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With individual sequencing, medicine may soon be custom-tailored to your own DNA.
by Erika Check Hayden

On September 4, geneticist Craig Venter invited the world to take a peek at his DNA. The first person ever to do so, the entrepreneur and science showman published his entire individual genetic sequence in a scientific journal. Replicating Venter’s $70 million technological feat is too costly for most of us, and it’s not clear what good it would serve to know that, like Venter, one has a genetic marker for wet earwax—or Alzheimer’s disease, which can’t be prevented or cured.

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Venter’s stunt is nevertheless a fitting symbol for 2007, a year marked by milestones in the quest for personalized medicine. “This will be seen as the year things turned the corner,” says Huntington Willard, director of the Duke Institute for Genome Science and Policy in Durham, North Carolina. “Patients are receiving genomic tests and benefiting from them; there are real live people being taken care of now.”

In February, for example, the Food and Drug Administration approved MammaPrint, a test designed to help breast cancer patients. MammaPrint surveys 70 genes in tumor cells, checking whether they’re turned on or off in an individual patient. By reading each patient’s total gene activity profile, doctors can predict whether a tumor is likely to spread and thus whether the patient needs to undergo chemotherapy in addition to surgery. The company behind the test, Agendia, based in the Netherlands, estimates that it will spare 60,000 American women unnecessary chemotherapy each year.

This year also marked the debut of a raft of tests based on genomics, the analysis of entire genomes. These tests are based on a catalog of human variation called the HapMap, which was released in 2005. HapMap is a directory of “single nucleotide polymorphisms,” or SNPs, places in the genome where differences between individuals (in the form of single chemical letters) appear in the DNA code. SNPs act like signposts, marking larger chunks of the genome that vary among individuals. By comparing SNPs in patients with a disease to SNPs in the HapMap, scientists can easily pinpoint the SNPs that are unique to that disease. Such SNPs can then guide scientists to the nearby genes that cause the disease, the same way a corner gas station might serve as a landmark to guide visitors to your neighborhood and eventually to your house.

Even before they determine the genetic culprit in a disease, however, scientists can use its SNP pattern to identify those who have the genetic signature of risk for that disease. This year, scientists found SNPs linked to type 2 diabetes, heart disease, obesity, and a long list of other ailments.

A number of companies are already selling tests based on these new findings. Iceland-based deCODE Genetics, for example, announced its launch in April of T2, a new SNP-­screening test for type 2 diabetes. Other companies are promising to bundle multiple SNP-based tests together, providing consumers a more complete health profile. Navigenics, for one, a company based in Redwood Shores, California, promises to “use the latest genetic science to illuminate the future of your health and arm you with the knowledge to change it for the better.”

A personal genome may one day become part of everyone’s medical record, providing powerful information about an individual’s genetic predispositions.

“Using genomics to make predictions about health is a powerful paradigm,” says Francis Collins, director of the National Human Genome Research Institute in Bethesda, Maryland. “We’re going to see a lot of these tests as we reveal more and more genetic changes linked to disease.”

The tests offered so far, however, cannot predict for sure whether a person will develop a given disease. Currently available tests reveal only the risk that one could become ill. It is unclear how that will help patients, Willard says: “How do you respond to a test that says your risk is elevated by 25 percent? That’s pretty meaningless; it’s open to all sorts of misinterpretation.” An employer, for instance, might refuse to give a high-stress job to an individual with an SNP profile unique to heart attack victims—even if that profile raises the risk of a heart attack only slightly.

Unfortunately, this year, lawmakers punted legislation designed to prevent such discrimination. In April, Congress was set to pass the long-delayed Genetic Information Nondiscrimination Act. The bill aims to prevent insurance or workplace discrimination based on genetic test results. It sailed through the House of Representatives, and President Bush promised to sign it. But at the last minute, Tom Coburn, Republican senator from Oklahoma, placed a hold on the bill because of its language concerning embryos and fetuses, among other things. The bill is now stalled.

This has not deterred those like Venter, who want to bare their genetic foibles to the world. Nobel Prize–winner James Watson, for instance, announced the completion of his personal genome sequence in May. He promised to publish it but hasn’t yet. Others, like futurist and tech guru Esther Dyson, are having parts of their genomes sequenced in a project led by geneticist George Church of Harvard University and MIT.

We don’t yet know enough about the genetic roots of disease to help these early adopters learn much from their genomes. But that will change, and scientists predict that a personal genome may one day become part of everyone’s medical record, providing powerful information about an individual’s genetic predisposition to disease.

Although that day is still a long way off, it’s much closer than it used to be, thanks to this year’s first steps toward personalized medicine, says Kathy Hudson, director of Johns Hopkins University’s Genetics and Public Policy Center in Washington, D.C. “For a long time, all the action in genomics was in the lab,” she says. “Now it’s spilling out into the real world, and that’s really exciting.”



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