Scientists have discovered a protein that stops breast cancer from spreading, offering hope for millions of women worldwide.

When tumour cells spread, they first enter the blood stream and grip onto the inner walls of blood vessels.

Now, a study has revealed cancer cells control a receptor protein called EPHA2 in order to push their way out of the vessels.

But when the EPHA2 receptor protein is ‘turned on’, the diseased cells remain trapped inside.

This means they cannot escape and travel to other parts of the body.

It means drugs could be developed to target the protein, saving the lives of hundreds of thousands of women who die from the disease every year.

Breast cancer is the most common cancer in women worldwide, with nearly 1.7 million new cases diagnosed in 2012, according to the World Cancer Research Fund.

Worldwide, it is estimated that around 522,000 women died from breast cancer in 2012, Cancer Research UK figures show.

Dr Claus Jorgensen, of The Institute of Cancer Research, London, said: ‘The next step is to figure out how to keep this receptor switched on, so the tumour cells cannot leave the blood vessels, stopping breast cancer spreading and making the disease easier to treat successfully.’

The study, funded by Cancer Research UK, used a technique that mapped how cancer cells interact and exchange information with cells that make up blood vessels.

Science information manager Nell Barrie said: ‘This is important research that teaches us more about how breast cancer cells move.

‘Research like this is vital to help our understanding of how cancer spreads, and how to stop this from happening.

‘More research is needed before this will benefit patients, but it is a jump in the right direction.’

The research was published in the journal Science Signaling.