Urinary extracellular vesicles: a rising star in bladder cancer management

Clinically, the detection of bladder cancer (BCa) typically requires cystoscopy, which is potentially harmful and sometimes accompanied by adverse effects. Thus, new biomarkers are desirable for improving the management of BCa. Recently, "liquid biopsy" has received enormous attentions and has been extensively studied due to its promising clinical implication for precise medicine. Especially, extracellular vesicles (EVs) have attracted strong interest as a potential source of biomarkers. EVs have been reported to be found in almost all types of body fluids and are easy to collect. In addition, EVs tightly reflect the current state of the disease by inheriting specific biomolecules from their parental cells. Urinary EVs have gained great scientific interest in the field of BCa biomarker research since urine is in direct contact with BCa and can contain large amounts of EVs from the tumour microenvironment. To date, various kinds of biomolecules, including noncoding RNAs, mRNAs, and proteins, have been investigated as biomarkers in urinary EVs. In this narrative review, we summarize the recent advances regarding urinary EVs as non-invasive biomarkers in patients with BCa. The current hurdles in the clinical implications of EV-based liquid biopsy and the potential applications of EV research are also discussed.