Prostate news article, October 2005
| TWO MORE MARKERS
TO POTENTIALLY SUPERCEDE PSA AS A MARKET FOR PROSTATE CANCER
Various authors Two articles in Cancer Research 2005 May;6(5):295-300. Reviewed by: Dr Charlotte Foley MA BMBCh MRCS |
The May (’05) edition of the journal Cancer Research contains two articles each proposing a new protein to potentially take the place of PSA as a marker for prostate cancer. Measuring blood levels of PSA helps greatly with diagnosis, predicting prognosis and gauging the response to treatments. However as a tumour marker it could be bettered as it is produced by normal prostate tissue too, and in substantial amounts by very large prostates. Only about a quarter of men with an ‘abnormal’ PSA will have cancer found in their prostate biopsies, while 15% of men with a ‘normal’ PSA level do harbour cancer.
Like PSA, both these molecules can be measured in small quantities in the serum. A group based in Ann Arbor in Michigan has been studying a molecule called huntingtin interacting protein-1 (HIP-1) which is more plentiful within prostate cancer cells. Though HIP-1 is not itself released into the blood stream, the immune system detects it as a foreign protein and makes antibodies against it, which are detectable at higher levels in the presence of prostate cancer. Unfortunately, accuracy is low and the two methods for measuring HIP-1 antibody levels do not always agree. Additionally, levels seem to vary at different times of testing and other cancers may also cause a positive test. Until these problems are solved it is of little use clinically.
A better candidate marker, catchily called ‘early prostate cancer antigen’ (EPCA) was first described by Professor Getzenburg from Johns Hopkins in 2004. They initially found this molecule in prostate biopsy tissue, in areas of cancer and adjacent normal tissue, in normal tissue in men who went on to develop cancer, but not in men with benign prostates. The next step towards clinical usefulness was to see if this EPCA molecule leaked into the blood stream, allowing its presence to be detected using just a blood test. When levels of EPCA were tested in blood from prostate cancer patients, other cancer patients, and healthy men, they were significantly higher in those with prostate cancer, less high for other cancers and low for those with prostatitis or benign conditions. This marker therefore seems very specific for prostate cancer and only slightly less sensitive. At the moment the researchers see this test as complementing PSA. However a larger trial and further refinements will help clarify its role in early diagnosis.
Bradley SV, Oravecz-Wilson KI, Bougeard G et al.
Serum antibodies to huntingtin interacting protein-1: a new blood test
for prostate cancer.
Cancer Research 2005; 65:4126-33.
Paul B, Dhir R, Landsittel D et al.
Detection of prostate cancer with a blood-based assay for early prostate
cancer antigen.
Cancer Research 2005; 65:4097-100.