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Promise and Progress - Cancer Causing Bacteria

Leading the Way Fall 2009 Winter 2010

Cancer Causing Bacteria

By: Valerie Mehl
Date: December 1, 2009

Nature Medicine, August 23, 2009

Bacteria that causes diarrhea have been linked to some colon cancers. The colon is home to the greatest concentration of bacteria in the body, and researchers have long thought
that perhaps they could play a role in the development of colon cancer.

Investigators Cynthia Sears, M.D., and Drew Pardoll, M.D., Ph.D., have homed in on one particular culprit called Bacteroides fragilis. People with a toxin-secreting form of the bacteria can have diarrhea and chronic inflammation of the colon. The persisting inflammation and the immune system’s reaction to it conspire to bring about genetic
changes in colon cells that remove important restraints on cell growth and can ultimately lead to tumors.

In animal studies, the team found that mice infected with the toxinsecreting strain of the bacteria recovered quickly from the diarrhea but soon developed inflammation, and
within a month the colons were pockmarked with tumors. Mice infected with the non-toxic strain of the bacteria did not have diarrhea, inflammation, or tumors.

The research team is working on blood tests that detect whether a person has been exposed to the toxin-secreting strain of the bacteria and, as a result, may be at higher risk for developing colon cancer. They also are exploring therapies that neutralize the bacteria and prevent it from inflaming the colon.

Funding for the study was provided by the Crohn’s and Colitis Foundation, the National Institutes of Health, Bernard Schwartz, William and Betty Topercer, Dorothy Needle,
Bud Swartz, and the Commonwealth Foundation.