Caspases and c-Jun N-terminal kinase (JNK) are acti-vated in tumor cells during induction of apoptosis. We investigated the signaling cascade and function of these enzymes in cisplatin-induced apoptosis. Treat-ment of Jurkat T-cells with cisplatin induced cell death with DNA fragmentation and activation of cas-pase and JNK. Bcl-2 overexpression suppressed activa-tion of both enzymes, whereas p35 and CrmA inhib-ited only the DEVDase (caspase-3-like) activity, indi-cating that the activation of these enzymes may be dif-ferentially regulated. Cisplatin induced apoptosis with the cytochrome c release and caspase-3 activation in both wild-type and caspase-8-deficient JB-6 cells, while the Fas antibody induced these apoptotic events only in wild-type cells. This indicates that caspase-8 activation is required for Fas-mediated apoptosis, but not cisplatin-induced cell death. On the other hand, cisplatin induced the JNK activation in both the wild-type and JB-6 cells, and the caspase-3 inhibitor Z-DEVD-fmk did not inhibit this activation. The JNK overexpression resulted in a higher JNK activity, AP-1 DNA binding activity, and metallothionein expression than the empty vector-transfected cells following cis-platin treatment. It also partially protected the cells from cisplatin-induced apoptosis by decreasing DEVDase activity. These data suggest that the cis-platin-induced apoptotic signal is initiated by the cas-pase-8-independent cytochrome c release, and the JNK activation protects cells from cisplatin-induced apop-tosis via the metallothionein expression.

Keywords: JNK., Apoptosis, Cytochrome c, Caspase, Cisplatin