Although factors have been identified that alter gastrin gene expression in in vitro studies, gastrin gene regulation in whole animal models is not clear. The epidermal growth factor (EGF) and tumor necrosis factor (TNFalpha) are among the factors that have been reported to activate the gastrin promoter. Thus, the goal of this project is to evaluate whether other protein factors present during Helicobacter pylori infection will alter gastrin gene expression. Hypergastrinemia, which is often associated with H. pylori infection, tends to increase the risk of gastric cancer. Thus, the role of two protooncogenes, c-myc and c-fos, in the activation of the gastrin gene will be addressed. This study also seeks to define whether c-Myc and c-Fos protooncoproteins, which are present during H. pylori infection, cooperate in the activation of the gastrin promoter. Transient transfects of human gastric adenocarcinoma AGS cell, human colon CCD-33Co cell, and rat pituitary adenoma GH/4 cell lines will be programmed to express a gastrin promoter reporter and an excess of c-Fos or c-Myc proteins. Changes in gastrin promoter activity following treatment will be evaluated by luciferase assays. Expression of the c-fox and c-myc vectors will be assessed by Western blot analyses of c-Fox and c-Myc protein levels. Immunofluorescent staining will be used to determine whether c-Myc and gastrin co-expressed in the same antral G cells. Dna binding of c-Myc protein will be evaluated by electrophoretic mobility shift assays (EMSAs). This study is meaningful because it seeks to evaluate role of protein factors present during H. pylori in gastrin gene expression and the possible cooperativity between c-Fos and c-Myc proteins in the induction of the gastrin promoter.
