Effect of GM-CSF deprivation on cell cycle distribution and apoptosis of TF-1 AML cells. TF-1 AML cells (3 × 10⁵cells/mL) were cultured for 2 days in the presence of GM-CSF (1 ng/mL), washed three times with PBS, and resuspended in fresh media without GM-CSF. (A) Cell cycle profile was determined by PI staining and flow cytometric analysis at 0, 2, 4, 8, and 16 hours after GM-CSF deprivation. (B) Apoptosis of TF-1 cells before and 16 hours after deprivation of GM-CSF was analyzed by DNA fragmentation.