Effect of inhibition of PI3-kinase activity on the proliferation and apoptosis of HCD57 and HCD-SREI cells. (A) Cells cultured in the presence of 1 U EPO/mL (HCD57, ◊; HCD57-SREI, ⊖) or absence of EPO (HCD57-SREI, x) were treated with LY294002 at the indicated concentrations for 72 hours, and the viable cells were counted in the presence of trypan blue. Values are expressed as a percentage of the corresponding control (treated with vehicle dimethylsulfoxide [DMSO]). Data are means ± SE of at least triplicate measurements. (B) Cells were cultured in the presence of 1 U EPO/mL (HCD57) or absence of EPO (HCD57-SREI). HCD-57 (lanes 2 through 6) and HCD57-SREI (lanes 7 through 11) cells were treated with vehicle DMSO (lanes 3 and 8), LY294002 at indicated concentrations (lanes 4 through 6 and 9 through 11), or untreated (lanes 2 and 7) for 24 hours. The genomic DNA was isolated and analyzed for fragmentation of DNA characteristic of apoptosis as described in Materials and Methods.