Expression and modification of Bcl-2 and HSP family members, and effect of Bcl-2 overexpression. (A) Relative levels of Bcl-2, Bcl-X_L, Bax, Bid (21-kDa proform), HSP70, HSP27, and α-tubulin (used as a control) in total cellular extracts (15 μg per lane) obtained from untreated U-937 cells (Cont), from cells treated for 14 hours with LY294002 alone, and from cells treated for the indicated time periods with 4 μMAs₂O₃, alone or in combination with LY294002, as determined by immunoblot. (B) Relative level of activated Bax in untreated cells (Cont), in cells treated for 14 hours with LY294002 alone, and in cells treated for 14 hours with As₂O₃ and camptothecin, alone or in the presence of LY294002, as determined by flow cytometry using the 6A7 antibody. The vertical, dotted lines represent the mean fluorescence value in the control, to better discern the displacement caused by the treatments. (C) Frequency of apoptotic cells (mean ± standard deviation of 3 determinations) in nontransfected (U-937) and Bcl-2-transfected (U4/Bcl-2) U-937 cell cultures at 24 hours of treatment with 4 μMAs₂O₃, alone or in combination with LY294002. All other conditions were as in Figure 1.