tumor progression. When a brain tumor loses its PTEN
genes, a low-grade cancer (right) is likely to become highly malignant ( left) .
scientists have discovered a gene, inactivation of which can help to take the brakes off the development of several major cancers, including those of the brain and prostate. The surprising finding, reported by a team in the issue tomorrow Science and a second in Nature Genetics , may help oncologists neighbor predict months could be at high risk for these cancers and also the brain or prostate tumors are highly malignant -. information that could help clinicians determine how aggressive they should be with surgery, chemotherapy or other treatments
The researchers began their hunt on chromosome 10, because they knew that this chromosome is partially or completely absent in a variety of cancers, particularly aggressive brain tumors called gliomas - a first indication of what he carries a tumor suppressor gene. To refine the location of the suspected gene, a team led by Ramon Parsons College of Columbia University of Physicians and Surgeons and Michael Wigler of Cold Spring Harbor Laboratory on Long Island compared equivalent sections of DNA from cells and normal cells from 65 breast cancers humans. They found that one genetic marker is absent in the two samples of breast cancer, as well as of certain tumor cell lines, prostate and brain. By comparing fragments of the target gene reported by the marker in a DNA database short pieces called expressed sequence tags, the researchers were able to reconstruct the entire gene. Their description of the gene, called PTEN (for phosphatase and tensin homologue deleted on chromosome 10 ), appears in Science .
The other group, led by cell biologist Peter Steck MD Anderson Cancer Center in Houston and Sean Tavtigian biotech firm Myriad Genetics in Salt Lake City, pursued the same gene in brain tumor cells . They called MMAC1 (for mutated in multiple advanced cancers 1 ), and issue a report Nature Genetics . "We started from two different places for two different reasons and we were in the same place at the same time," says Steck.
The new gene joined some 16 other tumors suppressors known. But while it is far from the first such gene discovered, cancer researchers are enthusiastic, because the early data indicate that PTEN could rank in importance with p53 and other tumor suppressors that have been linked to several types of tumors. "[ PTEN ] appears to be a major gene in some very important cancers," says Kenneth Kinzler, a molecular geneticist at Johns Hopkins University. In addition to prostate cancer, which affects approximately 317,000 men each year in the United States, and gliomas, still affecting 15,000 people, these might include breast and kidney cancer.
researchers still have much to do to find how much the loss of the gene could contribute to these cancers, although its sequence provides important clues. the PTEN protein appears to be a phosphatase enzyme that can counteract the work of kinases growth stimulators, which can help make cancer cells when they are mutated in a hyperactive form . Thus, PTEN "of the loss can lead to excessive cell growth. the loss of the gene could also help cancer cells invade other tissues, in which case the assessment PTEN "status could help predict the malignancy of a tumor. Steck said, "If you had a molecular marker that could help a clinician in this decision, it would be very important."
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