Characterization of Markers for Pancreatic Cancer Obtained by Proteomic Profiling.
Christopher Thompson, David Rundell, Shaiju Vareed, Vadiraja Bhat, Vihas Vasu, Mohsen Shabahang, James McLoughlin, Arun Sreekumar, Arundhati Rao. Scott & White Hospital, Temple, TX; Medical College of Georgia, Augusta; Agilent Technologies, Wilmington, DE
Background: Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer death in the United States. Currently, there are no clinically useful biomarkers for the detection of clinically occult PDAC. We are using a proteomics-based approach to identify possible PDAC biomarkers.
Design: 25 samples of pancreatic duct fluid (18 carcinomas, 7 benign) were analyzed using label-free mass spectrometry coupled to SDS-PAGE and Cation-Exchange Chromatography. 433 proteins were detected of which 56, including Purine Nucleoside Phosphorylase (NP), were found to be significantly elevated in PDAC. The expression of NP was then correlated to tissue expression by immunoblot and immunohistochemistry (IHC). Tissue microarrays (TMA) comprised of 76 PDAC, 9 pancreas mucinous cystadenomas, 12 intraductal papillary mucinous neoplasms (IPMN), 6 intraductal papillary mucinous carcinomas with and without invasion, 45 benign pancreatitis samples, and 44 carcinomas from non-pancreatic sites were examined. NP staining was scored for extent (0-4+) and intensity (0-3+) with a total staining score defined as the sum of the intensity and extent scores. Positive staining was defined as a total score > 4.
Results: Immunoblot analysis for NP in serum revealed two bands at ∼35 KDa, with a unique upper band seen in PDAC tissue and sera that was low to undetectable in benign cases. 61 of 76 PDAC cases were positive for NP by IHC. NP was predominantly negative (average total staining score=1) in cases of IPMN, IPM carcinomas, mucinous cystadenomas and pancreatitis. Weak NP staining (average total score =3) was noted in gastric and colonic adenocarcinomas. Adenocarcinomas from the breast and lung as well as hepatocellular and urothelial carcinomas were essentially negative.
Conclusions: NP 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. NP, the rate limiting enzyme in the purine salvage pathway, is operational during inflammation as well as neoplastic progression. This study highlights NP as a possible unique marker linking the pathogenesis of PDAC with antecedent pancreatitis. The absence of significant NP staining in pancreatic mucinous tumors may indicate different mechanistic pathways in these neoplasms.
Category: Special Category - Pan-genomic/Pan-proteomic approaches to Cancer
Tuesday, March 1, 2011 9:00 AM
Platform Session: Section H 1, Tuesday Morning