Species-specific role of gene-adjacent retroelements in human and mouse gastric carcinogenesis.

Helicobacter pylori (HP) infection promotes the recruitment of bone marrow stem cells into chronic gastritis lesions. Some of these marrow stem cells can differentiate into gastric epithelial cells and neoplastic cells. We propose that HP-associated methylation could stabilize trans-differentiation of marrow-derived stem cells and that an unstable methylation status is associated with a risk of gastric cancer. Pathobiologic behavior of experimental mouse gastric cancer is mild compared to invasive and metastatic human gastric cancer. Differences in epigenetic stabilization of adult cell phenotypes between humans and mice could provide a foundation to explore the development of invasive and metastatic gastric cancer. Retroelements are highly repetitive sequences that play an essential role in the generation of species diversity. In this review, we analyzed retroelements adjacent to human and mouse housekeeping genes and proposed a possible epigenetic mechanism for HP-associated carcinogenesis.