Broadcast: Mar 13, 2003

Researchers are developing a blood test to look for colon cancer. The blood test is designed to detect ²⁾abnormalities in genes that control cell growth. These genes are passed on by both parents, and operate like switches, with only one switched on at a time. Under normal circumstances, only one gene, or switch, is turned on, and the other is off.

But when both switches are stuck in the "on" position, it causes what experts say is a "loss of imprinting," or instructions to the cells, and the result can be colon cancer. Experts think loss of imprinting triggers up to 40 percent of colon cancer cases.

Andrew Feinberg, a professor of medicine at Johns Hopkins University in Baltimore, Maryland, and the study's co-author, says researchers have already observed loss of imprinting in colon cancer cells.

In the current study, published this week in the journal Science, investigators took the blood samples of 170 people with some sort of history of colon cancer.

"What we are doing is examining their normal cells, and finding that this abnormality of imprinting is present in normal cells, including circulating blood cells," Mr. Feinberg said. "And when it is abnormal, it is associated with an increased frequency of cancer of the colon, colon benign tumors and also a positive family history for colon cancer."

Those who had a personal history of colon cancer were nearly 25 percent more likely to have the loss of the imprinting marker in their blood.

Dr. Feinberg says investigators now want to work forward, studying people with no known history of colon cancer, to see if the test accurately predicts who is likely to develop tumors.

"If that turns out to be the case, which will take several years to find out, then it would be possible to screen people in general with this test, and identify those who are at risk of developing cancer, so that we could either catch it very early, or prevent it altogether," he said.

As is often the case with new procedures, Dr. Feinberg says, the screening test for colon cancer is expensive and difficult to perform. But his team is also looking at ways to simplify it and make it more affordable.

Jessica Berman VOA news, Washington.

1)    detect[di5tekt]vt. 发现,探知，查出，电子检波

2)    abnormality[7AbnC:5mAliti]n. 畸形,异常性