Chronic Cigarette Smoke Exposure Masks Pathological Features of <i>Helicobacter pylori</i> Infection While Promoting Tumor Initiation

Gastric cancer is the fifth most common cancer and the fifth leading cause of cancer deaths worldwide. Chronic infection by the bacterium Helicobacter pylori is the most prominent gastric cancer risk factor, but only 1% to 3% of infected individuals will develop gastric cancer. Cigarette smoking is another independent gastric cancer risk factor, and H. pylori-infected smokers are at a 2- to 11-fold increased risk of gastric cancer development, but the direct impacts of cigarette smoke (CS) on H. pylori pathogenesis remain unknown. In this study, male C57BL/6 mice were infected with H. pylori and began smoking within 1 week of infection. The mice were exposed to CS 5 days/week for 8 weeks. CS exposure had no notable impact on gross gastric morphology or inflammatory status compared with filtered-air (FA) exposed controls in mock-infected mice. However, CS exposure significantly blunted H. pylori-induced gastric inflammatory responses, reducing gastric atrophy and pyloric metaplasia development. Despite blunting these classic pathological features of H. pylori infection, CS exposures increased DNA damage within the gastric epithelial cells and accelerated H. pylori-induced dysplasia onset in the INS-GAS gastric cancer model. These data suggest that cigarette smoking may clinically silence classic clinical symptoms of H. pylori infection but enhance the accumulation of mutations and accelerate gastric cancer initiation. Prevention Relevance: These findings suggest that cigarette smoking suppresses pathophysiological hallmarks of H. pylori infection while accelerating gastric carcinogenesis. Therefore, smokers should receive screening for H. pylori infection to reduce gastric cancer risk. See related Spotlight, p. 257.