Priotities of Gene Therapy
Gene therapy is a relatively new area of medicine that attempts to apply recent advances in molecular biology, genetics and biotechnology to the treatment of human diseases. Gene therapy uses a set of approaches to the treatment of human disease based on the transfer of genetic material (DNA) into an individual. Gene delivery can be achieved either by direct administration of gene-containing viruses or DNA to blood or tissues, or indirectly through the introduction of cells manipulated in the laboratory to harbor foreign DNA. As a sophisticated extension of conventional medical therapy, gene therapy attempts to treat disease in an individual patient by the administration of DNA rather than a drug. (1)
Genetic manipulations, such as replacing defective or missing genes with healthy ones, can be used to alter germ cells (egg or sperm) and somatic cells. Theoretically germ-line gene therapy appears to have more advantages since it aims at preventing a genetic defect from being transmitted to future generations. However, the prospects of germ-line gene therapy look more remote due to many unresolved ethical and social problems as well as technical obstacles. (2) What is presently understood as gene therapy is, mostly, somatic cell gene therapy. By altering the genetic material of somatic cells onetime cures of devastating, inherited disorders may be potentially achieved. But, "in principle, gene therapy should be applicable to many diseases for which current therapeutic approaches are ineffective or where the prospects of effective treatment appear exceedingly low." (1) However, gene therapy is still extremely new and highly experimental. The number of approved clinical trials is small, and relatively few patients have been treated to date.
In 1991, Dr. H. French Anderson and his colleagues at the National Institute of Health initiated the first clinical experiment in human gene therapy. Their successful creation and introduction of an artificial human gene into the T cells of a young girl suffering from adenosine deaminase deficiency have brought to life many hopes for treating other genetic diseases. Among the first in that list were sickle-cell anemia, hemophilia, cystic fibrosis, muscular dystrophy, familial hypercholesterolemia (high serum cholesterol), and some cancers (melanoma, neuroblastoma, and brain tumors). The idea seemed simple and eloquent. Many inherited diseases are caused by a single faulty gene, and gene therapy would deliver the needed gene to a person's cells, which would then begin producing the missing essential substance. By 1995, there were 106 clinical trials (studies in humans) approved to test gene therapy for some of these diseases, and AIDS in the United States. (1) A number of impressive applications of the new recombinant DNA technology and the molecular pathology of single-gene disorders have been introduced.
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