Urinary biomarkers in prostate cancer detection and monitoring progression.

Prostate cancer (CaP) is the most common cancer in men and the second leading cause of cancer deaths in males in Australia. Although serum prostate-specific antigen (PSA) has been the most widely used biomarker in CaP detection for decades, PSA screening has limitations such as low specificity and potential association with over-diagnosis. Current biomarkers used in the clinic are not useful for the early detection of CaP, or monitoring its progression, and have limited value in predicting response to treatment. Urine is an ideal body fluid for the detection of protein markers of CaP and is emerging as a potential source for biomarker discovery. Gene-based biomarkers in urine such as prostate cancer antigen-3 (PCA3), and genes for transmembrane protease serine-2 (TMPRSS2), and glutathione S-transferase P (GSTP1) have been developed and evaluated in the past decades. Among these biomarkers, urinary PCA3 is the only one approved by the FDA in the USA for clinical use. The study of urine microRNAs (miRNAs) is another burgeoning area for investigating biomarkers to achieve a pre-biopsy prediction of CaP to contribute to early detection. The development of mass spectrometry (MS)-based proteomic techniques has sparked new searches for novel protein markers for many diseases including CaP. Urinary biomarkers for CaP represent a promising alternative or an addition to traditional biomarkers. Future success in biomarker discovery will rely on collaboration between clinics and laboratories. In addition, research efforts need to be moved from biomarker discovery to validation in a large cohort or separate population of patients and translation of these findings to clinical practice. In this review, we discuss urine as a potential source for CaP biomarker discovery, summarise important genetic urine biomarkers in CaP and focus on MS-based proteomic approaches as well as other recent developments in quantitative techniques for CaP urine biomarker discovery.