Genes are the basic structural and functional unit of one’s heredity. These genes make up various DNA sequences known as genotypes. These genotypes along with developmental and environmental factors are responsible for determining the corresponding phenotypes. The genes play a significant role in our health, to an extent that a defective gene can give rise to certain illness and diseases. Understanding this, researchers have been working for years on techniques for the modification of genes or the replacement of faulty genes with healthy ones for preventing, treating or curing a medical condition.

“Gene Therapy” is when certain DNA is introduced within a patient for the treatment of a genetic disease. This new DNA usually comprises of a functional gene aimed for correcting the effects of a mutation resulting into a disease. This technique holds promise for the treatment of a wide range of medical conditions such as diabetes, AIDS, hemophilia, cystic fibrosis, heart diseases and cancer. Scientists are still in the phase of studying when and how to use gene therapy. In the United states, gene therapy currently is only available as a part of clinical trial.

Types of Gene Therapy

Depending upon the types of cells treated, gene therapy can be classified into two types:
• Somatic Gene Therapy: This type of gene therapy transfers a section of DNA to every cell of the body excluding the ones that produce egg or sperms. The effects of this type will not be carried on to the next generation of the patient.
• Germline Gene Therapy: This type of gene therapy transfers a section of DNA specifically to the cells that are responsible for producing sperms or eggs. The effects of this type will be carried onto the subsequent generations.

Techniques of Gene Therapy

Gene Augmentation Therapy

This technique is utilized for the treatment of diseases that are caused via a mutation which terminates a gene from further producing a functional product, for example a protein. Owing to this therapy, DNA comprising of a functional version of the lost gene is added back within the cell. As a result, the new gene produces a functional product in ample levels required to replace the protein which was missing originally. This technique can find success only if the disease has reversible effects or if the disease has not caused a lasting damage to the patient’s body. This therapy may be useful for treating cystic fibrosis (loss of function disorder) by the introduction of a functional copy of the gene to correct the condition.

Gene Inhibition Therapy

This therapy is suitable for treating infectious diseases such as cancer and other ones which are inherited and caused due to inappropriate activity of genes. This technique aims in the introduction of a gene whose product will either inhibit the expression of some other gene or will interfere with the activity of another gene’s product. It basically eliminates the activities of genes that encourage disease-related cell’s growth. For instance, sometimes the overexpression of an oncogene results in cancer. Therefore, by diminishing that oncogene’s activity via gene inhibition therapy, further cell growth can be prevented as well as cancer can be stopped right in its tracks.

Specific Cell Killing Therapy

This therapy works by destroying or killing certain group of cells and is suitable for diseases such as cancer. It aims in the insertion of DNA within cells those are diseased resulting in specific cellular death. The aim can be achieved by any of the two ways: A “suicide gene” is contained within the inserted DNA which is responsible for the production of a highly toxic product that kills the diseased cells, or, the DNA that is inserted itself leads to a protein’s expression that flags the cells to be attacked by the immune system of the body. With this technique, specific targeting of cells is very essential for avoiding the killing of normally functioning cells.

Challenges Abound

• Delivery of the gene to the correct location and switching it on: Some cells of our bodies occasionally shut down genes which show unusual activity resulting in an obstruction. Thus, it is very crucial that the newly inserted gene is able to reach the targeted cell. Also, even after the correct cell has been targeted, the gene is required to be turned on.
• Avoidance of an immune response: Immune system works by fighting off intruders. At times, newly introduced genes are considered to be potentially-harmful intruders by the immune system. This challenge can be conquered by the use of vectors which are less likely in triggering an immune response.
• The new gene should not disrupt other genes’ function: Ideally, once the inserted gene is properly integrated within the patient’s genome, it will continue to work for the rest of their lives. But there also is a risk of the gene going and inserting into another gene’s path resulting in the disruption of its activity.
• High Costing: Since gene therapy often requires a case-by-case approach, it makes the whole technique very expensive.

Before being marketed by a company, a gene therapy product for use in humans needs to be tested for its effectiveness and safety. This therapy holds promise in transforming medicine and creating options for the patients who are battling difficult and almost incurable diseases. The technique continues to be a very crucial and active field of research aimed at the development of effective treatments for various life-threatening diseases.