By the double helix's 75th birthday, your genome might be as familiar as your shoe size. Helen Pilcher peers into the future of genetic medicine.
24 April 2003
Helen R. Pilcher
It's 2028. There's no room for technophobes in the medical profession. As a doctor swipes her patient's genetic ID card, the information downloads in seconds. A string of letters scrolls down her computer screen. These are the raw data of DNA, the code of life. For the patient, waiting anxiously, the news will be mixed. The results reveal that he carries a gene that increases his risk of cancer. But should he fall ill, his genes also predict the best therapy - a new tailor-made drug that brings with it an 80% chance of remission.
Could this be the future of medicine?
Fifty years ago, James Watson and Francis Crick described the structure of DNA, paving the way for modern genetics. The future might bring genetic diagnosis and bespoke medicines. Some scientists are optimistic. "We'll be able to give the right medicine for the right patient at the right dose," predicts geneticist Allen Roses of pharmaceutical company GlaxoSmithKline, UK.
Others are more cautious. Science is "inherently unpredictable", warns Simon Baumberg, a bacterial geneticist at the University of Leeds, UK. It's difficult to assess whether methods like this will really deliver.
Over the next 25 years, we will pin down the genes behind ever more ailments. "Cancers will be subdivided and reclassified taking into account genetic makeup," says cell biologist Paul Nurse, of Cancer Research UK.
Cancers might fall into hundreds or even thousands of types. This would allow researchers to design new treatments aimed at genetically distinct tumours. The first such therapy is already with us. Glivec is used to treat patients with chronic myeloid leukaemia, a disease that affects one to two people out of every 100,000.
The drug was designed using genetic knowledge. It targets an abnormal
piece of DNA in cancerous cells, killing them but sparing
healthy cells. After a year's treatment, 90% of patients are free of disease, and 50% show a complete or near disappearance of the abnormal gene that triggers the disease.
"I think we will see more drugs like Glivec over the next 25 years," predicts Nurse.
Hundreds of thousands of patients suffer unpleasant side-effects from their drugs. The powerful cocktails of treatments used to treat cancer can cause hair loss, nausea, bleeding and infection, for example. But mapping our DNA may help doctors to prescribe the safest, most effective medicine.
Of the three billion DNA letters in the human genome, well over 99% are identical from person to person. Nevertheless, the differences dotted throughout the sequence influence how we respond to drugs.
Five per cent of patients who are prescribed abacavir, an anti-HIV drug, are genetically susceptible to side-effects including fever, rashes, and digestive and breathing trouble.A scan of 200,000 single-letter changes can predict whether a patient will develop side-effects, so alternative treatments can be offered. In the future, scanning just ten DNA letters may offer the same level of prediction.
This technique will allow us to minimize side-effects and maximise drugs' effectiveness, says Roses. In the future, DNA from patients' blood samples could be compared with a bank of DNA sequences stored on a microchip. Roses is confident that chips like this will become available in one to three years.
So will we soon be carrying identity cards detailing our genetic makeup?
The American scientist Craig Venter, who led the private effort to sequence
the human genome, is already offering anyone the chance to buy his or her
own genetic barcode - for $710,000. Over time, he anticipates the cost
dropping to a more affordable $1,000.
Researchers are revelling in the recent completion of the human genome sequence. Venter and an international and publicly funded consortium published draft versions in 2001, but the code is now 98% complete - as good as it will get with current technologies.
"In 20 years' time, it's possible that newborn
babies could be given a partial genetic identity card,"
says Nurse. This would include information from an individual's genome sequence. "But just because we could do it doesn't mean we should," warns Nurse. At a UK Royal Society public meeting held in March this year, 50% of people were against the idea.
Genetics rarely predicts disease with any certainty, but it can show an increased risk. Women with altered forms of two genes called BRCA1 and 2, have a higher chance of developing breast cancer. "At the moment, prophylactic surgery is an option, but in the future, there may be preventative treatments or drugs," says Nurse.
Genetic ID cards could offer benefits for medical diagnosis, treatment and prevention. But regulation must keep pace with technology. We risk creating a genetic underclass of those susceptible to disease, who might encounter problems in obtaining insurance and employment.
"Given this complexity, we need to be extremely careful how this technology is used to shape our society," warns Nurse. "We need to discuss what genetics can and can't deliver and what sort of society we want as a result."
© Nature News Service / Macmillan Magazines Ltd 2003