Na-Sal induces apoptosis of acute myeloid leukemia cell lines. TF-1, U937, CMK-1, and K562 cells were either left untreated (□) or were treated with 0.5 (◊), 1 (○), 5 (▵), or 20 (⊞) mmol/L Na-Sal for the time indicated. Viability was determined by the trypan blue exclusion test. (B) Increased annexin V binding to TF-1 cells cultured in the absence (control) or in the presence of 4 mmol/L Na-Sal for 1 hour, 4 hours, 10 hours, or 20 hours. Annexin V binding and PI staining were analyzed by flow cytometry, as described in Materials and Methods. The percentage of cells positive for annexin V and/or PI is depicted in each quadrant.