Proteomic Analysis of Pancreatic Duct Fluid: Discovery of Novel Protein Expression in Pancreatic Ductal Adenocarcinoma
CN Thompson, A Sreekumar, VB Bhat, J Ojha, A Cashikar, TG Singh, P Ramalingam, JM McLoughlin, M Shabahang, A Werlang-Perurena, A Rao. Scott & White Hospital/Texas A&M, Temple, TX; Medical College of Georgia, Augusta, GA
Background: Pancreatic ductal adenocarcinoma (PDAC) usually presents at an advanced stage resulting in significant morbidity and mortality. Currently, there are no clinically useful biomarkers for the detection of occult PDAC. We are using a proteomics-based approach to identify possible PDAC biomarkers.
Design: 25 samples of pancreatic duct fluid (18 PDAC, 7 benign) were analyzed using OFFGEL-based protein fractionation coupled to tandem mass spectrometry. The mass spectrometry data was then searched against the Human IPI sequence database for matches. Synuclein A (SNCA) was one of the proteins elevated in pancreatic adenocarcinoma compared to controls. The expression of SNCA was then correlated to tissue expression by immunoblot and immunohistochemistry. Tissue microarrays were created from 22 archival specimens including 11 cases of PDAC and 11 cases of chronic pancreatitis. The SNCA staining intensity of ductal epithelial cells was graded on a 0-4+ scale.
Results: Thirty proteins were found to have differential expression in pancreatic duct fluid in PDAC compared to controls (p<0.05, FDR<10 %). Several of these proteins have been previously reported to be elevated in PDAC. Novel findings included increased expression of SNCA. Immunoblot analysis confirmed elevated levels of SNCA in pancreatic adenocarcinoma tissue compared to controls. Immunohistochemistry demonstrated 2+ diffuse staining of ductal epithelium for SNCA in 9 of 11 PDAC cases with 1+ staining of associated stroma compared to focal, 0-1+ staining in benign ductal epithelium. Strong staining was noted in both benign and tumor acini.
Conclusions: Synuclein A is overexpressed in pancreatic duct fluid and tissues derived from patients with pancreatic adenocarcinoma indicating that this protein may be involved in the pathogenesis of PDAC. Mechanistic understanding of its role in PDAC may reveal prognostically relevant pathways. The differential expression in malignant and benign ducts may also be diagnostically useful.
Category: Pan-genomic/Pan-proteomic Approaches to Diseases
Tuesday, March 23, 2010 8:45 AM
Platform Session: Section H 1, Tuesday Morning