Expression of NF-κB-related proteins and their modulation during TNF-α-provoked apoptosis in prostate cancer cells

BACKGROUND The involvement of TNF-a in cancer development is controversial, since this cytokine was reported to act either as tumor promoter or suppressor. TNF-a may activate signaling pathways critical for life/death decisions, such as mitogen-activated protein kinases (MAPKs) and the anti-apoptotic NF-?B pathway. In this work, we investigate the activation status of NF-?B-related proteins in human prostate cancerous versus normal epithelium, and the alterations in the NF-?B pathway in relation to cell death in TNF-a-treated LNCaP (androgen-independent cells) and PC3 (androgen-independent) prostate cancer cell lines. METHODS The expression of phospho-p38-MAPK, phospho-IKK-alpha/beta and phospho-I kappa B-alpha, total I kappa B-alpha, and p65-and p50-NF-kappa B, were analyzed by immunohistochemistry in cancerous and normal prostate samples. The toxicity of TNF-alpha in LNCaP and PC3 cells, with or without kinase and NF-kappa B inhibitors, was assessed by changes on viability (MTT assay) and apoptosis (loss of DNA, annexin-V binding, and caspase cleavage/activation). Expression of NF-kappa B related proteins in these cell lines was measured by Western blot. RESULTS. Phospho-IkB-alpha, phospho-IKK-alpha/beta and phospho-p38 levels, cytoplasmic p50 to I kappa B-alpha ratio, and nuclear p50 and p65, levels, were increased in cancerous epithelium, suggesting activation of the NF-kappa B pathway in prostatic malignance. TNF-alpha caused apoptosis with higher efficacy in LNCaP cells, and this response was potentiated by p38-MAPK inhibitor (LNCaP cells) and IKK-beta inhibitor (both cell lines). However, the protective action of IKK-beta was mediated by NF-kappa B only in LNCaP cells. CONCLUSIONS. IKK-beta mediates both NF-kB-dependent and -independent anti-apoptotic functions in prostate cancerous epithelium. IKK-beta and p38-MAPK may represent useful therapeutic targets against prostate cancer. Prostate 72: 40-50, 2012. (C) 2011 Wiley Periodicals, Inc.