BH3 profiling of primary ALL cells also shows a BCL-2 pattern. 10⁹ cells from primary sample L1 (A) or 3.5 × 10⁸ cells from primary sample L8 (B) were subjected to mechanical disruption and differential centrifugation. Isolated mitochondria were brought to a final concentration of 0.5 mg/mL and incubated with 100 μM peptides for 35 minutes at room temperature. Mitochondria pellet and supernatant were separated and analyzed using a cytochrome c ELISA kit. (C) Primary ALL cells were plated with or without stromal cells (Mihara, 2003 #654) with increasing concentrations of ABT-737. Apoptosis was assessed at 24 and 48 hours by counting annexin-V–positive cells by FACS analysis.