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A customized genetic profile to predict health

Feb 3, 2003
Faye Flam
Philadelphia Inquirer

In the near future, individuals may be able to pinpoint which diseases they should worry most about - heart disease, Alzheimer's, stroke, prostate cancer or multiple sclerosis.

The medical crystal ball will be high-tech, inexpensive, personal genetic testing, which could be available in just five to 10 years, according to some medical researchers.

"This will create a profound revolution in medicine," predicts Leroy Hood, a molecular biologist at the University of Washington. "Medicine will become predictive, preventive and personalized."

Hood and other scientists gathered last week in Los Angeles at a seminar focused on the increasing power of genetic testing.

Such testing will offer more than just a window on your future demise, Hood said. The same technology that exposes your personal health demons could also provide strategies to battle them - new drugs to "overcome the limitations of your genes."

The seminar was organized by Gregory Stock, director of the Program on Medicine, Technology and Society at the University of California, Los Angeles.

Stock said he believed humanity stood at the dawn of a revolution people would remember for millenniums.

"Genes are the biggest window into who we are, and we are drawing back the curtain," he said. "This will call into question what it means to be a human being."

The seminar was prompted in part by the completion three years ago of the $3 billion public and private undertaking known as the human genome project. The result was a sequence of letters that represented the entire genetic code - the full complement of DNA - for a small sample of people from different ethnic groups.

Hood said he believes that in a few years many people will have their own complement of DNA sequenced and stored on a floppy disc for less than $1,000.

The genome project didn't sort out which genes had any bearing on health or illness, but such work is under way.

Scientists are looking for what they call polymorphisms - places where the genetic code differs from person to person. Some of these differences have no apparent effect while others influence people's vulnerability to disease.

Some of the latest findings have come from Iceland, where Keri Stefansson of the private company DeCode has undertaken to analyze the DNA of the 275,000 residents of his country. So far, about 70,000 people have been analyzed.

Because Icelanders keep detailed genealogy and medical records, Stefansson said, he has been able to trace patterns of disease in families and then search the DNA for genetic differences that might be responsible. In one family, he said, there were cases of a variety of cancers - melanoma, prostate cancer, pancreatic cancer and breast cancer - all, he said, related to some genetic quirk present in that family.

He has also isolated a genetic variant that appears in about a third of Icelanders with schizophrenia. The gene, he said, helps in the remodeling and growth of neurons in the brain. The finding, he said, may help scientists understand what causes schizophrenia and perhaps lead to new treatments.

But some people may not want to know their own genetic heritage in too much gory detail.

"You're going to get a lot of information, why you get frequent colds, whether you'll get cancer or ALS or Alzheimer's disease, why you're a pain in the neck," said Nancy Wexler, a medical researcher from Columbia University. "All of these have genetic components."

The knowledge gained from genetic tests, she said, "is going to affect the rest of your life."

Wexler knows firsthand about contemplating such tests, she said, because she learned when she was in her 20s that her mother was ill with Huntington's disease, an incurable neurological disorder that strikes people around their 40s and leads to a slow, horrific death. Wexler's father told her and her sister that each of them had a 50-50 chance of inheriting their mother's fatal genetic disorder.

Wexler, 57, is probably safe, since she is past the age that most people with the disorder develop serious symptoms.

As a medical researcher, she went to Venezuela to study families in which the disease was particularly rampant, and eventually helped to isolate the genetic flaw, making it possible to test people for Huntington's disease.

But most people who live with those 50-50 odds opt not to take the test, she said, preferring to go on in uncertainty. She read some quotations from people who had the test and got bad news. "It was like a loss, a loss of dreams," one read.

As other tests come along to assess risk for other fatal and possibly incurable diseases, she said, people have to keep in mind that the knowledge is irreversible - you can't ever go back.

There may be other cases, however, where advance knowledge can save your life. Icelandic researcher Stefansson said his analyses uncovered a gene that influences whether people develop pulmonary obstructive disease (chronic bronchitis and emphysema). The disease is almost inevitable if people with the genetic variant are smokers. But if they don't smoke, they will almost certainly not get the disease.

Stefansson said he anticipated most of the genetic tests that would become popular would involve preventable diseases. That way doctors will no longer give everyone the same advice - don't smoke, drink in moderation, avoid saturated and hydrogenated fats, exercise.

Instead, he said, doctors will be able to pinpoint which parts of the standard medical mantra will be particularly important for each patient.

Hood said he foresaw the ability to isolate genes that influence behavior - including variants that make people prone to behave violently or otherwise inappropriately.

"I think inappropriate behavior will have to be treated the same way we treat cardiovascular disease or cancer," he said. "But this opens up fascinating questions about what is normal and what is abnormal."

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