Analysis of novel tumor markers in pancreatic and biliary carcinomas using tissue microarrays

Using global gene expression analyses, multiple novel tumor markers overexpressed in infiltrating ductal adenocarcinomas of the pancreas have recently been identified. However, the expression of these markers in morphologically similar adenocarcinomas of the biliary tree has not been investigated. The purpose of the present study was 3-fold. First, we used 8 markers that have been shown to be overexpressed in whole tissue sections of pancreatic adenocarcinomas to validate tissue microarrays (TMAs) created from a series of pancreatic adenocarcinomas (n=68). The labeling patterns of 6 epithelial markers (fascin, mucin 4, 14-3-3sigma, prostate stem cell antigen, topoisomerase IIalpha, and cdc2/p34) were concordant with previously published studies on whole tissue sections, yet required far fewer slides and reagents. Mesothelin, an epithelial marker, and heat shock protein 47, a marker of peritumoral desmoplasia, showed lower levels of expression in the TMAs when compared with whole tissue sections. Second, we examined the previously unknown expression of the same 8 novel tumor proteins in cancers of the biliary tree by using TMAs created from a series of intrahepatic cholangiocarcinomas, gallbladder adenocarcinomas, and adenocarcinomas of the distal common bile duct (n=38). Each of the 8 markers was overexpressed in the biliary cancers, ranging from 14% demonstrating at least focal labeling with prostate stem cell antigen to 100% labeling with cdc2/p34. Most of the markers showed lower frequencies of expression in the biliary tract carcinomas in comparison to the pancreatic adenocarcinomas. In addition, expression patterns varied with location in the biliary system (intrahepatic versus gallbladder versus distal common bile duct). These differences were statistically significant (P<0.05) for mesothelin, mucin 4, and heat shock protein 47. Finally, the expression of selected markers in neoplastic progression of gallbladder cancer was examined. Two markers, fascin and mesothelin, showed up-regulation of expression with transition from carcinoma in situ to invasive adenocarcinoma, implicating a role for these markers in neoplastic progression. The results of this study indicate that TMA technology provides valid and cost-effective means to screen large numbers of novel tumor markers, even in tumors such as pancreatic and biliary adenocarcinomas that characteristically have abundant desmoplastic stroma. In addition, novel tumor markers of pancreatic adenocarcinomas show similar, yet not identical, expression patterns in biliary carcinomas. Therefore, these markers are potentially useful in developing diagnostic tests and treatment paradigms for tumors involving the biliary system.