Gene therapy, the latest development in the medical field, is based on manipulating or altering genetic material, to treat as well as prevent the occurrence of certain diseases that are hard to cure with normal treatment. Gene therapy involves the insertion of genes, the biological unit of heredity, into the cells or tissues of individuals suffering from diseases like cancer.
Gene therapy was first conducted on September 14, 1990, by a group of physicians, consisting of W. French Anderson, M.D. and his colleagues R. Michael Blaese, M.D., C. Bouzaid and Kenneth Culver, M.D., from the U.S. National Institute of Health. It was performed on a four-year-old child suffering from 'Severe Combined Immunodeficiency', a rare genetic disease.
Gene therapy can be classified into two main types, germ line gene therapy and somatic gene therapy. Germ line gene therapy involves insertion of functional genes into the germ or reproductive cells (sperm and egg) of the body; while, in the case of somatic gene therapy, therapeutic genes are introduced into the somatic cells.
Gene therapy mainly involves the modification of genetic material (DNA and genes), and plays a key role in determining the traits and characteristics of individuals. It has added a completely new dimension to the treatment of cancer, which is caused by mutation or damage of DNA leading to uncontrolled growth of abnormal cells. Many researches have been carried out and some are still going on to discover the potential of gene therapy in the treatment of cancers of breast, lung, prostate, bone and leukemia. Different approaches of gene therapy to treat cancer basically concentrate, either on destroying or preventing the growth of cancerous cells, or improving the ability of the normal cells to fight against the cancerous cells.
If cancer is caused due to missing or altered genes, then gene therapy involves the replacement of these genes with the healthy ones. Besides, gene therapy can also be carried out to stimulate the immune system to attack the cancer cells. Through this technology, genes can be inserted into the patient's body; which, either instruct the cancer cells to produce certain proteins for inhibiting the cancer-causing oncogenes or stimulate the tumor suppressor genes. Some other studies are also ongoing to introduce genes into the cancerous cells, which can help to make the cancerous cells more responsive to various cancer treatments, including chemotherapy and radiation therapy. Besides, researches are also being carried out to reduce the side effects of various anti-cancer drugs, by increasing the resistance of the stem cells.
However, in gene therapy, genes are not directly inserted into the patient's body, but uses viruses for that purpose. The viruses, generally used for this therapy, include retroviruses, adenoviruses, herpes viruses, lentiviruses and poxviruses. Sometimes, liposome (a tiny vesicle found in a cell that stores and transports substances within a cell) is also used as a carrier in gene therapy. The viruses can be used both for the ex vivo, as well as in vivo gene therapies. The ex vivo gene therapy involves the collection of some blood or bone marrow cells from the patient. Then, the viruses with the necessary genes are introduced into the cells in a laboratory, which are then injected into the patient's body. On the other hand, in vivo gene therapy involves the direct insertion of viruses or liposomes that contain the desired gene into the patient's body.
However, gene therapy is not free from disadvantages. One of the most potential dangers associated with gene therapy, is the possibility of infection of the healthy cells caused by the viruses used for delivering the gene. Besides, if the genetic material is accidentally introduced into the germ cells, then the changes induced by it, would pass on to the next generation. Again, it is very important to insert the desired gene at the correct location, failure of which might result in genetic mutation and even cause cancer. More scientific researches are required to remove the drawbacks of gene therapy, so it can truly revolutionize the treatment of life-threatening diseases like cancer.
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