How Gene Doping Works

By: Susan L. Nasr  | 
Olympic swimmers Michael Phelps and Park Tae-Hwan
The virtual Michael Phelps and the real swimmer Park Tae-Hwan in the swimsuit that got people buzzing about bodily enhancement
Toru Yamanaka/AFP/­Getty Images

­Michael Phelps shared the spotlight at the Beijing Olympics with -- a swimsuit. The Speedo LZR racer swimsuit reportedly takes 20 minutes to put on, covers swimmers from chest to calf and, most important, smooths skin that normally "flaps" in the water. It gives swimmers a more frictionless glide. Oh, and it seems to help them smash world records.

The suit offers yet another example of athletes trying to winnow down a completion time when the body itself had reached its peak. Whether, like swim caps, we call these attempts "advances," or like steroids, we deride them as "doping," we can't avoid the bodily enhancements that turn up in sports.


What will we see next? Some officials say athletes will tamper with their very genes.

In gene doping, athletes would modify their genes to perform better in sports. We say would because no one has tried it y­et, as far as we know, says Dr. Theodore Friedmann, head of the World Anti-Doping Agency's (WADA) gene doping panel. "It will happen," he says, "but we don't know when."

How would athletes do it? They might add genes to the ones they were born with, or they might tinker with how the body uses the genes they have.

­Gene doping is an unintentional spin-off of gene therapy in which, doctors add or modify genes to prevent or treat illness. Gene doping would apply the same techniques to enhancing someone who is healthy. The line is fuzzy, but if the cells or body functions being modified are normal to start with, it's doping [source: Friedmann].

Two types of gene doping exist. In somatic cell modification, genes are modified in a bodily cell, like a lung or muscle cell. The changes aren't passed on to children. Today's gene therapy alters somatic cells. Germline modification, however, changes genes in a father's sperm, a mother's eggs or an embryo [sources: Hanna, Wells]. The genetic changes manifest in children and possibly in their children. So far, the U.S. government hasn't funded research on human germline modification, and other governments have banned it, so we'll talk about somatic cells [sources: Baruch, Hanna].

Read on to find out how future athletes might alter their genes.


I'll take the IGF-1 and Erythropoietin Genes, Please.

The Navigenics store for genetic testing
At the Navigenics store in New York City, you can sign up to have your DNA tested for various diseases. It doesn't look like there are any supplementary genes for sale, though.
Shaul Schwarz/­Getty Images

Tweaking a person's genes for sports could, at the outset, be as easy as choosing from a menu. Scientists know of 187 genes linked to human fitness or athleticism [source: Rankinen]. For instance, some genetic variations are linked to running the 2,000-meter particularly well [source: Cam]. "Tweaking" might mean adding copies of one of these nearly 200 genes or amplifying or lessening their activity in the athlete.

­Scientists don't know what many of these "sports" genes do. For safety's sake, an athlete might tweak a gene with a well-understood function. One potential candidate might be the IGF-1 gene for insulinlike growth factor-1, which repairs and bulks up muscles. The gene for erythropoietin (EPO), which boosts red blood cells thereby raising blood oxygen and endurance, presents another possibility. Athletes, particularly cyclists, have been known to dope with synthetic EPO [source: Wells].


Thanks to gene therapy, we have ways to send genes into the body. Scientists can inject vectors, which are just gene transporters in this case, into muscles or blood. They can also remove cells, modify their genes and then return the cells to the body, although athletes might not want the invasive procedure [source: Wells].

Viruses serve as popular vectors for shuttling a gene into a cell. Like little syringes, they naturally inject their genetic material into our cells. To re-engineer them for delivering human genes, scientists "clean out" the harmful parts of the virus, insert a human gene into the virus' genetic material and then inject the virus into the body. Another type of vector is a plasmid, a ring of bacterial DNA into which human genes can be added. When plasmids are injected into muscles and the muscles get an electric shock or ultrasound treatment, muscle cells take up the plasmids.

­Sound easy enough? There's a catch: delivering genes to the right cells. Otherwise, an athlete who wants bigger muscles might end up inadvertently making growth proteins appear in his eyes. Scientists can steer genes by injecting into muscles, so the genes only enter muscle cells. Or they can use a virus that infects only certain body parts. They can also let the genes enter cells liberally but make them activate only in certain cells. It's even possible to engineer a gene to make proteins only when the athlete "tells it to" by taking a drug.

Once a gene is incorporated into a cell, the cell is transduced. Transducing a whole body part, like a muscle, is hard; usually, only some cells cooperate. Inside cells, the gene will either stay in the nucleus, next to the chromosomes, or actually shove into a chromosome. As part of a chromosome, the gene can cause lasting change: It's passed on to new bodily cells when the transduced cell divides. Genes that don't shove into chromosomes will die when the cell dies. Once transduced, cells will follow the new genetic instructions and make the desired proteins. The athlete, of course, hopes that the proteins will change the way his or her body works in a way that boosts performance.

­Is our genetically modified athlete ready to run farther, jump higher, lift more weight or head for the hospital? Read on to find out.


Gene Doping Risks and Results

Injured soccer player
Athletes like Brittany Timko of the Canadian women's soccer team get hurt enough on the field without having to worry about whether gene doping will send them to the hospital, too.
Liu Jin/AFP/Getty Images

It's hard to say what would happen to an athlete who tried gene doping. In the world of human experiments, scientists have only transferred genes to make sick people healthy, not healthy people better.

Bioethicist Thomas Murray speculated on what would happen if an athlete were to use today's technology in an article for WADA's Play True magazine. He wrote that most athletes would get no boost beyond the placebo effect, many would be harmed and a few, very improbably, might get a temporary boost in performance. But Murray argued it wouldn't be enough to upset the competitive balance in Olympic sports. That's because scientists have trouble carefully controlling the results of gene delivery: They can't deliver a large effect without also delivering a large risk [source: Friedmann].


Consider the EPO gene. A drug called Repoxygen delivers the EPO gene with some controls, so that when blood oxygen dips below normal, the body makes enough red blood cells to restore normal oxygen. The gene then shuts off [source: Binley]. Athletes seeking an edge probably would want better-than-normal blood oxygen. They could try adding the EPO gene with no controls. But in healthy monkeys who received that treatment, blood became so thick with red blood cells that researchers had to bleed the monkeys to prevent heart failure and stroke. Eventually, the monkeys were euthanized [source: Svensson].­


­Other risks exist. Here's a big one: cancer. Cancer can happen if a genetic modification accidentally turns on a cancer gene or turns off a cancer-suppressing gene. An event like this caused leukemia in five children who received gene therapy for severe combined immunodeficiency. Their new ­genes inserted into a bad place on a chromosome and turned on cancer genes [source: Staal].

The athlete also could have an immune reaction. His or her body might attack the virus used to deliver the gene, the viral or bacterial genes themselves or the very protein meant to boost performance. The reaction could be mild, like a fever. But it could also be severe. Healthy monkeys died from severe immune reactions after "doping" with the EPO gene. The gene was injected into their muscles, which made a different EPO protein than the one naturally made in the liver. Their systems attacked both EPOs, and their bodies stopped making red blood cells [source: Gao].

The action of the genes can cause problems, too. For example, the genes for human growth hormone and IGF-1 tell cells to divide. If they get into the wrong cells, cells can divide uncontrollably and form tumors [source: Wells].

Even riskier, gene doping may permanently affect athletes. Doctors can't pry a gene out of a cell, and surgeons can't necessarily cut out transformed cells. They can try to treat unwanted effects, but rescue efforts have failed in gene therapy patients [source: Raper]. In addition, gene doping's long-term effects pose another mystery. What happens to athletes who try gene doping at age 20 when they get old? Scientists don't know. No one has followed gene therapy patients that long.

­So today, gene doping isn't safe. The athlete might experience nothing, or he or she could experience a fever or even a medical emergency. Would athletes who tried gene doping also get in trouble? Find out next.


Laws and Ethics Surrounding Gene Doping

Man with big arm muscles
If gene doping were legal and safe, would professional athletes all look like this?
Peter Cade/­Getty Images

­Gene doping is against the rules in many sports. In 2003, WADA put gene doping on its prohibited list [source: USADA]. Many sports governing bodies accept and use the list, thereby prohibiting gene doping for athletes participating in the Olympics, Paralympics and many other events [source: WADA]. However, the list isn't used in Major League Baseball, the National Basketball Association or the National Football League [source: Associated Press].

Scientists and doctors who inject genes into healthy people violate professional ethical codes. Universities and hospitals could penalize staff members for performing a human experiment not approved by an ethics committee. If the athlete were harmed, the doctor could be sued for malpractice and lose his or her medical license, says Maxwell Mehlman, a law professor at Case Western Reserve University School of Medicine.


But that said, the United States has no laws specifically banning gene doping. Genes aren't controlled substances, like heroin or steroids, so until laws are made, competitive athletes or just regular gymgoers could probably inject themselves with genes without going to court or jail, says Mehlman.

Laws aside, gene doping raises ethical issues, says Thomas Murray, president of the Hastings Center, a nonprofit bioethics institute in New York. Murray raises four arguments against allowing gene doping.

The first argument is the risk to the individual athlete, though the procedures will become safer and more reliable over time, he says. Second is unfairness. "Some athletes will get access to it before others, especially in safe and effective forms," he says. Third is the risk to other athletes. If gene doping were allowed, and one athlete tried it, everyone would feel pressured to try it so as not to lose. An enhancement arms race would follow. "Only athletes willing to take the largest amounts of genetic enhancements in the most radical combinations would have a chance at being competitive. The outcome would most assuredly be a public health catastrophe. And once everyone tried it, no one would be better off."

­Finally, gene doping would change sports, Murray says. "Sports are in part constituted by their rules," he explains. "What if I showed up to the New York [City] Marathon wearing rollerblades?...Or suppose I came to the high jump wearing springs on my shoes…Or what if we let the pitcher stand as close to the batter as he wants?"

If these exceptions were allowed, the meaning of each sport would change, Murray says. The New York City Marathon would become a roller derby. The high jump would become a contest for finding the biggest springs. The baseball pitcher would stand next to the catcher, and the batter would bunt. "All the stuff we like about baseball -- the variety, the art of the double play, the great catches -- would disappear," Murray says.

Athletes and audiences should decide what they value in sports and whether allowing gene doping would dissolve those aspects, Murray says. "That will help us decide where to draw the line."

Keep reading to learn what other crazy uses people have thought up for their genes, like curing baldness.


Frequently Answered Questions

What do you mean by gene doping?
Gene doping is the use of genetic engineering to artificially enhance the performance of an athlete. This can be done by either increasing the production of certain proteins that are beneficial for athletic performance, or by introducing new genes that confer a competitive advantage.

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  • Associated Press. "WADA Chief Urges Drug Tainted Sports to Clean Up." International Herald Tribune. August 10, 2008. (11/11/2008)
  • Baruch, Susannah et al. "Human Germline Genetic Modification: Issues and Options for Policymakers." Washington, DC: Genetics and Public Policy Center. May 2005. (11/11/2008)
  • Binley, Katie et al. "Long-term Reversal of Chronic Anemia Using a Hypoxia-Regulated Erythropoietin Gene Therapy." Blood. Vol. 100. No. 7. October 1, 2002.
  • Cam, F.S. et al. "Association between the ACE I/D gene polymorphism and physical performance in a homogenous non-elite cohort." Canadian Journal of Applied Physiology. Vol. 30. No. 1. February 2005.
  • Dillman, Lisa. "As Swim Records Fall, High-Tech Suit Faces Scrutiny." The Los Angeles Times. March 27, 2008. (11/11/2008)
  • Friedmann, Theodore. Personal interview. Conducted 10/29/2008.
  • Gao, Guangping et al. "Erythropoietin Gene Therapy Leads to Autoimmune Anemia in Macaques." Blood. Vol. 103. No. 9. May 1, 2004.
  • Geneforum. "Results from Oregon College Athlete Gene Doping Survey." 2005. (11/11/2008)
  • Grady, Denise. "A Lab Breeds a Mighty Mouse, With a Variety of Implications." The New York Times. May 1, 1997. (11/11/2008) 756C0A961958260&sec=&spon=&pagewanted=all
  • Hanna, Kathi. "Germline Gene Transfer." March 2006. (11/11/2008)
  • McCrory, P. "Super Athletes or Gene Cheats?" British Journal of Sports Medicine. Vol. 37. No. 3. June 2003.
  • Mehlman, Maxwell. Personal interview. Conducted 11/11/2008.
  • Murray, Thomas. "Gene Doping and Olympic Sport." Play True magazine. No. 1. 2005. (10/23/2008)
  • Murray, Thomas. Personal interview. Conducted 11/7/2008.
  • Rankinen, Tuomo et al. "The Human Gene Map for Performance and Health-Related Fitness Phenotypes." Medicine & Science in Sports & Exercise. Vol. 38. No. 11. November 2006.
  • Raper, Steven et al. "Fatal Systemic Inflammatory Response Syndrome in a Ornithine Transcarbamylase Deficient Patient Following Adenoviral Gene Transfer." Molecular Genetics and Metabolism. Vol. 80. No. 1. September 2003.
  • Staal, F.J.T. et al. "Sola dosis facit venenum. Leukemia in gene therapy trials: a question of vectors, inserts and dosage?" Leukemia. Vol. 22. No. 10. October 2008.
  • Svensson, Eric et al. "Long-term erythropoietin expression in rodents and non-human primates following intramuscular injection of a replication-defective adenoviral vector." Human Gene Therapy. Vol. 8. No. 15. October 10, 1997.
  • United States Anti-Doping Agency (USADA). "Guide to Prohibited Classes of Substances and Prohibited Methods of Doping." 2003. (11/20/2008)
  • Wells, D.J. "Gene Doping: the Hype and the Reality." British Journal of Pharmacology. Vol. 154. No. 3. June 2008.
  • World Anti-Doping Agency (WADA). World Anti-Doping Code: Code Acceptance. 2008. (11/11/2008)