Abstract A2: Autoantibody signature in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy characterized by rapid progression, invasiveness and resistance to treatments. Biomarkers for its early detection are lacking. In this study we used a proteomic-based approach to identify overexpressed and/or aberrantly modified antigens that could have diagnostic value by inducing an autoantibody response in PDAC. By using SERological Proteome Analysis (SERPA), we have identified nineteen tumor-associated antigens (TAAs) that were specifically recognized by IgG from PDAC patients. These autoantibodies were directed, with high frequency, against a number of metabolic enzymes and cytoskeletal proteins, mostly upregulated in PDAC. The protein most frequently recognized was α-enolase (ENOA), a glycolytic enzyme that can localize on the cell surface as a plasminogen receptor. ENOA was expressed on the surface of PDAC cells and elicited T cell proliferation and activation both in vitro and in vivo. Liquid chromatography-coupled tandem mass spectrometry (LC-MS/MS) studies have revealed that in PDAC ENOA is subjected to specific post-translational modifications (PTMs). Further characterization studies of the antibody response to ENOA revealed that PDAC patients specifically produce antibodies to ENOA isoforms that are phosphorylated at Serine-419. By exploiting a genetically engineered mouse model (GEM) spontaneously developing PDAC with a well-defined kinetic, we applied the SERPA approach with mouse sera to validate circulating antibodies to TAAs as early diagnostic tools in PDAC. Eight antigens able to induce the production of autoantibodies in pancreatic intraepithelial neoplasia (PanIN) were identified and five of them induced specific IgG also in PDAC patients. A plasma-membrane cytoskeleton linker molecule showed the highest frequency of autoantibodies in GEMs with early disease and in resectable PDAC patients. ROC analysis demonstrated that the combination of autoantibodies to Ser-419-phosphorylated ENOA in association with antibodies to this cytoskeletal protein and CA19.9 serum levels achieved approximately 97% diagnostic accuracy. In conclusion, our results demonstrate that the simultaneous capture of autoantibodies against a panel of pancreatic cancer-associated antigens might have diagnostic value in this tumor. Citation Format: Michela Capello, Michele Milella, Francesco Novelli, Paola Cappello, Sammy Ferri-Borgogno, Weidong Zhou, Giorgia Mandili, Claudia Fredolini, Isabella Sperduti, Federica Linty, Emanuel Petricoin. Autoantibody signature in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Progress and Challenges; Jun 18-21, 2012; Lake Tahoe, NV. Philadelphia (PA): AACR; Cancer Res 2012;72(12 Suppl):Abstract nr A2.