Brefeldin A induces apoptosis in PC-3 and MCF-7 cells at a concentration of 30 ng/ml. RT-PCR analyses showed up-regulation of CHOP/GADD153 and splicing of XBP-1 mRNA in brefeldin A-treated cells. CHOP promoter-luciferase reporter assays demonstrated activation of AARE, ERSE, and AP-1 elements of CHOP promoter by brefeldin A treatment. The activation of these elements was not affected by preincubation of cells with N-acetyl-cysteine (NAC), L-buthionine-(S,R)-sulfoximine (BSO), and c-Jun N-terminal kinase (JNK) inhibitor (SP600125), suggesting that activation of CHOP promoter by brefeldin A may not involve oxidative stress or JNK signaling pathway. On the other hand, brefeldin A-induced apoptosis was not affected by NAC and BSO pretreatment, but was completely suppressed by JNK inhibitor pretreatment. Our results suggest that although CHOP is up-regulated by brefeldin A, it is not a major mediator of brefeldin A-induced apoptosis.