Role of JNK in ABL-N-induced apoptosis. MDA-MB-231 cells were incubated with ABL-N (20 μM) and either SB203580 (20 μM) or SP600125 (30 μM), or a combination of both for 24 hours. (a) MDA-MB-231 cells were transfected with JNK siRNA (25 nM) or control siRNA (25 nM) for 48 hours, and cell lysates were subjected to Western blot with antibodies to JNK. (b) ABL-N-induced cell death was abrogated by inhibition of JNK using MTT assay. (c) Sub G1 DNA content was analyzed by flow cytometry. (d) Caspase-3 activity was determined by Caspase-Glo assay and the cleavage of PARP was analyzed via Western blotting. Data are expressed as the means ± SE of three independent experiments. (e) Effect of MAP kinase inhibitors on ABL-N-induced JNK activation. (f) Effect of caspase inhibitors on JNK activation. Cells pretreated with or without z-VAD-fmk (50 μM) or z-DEVD-fmk (50 μM, one hour) were further incubated with vehicle or 20 μM ABL-N for 24 hours. Data are representative of three independent experiments.