LC-1 and parthenolide induce time- and concentration-dependent apoptosis in primary CLL cells and follow the reduction of NF-κB. (A) CD19⁺ CLL cells were treated with LC-1 (0-10 μM) for 24 and 48 hours and were then labeled with annexin V and PI. The percentage of apoptotic cells was calculated as the sum of the upper and lower right quadrants (ie, annexin V⁺/PI⁺ and annexin V⁺/PI⁻). A concentration-dependent increase in annexin V⁺ cells was observed. (B) Normal CD19⁺ B lymphocytes derived from nonleukemic, age-matched, donors were more than 2-fold less sensitive to the apoptotic effects of LC-1 than CD19⁺ CLL cells (P < .001). (C) CLL cells were treated with LC-1 (0-5 μM) for 4 hours before harvesting and nuclear protein extraction. EMSA analysis (top panel) and quantification by densitometry (middle panel) revealed a dose-dependent decrease in NF-κB activity in the absence of detectable apoptosis (bottom panel) measured by annexin V and PI.