AR and prostate cancer: Of these, interleukin-6 (IL-6), a pleiotropic cytokine involved in the regulation of hematopoiesis, immune response, inflammation, bone metabolism and neural development (Kishimoto et al, 1992), has been regarded as one of the most important mediators during AI progression of prostate cancer through the ligand-independent activation of AR (Okamoto et al, 1997; Hobisch et al, 1998; Lou et al, 2000; Lin et al, 2001; Ueda et al, 2002a, 2002b; Lee et al, 2003).