LGR5 and adenoma: Their findings provide the characterization of the intestinal stem cell by lineage tracing using the expression of a single marker gene, LGR5. 21 In another study, Barker et al.21 demonstrated in a mouse model that LGR5-positive stem cells are the cells of origin of intestinal tumors by introducing adenomatous polyposis coli mutations into LGR5-positive stem cells, which stimulated adenoma formation in the small intestine and colon.22 These data suggest that LGR5 has an important role in colon cancer tumorigenesis.