Effects of broth culture filtrate protein of VacA+ Helicobacter pylori on the proliferation and apoptosis of gastric epithelial cells

Infection with Helicobacter pylori (H. pylori) may lead to chronic inflammation of the stomach epithelium, mucosal atrophy, imbalance of proliferation and apoptosis of epithelial cells; resulting in chronic gastritis, peptic ulcer, gastric cancer, and many other clinical outcomes. Why and how H. pylorus leads to gastric cancer is not clear yet. Through in vitro experiments, this study evaluated the effects of broth culture filtrate protein (BCF-P) from the supernatant of liquid culture media of H. pylori on proliferation and apoptosis of immortalized human gastric epithelial cell lines (GES-1) and gastric cancer cell lines (AGS). For the study, GES-1 and AGS cell lines mix with BCF-P and epidermal growth factor (EGF). MTT assay and flow cytometry (FCM) determined the levels of proliferation and apoptosis. Detected expression levels of cyclooxygenase-2 (COX-2) and Fas mRNA by reverse transcription (RT)-PCR. Also did analysis of the effects of BCF-P on epidermal growth factor receptor (EGFR) tyrosine kinase activity of GES-1 and AGS cells by non-radioactive enzyme-linked assay. The Student's t test and one-way analysis of variance (ANOVA) were used for statistical analysis. BCF-P inhibited proliferation of GES-1 and AGS cells in a concentration-dependent manner. The inhibition rates are respectively 68.7% in AGS and 61.4% in GES-1. With the same dose and time for inhibiting the proliferation, BCF-P failed to induce apoptosis of GES-1 and AGS cells. Effects of BCF-P reduced the expression of Fas mRNA of GES-1 and AGS cells (P < 0.05). This is consistent with the effects of EGF. BCF-P reduced the expression of COX-2 mRNA of AGS cells (P < 0.05). This is opposite to the effects of EGF (P < 0.05). Effects of BCF-P improved more than three times the EGFR tyrosine kinase activity of GES-1 and AGS cells. BCF-P inhibited the proliferation of AGS and GES-1 cells in vitro, unrelated to apoptosis. Effects of BCF-P on gastric epithelial cells in vitro are not equivalent to that of EGF.