Mammography can help spot tumours

It is a protein, called Brn-3b, which appears to feed the growth of certain breast tumours.

The University College London team believe that turning off this switch could stop aggressive tumours, which do not respond to chemotherapy, spreading.

The study, conducted with the help of experts at Guy's and St Thomas' hospital, appears in Cancer Research.

Brn-3b boosts the invasiveness of cancer cells, and contributes to the deadly nature of this disease Researcher Dr Vishwanie Budhram-Mahadeo

In the UK, nearly 41,000 women are diagnosed with breast cancer each year and nearly 13,000 will die from the disease.

Early detection and treatment improves the chance of survival.

Experts already know that breast cancers with higher levels of a protein called HSP27 are especially fast-growing and more resistant to treatment than some other forms of breast cancer.

The new research found that the switch Brn-3b makes cancer cells produce more HSP27.

Researcher Dr Vishwanie Budhram-Mahadeo said: "Brn-3b boosts the invasiveness of cancer cells, and contributes to the deadly nature of this disease.

Molecular fingerprint

"We can now work out strategies to deal with cancers with increased Brn-3b without adversely affecting the healthy cells around it that do not express high levels of the protein."

Derek Napier, chief executive of the Association for International Cancer Research, said: "These studies will pave the way for future research in which we can treat patients on the basis of the molecular fingerprint that will be specific and unique to every individual.

"This will allow therapy to be tailored to treat patients whose tumours have high levels of Brn-3b to reverse the growth of cancer cells while minimising the undesirable side effects of conventional therapies."

Pamela Goldberg of the Breast Cancer Campaign, said: "In the same way that breast cancer is not one disease, there will not be one cure.

"Each patient's breast cancer is different and it is only through advances in our understanding of the basic molecular changes that occur in cells to turn them cancerous that we will make progress in developing more effective methods of diagnosis and treatment of breast cancer - and hopefully help us prevent the disease in all women."

Dr Elaine Vickers of Cancer Research UK said: "This latest research adds to our understanding of Brn-3b, and further implicates it in breast cancer.

"Discovering proteins that are important to cancer cells, but less so to their healthy neighbours, is a springboard for developing new, more targeted treatments for the disease.