You probably never thought any good could come of diarrhea. A bane to travelers and danger to the very young, ill, and elderly, a bacterial infection that causes severe diarrhea helps protect against colon cancer, according to new research. Toxins created by the Escherichia coli bacteria keep tumors in check by slowing colon cell growth and may one day help doctors treat colon cancer.
People living in developing nations are much less likely to suffer from colon cancer than are people in industrialized nations such as the United States, where colon cancer is the second leading cause of cancer deaths. According to clinical pharmacologists Scott Waldman and Giovanni Pitari of Thomas Jefferson University in Philadelphia, the explanation lies in a previously unknown side effect of E. coli infection--which is a constant health hazard in many developing countries. The bacteria create a toxin that latches on to colon cells lining the intestine, disrupting the body's control of bowel fluids, and causing severe diarrhea. But the toxin also prevents tumor development, Waldman and Pitari report online this week in the Proceedings of the National Academy of Science.
Waldman and Pitari, working with clinical pharmacologist Andre Terzic at the Mayo Clinic in Rochester, Minnesota, tracked human colon cancer cells that they had treated with the E. coli toxin. The toxin touched off a biochemical cascade, ultimately opening a channel into the cells. This let calcium flood into the cells, which, for reasons the researchers don't yet understand, slowed the growth of cancerous cells by 50% to 60%. This is the first time a bacterial toxin has been shown to inhibit cancer growth, says Waldman.
The toxin may be a promising cancer treatment, says oncologist Ferid Murad of the University of Texas, Houston, calling the work a "significant contribution." And because the toxin homes in specifically on colon cells, adds Waldman, it should be effective against colon tumors that have metastasized and spread to other parts of the body.