The p38 transduction pathway in prostatic neoplasia

Abstract

It has been proposed that, among other cellular responses, TNF‐α induces not only cell death, but also cell proliferation by activation of p38. It has also been reported that IL‐1‐α favours cell proliferation by p38 activation. The aim of the present study was to evaluate upstream (α‐PAK, MEK‐6) and downstream (Elk‐1 and ATF‐2) components of the p38 transduction pathway in normal prostate, benign prostatic hyperplasia (BPH), and prostate carcinoma (PC). Immunohistochemical and western blot analyses were performed in 20 samples of normal prostate, 47 samples of BPH, and 27 samples of PC. In all normal prostates, immunoreactivity for p‐Elk‐1 and p‐ATF‐2 was observed in epithelial cell nuclei, but no expression of α‐PAK or MEK‐6. In BPH, there was expression of α‐PAK (cytoplasm) and MEK‐6 (cytoplasm), while the proportions of lesions that were immunoreactive for p‐Elk‐1 (nucleus and cytoplasm) and p‐ATF‐2 (nucleus) decreased. In PC, the percentages of cells that were immunoreactive for α‐PAK (cytoplasm) or MEK‐6 (cytoplasm) rose slightly in comparison with BPH, while the percentages of cells that were immunoreactive for p‐Elk‐1 (nucleus and cytoplasm) or p‐ATF‐2 (nucleus and cytoplasm) were much higher than in BPH. It is concluded that overexpression of α‐PAK, MEK‐6, p38, p‐Elk‐1, and p‐ATF‐2 in BPH, and more intensely in PC, enhances cell proliferation. In BPH, such proliferation is triggered by IL‐1 and in part counteracted by the TNF‐α/AP‐1 pathway, which promotes apoptosis. In PC, proliferation is triggered by IL‐1 and TNF‐α (the TNF‐α/AP‐1 pathway is diverted towards p38 activation). Since in a study of the same patients immunoexpression of IL‐1α and IL‐1RI was previously observed to be increased in PC, inhibition of p38 is a possible target for PC treatment, as this inhibition would both decrease IL‐1‐induced cell proliferation and increase TNF‐α‐induced cell death. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.