Expression of cathepsin E in pancreas: a possible tumor marker for pancreas, a preliminary report

Ductal cancers of the pancreas frequently express markers of gastrointestinal epithelial cells. Cathepsin E (CTSE) is a non-secretory, intracellular, but non-lysosomal proteinase found in the highest concentration in the superficial epithelial cells of the stomach. The aims of our study were to examine the expression of CTSE in the pancreas, to establish an assay system of CTSE and to evaluate the diagnostic usefulness of CTSE in the pancreatic juice. Eleven patients with pancreatic ductal adenocarcinoma, 10 with mucin-producing adenoma, 3 with intraductal papillary hyperplasia and 43 with chronic pancreatitis were examined. Surgically resected pancreatic tissues were subjected to immunohistochemistry for CTSE. Pancreatic juice was collected from the patients and subjected to sandwich ELISA and Western analysis for detecting CTSE. Positive staining for CTSE was observed in pancreatic ductal adenocarcinoma by immunohistochemistry. CTSE was also expressed in mucin-producing adenoma, intraductal papillary hyperplasia and mucinous hyperplasia. CTSE in the pancreatic juice was present in 8 of 11 patients with pancreatic ductal adenocarcinoma, 5 of 10 patients with mucin-producing tumor, 1 of 3 patients with intraductal papillary hyperplasia and 4 of 43 patients with chronic pancreatitis. The detection frequency of CTSE in the pancreatic juice was significantly higher in the patients with pancreatic ductal adenocarcinoma than in the patients with chronic pancreatitis. Our findings suggest that the expression of CTSE is associated with the pathogenesis of pancreatic ductal adenocarcinoma, that CTSE in the pancreatic juice seems to be a useful marker for a definitive diagnosis and that CTSE may be expressed at a relatively early stage of multistep carcinogenesis in pancreatic lesions.