Diarrhea bug may prevent cancer
Study: Bacterial toxin inhibits growth of malignant cells
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Call it Montezuma’s Revenge, traveler’s trot or simply a nuisance, diarrhea may do at least one good deed by protecting people against colon cancer, researchers reported Monday.
They said their findings offer one possible explanation for why people in poorer countries seem less prone to colon cancer, the fourth leading cause of cancer in the world and the third biggest cause of cancer deaths in the United States.
The study, published in this week’s issue of the Proceedings of the National Academy of Sciences, focuses on one of many bacteria that can cause diarrhea. Worldwide, diarrhea caused by a variety of microbes kills two million children a year, but adults develop a partial immunity.
The toxin produced by the bacteria — in this case toxic strains of the common Escherichia coli or E. coli bug — irritates the lining of the bowel but may also interact with cells in a way that prevents them from becoming cancerous, the researchers said.
Giovanni Pitari and colleagues at Thomas Jefferson University in Philadelphia started their research after noting that while colon cancer is very common in the developed world, it is uncommon in developing countries.
“Over half a million patients suffer from colorectal cancer in industrialized nations, yet this disease exhibits a low incidence in underdeveloped countries,” Pitari and colleagues wrote in their report.
They compared the incidence of “traveler’s diarrhea” against that of colon cancer, and showed that in countries where “Delhi belly” is most common, including the Indian subcontinent, Africa and Mexico, colon cancer was increasingly less common.
Where colon cancer is highest — New Zealand, Australia, the United States and western Europe — traveler’s diarrhea is rare.
Toxin prevented cell growth
Pitari’s team analyzed the toxins produced by E. coli, first adding them to a dish full of dividing cancer cells. The cells, which like most cancer cells had been growing and dividing rapidly, slowed their pace to a crawl.
They tested the toxin’s precise action on cells and found it acted like guanylin and uroguanylin — two compounds that naturally limit the growth of colon cancer cells.
The finding not only helps explain why colon cancer is a disease of developed countries, but may offer new approaches to treating or preventing the disease, Pitari’s team said. Other approaches are known to help prevent colon cancer — including a diet rich in fruits and vegetables, quitting smoking and doing exercise.
Smoking can damage the DNA in cells, helping them become cancerous, while eating fruits and vegetables helps prevent damage to DNA from occurring in the first place.
This article reprinted with the permission of MSNBC
