The most deadly feature of breast cancer is when it disperses from the breast, causing tumours to develop in other parts of the body.
But now researchers say they have found a way of stopping this process, known as metastasis, after pinpointing the gene which controls the spread of the cancer.
By removing this gene from cancer cells the American teams of scientists were able to halt its progress and even turned the cancer cell back to normal.
The genetically modified brown eggs produced by a flock of designer hens at the Roslin Institute near Edinburgh are the biotechnological equivalent of a Fabergé.
Several generations of Isa Brown hens – a prolific egg-laying French cross between Rhode Island Red and Rhode Island White – have been bred from “founder birds” that were genetically altered by Dr Helen Sang and her team to contain human genes.
Each gene provides the recipe for the production of a corresponding human protein. In the Roslin Institute hens the human protein is found only in their eggs, reducing the risk of harm to the hens themselves.
The egg proteins are rich in expensive drugs that can fight cancer and other diseases, with each egg containing enough medicine to treat a handful of patients each year.