CD437-mediated apoptosis in primary leukemia cells. Leukemic blasts were isolated as described in the Materials and Methods. Cells were exposed to 1 μmol/L CD437 for various periods of time and PARP cleavage was assessed as previously described. (A) Leukemic cells exposed only to vehicle for 48 hours. (B) Leukemic cells exposed to 1 μmol/L CD437 for 48 hours. (C) CD437-mediated PARP cleavage. Lanes 1 and 3, cells exposed to vehicle only for 24 and 48 hours, respectively. Lanes 2 and 4, cells exposed to 1 μmol/L CD437 for 24 and 48 hours, respectively.