E. Coli causes diarrhea, and may fight cancer as well

MANY a stalwart man trembles at the mention of the word “colonoscopy.” Odysseus braved Hades and defied the dreaded Scylla, but never did he confront the neighborhood proctologist. Yet colorectal cancer, the fourth leading cause of cancer worldwide, claims tens of thousands of lives each year, and is not a disease easily wiped aside. Maybe, suggests Dr. GianMario Pitari of Thomas Jefferson University, we can flush it out.

A few years ago, Pitari noticed that countries with low colorectal cancer rates tended to have high rates of E. Coli-related infections, and vice versa. High levels of E. Coli correlate with many other indicators (including poverty and crime), but the fact that both gastroenteritis and colon cancer affect the lower-intestinal region led Pitari to hypothesize that the one might influence the other. Perhaps the recent onslaught of food scares has given this friendly bacterium a bad rap.

Perhaps not. In its most common form, E. Coli benignly resides in our intestines, absorbing vitamins and digesting other harmful bacteria. However, certain strains of the bacteria are severely toxic. Enterotoxigenic E. Coli (ETEC) is one such strain, quite familiar to travelers who test their mettle against tap water in developing countries. Via a well-known cellular pathway, ETEC produce toxins that cause intestinal cells to secrete water and electrolytes. In time, this secretion eventually results in severe diarrhea and other cholera-like symptoms.

That cellular pathway has been known for some time. What Pitari’s team discovered, in a study published February 19 in the journal Proceedings of the National Academy of Sciences, is that ETEC-produced toxins are also involved in an entirely different pathway. When the toxins bind to cell receptors, they not only cause secretion but also open ion channels, letting calcium flow into the target cells. This calcium, in turn, blocks DNA synthesis and suppresses cell division. Big news if you’re interested in stopping cell replication, as most cancer researchers are.

In vitro, the researchers found that the ST enterotoxin greatly inhibited the growth and spread of colon cancer cells. While the petri dish is a far cry from the human body, it is certainly possible that these toxins could be used in future cancer therapy. After having a tumor removed, for instance, the toxins could be used to prevent the cancer’s recurrence or metastasis. The approach is less aggressive than chemotherapy, which kills healthy and cancerous cells alike.

The best part is, Montezuma need not exact his revenge for the treatment to be effective. The calcium-promoting pathway is distinct from the runs-inducing pathway. Still, Dr. Stephen Carrithers of the University of Kentucky makes an astute observation: “If the sacrifice is for one to have occasional diarrhea yet prevent the [tumors] in the colon from ever forming or progressing, it's worth it."