STAT3 and prostate cancer: Evidence in clinical tissue to support these in vitro observations are sparse, although it is reported that IL-6 receptor expression is eightfold higher in prostate cancer tissue compared to normal tissue (Giri et al, 2001) and that phosphorylated STAT3 is observed in 82% of human prostate tumours and expression levels correlate with Gleason score (Barton et al, 2004).