Aims: Tumour necrosis factor (TNF)-alpha induces death or cell proliferation by activation of nuclear factor (NF)-kappaB, also activated by interleukin (IL)-1 alpha. The aim was to investigate upstream and downstream components of NIK transduction pathway in normal (NP), benign prostatic hyperplasia (BPH), prostatic intraepithelial neoplasia (PIN) and prostatic carcinoma (PC).
Methods and results: Immunohistochemistry and Western blotting were performed. In NP, the cytoplasm of epithelial cells was intensely immunoreactive to IL-1 receptor-associated kinase (IRAK), TNF receptor-associated factor (TRAF)-6, NF-kappaB inducing kinase (NIK), I kappa kappa alpha/beta, I kappaB alpha and p-I kappaB; weakly to NF-kappaB-p50; and negative to NF-kappaB-p65. BPH samples were intensely immunoreactive to IRAK, TRAF-6, NIK, I kappa kappa alpha/beta, I kappaB alpha, p-I kappaB; weakly to NF-kappaB-p50 and NF-kappaB-p65. Whereas low-grade PIN showed intermediate results between NP and BPH, results in high-grade PIN were similar to those found in PC (low Gleason). In PC, immunoreactivity was intense for IRAK, TRAF-6, NIK, I kappa kappa alpha/beta (increasing with Gleason), I kappaB alpha, p-I kappaB (decreasing with Gleason); weak for NF-kappaB-p50 and NF-kappaB-p65 (decreasing with Gleason). Nuclear NF-kappaB was observed in PC.
Conclusions: NF-kappaB enhances cell proliferation, but also ATF-2 or Elk-1. Since IL-1 and TNF-alpha are related to inflammation and their immunoexpression increases in PC, inhibition of these cytokines might be a possible target for PC treatment, because they decrease the activity of all transduction pathway members that activate transcription factors such as NF-kappaB, Elk-1 or ATF-2.