Urinary Exosomal CA9 mRNA as a Novel Liquid Biopsy for Molecular Diagnosis of Bladder Cancer

OBJECTIVE: The objective of this study was to assess the possibility of using urinary exosomal CA9 mRNA as a novel liquid biopsy for the molecular diagnosis of bladder cancer. PATIENTS AND METHODS: A total of 168 bladder cancer patients and 90 control subjects were included in the study. An isolation kit was used to isolate urinary exosomes. Transmission electron microscopy (TEM) was used to examine the presence of exosomes. Flow cytometry was used to examine the exosomal marker CD63. The expression level of exosomal CA9 mRNA was detected by RT-qPCR. The diagnostic performance of urinary urinary exosomal CA9 mRNA was evaluated. RESULTS: TEM confirmed the enriched exosomes from urinary bladder patients. Flow cytometry indicated a strong positive expression of exosome marker CD63. Successful extraction of RNA was performed from exosome samples. The level of urinary exosomal CA9 mRNA was significantly higher in bladder cancer group than in control group (p<0.001). The area under the ROC curve was 0.837 (95% CI: 0.743–0.859) with a sensitivity of 85.18% and a specificity of 83.15% for the diagnosis of bladder cancer. CONCLUSION: We found that the urinary exosomes were abundant in the urine of bladder cancer patients. CA9 mRNA could be detectable in urinary exosomes. The urinary exosomal CA9 mRNA may present a new liquid biopsy for the diagnosis of bladder cancer.