US and UK scientists are developing a test for prostate cancer that uses samples of prostate fluid taken through a needle inserted under local anasthetic and takes less than three minutes to complete.
The research is being led by Professor David Parker at Durham University in the UK, whose team, together with scientists from the University of Maryland in the US, are working on a method that measures levels of citrate and lactate in bodily fluids. They published a paper about it recently in Organic and Biomolecular Chemistry.
Citrate and lactate are “anions” or negatively charged molecules that are formed during cell metabolism and whose levels change when cancers grow. For example, citrate levels in prostate fluid go down as prostate cancer progresses.
Parker said in an interview that these two chemicals are important markers for disease.
Parker’s team use the fact that citrate and lactate anions bind to various luminescent europium complexes. Once bound to the complexes, the new compound “glows” with an intensity that depends on how much anion is present. He and his team have worked with other types of responsive complexes before, the lanthonide complexes, and drew on this experience to create the new ones.
The researchers then developed calibration curves that related the intensity of luminescence with different levels of anion. This is the core of the test: basically the intensity of the glow shows how much biomarker is present in the sample.
To check the test, the scientists compared its results with those of current tests that use enzyme methods to measure levels of citrate and lactate. Although reliable, enzyme methods take much longer, hence the attraction of a faster alternative.
Parker and colleagues found that the luminescent test showed similar results to the enzyme test.
A Prasanna de Silva, chair of organic chemistry at Queen’s University Belfast, UK, said that the new test was:
“A convenient and quick method which provides early warning of prostate cancer which will bring relief to many men.”
Parker said the test is currently being evaluated for commerical use.
“Ultimately this could form the basis of a simple screening procedure that could be carried out in local surgeries up and down the country,” he said.
However, it is still early days and the researchers still have to prove the test is reliable over a large number of samples.
John Neate, chief executive of the Prostate Cancer Charity in the UK also reminded the BBC that the test was an invasive procedure that required a needle to be inserted into the prostate under anasthetic, and it could only give a preliminary diagnosis which would have to be confirmed with another invasive procedure, the biopsy, to see how aggressive the cancer might be, before determining treatment.
“The researchers hope to able to refine the test by using samples of seminal fluid which may be easier to obtain. If this was the case, it would be easier to see how this test could take a useful place in clinical practice,” said Neate.
Men will welcome the new test if it means they don’t have to wait 2 weeks to find out the result like they currently have to with the PSA blood test, which is also unreliable.
Prostate cancer affects 34,000 and kills 10,000 men in the UK every year. One of the problems is reliable diagnosis, and current methods sometimes lead to unnecessary treatment, which carries the risk of incontinence and impotence.
“A europium luminescence assay of lactate and citrate in biological fluids.”
Robert Pal, David Parker and Leslie C. Costello.
Org. Biomol. Chem., 2009, 7, 1525
DOI: 10.1039/b901251f
Sources: RSC Publishing, BBC News.
Written by: Catharine Paddock, PhD