Scientists make breakthrough in breast cancer study

9.00am - By MARTIN JOHNSTON

New Zealand scientists believe they have cracked one of the secrets of why most breast cancer cells have the power to invade other parts of the body. They predict the breakthrough could lead to drugs to halt the disease.

The researchers, led by Associate Professor Peter Lobie, at Auckland University's Liggins Institute, have found that only those breast cancer cells that produce a substance called human growth hormone are invasive, spreading to other parts of the body.

Those that do not produce the hormone are not invasive, however 98 per cent of breast cancer cells produce the hormone.

If breast cancer is detected before it has spread beyond the breast, it can be cured. It is more deadly if it spreads to other organs such as the liver and lungs.

Breast cancer is the leading cause of cancer deaths among New Zealand women. More than 2000 women a year are diagnosed with the disease and it kills over 600.

Professor Lobie is overseas and could not be contacted. His team's findings are being published today in the prestigious American journal, Proceedings of the National Academy of Sciences.

The Liggins Institute said yesterday the research suggested tumours metastasised (became invasive) in response to growth hormone produced in the breast.

Liggins director Professor Peter Gluckman said production of the hormone made breast cancer cells and their neighbours invasive. In the absence of it, cells were encapsulated, effectively becoming a local tumour which could be disfiguring but which was not life-threatening.

But the research did not show what determined whether the cancer cells made the hormone or not.

He said the findings opened up a whole new area of cancer research.

"It depends if the work pans out. If the arguments as we have advanced them in the paper and all the evidence we have there [are confirmed] then we are on the basis of having techniques to change the biology of breast cancer cells from being invasive to non-invasive.

"That would reduce dramatically the risks of mortality in breast cancer."

The growth hormone made by the breast is different from normal growth hormone made by the pituitary gland, and from the synthetic version of the hormone which is used therapeutically to treat people who are not growing enough. Injections of the synthetic hormone do not induce the effects found in the Lobie experiments.

Professor Gluckman said the hormone was not present in the normal breast.

Drugs called growth hormone antagonists had already been produced, to treat tumours in the pituitary gland when it produced too much of the hormone. These drugs could be used to treat breast cancer.

Although it could take years to produce new anti-breast-cancer drugs from the research, it was likely that human clinical trials would start soon to test the growth hormone antagonists, he said.

"I'm quite sure oncologists will start thinking about clinical trials with the available drugs while we work on better drugs, which we're already working on."

He said Professor Lobie's work, which involved human breast cancer cells tested in test tubes and in mice, might also apply to bowel cancer.

Breast Cancer Foundation medical committee chairwoman Dr Belinda Scott, a surgeon, said the findings were exciting.

"We've always been trying to find out why cells become invasive or not. When we look at a lot of pre-cancers in some of those women followed they never go on to invasive cancer and nobody knows why."

"If we can start using something of those anti-human growth hormone products that opens up a whole new field."

But Cancer Control Taskforce member Associate Professor John Collins, a retired surgeon, said it was a long road to turn such findings into useful treatments.

"It may have interesting ramifications for the management of breast cancer, but like many before we wait to see what comes out of the clinical trials."