Effects of activated Notch1 on HL-60 cell cycle kinetics. (A) HL-60 MSCV-GFP, HL-60 MSCV-ICN/GFP, and MSCV-ICNΔAR/GFP cells cultured in growth media were obtained and stained with the DNA dye TOPRO-3. Cell cycle distribution was analyzed gating on GFP-positive cells. (B) Cells were synchronized as described, and aliquots were obtained every 6 hours after 30 minutes of incubation with BrdU. Samples were stained with anti-BrdU MoAb and propidium iodide before FACS analysis. Columns represent the average of five experiments and express the percentage of cells that were in S-phase by their positivity to BrdU staining. Bars represent standard error. The difference between HL-60 MSCV-GFP and HL-60 MSCV-ICN/GFP populations is statistically significant (P = .04).