Role of HspB and CagA in molecular pathogenesis of Helicobacter pylori-positive gastric cell

Adenocarcinoma of the stomach is one of the most common cause of cancer mortality in the world. H. pylori has been implicated in gastric carcinogenesis only on the basis of epidemiological studies. However, direct experimental evidence demonstrating a causal role for H. pylori in carcinogenesis has been lacking. Only recently it has been demonstrated that long-term infection with H. pylori induces adenocarcinoma in mongolian gerbils. Aim of the work was to evaluate the effects of two H. pylori proteins, CagA and HspB, on cell kinetics and the ability to selectively affect the expression of cell cycle related proteins using epithelial cell line (AGS). Using a genomic library of H. pylori we were able to isolate and clone in a pcDNA3 vector two proteins expressed from the H. pylori CagA and HspB. These proteins were overexpressed in a gastric cell line (AGS). The effects of these proteins on the proliferation rates of the cells transfected were analyzed by poliferation assay. Immunoblots screening was performed on cell lysates with antibodies against the major proteins known to regulate the cell cycle checkpoints. Moreover the same cells were analyzed by flow cytometry. After over expression, in AGS cells of CagA and HspB, we observed an increase of proteins involved on the G1/S checkpoint. We demonstrated that the process of transformation from normal gastric mucosa to carcinoma is characterized by increased cell proliferation. Proteins expressed from H. pylori may act as a promoter in gastric carcinogenesis by causing a state of increased gastric epithelial proliferation. This data taken together provide additional information to further enhance our understanding of the molecular mechanism by which H. pylori proteins alter the growth status of the cell.