Background: Localization of human regenerating gene (reg) mRNA and its product was investigated in normal and neoplastic human pancreas with the in situ hybridization method and immunohistochemical studies.
Methods: Both reg mRNA and reg protein were observed in acinar cells of the pancreas, but neither was found in ductal or islet cells. Immunoreactive reg was observed in an acinar cell carcinoma, a pancreatoblastoma, a solid and cystic tumor, and 5 of 20 duct cell carcinomas, but it was not found in 15 endocrine tumors and 2 microcystic adenomas.
Results: For comparison with reg, alpha-1-antitrypsin (AAT), lysozyme, chromogranin A (CMG), CA 19-9, carcinoembryonic antigen (CEA), cytokeratin, vimentin, and alpha-fetoprotein (AFP) were assessed in those tumors. An acinar cell carcinoma and a pancreatoblastoma had positive results for AAT, lysozyme, cytokeratin, and AFP but negative results for vimentin. An acinar cell carcinoma showed cells focally immunoreactive for CMG and CEA. A solid and cystic tumor had strongly positive results for AAT and vimentin and focally positive results for CMG and pancreatic hormones. Microcystic adenomas had abundant glycogen and strong immunoreactivity for cytokeratin. Ductal cell carcinomas showed cells focally positive for AAT, lysozyme, CMG, CA 19-9, and CEA.
Conclusions: The localization of reg protein was not consist with that of any other proteins examined in the current study. Thus, reg protein was considered a useful marker for acinar cell differentiation; however, ectopic expression of reg also was observed in ductal cell carcinomas. In ductal cell carcinomas, expression of reg immunoreactivity was considered as one of phenotypic heterogeneity, as seen in AAT, lysozyme, and CMG immunoreactivity.