The H. pylori of colon cancer?

The links between some chronic infections and cancer are well established – think of Helicobacter pylori and gastric cancer – and a recent paper in Nature Medicine shows that a common human colonic bacterium can cause cancer in a mouse model. The bacterium involved, enterotoxigenic Bacteroides fragilis (ETBF), secretes a metalloprotease toxin (fragilysin) and can cause inflammatory diarrhoeal disease, but also asymptomatically colonises as a commensal in a significant proportion of the human population. The authors, from Johns Hopkins University School of Medicine, show that the colitis caused by ETBF strongly induced colonic tumors in cancer-susceptible multiple intestinal neoplasia (Min) mice and describe a novel mechanism involving the endogenous T cell immune response. They suggest that ETBF is a human oncogenic bacterium and that this ties-in with a previous study indicating an increased prevalence of ETBF in colorectal cancer patients.