Montezuma takes revenge on cancer

Tourists' plague may protect the gut from tumours.
11 February 2003

BRIAN FISKE

E.coli release a toxin that floods the gut with fluid. © Corbis

Toilet-bound tourists take comfort: the toxin that causes travellers' diarrhoea could be used to stymie colon cancer - without causing the runs.

Many a tourist falls victim to noxious Escherichia coli bacteria after consuming contaminated food or water. The bug releases a toxin that floods the gut with fluid, causing watery diarrhoea.

The same toxin may help fight colon cancer, says GianMario Pitari of Thomas Jefferson University in Philadelphia - by opening intestinal cells to calcium ions. This appears to stall the uncontrolled cell division that causes cancer.

By stopping a growing tumour, the toxin could give doctors more time to eradicate it with surgery. It might also be used to prevent the spread of colon cancer to other parts of the body, adds Pitari - the hope is "to keep the cancer at bay", he says.

"It's a provocative study," comments cancer researcher Judah Folkman of the Children's Hospital in Boston, Massachusetts. "It should lead to some fruitful possibilities."

Inner guard

Unlike some cancer drugs, the E. coli toxin targets - but does not kill - intestinal cells. Existing chemotherapy destroys both cancer cells and healthy tissue elsewhere in the body, causing unpleasant side effects such as nausea.

The team had previously shown that the toxin slows the growth of cancerous cells in the lab. It opens two pores in gut cells, they now show: one that lets fluid out, causing diarrhoea, the other that lets protective calcium ions in¹.

To avoid diarrhoea, Pitari suggests that the anti-cancer toxin could be used in combination with other drugs. His group next plans to test the toxin in animal models of cancer.

Colon cancer is around four times more prevalent in industrialized countries than in developing nations. The high-fat diets more common in Western countries are thought to put people at risk.

Pitari suggests that those living in developing countries might also be protected by the abundance of diarrhoea-causing bugs - but this link has yet to be confirmed. "It's a strong correlation, but it doesn't prove cause," cautions Folkman.

Meanwhile, tourists are best advised to avoid that tap water - being exposed once to the toxin while on vacation will probably not protect you from future colon cancer, cautions Pitari.

Brian Fiske is an Associate Editor of Nature Neuroscience

1. Pitari, G. M. et al. Bacterial enterotoxins are associated with resistance to colon cancer. Proceedings of the National Academy of Sciences, published online, doi:10.1073/pnas.0434905100 (2003). |Article|