As₂O₃ combined with AA induces apoptosis in su-DHL-4 cells. (A) Morphologic features of apoptosis. Cells were treated for 24 hours. 1, Without treatment; 2, As₂O₃ (1 μmol/L); 3, AA (62.5 μmol/L); 4, As₂O₃ (1 μmol/L) with AA (62.5 μmol/L). Apoptotic cells were determined with fluorescence staining as described in Materials and Methods. (B) DNA fragmentation. Cells were treated for 24 hours and total DNA was isolated and separated on agarose gel. DNA ladder was visualized with EB as described in Materials and Methods. Lane M, size markers, λ DNA HindIII digest and φx174 RF DNAHaeII digest; lane 1, control; lane 2, As₂O₃ (1 μmol/L); lane 3, AA (62.5 μmol/L); lane 4, As₂O₃ (1 μmol/L) + AA (62.5 μmol/L); lane 5, AA (125 μmol/L); lane 6, As₂O₃ (1 μmol/L) + AA (125 μmol/L). (C) Activation of CPP32 and effect on Bcl-2 by treatments as in B.