It is most likely that many genes are involved in the development and progression of prostate cancer - each controlling a different step in the process

Arul Chinnaiyan, University of Michigan

Prostate cancer affects 21,000 men in the UK each year and proves fatal for around 10,000.

The team from University of Michigan Medical School used advanced DNA microarray technology in their research.

The technique allows scientists to simultaneously screen large numbers of patient samples containing thousands of genes at once.

The AMACR protein is present in large amounts only in malignant cells and is easily visible when stained.

It is an enzyme involved in fat metabolism called a-methylacyl-CoA racemase, or AMACR.

It is the first time it has been linked with any type of cancer.

The researchers detected high levels of the AMACR protein in over 95% of more than 300 prostate tissue samples that contained localised cancer.

In benign prostate tissue, or tissue with non-malignant cell changes, there was either very little, or no AMACR protein.

The researchers tested tissues of 94 prostate needle biopsies, detecting the protein by staining. The tests were 97% sensitive.

AMACR is one of approximately 20 genes which are overexpressed consistently in prostate cancer.

The researchers found the AMACR protein was overexpressed in other cancers including bowel, ovarian, breast, bladder, lung, renal cell, lymphoma and melanoma - with the highest amounts present in bowel and prostate cancer.

'Cancer-specific'

Arul Chinnaiyan, associate professor of pathology at University of Michigan medical school, who worked on the research, said: "Previous prostate cancer studies focused on one gene at a time.

"With DNA microarray technology, we can look at thousands of genes in prostate cells simultaneously.

"This is important, because it is most likely that many genes are involved in the development and progression of prostate cancer - each controlling a different step in the process."

Mark Rubin, who also worked on the study, added: "The beauty of AMACR is that it is cancer-specific and concentrated only in malignant cells.

"PSA can't differentiate between cell changes caused by cancer and those caused by benign changes in the prostate.

"As a result, PSA tests have a high rate of false positives, which can mean repeat needle biopsies and unnecessary surgery."

Research looking at a much larger number of prostate tissue samples are planned.

The beauty of the PSA test is that it can be performed on a blood sample so it is quick and painless

Dr Charlotte Bevan Prostate Cancer Charity

Dr Charlotte Bevan from the Prostate Cancer Charity, told BBC News Online DNA microarrays was an exciting new technique which was certain to identify new candidates for cancer markers or genes involved in the progression of the disease.

She added: "AMACR is potentially exciting in that it appears to be a marker that could differentiate between prostate cancer and benign conditions, something the PSA test is unable to do.

"However, the beauty of the PSA test is that it can be performed on a blood sample so it is quick and painless.

She added: "At present, testing for AMACR means that a needle is inserted into the prostate gland, which is a more invasive procedure.

"This is usually carried out only if a PSA test is positive.

"Until an AMACR test which is as quick and painless as the blood test is devised, we feel that it is unlikely to take over from PSA as the first line diagnosis for prostate cancer."

The research is published in the Journal of the American Medical Association.