Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, August 19, 1993 TAG: 9308190017
SECTION: NATIONAL/INTERNATIONAL PAGE: A-12 EDITION: METRO
SOURCE: Associated Press
DATELINE: BOSTON LENGTH: Medium
They estimate these genetic variations are somehow involved in one in 11 cases of cancer of the breast, colon and bladder, and a substantial proportion of leukemia and lung and prostate cancer.
The mutations they found appear to roughly double the risk of cancer. Twenty percent of all people with the common forms of cancer carry them, as do 10 percent of all healthy people.
The discovery gives important clues for cancer research, but there's no reason - at least yet - to search people's genetic material for the mutations, said Dr. Theodore G. Krontiris of New England Medical Center, whose finding builds on earlier work by his team and other researchers.
For years, the search for the genetic underpinnings of cancer has focused on specific genes that lead to cancer when they become mutated. Recently, scientists have begun to look at the seemingly meaningless code that fills up the chromosomes between genes.
Of particular interest are multiple copies of short stretches of genetic code. These bits, called minisatellites, might repeat the same genetic sequence 50 or 100 times.
Minisatellites are scattered through the human library of genes, and many appear closely linked with genes that contain the code to manufacture essential proteins.
One gene, H-ras, is well known to cause cancer when it becomes mutated. In the latest work, the scientists found that errant forms of a minisatellite somehow seem to interfere with the workings of normal versions of the H-ras gene, triggering cancer in a completely different way.
Krontiris and colleagues first noticed the apparent association among mutant minisatellites, H-ras and cancer several years ago. In the latest report, published in today's New England Journal of Medicine, he combined his own with 22 other studies to estimate the strength of this link.
"We have solidified the association," said Krontiris. "Where we are headed is trying to determine why."
Everyone inherits two copies, or alleles, of the minisatellite linked to H-ras. Throughout the population, there are four normal versions of the minisatellite. The cancer risk goes up when people inherit a mutant variation.
However, Krontiris said, "It's too early, given what we can do about cancer, to put it into mass screening."
Krontiris said he suspects that the mutant minisatellite messes up the normal control of the H-ras gene so it manufactures protein improperly.
by CNB