The gene, which stimulates the cancer cells to commit suicide and leaves healthy cells untouched, has proved successful in the first phase of tests on patients with advanced breast cancer carried out by the Imperial Cancer Research Fund.

The success of the trial, at London's Hammersmith Hospital, has raised hopes that it could eventually lead to a cure for breast cancer, and other forms of the disease.

Professor Nick Lemoine, who headed the trial carried out at London's Hammersmith Hospital, said: "This ability to target tumour cells based on their molecular profile is very encouraging.

"It's like a smart missile which homes in on the cancer cell - we can pick it out even when it's surrounded by a crowd of normal cells."

An Imperial Cancer spokesman said: "They demonstrated that it was able to convert a harmless chemical into a powerful anti-cancer drug - precisely where it was needed."

The next step will be to test the drug on other types of cancer such as ovarian and pancreatic cancer.

Suicide gene

Treatment worked for breast cancer patients

During the tests, the first of their kind in Britain, the women were injected with the "suicide gene" straight into skin nodules formed by cancer cells that had spread from the women's main tumours.

The cell suicide gene works by converting a harmless chemical into a powerful anti-cancer drug.

The chemical was slowly infused into a vein 48 hours after the initial injection of the cell suicide gene.

Although it was carried throughout the body, the chemcical only became active in those cancer cells that been been injected with the suicide gene.