Nuclear localisation of nuclear factor-kappaB transcription factors in prostate cancer:: an immunohistochemical study

Several reports suggest that the canonical nuclear factor-kappaB (NF-kappa B) pathway is constitutively activated in a subset of prostate cancer cells. However, except for RelA (p65), little is known about the status of NF-kappa B transcription factors in prostate cancer tissues. To clarify the status of NF-kappa B subunits, we analysed the expression and subcellular localisation of RelA, RelB, c-Rel, p50, and p52 on tissue array sections containing respectively 344, 346, 369, 343, and 344 cores from 75 patients. The subcellular localisation of NF-kappa B factors was tested against relevant clinical parameters ( preoperative prostate-specific antigen, pathological stage, and postoperative Gleason grade). With the exception of c-Rel, each subunit was detected in the nucleus of cancer cells: significant nuclear expression of RelB, RelA, p52, and p50 was seen in 26.6, 15.6, 10.7, and 10.5% of cores, respectively. Surprisingly, cores expressing both nuclear RelA and p50 canonical pathway proteins were less frequently observed than cores expressing other subunit combinations such as RelB - p52 and RelA - RelB. In addition, the nuclear localisation of RelB correlated with patient's Gleason scores ( Spearman correlation: 0.167; P = 0.018). The nuclear localisation of both canonical and noncanonical NF-kappa B subunits in prostate cancer cells suggests for the first time that different NF-kappa B pathways and dimers may be activated in the progression of the disease.