NAC treatment abolishes PTL apoptosis induction in AML cells. Percent viability of CD34⁺ cells from 3 different AML specimens treated with increasing concentrations of PTL. Cells were precultured with 800 μM NAC (- - -) versus untreated controls (—) for 1 hour and immediately washed and treated with PTL for 18 hours. Specimens shown correspond to AML5 (□), AML10 (⋄) and AML15 (▵).