Read a related editorial: Where do nutrititional supplements fit in sport?
THE Beijing Olympics have long been tipped as the event where athletes might first try modifying their genes to boost performance (Â鶹´«Ă˝, 15 January 2000, p 24). “Gene doping” is attractive because it prompts the body to make hormones that are indistinguishable from the ones we make naturally. That makes cheats harder to spot. So will gene doping make its debut at Beijing?
Scientists have shown it is possible to use gene therapy to boost stamina and strength in animals (see table). And although their ultimate goal is to treat muscle-wasting diseases such as muscular dystrophy in humans, these labs have attracted interest from the sporting community. Lee Sweeney of the University of Pennsylvania in Philadelphia says he received 50 calls a week at one point, after his lab reported quadrupling the muscle mass of mice in 2007 by silencing the gene for myostatin.
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But now calls are down to two a week and interest seems to be waning. Sweeney suspects it is because athletes realise that pulling off gene doping in people remains a challenge. “Coaches have stopped calling altogether,” he says. “They realise it’s not so easy.”
One technique would involve injecting a virus containing desired genes and using this to modify the person’s DNA. But viruses might not deliver the gene to enough cells for it to make a difference. And if they do, there’s no guarantee genes will get switched on or make enough protein anyway. Viruses might load their gene near to an “oncogene”, triggering cancer, or be attacked and destroyed by the immune system before they could deliver genes.What’s more, detectable traces of the virus might linger in the body.
An alternative is to use a loop of “naked” DNA called a plasmid, which isn’t incorporated into the genome and so might be easier to pull off – and safer. “Naked DNA is easier,” says , who researches muscular dystrophy and gene therapy at Imperial College London. However, he says getting enough plasmid into a muscle to make a difference is likely to be a problem. “If only 1 or 2 per cent of muscle fibres are altered, that’s not enough,” he says. As a result, he says gene doping is unlikely to be on the cards this Olympics. “I would be absolutely astounded if there was a gene-doping scandal in Beijing.”
Further along the line, these challenges may be overcome. But by then athletes will have even more reason to avoid gene doping – they might get caught. The world anti-doping authority is taking steps to detect gene cheats. WADA will soon be looking for the physiological consequences of cheating, rather than for substances themselves. Each athlete will serve as his or her own physiological index, providing baseline patterns of gene activity, protein production and metabolic activity against which any drastic changes can be spotted.
WADA is also supporting research into abnormalities in gene-doped animals. “We have preliminary evidence that we find changes in the saliva,” says Theodore Friedmann, head of WADA’s programme to tackle gene doping.
Genetics – Keep up with the pace in our continually updated special report.
