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Scientists discover way to stop breast cancer spreading

Scientists have found a way of preventing the spread of breast cancer, in a study that could lead to new forms of treatment based on preventing tumours from moving from one part of the body to another.

Most deaths from cancer occur when tumours spread from their site of origin and the researchers believe they have found a way of manipulating the set of genes that appear to control the lethal movement of breast tumour cells into the bones and lungs.

The scientists hope that the activity of the genes overseeing this migration, or metastasis, of tumour cells can be analysed in patients to determine their health risks. It may also be possible in the future to manipulate the genes directly in a patient to prevent a cancer from spreading. The study has so far been carried out on laboratory mice but the scientists have also analysed breast tumour cells of real patients and believe that the findings could lead to new treatments for the disease based on preventing cancer metastasis.

Dr Joan Massague, of the Memorial Sloan-Kettering Cancer Centre in New York, said the study was based on analysing small fragments of RNA, a molecule that controls the activity of genes in the cells. The small RNAs found by the scientists inside human cancer cells appear to control the genes that determine whether the tumour begins to migrate away from the site of origin in the breast.

The small RNA molecules seem to stop the tumours from spreading by switching off these migration-determining genes. When the levels of RNA fall, the tumours start to move from the breast into the lungs and bone, Dr Massague said. "We now have a better understanding of the role this molecular pathway plays as a suppressor of breast cancer's ability to spread to the lung and bone, and we have identified the genes involved in that process. These findings may enhance our ability to come up with more effective drugs to prevent or treat cancer metastasis," he said.

In a study published in the journal Nature, the scientists noticed that human breast cancer cells spread quickly in mice when certain types of RNA molecule are present in low levels. When the scientists artificially boosted these levels of RNA, the cancers did not spread within the mice. When the scientists analysed breast cancer cells from 20 patients they also found a similar, direct correlation between the levels of these RNAs and the readiness of the tumour to spread.