Johns Hopkins Health Alert
PCA3 and Gene Fusion: Two New Prostate Cancer Biomarkers in Development
Biomarkers are substances like prostate-specific antigen (PSA) that can be measured in blood, urine or other body fluids and used to detect or monitor a disease. Researchers are investigating a number of potential biomarkers that, in the future, may improve upon the PSA test's ability to detect prostate cancer and identify potentially life-threatening tumors. Two promising biomarkers are PCA3 and gene fusion.
PCA3. PCA3 is a test that measures a gene that is overexpressed (60 to 100 times greater) in prostate cancer cells versus noncancerous cells. Cells shed by the prostate containing the PCA3 gene are detectable in the urine. Researchers report that the lower the level of PCA3 in the urine, the less likely prostate cancer is present. Because PCA3 is not produced or is produced only minimally by noncancerous cells, the presence of conditions like benign prostatic hyperplasia (BPH) or infection is less likely to produce falsely elevated PCA3 levels. PCA3 testing is most reliable when done in conjunction with a digital rectal exam (DRE).
Researchers report that when performed after a DRE, the results from PCA3 testing are valid in 98 percent of the cases. If the test is performed without a DRE, validity drops to 80 percent. Researchers believe that rather than replacing PSA screening, the PCA3 test may help identify or rule out cancer in men with elevated PSA levels but no prostate cancer on the initial biopsy. In addition, some evidence suggests that the test may be useful in helping to identify men who are appropriate candidates for active surveillance. Currently, PCA3 testing is available only through clinical trials in the United States.
Gene fusions. A gene fusion is a hybrid gene formed from two previously separated genes. Scientists have discovered that many prostate cancer patients have gene fusions involving the ERG and TMPRSS2 genes that create a new gene that is thought to promote the development of prostate cancer -- and, possibly, a more aggressive form of the disease. Gene fusions are now being detected in urine and have promise as new biomarkers for prostate cancer. More research is needed, however, before this method of testing moves into the mainstream.
Posted in Prostate Disorders on June 1, 2011
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