Transcriptional regulation of bcl-2 by nuclear factor κB and its significance in prostate cancer

This work presents direct evidence that the bcl-2 gene is transcriptionally regulated by nuclear factor-κB (NF-κB) and directly links the TNF-α/NF-κB signaling pathway with Bcl-2 expression and its pro-survival response in human prostate carcinoma cells. DNase I footprinting, gel retardation and supershift analysis identified a NF-κB site in the bcl-2 p2 promoter. In the context of a minimal promoter, this bcl-2 p2 site 1 increased transcription 10-fold in the presence of the p50/p65 expression vectors, comparable to the increment observed with the consensus NF-κB site, while for the full p2 promoter region transcriptional activity was increased sixfold by over-expression of NF-κB, an effect eliminated by mutating the bcl-2 p2 site 1. The expression of Bcl-2 has been linked to the hormone-resistant phenotype of advanced prostate cancer. Here we show that an increase in the level of expression of Bcl-2 in the human prostate carcinoma cell line LNCaP observed in response to hormone withdrawal is further augmented by TNF-α treatment, and this effect is abated by inhibitors of NF-κB. Concomitantly, bcl-2 p2 promoter studies in LNCaP cells show a 40-fold increase in promoter activity after stimulation with TNF-α in the absence of hormone.