Inflammation is the fuel that feeds the cancer flame. So how do we fight back?

• Author: Balkwill, Frances

Byline: Frances Balkwill

Inflammation is the body's first line of defence against insult. Without inflammation, most of us would not make it past the first year of life. This rapid reaction force fights infections, heals wounds and helps our more sophisticated adaptive immune system generate a longer-lasting specific response. But there is a downside to this powerful response; sometimes inflammation fails to resolve. Indeed, chronic and often low-level inflammation underlies many of the diseases of middle and old age: cardiovascular disease, diabetes, arthritis, dementia - and cancer.

If genetic damage is the match that lights the cancer fire, inflammation is the fuel that feeds the flames. There are multiple lines of evidence that support this idea. Some chronic inflammatory diseases increase the risk of developing a cancer - for instance hepatitis, inflammatory bowel disease and pancreatitis. Cancer can also cause inflammation - genetic damage to a cell with malignant potential attracts inflammatory cells that begin to fuel the cancer flames. Cancers are not just masses of malignant cells but complex 'rogue organs' where normal cells are recruited and corrupted to help the cancer grow and spread. This rogue organ is known as the tumour microenvironment and is usually abundant in inflammatory cells and molecules.

As chronic low level inflammation promotes cancer, are anti-inflammatory drugs useful in cancer prevention and treatment? Over the past twenty years or so experiments in many different mouse models of cancer clearly showed that targeting inflammatory cells or molecules could slow down cancer growth and spread, and if this was done in the earliest stages, cancers could be prevented. The latter finding was replicated in clinical trial of people taking aspirin to prevent cardiovascular disease. These trials, carried out on tens of thousands of people over 10 years or more, show that aspirin reduces the development and spread of certain cancers. However, it is not clear if aspirin benefits all people: the risk of stomach bleeding is increased for instance, and there may be no effect in older people (70+). More research is certainly needed to understand the cancer-preventative actions of this oldest of drugs.

An exciting discovery

Another more recent clinical trial has excited those of us working on cancer and inflammation. A molecule called interleukin-1 beta (we'll call it IL-1) is one of the major players in human inflammation...