From Infection To Inflammation To Cancer: Scientists Offer New Clues


Chronic inflammation of the liver, stomach or colon, often as a result of infection by viruses and bacteria, is one of the biggest risk factors for cancer of these organs. Scientists at the Massachusetts Institute of Technology (MIT) in the US have been researching this for over three decades, and now in a new paper published online this week they offer the most comprehensive clues so far about the potential underlying molecular mechanisms.

A bacterium called Helicobacter pylori causes stomach ulcers and cancer in humans. Helicobacter hepaticus has a similar effect in mice, so the researchers used it as a model to study how such a bacterial infection alters genes and chemicals in the liver and colon.

They write about their findings in a paper that appeared online in the 11 June issue of the Proceedings of the National Academy of Sciences, PNAS.

One of the four senior authors of the paper is Peter Dedon, a professor of biological engineering at MIT. Biological engineering is where molecular life scientists work with engineers to discover how biological systems function; the resulting knowledge can be used to develop new medical technologies.

Dedon and his co-authors hope their findings will help other researchers develop ways to predict the health problems caused by chronic inflammation and design drugs to stop it.

"If you understand the mechanism, then you can design interventions," he said in a statement. "For example, what if we develop ways to block or interrupt the toxic effects of the chronic inflammation?"

Inflammation is a natural body reaction to an infection or wound, but if the inflammation persists too long, it can damage healthy tissue.

A study published recently in The Lancet found that inflammation caused by infections account for around 16% of new cancer cases worldwide.

Inflammation begins when the immune system detects cell damage or pathogens: both of these are potential threats to health. This triggers a surge of immune cells called macrophages and neutrophils that come along to clean up and remove the threat. They engulf the invading organisms, dead cells, debris and materials released by dead or damaged cells, such as proteins, nucleic acids and other molecules.

As well as removing these materials, the immune cells produce highly reactive chemicals to break down the bacteria. And it appears that it is this part of the process that is linked to cancer risk, because, as Dedon explained, "in engulfing the bacteria and dumping these reactive chemicals on them, the chemicals also diffuse out into the tissue".

If the inflammation persists, the tissue is constantly bathed in the reactive chemicals.

For the new study, which was funded by the National Cancer Institute, Dedon and colleagues studied mice infected with H. hepaticus for 20 weeks. After 10 weeks, the mice developed severe colitis and hepatitis, and at 20 weeks, some had also developed colon cancer.