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Tuesday, 31 July, 2001, 09:01 GMT 10:01 UK
Gene link shared by killer cancers
The gene plays a crucial role in preventing cancer
A gene that goes wrong in over half of all bowel cancers seems to play an important role in the development of breast cancer too.

The gene in question normally defends the body from cancer.

But researchers from Yamagata School of Medicine in Japan found that the gene was switched off in over a third of the breast tumours they tested.

This gene could now be a valuable target for breast cancer drugs of the future

Dr Gen Tamura
If scientists can confirm the importance of the gene - called Adenomatous polyposis coli (APC) - in breast cancer, the discovery might lead to earlier detection of the disease, better treatments, or even ways of preventing it from developing.

Previous studies had failed to find a genetic link between bowel and breast cancer, because the APC gene is inactivated in different ways in the two diseases.

Diferent mechanisms

In bowel cancer, the DNA sequence of the APC gene is often mutated so that it reads incorrectly.

However, in breast cancer the gene is left intact, but is switched off by a chemical process called DNA methylation.

Tumour cells often use methylation to switch off genes that protect the body from cancer.

But scientists are now hopeful that drugs to reverse the process could be a potent way of treating or preventing the disease.

Team leader Dr Gen Tamura said: "We already knew the APC gene was important in bowel cancer, but to find that it's switched off in so many breast cancers is really exciting.

"This gene could now be a valuable target for breast cancer drugs of the future."

The APC gene is known as a 'tumour suppressor' because it acts as a brake to prevent cells from dividing out of control.

When the APC gene goes wrong, the brake is removed, clearing the way for cancer to develop.

Two genes

A healthy person needs two APC genes - one from each parent - to be properly protected from tumours.

If someone is born with a damaged APC gene, they often go on to develop an inherited form of bowel cancer called Familial Adenomatous Polyposis.

In this disease, the inside of the gut wall becomes lined with precancerous polyps - putting the person at a much higher risk than normal of developing a fully blown tumour.

The APC gene is also often mutated in non-inherited forms of bowel cancer.

In breast cancer, only about 6% of tumours have mutant copies of APC.

However, Dr Tamura still suspected that it might be important in the development of the disease. His team tested 50 breast tumours to see if their APC genes had been switched off by methylation.

In 18 of the 50, at least one of the two APC genes was turned off.

The researchers also tested 21 healthy tissue samples, and found that in these APC was never switched off.

Dr Tamura sadi: "The fact that we only found inactivation of APC genes in breast tumours, and not in normal tissue, suggests these changes are specific to the disease and may be important in its development."

Professor Gordon McVie, director general of The Cancer Research Campaign, said: "Each type of cancer is different, but some of the underlying genetic causes are common to many forms of the disease.

"Finding these key genes is one of the prime aims of the current genetic revolution, and will pave the way to the next generation of anti-cancer drugs."

The research is published in the British Journal of Cancer.

See also:

13 May 01 | Health
Simple test for cancer gene
24 Oct 00 | Health
Breast gene radiation fears eased
26 Feb 01 | Health
Gene therapy 'prevents cancer'
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