Discovery of Potential Bladder Cancer Biomarkers by Comparative Urine Proteomics and Analysis

Our study focused on urine protein of patients with bladder cancer. By using 2-dimensional electrophoresis with matrix-assisted laser desorption ionization time-of-flight mass spectrometry, we identified 14 differentially expressed protein spots between 3 patients with bladder cancer and 3 normal controls. Apolipoprotein A-I is one of the proteins that was at increased levels in the bladder cancer urine specimens, and it was confirmed by using Western blot analysis. We concluded that 14 differential spots included apolipoprotein A-I and could be potential urinary biomarkers for bladder cancer. Objective: We searched for bladder tumor markers by analyzing urine samples from patients with bladder cancer and from normal controls. Methods: Proteins in urine samples of patients with bladder cancer and with normal controls were systematically examined by 2-dimensional electrophoresis combined with matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The expression of the protein apolipoprotein A-I (apoA-I) was confirmed by Western blot analysis and further evaluated. Results: We successfully obtained the 2-dimensional electrophoresis gel maps of urinary proteins in patients with bladder cancer and in normal controls. Thirty differentially expressed protein spots were successfully matched by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Combined with the SWISS-PROT database, only 14 proteins (beta-2-microglobulin, fatty acid-binding protein adipocyte, gelsolin, isoform 1 of gelsolin, myoglobin, isoform 2 of fibrinogen alpha chain, apoA-I, prostaglandin D 2 synthase 21 kDa [ brain], protein AMBP, transthyretin, keratin type II cytoskeletal 1, type II cytoskeletal 8, putative uncharacterized protein ALB, putative uncharacterized protein MASP2 [ fragment]) were identified, including 2 putative proteins. Furthermore, apoA-I was confirmed by Western blot analysis, and the high level of apoA-I was found in urine samples from patients with bladder tumors compared with normal controls. Conclusions: Analysis of urinary proteome may be a feasible, noninvasive, and efficient strategy for searching for potential bladder tumor biomarkers. A significant relationship of expressed apoA-I was established between bladder cancer and normal controls. We concluded that 14 differential spots included the apoA-I and would be potential urinary biomarkers for the diagnosis and surveillance of bladder cancer. Clinical Genitourinary Cancer, Vol. 11, No. 1, 56-62 (C) 2013 Elsevier Inc. All rights reserved.