In general, genetic enhancement refers to the transfer of genetic material intended to modify nonpathological human traits. The term commonly is used to describe efforts to make someone not just well, but better than well, by optimizing attributes or capabilities -- perhaps by raising an individual from standard to peak levels of performance. When the goal is enhancement, the gene may supplement the functioning of normal genes or may be superseded with genes that have been engineered to produce a desired enhancement. Furthermore, gene insertion may be intended to affect a single individual through somatic cell modification, or it may target the gametes, in which case the resulting effect could be passed on to succeeding generations.
In a sense, the concept of genetic enhancement is not particularly recent if one considers genetically engineered drug products used to alter physical traits as genetic enhancements. For example, human growth hormone (HGH), which before 1985 could be obtained only in limited quantities from cadaveric pituitary glands, now can be produced using recombinant DNA technology. When its supply was more limited, HGH was prescribed for children with short stature caused by classical growth hormone deficiency. However, with the advent of recombinant DNA manufacturing, some physicians have begun recommending use of HGH for nonhormone-deficient children who are below normal height.
Animal experiments to date have attempted to improve such traits as growth rate or muscle mass. Although this research is focused on developing approaches to treating human diseases and conditions, it is conceivable that developments resulting from this research could be more broadly applied to enhance traits rather than correct deficiencies.
Recently, Schwarzenegger mice have been bred - laboratory animals whose bodies have expanded rapidly after the injection of a gene that causes muscles to grow. The mice are the first stage in the development of treatments intended to coax the bodies of seriously ill patients with degenerating diseases to recreate damaged tissue (e.g., muscular dystrophy). In the world of sports, this technology could potentially be used to improve athletic performance without being detected.
Similar interventions could help delay the aging process. For example, a gene called MGF (Mechano-growth factor) regulates a naturally occurring hormone produced after exercise that stimulates muscle production. Levels of MGF fall as we age, which is one reason why muscle mass is lost as we grow older. A treatment to build up muscles would allow us to remain able-bodied and independent much longer. IGF-1, another muscle-building hormone, has produced increased muscle mass in laboratory mice. Theoretically, gene insertion of IGF-1 could produce an equally impressive effect in humans.
Efforts to genetically improve the growth of swine have involved the insertion of transgenes encoding growth hormone. Nevertheless, despite the fact that growth hormone transgenes are expressed well in swine, increased growth does not occur. Another effort aimed to enhance muscle mass in cattle. When gene transfer was accomplished, the transgenic calf initially exhibited muscle hypertrophy, but muscle degeneration and wasting soon followed and the animal had to be destroyed.
Gene transfer at the embryonic stage through a technique called pronuclear microinjection is another approach being tested in animals. However, current knowledge from animal experiments suggests that embryo gene transfer is unsafe, as its use results in random integration of donor DNA, a lack of control of the number of gene copies inserted, significant rearrangements of host genetic material, and a 5 to 10 percent frequency of insertional mutagenesis. In addition, this technique would necessarily be followed by nuclear transfer into enucleated oocytes, a process that in at least two animal models is associated with a low birth rate and a very high rate of late pregnancy loss or newborn death. Thus, many believe that the use of gene transfer at the embryonic stage for enhancement would reach far beyond the limits of acceptable medical intervention.
Greater success has been achieved in genetic enhancement of plants, which are more easily manipulated genetically and reproductively. However, the state of knowledge in humans and other complex organisms does not allow for the controlled genetic modification of even simple phenotypes.
For example, in humans, for whom more complex traits such as intelligence or behavior are concerned, the limitations are more pronounced. The genome provides only a blueprint for formation of the brain. The complex and subtle details of assembly and intellectual development involve more than direct genetic control and are subject to inestimable stochastic and environmental influences. Despite the technical limitations, it is possible that eventually enhancements using techniques initially intended to restore deficiencies could be redirected to improve memory and problem-solving, reduce the need for sleep, increase musical capacity, attain desirable personality traits, protect against cardiovascular disease or cancer, or increase longevity.
One of the areas in which genetic enhancement might find initial application is in sports. At the 1964 Winter Olympics in Innsbruck, a cross-country skier from Finland who won two gold medals was later found to have a genetic mutation that increased the number of red blood cells in his body because he could not switch off erythropoetin (Epo) production. This mutation increased the athlete's capacity for aerobic exercise. A synthetic version of Epo is currently used to treat anemia, but it has also been abused by athletes to heighten their stamina. For example, in the 1998 Tour de France, a team was thrown out of the race, and two top cyclists admitted taking the drug. Recent efforts to deliver the Epo gene into patients' cells would eliminate the need for regular injections, but this process could also be abused by athletes.
Genetic enhancement raises a host of ethical, legal and social questions. What is meant by normal? When is a genetic intervention "enhancing" or "therapeutic?" How should the benefit from a genetic enhancement be calculated in comparing its risks and benefits? Would people who have been genetically enhanced enjoy an unfair advantage in competing for scarce resources? That is, will genetic enhancement be available to all or only to the few who can afford to purchase it using their personal finances? These questions relate to the two major concerns presented by genetic enhancement: the undermining of the principle of social equality and the problem of creating an unfair advantage that would be enjoyed by enhanced individuals.
Some have speculated that genetic enhancement might affect human evolution. Philosophical and religious objections also have been raised, based on the belief that to intervene in such fundamental biological processes is "playing God" or attempting to place us above God. People from various perspectives believe that any interference with the random offerings of nature is inherently wrong and question our right to toy with the product of years of natural selection. Geneticists have countered that the power to control human evolution is unlikely, as the evolution of the human species is a nonrandom change in allelic frequencies resulting from selective pressure. The change progresses over generations because individuals with specific patterns of alleles are favored reproductively. If new alleles were introduced by gene transfer, the impact on the species would be negligible. Moreover, there is no certainty that genetically enhanced individuals would have greater biological fitness, as measured by reproductive success.
In general, however, ethical and social concerns center not so much on the improvement of traits for alleviation of deficiencies or on the reduction of disease risk, but on the augmentation of functions that without intervention would be considered entirely normal. For some individuals, technologies that can enhance traits are even more attractive than those that would merely duplicate them (e.g., cloning). And, although the distinctions between cure and enhancement might be obvious to some, they can lose meaning in medical practice or in formulating health policy. For example, interventions that begin in an effort to cure could slide quickly toward interventions that enhance.
The questions raised above also create significant new challenges to our regulatory capabilities.
On September 11, 1997, the National Institutes of Health (NIH) convened a conference on genetic enhancement. The meeting was prompted by a request to NIH to approve a protocol for conducting a gene therapy experiment on healthy volunteers, rather than on patients. Although the experiment was part of an effort to develop treatments for cystic fibrosis, the proposed use of healthy subjects raised, for the first time, the questions of whether and in what circumstances it was appropriate to use gene insertion technology in healthy volunteers. Exactly how to regulate this potential use of genetic technology remains unclear.
In order for the Food and Drug Administration (FDA) to control the introduction and use of genetic enhancement technologies, these techniques would have to be considered to be drugs, biologics, or medical devices, categories for which FDA has the authority to regulate genetic enhancements. Regarding drugs used for enhancement purposes, the definition of a drug in the Federal Food, Drug, and Cosmetic Act includes not only "articles intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease in man" but also "articles (other than food) intended to affect the structure or function of the body of man." The agency has relied on this definition to assert drug regulatory authority over products such as wrinkle creams and tanning agents that are intended to enhance the appearance of the body but that achieve results by affecting the body's structural or functional components. The agency will be challenged by the need to determine when enhancement is "genetic" (versus nongenetic, for example, liposuction or cosmetic surgery) and when genetic manipulation is "enhancement." In addition, FDA's ability to regulate genetic enhancements in the traditional areas of safety and efficacy will be put to the test by data deficiencies and the subjectivity of judgments about risk and benefit. In addition, enhancement techniques are likely to emerge as unapproved or off-label uses of approved products, uses over which FDA lacks effective regulatory control.
Prepared by Kathi E. Hanna, M.S., Ph.D., Science and Health Policy Consultant
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Last Reviewed: April 2006