Tuesday, July 29, 2008

Blood test could be cancer 'crystal ball'

By Roger Highfield, Science Editor

A simple blood test that could act as a "crystal ball" to detect early signs of cancer could be tested on patients within two years.
Scientists have shown the test works in picking up signs of prostate cancer and say it could potentially also be used for other cancers ranging from breast to lung.

Although a range of teams around the world are developing tests for proteins that signal cancer is developing, a new approach is outlined today by scientists at Fred Hutchinson Cancer Research Centre, Seattle.

They have found that scraps of genetic material - called microRNAs - that turn genes on and off are released by cancer cells to circulate in the blood, where they can be detected more easily than proteins.

The molecules have the potential to become a new class of "biomarkers" to reveal the presence of cancer at its earliest stages, which would make treatment more effective, reports the team led by Dr Muneesh Tewari in the Proceedings of the National Academy of Sciences.

Dr Tewari tells the Telegraph that these new diagnostic tests could start being studied in large clinical trials for cancer detection in two years.

MicroRNAs have advantages over protein-based early-detection systems, including that they can be detected potentially in smaller quantities and that the technology exists to rapidly develop early-detection tests, said Dr Tewari, who has been studying how the scraps of genetic code sometimes fail to hold cell growth in check in prostate and ovarian cancers.

"Current technology for developing tests to measure microRNAs in clinical samples is quite advanced, whereas the bottleneck for developing protein-based biomarkers is the slow process of generating assays for measuring specific proteins," he said.

The next steps, now that a proof of principle has been established, are to identify specific microRNAs that can signal the presence of a variety of solid-tumour cancers - breast, lung, prostate, skin and so on - at an early stage, and to further develop the technology to detect minute quantities.

For the study, Dr Tewari and colleagues tested blood from mice and humans with advanced prostate cancers, as well as that from healthy controls, and could distinguish which individuals had cancer based on blood microRNA measurement.

"MicroRNAs, which weren't previously thought of as markers of cancer in the blood, are a worthwhile class of molecules to study for the purpose of early cancer detection," Dr Tewari said.

MicroRNAs play a key role in a wide range of normal cell processes, including embryonic development and cell differentiation, and are often misregulated in cancer. During the course of those experiments, the scientists found that microRNAs circulate in the blood outside of cells and are remarkably stable.

Original here

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