NEW YORK, Nov 03 (Reuters Health) -- A genetic mistake found in colon cancer cells can also be found in the normal tissue of these cancer patients, report researchers at Johns Hopkins University School of Medicine.
The finding may lead to a new way to identify healthy people at risk for colorectal cancer, according to the report in the November issue of Nature Medicine.
"This would offer clear advantages for prevention and treatment prior to tumor development," according to a statement from the journal editors.
Overall, 44% of colon cancer patients had a genetic anomaly, known as loss of imprinting (LOI), in both their cancer cells and normal colon tissue. About 12% of healthy people also had LOI in the cells of the colon even though they had no signs of cancer, according to the study of 43 subjects.
"In the long run, what we hope is that we might be able to use this test as a way of identifying people who might be at risk of developing cancer, before it actually starts," said senior investigator Dr. Andrew P. Feinberg, of Johns Hopkins University, in an interview with Reuters Health. "It's very unusual in cancer to find a genetic change that's present in the normal cells. Normally, the changes that we see in genes in cancer affect just the cancer and are not present in the normal cells, except for very rare hereditary cancer syndromes."
Imprinting is a normal process by which only one of two matching genes -- one inherited from each parent -- is switched off. When this imprinting is lost, overproduction of particular gene product may promote the growth of cancer.
Feinberg and colleagues looked specifically at the gene for a growth-promoting gene called IGF2, in which the gene inherited from the mother is usually switched off.
The results document "the first gene alteration (to our knowledge) detected at high frequency in the normal tissue of cancer patients in the general population," the research team writes.
If susceptible patients could be identified, one potential therapy would be to restore the imprinting in tumor cells using drugs, Feinberg said.
"In test tubes, we've done this in a childhood tumor and also in colon cancer," he said. "The potential for intervention of imprinting is very appealing -- that's one of the reasons I work on it," Feinberg added.
SOURCE: Nature Medicine 1998;4:1236-1237, 1276-1280.
