KLK3 and Familial prostate cancer: More importantly, human kallikrein 3 also known as prostate-specific antigen (PSA) and used as prognostic tumor marker in prostate cancer diagnosis was more than 7-fold upregulated in CD133-positive prostate CSCs compared to other (CD133-negative) prostate cancer cells [85] supporting the concept within a CSCN that CSCs acquire increased migratory and metastatic potential.