Apoptotic pathways controlled by the Rel/NF-kB family of transcription factors may regulate the response of cells to DNA damage. Here, we have examined the NFkB status of several prostate tumor cell lines. In the androgen-independent prostate tumor cells PC-3 and DU-145, the DNA-binding activity of NF-kB was constitutively activated and IkB-a levels were decreased. In contrast, the androgen-sensitive prostate tumor cell line LNCaP had low levels of NF-kB which were upregulated following exposure to cytokines or DNA damage. The activity of the IkB-a kinase, IKKa, which mediates NF-kB activation, was also measured. In PC-3 cells, IKKa activity was constitutively active, whereas LNCaP cells had minimal IKKa activity that was activated by cytokines. The anti-in¯ammatory agent ibuprofen inhibited the constitutive activation of NF-kB and IKKa in PC-3 and DU-145 cells, and blocked stimulated activation of NF-kB in LNCaP cells. However, ibuprofen did not directly inhibit IkB-a kinase. The results demonstrate that NF-kB is constitutively activated in the hormone-insensitive prostate tumor cell lines PC-3 and DU-145, but not in the hormone responsive LNCaP cell line. The constitutive activation of NF-kB in prostate tumor cells may increase expression of anti-apoptotic proteins, thereby decreasing the e ectiveness of anti-tumor therapy and contributing to the development of the malignant phenotype.

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