The proportion of spontaneously apoptotic B-CLL cells is increased by treatment with calpeptin.

Apoptotic (FITC-annexin–binding) cells were detected by flow cytometry. Bars represent means from 3 separate experiments ± SD. (A) Proportion of apoptotic, annexin-binding cells in untreated control (control) and cells treated with calpeptin (calpeptin), rabbit muscle m-calpain inhibitor (calpastatin), and protease inhibitor cocktail (cocktail), as in “Patients, materials, and methods.” The differences between proportions of apoptotic cells in control and inhibitor-treated samples are statistically significant (**calpeptin, paired t test, P < .0001; *calpastatin, paired t test, P < .02). (B) Proportion of necrotic cells staining with propidium iodide (PI⁺) in the same samples shows high toxicity of protease inhibitor cocktail but not of selective calpain inhibitors.