Human urinary exosomes in bladder cancer patients: properties, concentrations and possible clinical application
OBJECTIVE: High grade bladder cancer is extremely aggressive. Early detection is thus an important challenge. Development of non-invasive diagnostic tools particularly using urine samples could be of importance in the diagnosis and surveillance of these patients. Exosomes are small vesicles present in the urine and have the potential to be used as biomarkers of cancer. Thus studies of the properties and concentrations of these particles in bladder cancer patients are of importance.
MATERIALS AND METHODS: The concentration of exosomes present in urine was determined by nanoparticle tracking analysis using a Nanosight LM10 unit. Clinical urine samples were routinely collected and fixed using Preservcyt. The morphology of exosomes was studied in electron micrographs and characteristic exosome markers using Western blots.
RESULTS: The exosome concentration of fixed samples stored at room temperature was constant for 48 hours and the same as fresh samples. Exosomes derived from patients presenting for a transurethral resection of their bladder tumor exhibited the exosome markers ALIX and TSG101 and also the classic cup shaped appearance in electron micrographs. The concentration of exosomes in patients presenting for transurethral resection of a bladder tumor was significantly greater than in patients presenting for check cystoscopy with no recurrence (median 77.2 compared with 38.8 × 108, P<0.001). A ROC analysis (area under the curve 77.4%) suggested that a suitable cut-off concentration of 85 × 108 is associated with a sensitivity of 43% and specificity of 91% for diagnosing bladder cancer.
CONCLUSIONS: Thus the concentration and properties of exosomes can be conveniently studied in fixed urine samples derived from bladder cancer patients. The characteristic properties of exosomes were preserved and increased numbers were found in patients presenting for transurethral resection of their tumor. With an appropriate cut-off value, urinary exosome concentrations may have utility in excluding a cancer recurrence when monitoring patients successfully treated for bladder cancer.
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