Tumours detected by metal

November 7, 1997

Chemistry is helping to find and fight cancer and make cleaner fuel

THE LATEST in chemistry technology is being used to improve the detection of cancerous tumours in humans.

For many years chemists have provided the technology that allows doctors to pinpoint the exact location of tumours in the body. But now they are investigating new methods that could more effectively target cancerous tissue.

Work in the late 1980s developed gamma ray isotopes which, when injected into the body, would pinpoint a tumour. Durham University chemists were among those who engineered the tiny gamma-emitting isotopes, enclosed in a molecular prison so they could not leak into the body and attached to a targeting vehicle that moved straight to the site of the tumour.

Scientists used fragments of monoclonal antibodies on the surface of the prison to recognise antigens presented on the surface of the cancer cells.

But with more than 200 different forms of cancer, most with different antigens present on their surfaces, scores of separate antibody vehicles would have to be built if this method was to be extended beyond a few cancers.

Researchers at Durham have therefore now begun to hunt for more simplistic ways of targeting cancers.

Magnetic Resonance Imaging is already being used, with some success, to pinpoint certain cancers, particularly those in the brain. The MRI differentiates between different tissue types in the body. But researchers are now trying to improve the differentiation between healthy and abnormal tissue.

David Parker, professor of chemistry at Durham, is looking at adding different contrast agents that he hopes will improve the differentiation.

Drawing on earlier work, the Durham chemists have replaced the gamma source in the molecular prison with gadolinium, a highly magnetic metal that could cause toxic effects if it escaped the molecular prison and dissolved in the body.

Once injected, the metal can be followed on the MRI as it moves through the body's blood system. Work at the Royal Marsden Hospital, in conjunction with Durham, has shown that, in vivo, the metal moves more slowly away from tumour tissue than from healthy areas. This means that an exact location for the tumour can be determined.

Professor Parker said: "The differentiation was unexpectedly significant. This offers an interesting new way of imaging tumours. I believe MRI is very much the imaging technology for the next century. We now have one broad spectrum agent that will have the same differentiation effect irrespective of the tumour type."

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