ST1926 induces cell cycle arrest and massive apoptosis in malignant T cells. (A) Effects of ST1926 on the cell cycle distribution of HuT-102, MT-2, Jurkat, and MOLT-4 cells. Cells were treated with 1 μM ST1926 up to 48 hours and stained with propidium iodide (50 μg/mL), and cell cycle analysis was performed using a FACScan flow cytometer. The pre-G₁ percentage represents apoptotic cells. Cycling cells, the sum of (S + G₂/M) phases, are a percentage of nonapoptotic cells. Percentage cells in G₁ phase are calculated as 100 − (S + G₂/M). The results represent the average of 3 independent experiments ± SE. (B) TUNEL analysis of HuT-102, MT-2, Jurkat, and MOLT-4 cells treated for 48 hours with 1 μM ST1926 concentrations. The results are representative of 2 independent experiments.