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Gene Therapy Fields of Medicine

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     Gene therapy is one of the promising fields of medicine which helps to treat and prevent incurable diseases. Some genetic diseases do not become manifest until well after birth, in some cases not until adulthood. In this case, gene therapy helps to identify and replace defective genes by healthy ones.

    Genes are specific sequences of nucleotides arranged along a DNA strand, with start and stop signals, and written in a triplet-based code that scientists can read. Genes dictate the sequences of amino acids that make up the proteins in our bodies. Genetic diseases (diseases caused by defective genes) arise when these genes accumulate mutations, and an understanding of exactly what mutations are is important in understanding what gene therapy is intended to correct. Genetic mutations refer to any alteration in the inherited nucleic acid sequence of the genotype of an organism. Traditionally, geneticists defined mutations operationally; i.e., only in terms of those genotypic changes resulting in some change in the resulting phenotype. However, as scientists developed the ability to measure changes directly in DNA itself, the definition of mutation has expanded to include any alteration in DNA, whether or not the alteration occurs in a gene, and whether or not the altered gene results in an altered phenotype (Walters & Palmer, 1997).

    The transcription and translation processes involved in reading the genes that are a natural part of a cell’s own DNA are exactly the same processes used to “read” foreign genes introduced into a cell in the treatment known as gene therapy. The detailed knowledge gained over the past four decades about how these processes work in a living cell is the foundation upon which molecular medicine is built. “Gene therapy is a technique for correcting defective genes responsible for disease development” (Gene Therapy, 2005). The fact that all living cells are diploid, i.e. have two copies of every gene, has important implications for genetic disease and for gene therapy. In almost all cases, a single good copy of a gene is sufficient to maintain biological function. That means that in order for an animal to suffer from a genetic deficiency, both copies of a given gene must be defective. That is the main reason that genetic diseases are relatively rare. But since one copy of a gene is usually sufficient for function, doctors do not have to repair nature’s mistake fully; it is enough to replace or repair only one of the defective genes. Efficacy of gene therapy “has been shown in viral diseases (such as HIV/AIDS, influenza, human papillomavirus infection, various hepatitis strains, smallpox, and SARS), neurodegenerative diseases (such as Parkinson disease, amyotrophic lateral sclerosis, and Alzheimer disease), cancer, inflammatory diseases (such as rheumatoid arthritis), and autoimmune diseases (such as type 1 diabetes mellitus)” (Hood 2004, p. 225).

    Gene therapy clinical trials were begun in 1990. Over two hundred clinical trials for a number of additional genetic disorders, as well as cancer and AIDS, have cleared federal regulatory agencies; most are already underway. The scientific and medical communities are watching these trials closely, and so will the public. There will likely be close media coverage of the progress of patients involved in one or another of these medical dramas. The challenges posed by these first trials, scientific, medical, and ethical,  are fairly typical of what doctors will see in the treatment of medical problems as wide-ranging as vascular disease, hemophilia, arthritis, and liver disorders (Walters & Palmer, 1997).

    “The first actual use of gene therapy began in September 1990, with the treatment of a child suffering from a rare genetic immunodeficiency disease caused by the lack of the enzyme adenosine deaminase” (Grace 1998, p. 39). In spite of great advantages and benefits promised by gene therapy, David, known as “bubble boy”, died in several months. “In September 1999, a patient died from a reaction to a gene therapy treatment at the University of Pennsylvania’s Institute of Human Gene Therapy in Philadelphia” (Thompson 2000, p. 20). In spite of past failures, there were several successful gene therapy trials including Ashanthi DeSilva and Cynthia Cutshall suffered from inherited immune disorder called Severe Combined Immune Deficiency. In 1998, French scientists successfully treated SCID in four children. The same year, Children’s Hospital of Philadelphia, Stanford University and Avigen, Inc. announced successful results in treatment of hemophilia B patients (Thompson 2000, p. 20). Early results were successful and helped to improve immune function.

    The main benefits of gene therapy include treatment of incurable diseases and increasing life span. Gene therapy could provide benefits that are wide ranging, and have significant effects on the lives of many people. Unfortunately, the world media decided to concentrate on many of the misuses. Positive education on the use of this technology would help to educate the public about the benefits of gene therapy and its advantages for general public. More positively, gene therapy could lead to development of replacement organs and non-surgical treatment of diseases. This technique would never lead to a completely cloned human being but only to some cells which probably would be able to be induced to specific types of cellular differentiation Many laboratories and industries are gearing up to expand current screening and testing by molecular techniques. Such screening for breast cancer genes and a variety of inborn errors is already available. Gene therapy allows to test, identify genetic deficiencies and ‘correct’ defective genes before the birth. “If they are successful, engineered stem cells may eventually provide a way of permanently curing most, if not all genetically determined diseases of the blood and circulatory system” (Grace 1998, p. 40). Gene therapy allows doctors to treat HIV and AIDS. Gene-based strategies for treating AIDS fall into several distinct categories. Each category is based on the idea that we may never be able completely to rid HIV-infected patients of their virus. Rather, we must focus on neutralizing the virus’s ability to replicate or to express itself in an infected cell. Some of the many approaches currently being explored for AIDS treatment are described in the following sections. The only AIDS treatment currently approved for standard use is aimed at preventing HIV from expressing itself in cells, and centers around a single type of drug, the best known example of which is azidothymidine (AZT). Given the nearly one-hundred-percent lethality of AIDS, and the lack of truly effective therapeutic approaches for controlling HIV expression and function, aggressive development of novel treatment strategies is still desperately needed (Walters & Palmer, 1997). Approaches based on molecular medicine and gene therapy are under active investigation in laboratories all over the world. The underlying rationale for these approaches is that this disease is caused by genes that, through retroviral integration into the human genome, have become the equivalent of endogenous human disease-causing genes, and the affected cells can be treated accordingly. Like most cancers, AIDS is not a disease caused by a single defective gene that can be replaced with a good copy of a known human gene. Walters and Palmer (1997) state that it is useless to plan for any type of genetic improvement if we do not provide an environment within which an individual can best use his strong qualities and obtain support for his weak qualities. Also, “Gene therapy is still a very crude way of treating very complicated problems: it is hard to get new genes to go where they’re needed, and hard to keep them from going where they’re not wanted” (King 2003, p. 23). Social and medical measures are of extreme importance in this regard.

    In spite of benefits, gene therapy has some risks for patients and society. The information provided by genetic testing can have profound effects on the lives of those involved, for example in the areas of health insurance and employment. In some cases, germline gene therapy could violate human rights and dignity. “Another concern, shared by people at large, was that full knowledge of the human genome was a scary sort of power, evoking the story of Frankenstein” (Grace 1998, p. 39). The major concern expressed by ethicists is that modern science and biomedicine cannot control genetic mutations and results of experiments. Complex regulations are laid down defining the conditions under which recombinant DNA of any kind could be used in laboratory experiments. Also, “critics of gene therapy fear it is being introduced too quickly and that the adenovirus itself can cause damage to patients” (Palfreyman 2000, p. 9). As genetic information acquires greater predictive value, those individuals with private knowledge that they are endowed with a generally disease-free genotype could choose to pay for minimal or no health insurance, whereas those who knew they were likely to develop a serious malady during their lifetime would want maximal coverage. This would almost surely bankrupt private insurers. This is a uniquely American dilemma, for the United States alone, among the major industrialized countries of the world, relies heavily on private insurers to underwrite medical-care costs for its citizens. The present system places insurers and the insured in an adversarial situation. Insurers want as much information about potential clients as possible, so they can minimize their risk, or at least adjust premiums to reflect the risk; persons seeking insurance want to keep that information away from private insurers, for essentially the same reason.

    Genetic problem has a great impact on modern medicine and life of every individual allowing doctors to treat incurable disease and increase life span. Instance, where one prospective parent is known to carry a potentially harmful gene, it is now possible through standard genetic screening techniques to detect the presence of this gene either in the eggs, prior to fertilization in vitro (in those cases where the mother is the sole carrier of the defective gene), or in the cells of the early embryo. Thus the unanticipated harmful consequences in the end may outweigh its anticipated benefits (Walters & Palmer, 1997).

    A good deal of tension developed between Research Universities, where nearly all of these experiments with recombinant DNA are taking place, and the surrounding communities. After some of the abortive attempts at gene therapy in the late 1970s, religious leaders had presented a concern about such tinkering with God’s work; the result was formation of a special Presidential Commission on the ethics of gene therapy. Gene therapy can cause certain social and economic changes. For instance, if the majority of humans lived to an average age of 120, much less to 140, it would change social infrastructure and economic environment. Thus, the future will bring technology putting DNA arrays on microscopic slides (chips) which will be able to predict with greater or lesser certainty what common illnesses individuals are susceptible to, when they might get ill and perhaps even when they might die (Walters & Palmer, 1997). Such knowledge would clearly be of great interest for insurance companies and perhaps employers. Society must force legislators to protect genetic (and medical) confidentiality from potential discriminatory practices (Walters & Palmer, 1997).

    I believe the duty of scientists is to make sure that any research that is being done finds its way into the public domain as soon as possible so that a regulatory view can be taken on it, both nationally and internationally. The obligation of scientists is to pass that information on. It is not to make those ethical judgments themselves. Most people in the field advocate restricting gene therapy to somatic gene therapy in order to avoid introducing foreign genes into the germ line to be passed to the offspring of the treated individual. The recent suggestions for gene therapy may result in the inadvertent introduction of the therapeutic gene into the germ line of the fetus. In fact, with other new techniques now becoming practical, germ line gene therapy, even as a concept, becomes unnecessary. The reason for skepticism about the relevance of ethics to gene therapy is that a large number of people in positions of authority doubted that ethics would make any difference to the pace or path that gene therapy takes. The requirement of informed consent in recruiting subjects to biomedical research is, however, a relatively recent innovation.

    References

    Adams, H. A (2004). Human Germline Modification Scale. Journal of Law, Medicine & Ethics, 32 (1), 164.
    Gene Therapy. (2005). Retrieved 06 April, 2007, form http://www.ornl.gov/sci/techresources/Human_Genome/medicine/genetherapy.shtml
    Grace, E.C. (1998 January-February). Better Health through Gene Therapy. The Futurist, 32 (1), 39-41.
    Hood, E. (2004). RNAi: What’s All the Noise about Gene Silencing? Environmental Health Perspectives, 112 (4), 224-226.
    King, Nancy M.P. (2003). Accident & Desire Inadvertent Germline Effects in Clinical Research. The Hastings Center Report, 33 (2), 23.
    Palfreyman, L. (2000, January 30). US Death Fails to Stop Gene Therapy Scheme. Sunday Mercury (Birmingham, England), 9.
    Thompson, L. (2000, September). HUMAN GENE THERAPY: Harsh Lessons, High Hopes. FDA Consumer, 34 (5), 19-28.
    Walters, L., Palmer, G.L. (1997). The Ethics of Human Gene Therapy. New York: Oxford University Press.

     

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