Stem cells guilty of spreading cancer

Scientists in the United States have found that stem cells which are normally associated with potential cures and treatments can also promote the spread of cancer.

A study by researchers at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, found that stem cells taken from bone marrow can drive breast cancer cells to invade other parts of the body.

Stem cells are immature cells which can develop into different kinds of tissue and scientists are optimistic that in the future they will be used to treat a range of diseases such as Parkinson's and type 1 diabetes.

Mesenchymal stem cells (MSCs) are found in the bone marrow, and are a "master cell" used by the body to help generate new bone, fat, cartilage and muscle.

MSCs were already regarded as a rather suspicious bunch after it was noticed that they naturally migrate in large numbers to tumour sites but they also gravitate naturally to wound areas where they appear to assist in the healing process.

The scientists found when they mixed human breast cancer tumours in mice with MSCs, they dramatically increased the potential of the cancer cells to metastasise; in fact seven times more cancer spread to the lungs compared with breast cancer tumours not tampered with.

Fortunately the process appears to be reversible and understanding how this happens could very well lead to ways of reducing the metastasis, or spread, of cancers.

The research has also highlighted a potential treatment to block the changes; a chemical called cytokine CCL5, produced by the stem cells, had an effect on breast cancer cells in the laboratory.

Medication that blocks the action of this is already used to help patients with HIV - and the researchers suggest it should be tried on patients with spreading cancer.

The scientists, led by Dr. Robert Weinberg suggest that the presence of the stem cells produces genetic changes in the cancer cells that make them metastasise - but once the cells spread, they change back to their original genetic state.

The study appears in the journal Nature.