In the search of novel urine biomarkers for the early diagnosis of prostate cancer. Intracellular or secreted proteins as the target group? Where and how to search for possible biomarkers useful in the everyday clinical practice

Objective: To search which category of proteins can be detected in urine in order to examine subsequently its ability to improve our accuracy for the diagnosis of Prostate Cancer (PCa) as biomarkers in clinical useful fluids like urine and serum. Material and method(s): Urine samples of 127 patients were obtained after a vigorous transrectal prostatic massage to both lobes. The patients were considered to have a high risk for PCa according to their PSA (> 4 ng/ml), their digital rectal examination (DRE) (positive for suspicious prostatic lesions) or to their abnormal PSA kinetics (PSA velocity (PSAV > 0.75 ng/mL). All patients subsequently were subjected to an extended 10-core per prostatic lobe TRUS-b (total 20 prostatic samples). The proteins that were chosen to be detected in the urine samples with Western-blot, as possible biomarkers, were Glutathione peroxidase 3 precursor (GPx3), Cofilin-1 (CFL1), Heat shock protein-90β (HSP 90β), Zinc alpha 2-glycoprotein (ZAG) and secreted protein acidic and rich in cysteine (SPARC).These proteins have been detected previously in the prostatic tissue by proteomics proving their discriminative ability between patients with prostate cancer and benign prostatic hyperplasia. Result(s): From the five proteins, only the secreted Zinc alpha 2-glycoprotein was detected in urine showing a promising ability in the improvement of our diagnostic accuracy for the early diagnosis of prostate cancer. Conclusions: From various categories of proteins that have already been detected in the tissue of prostate by proteomics, only secreted protein Zinc alpha 2-glycoprotein showed a clear signal in the urine, proving its discriminative potential for the early diagnosis of PCa.