KLK3 and prostate cancer: Although PSA, the tumor-associated serum protein marker, is useful for monitoring prostate cancer progression, it is insufficient for diagnosing primary cancers or even early prostate cancer detection mainly due to its limited specificity at the desired sensitivity (Pannek and Partin, 1998, Djavan et al. 1999; Petricoin et al. 2002b; Adam et al. 2002; Qu et al. 2002; Wang et al. 2005; Engwegen Judith et al. 2006).