This protein biochip system quantitatively measured 12 common tumor markers, including cancer antigen (CA)125, CA15-3, CA19-9, CA242, carcinoembryonic antigen (CEA), R-fetoprotein (AFP), prostate specific antigen (PSA), free-prostate specific antigen (f-PSA), human growth hormone (HGH), β-human chorionic gonadotropin (β-HCG), neuron-specific enolase (NSE) and ferritin (FER), in the serum and was tested in clinically confirmed cancer patients and apparently healthy individuals. Here, KLK3 is linked to cancer.