(ChemotherapyAdvisor) – A specific strain of Escherichia coli (E. coli) associated with colorectal inflammation promotes development of colorectal cancer in mice, according to an international team of researchers. This conclusion is based on a study entitled “Intestinal Inflammation Targets Cancer-Inducing Activity of the Microbiota,” which was published online in Science on August 16.

The design of this study is based on several studies that have demonstrated an association between inflammation in the human colon, as observed in inflammatory bowel disease and Crohn’s disease, and the development of colorectal cancer. In this study, the investigators aimed to determine whether E. coli bacteria, which are normally found in the human colon, actually cause the level of inflammation associated with the development of colorectal cancer. To meet their aim, the investigators used a mouse model of human colitis to investigate whether inflammation due to the presence of a specific strain of E. coli, known as NC101, could lead to development of colorectal cancer. Approximately two-thirds of patients with colorectal cancer carry the same bacterial strain in their colon. 

NC101 bacteria were allowed to colonize the colon in these mice, an event that promoted the development of invasive colorectal carcinoma. These bacteria produce a toxin that is encoded in their pks gene. When the pks gene was removed from these bacteria prior to colonization, tumor multiplicity and invasiveness was decreased, but intestinal inflammation was still present, implicating this gene in the development of colorectal cancer development.

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“Mucosa-associated pks-positive E. coli were found in a significantly high percentage of inflammatory bowel disease and colorectal cancer patients, suggesting that in mice, colitis can promote tumorigenesis…,” the investigators concluded.