To investigate regulation of the OSR by H. pylori, we first analyzed expression of p14ARF protein, which plays a central role in the OSR, using immunohistochemistry (IHC) in gastric biopsies collected from H. pylori-infected patients and uninfected control subjects (20 patients; 10/group) who were diagnosed with active chronic gastritis. The gene discussed is CDKN2A; the disease is chronic gastritis.