ID1 and benign prostatic hyperplasia: In human specimens, Id-1 expression in prostate cancer is increased in comparison to benign prostatic hyperplasia specimens (Ouyang et al, 2002a), and increased expression of Id-1 is correlated with Gleason score, reflecting the aggressive nature of Id-1-positive prostate cancers (Ouyang et al, 2002a; Coppe et al, 2004; Yuen et al, 2006).