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April 3, 2002

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A New Genetic Marker for Prostate Cancer

By Kate Wong

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To screen for prostate cancer, physicians have long relied on a blood test that searches for abnormally high levels of a protein known as prostate specific antigen (PSA). The problem is, because benign changes in the prostate can also produce elevated levels of PSA, the test has a fairly high rate of false positives. The results of a new study suggest that a more specific test may lie within reach, however. According to a report published today in the Journal of the American Medical Association, researchers have identified a gene that is overexpressed in prostate cancer tissue and found only in malignant cells. The protein produced by this gene, they say, could serve as the basis for a more accurate and sensitive screening test for the cancer, which affects one in nine men over the age of 65.

Using so-called DNA microarray technology, Mark A. Rubin and Arul M. Chinnaiyan of the University of Michigan identified 20 genes that are consistently overexpressed in cancer. High levels of one resulting protein--an enzyme called a-methyl-CoA racemase, or AMACR--showed up in roughly 95 percent of more than 300 prostate tissue samples containing localized cancer, they report. Conversely, the protein did not appear in benign prostate tissue. Subsequent needle biopsies of 94 of the samples showed AMACR expression to have 97 percent sensitivity and 100 percent specificity for detecting prostate cancer.

"The results of this study suggest that AMACR may be a useful addition to current diagnostic tools for detecting prostate cancer, although these findings require further evaluation in larger studies," Rubin and Chinnaiyan write. They add that although the AMACR turns up in the highest amounts in prostate and colorectal cancer, they also found it in ovarian, breast, bladder and lung cancer, suggesting that it could serve as a diagnostic biomarker for these types as well.

Kate Wong is an award-winning science writer and was formerly senior editor for features at Scientific American, where she focused on evolution, ecology, anthropology, archaeology, paleontology and animal behavior. She is fascinated by human origins, which she has covered for nearly 30 years. Recently she has become obsessed with birds. Her reporting has taken her to caves in France and Croatia that Neandertals once called home to the shores of Kenya’s Lake Turkana in search of the oldest stone tools in the world, as well as to Madagascar on an expedition to unearth ancient mammals and dinosaurs, the icy waters of Antarctica, where humpback whales feast on krill, and a “Big Day” race around the state of Connecticut to find as many bird species as possible in 24 hours. Wong is co-author, with Donald Johanson, of Lucy’s Legacy: The Quest for Human Origins. She holds a bachelor of science degree in biological anthropology and zoology from the University of Michigan. Follow her on Bluesky @katewong.bsky.social

More by Kate Wong

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