Discovery of Apo-A1 as a potential bladder cancer biomarker by urine proteomics and analysis

•Urine proteomics is promising for biomarker identification of bladder cancer.•Urine Apo-A1 could be a potential biomarker of bladder cancer.•Apo-A1 level could be an auxiliary examination for exfoliative urinary cytology. Bladder cancer is clinically characterized by high recurrent rate and poor prognosis and thereby patients need regular re-examinations which are invasive, unpleasant, and expensive. A noninvasive and less expensive method for detecting and monitoring bladder cancer would thus be advantageous. In this study, by using the two-dimensional electrophoresis (2-DE) approach with subsequent mass spectrometry (MS), we demonstrated the increased expression of apolipoprotein-A1 (Apo-A1) in individual urine from patients with bladder cancer, which was confirmed by Western blot results. A further analysis of the urinary Apo-A1 levels by an enzyme-linked immunosorbent assay yielded results that were consistent with the Western blot, and suggested Apo-A1 could provide diagnostic utility to distinguish patients with bladder cancer from healthy controls at 19.21ng/ml. Further validation assay in a larger number of urine samples (n=379) showed that Apo-A1 could be used as a biomarker to diagnosis bladder cancer with a sensitivity and specificity of 89.2% and 84.6% respectively. Moreover, the application of exfoliative urinary cytology in combination with the urine Apo-A1 detection could significantly increased the sensitivity in detecting bladder cancer. Our data showed a significant relationship of expressed Apo-A1 was established between bladder cancer and normal controls. Apo-A1 could be a potential biomarker for the diagnosis of bladder cancer.