Effects of HA14-1 and/or 17-AAG on HL-60 cell types. (A) Ectopic overexpression of Bcl-2 confers resistance against HA14-1—induced apoptosis of HL-60 cells. HL-60/Neo (▪) and HL-60/Bcl-2 (▦) cells were treated with indicated concentrations of HA14-1 for 16 hours. Following this, cells were harvested and stained with annexin V, and the percentages of positively stained apoptotic cells were determined by flow cytometry. The bar graphs represent mean ± SE of 3 experiments. (B) Cotreatment with HA14-1 enhances 17-AAG—induced apoptosis of HL-60/Bcl-2 cells. HL-60/Bcl-2 cells were incubated with 15 μM HA14-1, with or without 5.0 μM 17-AAG, for 16 hours. Following this, the percentage of apoptotic cells was determined by annexin V (AV, ▪) or propidium iodide (PI, ▦) (for sub-G1 fraction) staining followed by flow cytometry. Values represent the mean ± SE of 3 experiments.