed by the diphenylamine assay. Data are means ± SD from three independent experiments; ∗, P < 0.01 relative to 0.1% DMSO-treated control HL60 cells (by Student’s t test).