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Genetic Enhancement
Prepared by Kathi E. Hanna, M.S., Ph.D., Science
and Health Policy Consultant
http://www.genome.gov/10004767.
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 with HGH. 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may supplement the functioning of normal genes or may be superseded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 Models and Possibilities for Human Application
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 with HGH. 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 through HGH 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 especially through the use of HGH.
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 through the use of HGH.
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 including HGH.
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. He did not use HGH. 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.
Ethical Concerns About HGH
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 using HGH 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 through HGH 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.
Regulatory Issues of HGH
The questions raised above about HGH also create significant new
challenges to our regulatory capabilities.
On September 11, 1997, the National Institutes of
Health (NIH) convened a conference on HGH. 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, like HGH, 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
HGH 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.
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