Based on these studies, it can be concluded that the ABCG2 gene has no connection with the development of peptic ulcers, although Helicobacter pylori infection may lead to increased expression levels of ABCG2 mRNA, because, with the more intense infection with bacterium, a higher level of ABCG2 expression was observed. This evidence concerns the gene ABCG2 and peptic ulcer disease.