cis-Diamminedichloroplatinum(II) (CDDP) is a chemotherapeutic agent known to inhibit DNA, RNA, and protein synthesis. The cytotoxicity of this drug is thought to result from the formation of DNA intrastrand cross-links. The present work demonstrates that treatment of human myeloid leukemia cells (HL-60, U-937, and KG-1) with CDDP is associated with increased expression of the c-jun gene and that this effect is related to activation by a transcriptional mechanism. The results also demonstrate that treatment with CDDP is associated with increases in protein kinase C (PKC) activity. Furthermore, the finding that pre-treatment with H7, an inhibitor of PKC, abrogates the effect of CDDP on c-jun expression suggested the involvement of PKC in this process. Down-regulation of PKC by prolonged pretreatment with 12-O-tetrade-canoylphorbol-13-acetate was also associated with inhibition of CDDP-induced c-jun expression. The results further demonstrate that there is a temporal relationship between the CDDP-induced increase in c-jun expression and the occurrence of internucleosomal DNA cleavage characteristic of programmed cell death. These findings suggest that c-jun may be involved in the cellular response to DNA-damaging agents, such as CDDP, and that this effect may be mediated by a PKC-dependent pathway.

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This investigation was supported by USPHS Grants CA42802 and CA34183 awarded by the National Cancer Institute and by a Burroughs Wellcome Award in Clinical Pharmacology (D. K.).

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