To determine whether constitutive activation of STAT3 is associated with prostate cancer in vitro and in vivo, we first examined activated STAT3 expression by Western blotting with anti-pSTAT3 (Tyr-705) antibody in human PC3M-1E8 prostate cancer cells and a series of 14 primary prostate tumor (T) specimens with matched adjacent nontumor (N) prostate tissues. The gene discussed is STAT3; the disease is prostate cancer.