Gene Therapy - The Future Is Here! (cont.)
Uses of gene therapy
Gene therapy is being used in many ways. For example, to:
A large variety of genes are now being tested for use in gene therapy. Examples include: a gene for the treatment of cystic fibrosis (a gene called CFTR that regulates chloride); genes for factors VIII and IX, deficiency of which is responsible for classic hemophilia (hemophilia A) and another form of hemophilia (hemophilia B), respectively; genes called E1A and P53 that cause cancer cells to undergo cell death or revert to normal; AC6 gene which increases the ability of the heart to contract and may help in heart failure; and VEGF, a gene that induces the growth of new blood vessels (angiogenesis) of use in blood vessel disease.
A short synthetic piece of DNA (called an oligonucleotide) is being used by researchers to "pre-treat" veins used as grafts for heart bypass surgery. The piece of DNA seems to switch off certain genes in the grafted veins to prevent their cells from dividing and thereby prevent atherosclerosis.
Delivery of genes into cells
Gene delivery can be used in cells that have been removed from the body (ex vivo gene therapy) or in cells that are still in the body (in vivo gene therapy). Genes can be delivered into cells in different ways. The selection of a gene delivery system depends on the target cell, the duration of gene expression required for therapeutic effect, and the size of the piece of DNA to be used in the gene therapy.
Genes can be carried into cells by viruses. Viral vectors or carriers take advantage of the natural ability of a virus to enter a cell and deliver genetic material to the nucleus of the cell that contains its DNA. In developing virus carriers, the DNA coding for some or all of the normal genes of the virus to be used as a carrier are removed and replaced with a treatment gene. Most of these virus carriers are engineered so that they are able to enter cells, but they cannot reproduce themselves and so are innocuous.