ROANOKE TIMES
Copyright (c) 1997, Roanoke Times
DATE: Saturday, March 29, 1997 TAG: 9703310023
SECTION: NATIONAL/INTERNATIONAL PAGE: A-3 EDITION: METRO
DATELINE: WASHINGTON
SOURCE: ASSOCIATED PRESS
While enthusiastic about the discovery, researchers caution the finding gives no help to current patients.
A mutated gene that helps unleash killer cancers of the brain, breast and prostate has been identified by two teams of researchers working in separate labs.
The earliest use of the discovery, one researcher said, may come in using a gene test to identify patients whose cancer is likely to be fast growing. Doctors could then treat them more aggressively.
A normal form of the gene acts as a tumor suppressor, the scientists found, but in its mutated form it is linked to highly aggressive cancers that are difficult to treat and often lethal.
The researchers cautioned that the finding gives no help to current cancer patients.
``This is an exciting discovery, but we don't want to exaggerate it,'' said Dr. Ramon Parsons of the Columbia-Presbyterian Medical Center in New York. ``It will require a lot of work before it has clinical applications. You have to be realistic.''
One team that identified the gene was led by Parsons and Michael Wigler of Cold Spring Harbor Laboratory in New York. They named the gene PTEN and are publishing their study in the journal Science.
Another team, led by Peter Steck of the M.D. Anderson Cancer Center in Houston, isolated the same gene at about the same time and named it MMAC1, for mutated multiple advance cancers. Steck's study is to be published in April in Nature Genetics.
The researchers found that the gene was missing or mutated in a high percentage of brain, breast and prostate cancers, but there is some evidence that it is also a factor in other cancers.
Both Parsons and Steck said when the gene is functioning normally, it may regulate an enzyme that stimulates cell growth.
The mutated PTEN gene appears most frequently in cancers that are expanding wildly, Parsons said. This suggests that the PTEN mutation does not start the cancer, but removes a growth regulator protein that allows cancer to grow without restraint and, perhaps, to seed elsewhere in the body.
Steck agreed, noting ``we can't exclude the possibility that it initiates cancer, but we find it much more associated with advanced cancer.''
Scientists have now found at least 17 genes that act as cancer suppressors by controlling cell growth and division. This anti-cancer protection is lost when a suppressor gene is missing or mutated. Cancer can result if there are enough gene malfunctions to remove any brake on cell division.
``You need multiple gene mutations to get a tumor,'' said Parsons.
Kenneth Kinzler, a cancer researcher at Johns Hopkins University in Baltimore, said identifying the PTEN/MMAC1 gene is ``a very neat finding that is important because it defines a new type of tumor suppressor gene.''
The gene may play a role in regulating phosphatases, an enzyme that removes phosphates from proteins, Kinzler said. Some cancer-causing processes are thought to involve adding phosphates to proteins and a normal PTEN gene may prevent this, he said.
Dr. Richard Klausner, director of the National Cancer Institute, said in a statement that the discovery ``is one of the first genes to be implicated in aggressive and generally fatal brain tumors, a type of cancer in which we desperately need clues that the PTEN gene may offer.''
Brain cancer is diagnosed annually in about 17,000 Americans. About 75 percent of them die within five years.
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