Exosomes as diagnostic and prognostic tools in prostate cancer

Prostate cancer (PCa) is the second most common cause of cancer-related mortality among men in the developed world. The emergence of more specific biomarkers for PCa is a necessity nowadays, especially owing to the lack of specificity of prostate-specific antigen test for the detection of PCa that could lead to unnecessary prostate biopsies. The discovery of novel biomarkers for PCa in complex fluids, such as serum and urine, remains a challenge. Several recent studies have reported that many cancer-derived proteins and RNAs (e.g., PCA3 and TMPRSS2-ERG) are secreted through small vesicles known as exosomes. Exosomes are nano-membrane vesicles with a diameter of 30–200 nm that various cell types secrete during physiological and pathophysiological conditions. Urinary PCa-derived exosomes as noninvasive urinary markers could be promising sources of novel biomarker discovery. Advancement of comprehensive analysis has resulted in the discovery of several urinary PCa-derived exosome biomarkers that can help in the decision to carry out prostate biopsy or in the design of a therapeutic strategy.