Diseases targeted for treatment by gene therapy

The potential scope of gene therapy is enormous. More than 4,200 diseases have been identified as resulting directly from abnormal genes, and countless others that may be partially influenced by a person's genetic makeup. Initial research has concentrated on developing gene therapies for diseases whose genetic origins have been established and for other diseases that can be cured or improved by substances genes produce.

The following are examples of potential gene therapies. 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, (the cells that line the inner and outer skin layers) that cover the air passages of the nose and lungs. Without this regulation, patients with cystic fibrosis build up a thick mucus that makes them prone to lung infections. A gene therapy technique to correct this abnormality 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. Researchers announced in 2004 that they had, for the first time, treated a dominant neurogenerative disease called Spinocerebella ataxia type 1, with gene therapy. This could lead to treating similar diseases such as Huntingtons disease. They also announced a single intravenous injection could deliver therapy to all muscles, perhaps providing hope to people with muscular dystrophy.

Familial hypercholesterolemia (FH) also is an inherited disease, resulting in the inability to process cholesterol properly, which leads to high levels of artery-clogging fat in the blood stream. Patients with FH often suffer heart attacks and strokes because of blocked arteries. A gene therapy approach used to battle FH is much more intricate than most gene therapies because it involves partial surgical removal of patients' livers (ex vivo transgene therapy). Corrected copies of a gene that serve to reduce cholesterol build-up are inserted into the liver sections, which then are transplanted back into the patients.

Gene therapy also has been tested on patients with AIDS. 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 like pneumonias and cancer. In one approach, genes that produce specific HIV proteins have been altered to stimulate immune system functioning without causing the negative effects that a complete HIV molecule has on the immune system. These genes are then injected in the patient's blood stream. Another approach to treating AIDS is to insert, via white blood cells, genes that have been genetically engineered to produce a receptor that would attract HIV and reduce its chances of replicating. In 2004, researchers reported that had developed a new vaccine concept for HIV, but the details were still in development.

Several cancers also have the potential to be treated with gene therapy. A therapy tested for melanoma, or 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. In 2003, researchers reported that they had harnessed the cell killing properties of adenoviruses to treat prostate cancer. A 2004 report said that researchers had developed a new DNA vaccine that targeted the proteins expressed in cervical cancer cells.

Gaucher disease is an inherited disease caused by a mutant gene that inhibits the production of an enzyme called glucocerebrosidase. Patients with Gaucher disease have enlarged livers and spleens and eventually their bones deteriorate. Clinical gene therapy trials focus on inserting the gene for producing this enzyme.

Gene therapy also is being considered as an approach to solving a problem associated with a surgical procedure known as balloon angioplasty. In this procedure, a stent (in this case, a type of tubular scaffolding) is used to open the clogged artery. However, in response to the trauma of the stent insertion, the body initiates a natural healing process that produces too many cells in the artery and results 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 contains vectors for genes that reduce this overactive healing response.


Regularly throughout the past decade, and no doubt over future years, scientists have and will come up with new possible ways for gene therapy to help treat human disease. Recent advancements include the possibility of reversing hearing loss in humans with experimental growing of new sensory cells in adult guinea pigs, and avoiding amputation in patients with severe circulatory problems in their legs with angiogenic growth factors.