UK scientists have discovered a new route to a potential cure for breast cancer, one that focuses on how the cancer manipulates genetic pathways to spread through the body, rather than on how tumors develop in the first place. They are already working on a new drug to switch off the cancer's effect on the pathways and say it could be ready in a couple of years, but experts suggest this could be rather optimistic.

The landmark study was the work Dr Justin Stebbing of Imperial College London (ICL) and other colleagues from ICL and also from the Howard Hughes Medical Institute, Cold Spring Harbor Laboratory in New York, USA. They have written a paper on it in the 24 August online before print issue of the Proceedings of the National Academy of Sciences, PNAS.

Stebbing, who is senior lecturer and consultant medical oncologist at ICL was reported by the Daily Express as telling the media that the new discovery was a "step on the way" to a potential cure for breast cancer.

"It helps us understand the way breast cancer cells grow and divide and if we understand this then we understand how to stop it," said Stebbing.

Breast cancer is the most common cancer of women in the western world, in Britain alone it kills 12,000 women a year.

In most cases the cancer depends on estrogen to fuel tumor growth, and current treatments focus on inhibiting the activity of the estrogen receptor. These treatments, for example tamoxifen, have been very successful at reducing deaths from breast cancer.

"The estrogen receptor is incredibly important in breast cancer," said Stebbing.

"Most of the treatments around treating breast cancer are blocking it or inhibiting the oestrogen but despite that about half of all women relapse," he added.

Many patients relapse because they eventually become resistant to hormone therapies.

Cancer is essentially a process where cell growth gets out of control. One of the ways that healthy cells stop growth getting out of control is via microRNA molecules that use genetic pathways to control various cellular processes in the body, such as making proteins.

As Stebbing explained:

"The way to cure breast cancer or any cancer is by fundamental biological understanding of what turns cells on and off, stopping the way tumours grow."

Stebbing and colleagues' breakthrough has been to discover how cancer cells switch off the microRNA molecules that control cell division to unleash the growth and proliferation of malignant cells.

"We can use these microRNAs as a new treatment and make them do what current drugs don't do," said Stebbing.

He said they had found a new microRNA pathway that the estrogen receptor activates. In normal cells estrogen encourages the production of microRNAs, but then as more of them are produced, they switch off estrogen activity, and this keeps cell division under control. Stebbing described this as a "perfect circle".

"But in breast cancer cells, production of the molecules is turned off," said Stebbing, and this is how the control over cell division is then lost and the malignant cells proliferate.

So their aim is to produce a drug that restores the "perfect circle" by stopping the deactivation of the microRNAs.

"If we know how to stop it then we can cure it. This only applies in oestrogen positive breast cancer but this could save millions of lives," said Stebbing.

Experts welcomed the discovery but had reservations about a drug being available soon.