Inhibition of elastase reduces AML-cell proliferation while maintaining normal undifferentiated CD34⁺cells. (A) AML cell lines (U937 and ML-2), primary AML cells, and CB CD34⁺ cells were cultured for 3 to 7 days with or without EI (10 μg/mL), and the number of viable cells was determined using trypan blue exclusion. Results are shown as percentage of viable cells compared with CTL-untreated cells plotted as 100%; ^*P ≤ .005. (B) CB CD34⁺ cells were cultured for 3 days with or without EI (10 μg/mL). The percentage of CD34⁺/CD38^- cells was determined by flow cytometry. Results are mean ± SE of 4 independent experiments; ^*P ≤ .05.