Cancer sera contain antibodies that react with autologous cellular antigens. Here, we report the use of a novel native antigen-based platform, the "reverse capture" autoantibody microarray, for identification of autoantigens against which autoantibody expression may be used to differentiate between patients with prostate cancer and benign prostate hyperplasia (BPH). Serum samples were collected at our institution from patients with BPH and patients with prostate carcinoma with similar blood prostate-specific antigen levels. IgG was purified from individual prostate cancer sera, differentially labeled with fluorescent dyes, and competitively hybridized against purified IgG from a group of well-characterized BPH control patients on our reverse capture microarray platform. For each experiment, we performed a two-slide dye-swap. Using this platform, we identified 28 unique antigen-autoantibody reactivities that have the potential to discriminate prostate cancer from BPH. These autoantigens, with p-values ≤0.01, can be placed into the following general categories: protein kinases, cell-cycle regulators, cancer-growth factors, apoptosis mediators, and transcription factors. In addition, only 1 of the 28 autoantigens remained differentially targeted by autoantibodies in post-surgical prostate cancer patients after a minimum 1-year follow-up. Autoantibody profiling using this platform may be a useful tool for differentiating between malignant and benign diseases of the prostate.
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