Some bacteria in the intestinal flora can cause colon cancer, and a study in this week's Nature Medicine discloses a molecular mechanism for this undesirable effect.
Cynthia Sears and her colleagues explored how intestinal colonization by enterotoxigenic Bacteroides fragilis (ETBF) can lead to colon cancer. The group found that, whereas both ETBF and nontoxigenic B. fragilis (NTBF) can colonize the guts of mice, only ETBF triggers colonic inflammation and tumors. ?These symptoms are associated with increased cellular signaling by interleukin-17 (IL-17). Crucially, blocking signaling mediated by IL-17 or IL-23, a cytokine that amplifies IL-17 responses, prevented ETBF-induced inflammation and tumor formation.
These findings reveal an IL-17-dependent pathway for inflammation-induced cancer by a common intestinal bacterium. This provides new insight into the mechanism of human colon cancer and opens new therapeutic avenues to be explored.