Enzyme that plays an important role in the formation of breast tumours identified

Scientists have identified an enzyme that plays an important role in the formation of breast tumours.

A team of US scientists found that the enzyme lysyl oxidase (LOX) alters the structure of collagen - the major component of connective tissue - in the cells surrounding the growing tumour.

LOX was already known to be involved in the spread of cancer, but the latest study - which appears in the journal Cell - is the first to show its role in the development of primary tumours.

Researchers found that the enzyme is involved in a process called 'cross-linking', which causes tissue to become more fibrous.

This is characteristic of the tissue surrounding breast tumours, which tends to be much more stiff and fibrous than healthy tissue.

The researchers showed that high levels of LOX were associated with higher levels of collagen in mammary glands, stiffer tissue and with tumours that were more likely to invade the breast tissue.

When they blocked the action of LOX, they found that the collagen in the mammary glands had fewer cross-links and that the tissue was less fibrous.

The tissue also tended to have fewer and smaller tumours which were less aggressive than usual.

Study co-author in the UK, Dr Janine Erler from The Institute of Cancer Research, commented: "Our study shows that stiffening of the breast tissue controlled by enzymes such as LOX is a key factor in cancer development, suggesting these enzymes are a promising candidate drug target.

"The enzyme triggers a clear physical change in breast tissue and, if we could stop this happening, we expect it would slow the growth of any cancers that did develop and make them easier to eradicate."

Lead author Professor Valerie Weaver, from the University of California, San Francisco, noted: "This study may also help explain why the rate of breast cancer increases dramatically with age - aged tissues are stiffer and contain higher levels of abnormal collagen cross-links."

She concluded: "I'm cautiously optimistic. We still have a lot more work to do, but this is certainly exciting."

Dr Laura Bell, Cancer Research UK's science information officer, commented: "This interesting laboratory study points yet another finger at the LOX enzyme as a key player in breast cancer growth and spread.

"Although at an early stage, this research could help scientists to prevent and treat cancer in the future - the next steps will be to find out if LOX can be switched off and whether this helps to prevent tumours forming or slows their growth."