Treatment Update: Gene Therapy with Charles Link, MD, FACP

By Charles J. Link
WebMD Live Events Transcript

Charles Link, MD, FACP discusses the mechanism, use and future of gene therapy for cancer treatment.

The opinions expressed herein are the guests' alone and have not been reviewed by a WebMD physician. If you have questions about your health, you should consult your personal physician. This event is meant for informational purposes only.

Moderator: What exactly is gene therapy? How does it work?

Dr. Link: Gene therapy is a field where a piece of genetic information is transferred into a cell. The cell then uses the gene to produce a product that treats a disease such as cancer. The usual method to deliver a gene into a cell uses an artificial virus to move the gene. This is how a cold virus, for example, expresses genes in us when an infection occurs. The difference is that in this setting the virus used to deliver the gene cannot replicate or cause an infection.

Moderator: As everyone is probably aware, human gene therapy has been under a great deal of scrutiny lately. What is the research community doing as result?

Dr. Link: The community fells strongly that the types of therapy under development will be important for the future of medicine and that, like all new technology, careful attention to detail is required to move the field forward.

Moderator: How do you "program" the virus to perform the correct task?

Dr. Link: There are several different things that can be done to "program" a virus. It can be designed so that it is only active in a specific type of cell or tissue in the body. It can be designed to enter only a specific cell in the body, or drugs can be used to turn the gene on and off when you want it on or off. It can be used in several ways depending on the disease situation. In the case of a genetic disease where a gene abnormality exists that leads to disease, knowing the gene can be used to construct a virus with a repaired version of the gene. In this case, the virus then delivers a correct copy of the gene to fix the broken gene (mutated). In the case of cancer, genetic information can allow a scientist to develop a new strategy to kill the cancer cell through its soft spot, meaning how it is different form a normal cell.

Moderator: Is gene therapy designed as a cure or just a way to treat symptoms?

Dr. Link: It depends on the situation, it has been used for both.

Moderator: What is it in terms of cancer?

Dr. Link: Some cancer trials have been aimed at trying to cure cancer patients, but most have been designed to reduce the amount of cancer in someone to help them but not cure them.

Moderator: Can gene therapy change inherited traits?

Dr. Link: No, current gene therapy trials are designed to fix tissues in the body (so called somatic gene therapy) and not to change any inherited genes (germ cells). Since the ovary and testes are not ... genetically changed, the offspring are not affected. This is actually an important safety concern. Researchers go to great efforts to make sure that the germ line (ovary or testes) is not affected.I think that once someone truly understands what a gene does and has established its level, say in cancer cell compared to a normal cell, it's OK to patent it. This leads to investment that allows drugs to be developed. However, a gene sequence alone that has not been shown to have an effect or difference between a normal and cancer cell, for example, should not be patented or a least not patented for any way it might be used in the future.

The testes are the source of the genetic material from the male that mixes with the egg from the ovary of the female. Therefore, if new genes were transferred to the testes there would be a risk of having an inherited new gene in a child conceived from that sperm. I wanted to add that in the United States no experiments have ever been considered to change the inheritance of future generations. The gene therapy starts and stops within each individual patient. There are a number of different viruses that are being explored to use as gene delivery vehicles. In any given situation you need to use the right tool for the job. Some viruses do transient gene transfer, while others change things long term.

Moderator: Are there side effects to gene therapy being used a cancer treatment?

Dr. Link: As an oncologist, I have never seen a therapy for cancer without side effects and gene therapy is no exception. People in the field do believe thus far that gene therapy has far fewer side effects than, say, chemotherapy. But the track record and effectiveness of chemotherapy is far superior. Gene therapy is in its infancy as a field. But we expect it will lead to major advances in many diseases, including cancer.



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