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Scientists have made a major advance in understanding the genetic causes of prostate cancer, opening a new front in the battle against the most common malignant disease in men.
Seven genetic mutations have been identified that are present in over half of all new cases of prostate cancer, diagnosed in 35,000 men a year in the UK.
The discovery helps explain why the disease runs in families. Each individual mutation increases the risk by up to 60 per cent and when all seven are present, the risk is raised threefold.
This breakthrough means a new genetic test for prostate cancer could be developed to identify men at high risk who could be targeted for regular screening and early treatment.
Two of the seven genetic mutations identified could lead to the development of new treatments and a more accurate blood test for the cancer.
Ros Eeles, of the Institute of Cancer Research in London, who led the study, said that it was the culmination of 13 years' work involving 10,000 patients and the analysis of three billion genetic variations.
"We are very excited. This is a big step forward. To have seven hits fall out of a genome-wide study is very unusual," said Dr Eeles.
"These results will help us to more accurately calculate the risk of developing prostate cancer and may lead to the development of better targeted screening and treatment."
The study, funded by Cancer Research UK, involved collaboration between scientists in the UK and Australia.
The advance marks the latest triumph for the new science of genetic profiling, which is transforming understanding of the genetic basis of disease. Last May, scientists announced the discovery of four new genes which increase a woman's risk of breast cancer. Similar advances have been made in bowel and lung cancer.
"These findings show genetic medicine is going to happen," Dr Eeles said. "We will be starting research this year on developing a genetic test [for prostate cancer] which could be available in three to four years. But we need to ask first who should provide it and how it should be done. It would be irresponsible for a genetic testing company to develop this and sell it over the web."
Use of such a test would raise ethical and practical issues. Any man identified as at high risk of developing the cancer would face a lifetime of screening tests to check if the disease was present, followed by treatment of uncertain effectiveness and with a risk of side-effects. The implications of undergoing the test needed to be carefully thought through before making it available, Dr Eeles said.
One of the genes identified, LMTK2, codes for a signalling protein called kinase which is also altered in some other cancers and in Alzheimer's disease. This offered the prospect of a single treatment target for the two diseases.
"Drugs against these types of kinase are already being developed. We may end up with a drug that targets Alzheimer's and prostate cancer," Dr Eeles said.
A second gene, MSMB, identified codes for a protein whose level in the blood falls as prostate cancer develops. This has raised hopes of developing a more accurate blood test.
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