BACKGROUND. The Reg gene is known to be involved in the growth of not only pancreatic B-cells, but also epithelial cells of the gastrointestinal tract and carcinoma of its lineage. METHODS. Because, to the authors' knowledge, no studies have been reported regarding REG expression in gastric carcinoma, the authors investigated REG mRNA and REG protein expression using reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot analysis, and immunohistochemical study and correlated the results with the clinical features of gastric carcinoma. RESULTS. Using RT-PCR and Western blot analyses, reg mRNA and 16-kilodalton REG proteins were detected in two of eight human gastric carcinoma cell lines. Cytoplasmic localization of REG proteins in the cell lines was confirmed by fluorescent immunocytochemistry. The RT-PCR analysis revealed the presence of REG mRNA in as many as 77% (87 of 112 tumors) of primary gastric carcinoma tumors. Screening of a total of 195 patients with primary gastric carcinoma using immunoperoxidase staining revealed positive REG immunoreactivity in 60 of the 195 primary tumors (31%). REG expression in infiltrating tumors was found to be significantly higher compared with localized tumors (P < 0.05). Strong REG expression was noted in the cytoplasm of signet ring cell carcinoma tumors at a significantly higher incidence than in nonsignet ring cell tumors. Moreover, patients with REG-negative differentiated adenocarcinoma were found to have a significantly better prognosis compared with patients with REG-positive tumors. The incidence of venous invasion of REG-positive tumors was significantly higher than that of REG-negative tumors. CONCLUSIONS. The results of the current study suggest that the expression of the REG gene is closely related to the infiltrating property of gastric carcinoma, and may be a prognostic indicator of differentiated adenocarcinoma of the stomach.
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