Down-regulation of procaspase-2L expression delays anti-Fas Ab–induced apoptosis in U937/AS3 cells.

(A) At indicated times after anti-Fas Ab treatment (x-axis; hours), DNA fragmentation was quantified by a DNA filter elution assay in U937/neo (●) and U937/AS3 (○) cells. Data points, means of 2 independent experiments in triplicate; bars indicate SD. (B) Morphologic aspect of control and anti-Fas Ab–treated (CH11 50 ng/mL, CHX 0.8 μg/mL; 24 hours) U937/neo and U937/AS3 cells stained by Hoeschst 33342 (magnification × 40). (C) Flow cytometry profile of FITC-conjugated annexin V and propidium iodide (PI)–labeled U937/neo and U937/AS3 at various times after anti-Fas Ab treatment. Percentages of annexin V⁺ cells are indicated. The percentage of labeled cells with PI did not exceed 10%, 15 hours after treatment.