Gut microbes combine to cause colon cancer, study suggests

Two types of bacteria commonly found in the gut work together to fuel the growth of colon tumors, researchers reported on Thursday. The findings, published in the journal Science, suggest that certain preventive strategies may be effective in the future, like looking for the bacteria in the colons of people getting colonoscopies. If the microbes are present, the patients might warrant more frequent screening; eventually people at high risk for colon cancer may be vaccinated against at least one of the bacterial strains. Two types of bacteria, Bacteroides fragilis and a strain of E. coli, can pierce a mucus shield that lines the colon and normally blocks invaders from entering, the researchers found. Once past the protective layer, the bacteria grow into a long, thin film, covering the intestinal lining with colonies of the microbes. "Bacteria are there at the very earliest stages," said Matthew Meyerson, MD, director of cancer genomics at the Dana-Farber Cancer Institute in Boston. "This is a big step forward in understanding what is the role of the microbiome in colon cancer."