Stem cells and Helicobacter-induced gastric cancer: where do we stand at the end of 2006

The process of carcinogenesis, which may well extend over decades, provides an excellent opportunity for early detection and intervention to prevent development of gastric cancer. Evidence supporting a causal association between such tumour and Helicobacter infection has been demonstrated by epidemiological data, ecologic studies and, in experimental animal models. Lately, an increasing amount of evidences point out to bone marrow stem cells (BMSC) as target of neoplastic transformation. The term BMSC includes a heterogenous group of cells that both in vivo and in vitro studies, have shown to have plasticity, with their ability to acquire features of mesoderm, ectoderm and endoderm. In the gastric setting, a recent experiment in C57BL/6 mice has permitted to show that BMSC are the cell of origin of Helicobacter-induced gastric cancer. Based on these results, a model for epithelial cancer by which chronic inflammation leads to tissue injury and with time, to tissue stem cell failure, has been proposed. This phenomenon would induce the recruitment and engraftment of BMSC into the tissue stem cell niche. During differentiation, BMSC fail to regulate growth programme appropriately and progress through stages of metaplasia and dysplasia. Due to several reasons, in humans, data are conflicting. Further studies may shed light on the molecular bases of gastric lesions, leading to the development of preventive strategies.