Abstract
ABSTRACTHelicobacter pylori is a spiral microaerophilic Gram-negative bacterium which colonizes the gastric mucosa of the human stomach. Infection with H. pylori is associated epidemiologically with development of gastric cancer. To better understand the role of H. pylori in carcinogenesis, strains isolated from patients with gastric cancer and other gastric-associated diseases were analyzed. The aim was to investigate the relationship between virulence factors of H. pylori and gastric cancer disease. The cytotoxin-associated gene (cagA) was detected by polymerase chain reaction (PCR). Patients with peptic ulcer diseases were all infected with cagA+ strains. Forty-nine of 50 (98%) strains from patients with gastric cancer and 54 of 57 (94.7%) strains from patients with non-ulcer dyspepsia were detected as cagA+. Unlike Western countries, we could not conclude any significance between cagA status and specific disease because of the predominance (98%) of cagA+ strains in Taiwan. The cytoplasmic urease activity was examined in 60 strains, but showed no difference between cancer and non-cancer groups. The activity of vacuolating toxin (VacA) was assayed on HeLa, RK13, and AGS cell lines. The m1T-type VacA was associated with higher cytotoxicity than m2-type. The m2 toxin had poor vacuolating activity on HeLa cells but was still active on RK13 and AGS cells. The m1T toxins were significantly less toxic on RK13 cells than on HeLa and AGS cells (P < 0.05). AGS cells were more sensitive to VacA toxin. These results may be explained by the polymorphism in expression of the VacA receptor between cell lines. It is of interest that m1T strains were found more frequently in patients with gastric cancer (P < 0.001) than with other diseases, implicating the possible role of vacA in the carcinogenesis of H. pylori. The vacuolating activity was also higher in strains isolated from cancer patients (P< 0.05), possibly due to higher proportion of m1T strains. The role of m1T type toxin in the pathogenesis of gastric cancer still need evaluated.