Detection of tumor-associated antigens in culture supernatants using autoantibodiesin sera from patients with bladder cancer

Secreted proteins play essential roles in the process of tumorigenesis, and the analysis of tumorsecretedproteins has been suggested as a promising strategy for identifying cancer biomarkers. Inthis study, we performed proteomic analysis to identify proteins secreted from bladder cancer celllines that are recognized by autoantibodies in sera from patients with bladder cancer. In addition,autoantibodies against the identified proteins were validated using a dot-blot array with sera frompatients with bladder cancer and normal controls. As the results, we detected twenty-five and thirty-two immunoreactive spots in sera from patients with high- and low-grade bladder cancer, respectively.In addition, validation analysis revealed that serum IgG levels of anti-calreticulin andmatrix metalloproteinase-2 (MMP2) autoantibodies were significantly higher in bladder cancer patientsthan in normal controls (both P < 0.05). Furthermore, the serum IgG level of anti-MMP2autoantibody was significantly higher in patients with high- compared to low-grade bladder cancer(P < 0.05). On multivariate analysis, the serum IgG level of anti-MMP2 autoantibody was an independentpredictor of cancer-specific survival (P < 0.05). Based on these findings, serum IgG levelsof anti-calreticulin and MMP2 autoantibodies may be novel biomarker candidates for bladdercancer and its clinical outcome.