A breakthrough discovery about the way cancer cells behave could lead to new drugs to stop the disease spreading.

Experts have unlocked the secret of a protein which stops cancer cells from migrating around the body.

It might be possible to mimic its action, and "anchor" cancer to prevent secondary tumours developing. The movement of cancer from the primary tumour to other parts of the body is the main reason the disease is so lethal.

Mena - a protein found in excessive amounts in tumours - plays an important role in helping all cancers to spread.

Another protein, tes, acts against cancer by preventing cell growth and stopping tumours from forming. Tes can attach itself to mena and stop cancer cells migrating.

However, in many cases, mena is found in such large quantities that tes cannot stop the disease spreading. Now researchers have discovered the mechanism by which tes locks on to mena to stop the spread of cancer.

The discovery offers the possibility of developing drugs which could block the action of mena by mimicking that of tes.

Preventing the spread of cancer is one of the major challenges for researchers so the findings, by Cancer Research UK scientists, are exciting. Their study was published yesterday in the journal Molecular Cell.

The lead author, Dr Michael Way, based at Cancer Research UK's London Research Institute, said: "Our findings represent a new way to regulate a key family of proteins involved in cell crawling that will change the way researchers see current models of cell migration - an important aspect of the spread of cancer."

Dr Lesley Walker, director of science information at Cancer Research UK, said: "Cancer cells use many complex processes when they break away from their tumour and spread.

"Understanding these mechanisms and increasing our knowledge about this pro- tein can hopefully help us to develop more effective cancer treatments in the future."

About 20,000 people died from cancer every day across the world this year, according to recent figures.

One in three people will be diagnosed with cancer at some point in their life.

Scientists are gradually developing a deeper understanding of the causes of cancer, investigating the complex interaction of chemicals, genetics, ageing and diet.

Research has been dominated recently by the discovery of techniques that involve scouring the whole human genetic code for mutations linked to cancer.

In one case, researchers found genes responsible for a syndrome that increases bowel cancer risk in Ashkenazi Jews.

Dr Walker said Cancer Research UK was launching a series of genome-wide studies, including searches for genes that influence lung and ovarian cancer risk.

Among other breakthroughs announced in the past year is a faster way to assess whether breast cancer has spread with a molecular test to detect metastatic breast cancer, and a new blood test which could improve the odds of catching lung cancer earlier, when it is more easily treated.