Gene Therapy

The potential scope of gene therapy is enormous. More than 4,200 diseases have been identified that result directly from defective genes. People suffering from cystic fibrosis lack a gene needed to produce a salt-regulating protein. This protein regulates the flow of chloride into epithelial cells, which cover the air passages of the nose and lungs. Without this regulation, cystic fibrosis patients suffer from a buildup of a thick mucus, which can cause lung infections and respiratory problems, which usually leads to death within the first 30 years of life. A gene therapy technique to correct this defect might employ an adenovirus to transfer a normal copy of what scientists call the cystic fibrosis transmembrane conductance regulator, or CTRF, gene. The gene is introduced into the patient by spraying it into the nose or lungs.

Familial hypercholesterolemia (FH) is also an inherited disease, resulting in the inability to process cholesterol properly, which leads to high levels of artery-clogging fat in the blood stream. FH patients often suffer heart attacks and strokes because of blocked arteries. A gene therapy approach to battle FH that is currently being investigated involves partially and surgically removing the patients liver (ex vivo transgene therapy). Corrected copies of a gene that serve to reduce cholesterol build-up are inserted into the liver sections, which are then transplanted back into the patient.

Gene therapy has also been tested on AIDS patients. AIDS is caused by the human immunodeficiency virus (HIV), which weakens the body's immune system to the point that sufferers are unable to fight off diseases such as pneumonia. An approach to treat AIDS is to insert genes into a patients bloodstream that have been genetically engineered to produce a receptor that would attract HIV and reduce its chances of replicating.

Several cancers also have the potential to be treated with gene therapy. A therapy that is currently being tested for the treatment of melanoma (a form of skin cancer), involves introducing a gene with an anticancer protein called tumor necrosis factor (TNF) into test tube samples of the patient's own cancer cells, which are then reintroduced into the patient. In brain cancer, the approach is to insert a specific gene that increases the cancer cells susceptibility to a common drug used in fighting the disease. Gene therapy can also be used to treat diseases that involve dysfunctional enzymes. For example, Gaucher's disease is an inherited disease caused by a mutant gene that inhibits the production of an enzyme called glucocerebrosidase. Gaucher patients have enlarged livers and spleens and eventually their bones fall apart. Clinical gene therapy trials focus on inserting the gene for producing this enzyme.

Gene therapy is also being considered as an approach to solving a problem associated with a surgical procedure known as angioplasty. In this procedure, a type of tubular scaffolding is used to open a clogged artery. However, in response to the trauma of the scaffold insertion, the body often initiates a natural healing process resulting in restenosis, or reclosing of the artery. The gene therapy approach to preventing this unwanted side effect is to cover the outside of the stents with a soluble gel. This gel is designed to contain vectors for genes that would reduce restenosis.