Somatic gene therapy involves altering the genetic makeup of the somatic (body) cells of the person undergoing the gene therapy. These cell changes are not passed on to the next generation because they are not changes to sperm or egg cells (which carry the chromosomes that are passed on), but only body cells. This is the same sort of theory that suggests that if you have a scar from a fall on your left knee you will not pass that scar onto your child. (6)

How is Somatic Gene Therapy Done?

Since somatic gene therapy is not the focus of our report because it concerns the somatic cells and not the germ cells, our explanation will be brief. To be rather short and sweet, somatic gene therapy involves the changing of the genetic code of specific cells of an individual using an efficient DNA delivery system. This genetic alteration can be done by methods of In-Vivo or Ex-Vivo therapy.

How is Somatic Gene Therapy being used today?

The uses of somatic gene therapy are being developed at an astonishing rate, and it is beyond the scope of this website to discuss all its current or anticipated uses. To give a sampling, we will note that somatic sene therapyis used to treat such varied diseases as Hemophilia, Muscular Dystrophy, Severe Combined Immune Deficiency (the disease suffered by David, the boy in the bubble). Somatic gene therapy is also being used to treat cancer, and it is hopeful that eventually the number of diseases subject to treatment by somatic gene therapy will increase exponentially. (9) Right now, a total of 600 clinical trials of somatic gene therapy are being carried out with human subjects in the USA! (12)

What are the drawbacks and strengths of Somatic Gene Therapy?

Because somatic gene therapy does not affect the germ cells and therefore the genetic alterations will not be passed on to the next generation, it does not raise the same sort of ethical questions that germline gene therapy raises. However, this lack of transmission of alterations can be seen as a drawback as well, because diseases must be treated one patient at a time. If a woman has a cancerous tumor that is treated using somatic gene therapy, her children will be no less likely to develop cancer when they grow older. In some sense, somatic gene therapy treats the symptoms, but by no means does it go to the root of the problem. Although somatic gene therapy is "easier" to use than germline gene therapy, the mechanisms involved are by no means simple nor have they been perfected. Vectors are tricky to use… in some cases, vectors copy their chromosomes onto different genes, thus the therapy is of little benefit to the patient if it does not alter the genes it was intended to alter! (See vectors for more information.) In addition, the body occasionally reacts to vectors by mounting an immune response against the vector introduced into the system. A tragic example of this type of reaction is the death of Jesse Gelsinger.

Jesse Gelsinger, an 18-year-old who was undergoing gene therapy for the treatment of an enzyme deficiency, died four days after being injected with corrosive genetic material. In 1997. The virus injected into his body supposedly initiated an unusual immune response that resulted in the shutdown of several of his organ systems and subsequent death. (7) Of course, Jesse's response to gene therapy is extremely unusual, but as with any research that involves human death, it has made the medical community ponder the inherent risk in human gene therapy research.