Supplementary Material for: Proteomic Analysis of Pancreatic Ductal Adenocarcinoma Compared with Normal Adjacent Pancreatic Tissue and Pancreatic Benign Cystadenoma

Background: Dual expression of potential biomarkers in both benign and malignant pancreatic tumors was a major obstacle in the development of diagnostic biomarkers of early pancreatic cancer. Methods: To better understand the limitations of potential protein biomarkers in pancreatic cancer, we employed two-dimensional difference gel electrophoresis technology and tandem mass spectrometry to study protein expression profiles in pancreatic cancer tissues, benign pancreatic adenoma and normal adjacent pancreas. Seven differently expressed proteins were selected for validation by Western blot and/or immunohistochemistry. Results: 21 spots were overexpressed and 24 spots were downexpressed in pancreatic cancer compared with benign and normal adjacent tissues. Our study demonstrated that three candidate pancreatic ductal adenocarcinoma biomarkers identified in previous studies, fructose-bisphosphate aldolase A, α-smooth muscle actin and vimentin, were also overexpressed in pancreatic cystadenoma, which might lower their further utility as biomarkers for pancreatic cancer. Aflatoxin B1 aldehyde reductase (AKR7A2) was confirmed to be only highly expressed in pancreatic cancer, not in normal adjacent pancreas and benign tumors. Conclusions: The protein profile pattern of pancreatic cystadenoma was more similar to normal adjacent pancreas than pancreatic cancer. We identified panels of the upregulated proteins in pancreatic cancer, which have not been reported in prior proteomic studies. AKR7A2 may be a novel potential biomarker for pancreatic cancer.