What Is Gene Therapy?
Gene therapy is the introduction, removal or change of genetic material, specifically DNA (deoxyribonucleic acid) or RNA (ribonucleic acid), in the cells of a person. Most gene therapies are investigational treatments, meaning their safety and long-term effects are still being studied in clinical trials. 1
Genes are found in the body’s cells and are made of up of DNA. Some genes tell the body how to make molecules called proteins.2
Proteins do many important jobs in cells. Some proteins give cells structure. Other proteins protect cells from viruses and bacteria, while others move waste out of cells.3
Sometimes, a person is born with a gene that does not work properly. This is called a mutation. The mutation doesn’t allow the gene to give the right directions to the body. In some cases, gene mutations can cause disease.4 The goal of gene therapy is to replace a non-working gene with a working copy.5
| Review of Important Words | |
|---|---|
| Genes | Genes provide the instructions for cells to make proteins. Genes carry information that determines your traits, such as height and hair color. |
| DNA | Deoxyribonucleic acid, or DNA, is the material that makes up genes. DNA is inherited from a person’s mother and father. |
| Gene mutation | A permanent change in DNA that differs from what is found in most people. Gene mutations can cause genes to stop working or to work incorrectly.6 |
| Cells | Cells are the basic building blocks of all living things.7 |
| Proteins | Proteins are molecules in the body that do most of the work in cells.3 |
| Vector | A vector helps carry the gene into the cell during gene therapy. It is usually a virus that has been changed so it does not cause infection. |
| Adeno-associated virus (AAV) | A type of virus that is used in gene therapy to carry genetic information into a cell. It is changed so that it cannot make copies of itself. |
How Does Gene Therapy Work?
There are different types of gene therapy. The gene therapy used will depend on the type of disease being treated.
| Gene Replacement | Gene Silencing | Gene Addition | Gene Editing |
|---|---|---|---|
| Gene replacement therapy introduces a working copy of the gene into the cell to do the job that the missing or mutated gene could not do. Sometimes this is also called gene transfer. | Gene silencing introduces a gene that can stop the genetic instructions in a cell from producing a protein that causes disease.5 | Scientists can add new genes to cells using gene therapy to help treat complex diseases. For example, gene addition can be used to attack tumor cells or stop tumors from growing.8 | Gene editing is when scientists add, remove, or change the DNA of a specific cell or cells in the body to correct an existing gene mutation.9 |
| Gene Replacement |
|---|
| Gene replacement therapy introduces a working copy of the gene into the cell to do the job that the missing or mutated gene could not do. Sometimes this is also called gene transfer. |
| Gene Silencing |
|---|
| Gene silencing introduces a gene that can stop the genetic instructions in a cell from producing a protein that causes disease.5 |
| Gene Addition |
|---|
| Scientists can add new genes to cells using gene therapy to help treat complex diseases. For example, gene addition can be used to attack tumor cells or stop tumors from growing.8 |
| Gene Editing |
|---|
| Gene editing is when scientists add, remove, or change the DNA of a specific cell or cells in the body to correct an existing gene mutation.9 |
Patients can receive gene therapy in different ways. Gene therapies are usually given in a hospital by infusion or injection.10
More on Gene Transfer and Vectors
It is difficult to insert a new gene into a cell in the body. First, scientists must figure out which gene or genes are causing a disease. Next, they must create a working copy of the gene or genes in a laboratory. Once they create a working copy of the gene, it must be placed into a vector. A vector is a carrier that allows the new gene to enter the cell. Once the gene is successfully inside of the cell, it can potentially help make working proteins that the body needs. In this way, gene therapy corrects the cause of the disease, rather than only treating symptoms.11
Vectors are often made from viruses because viruses can easily enter cells. The viruses that are used for gene therapy are changed so that they cannot cause disease. The type of vector used depends on the disease.
- The vector types that are used today are different from the ones used in previous gene therapy trials.
- Today’s vectors have been tested more robustly than those used in the past.
- The adeno-associated virus (AAV) is a common type of vector.
- Many versions of the AAV vector have been studied in animals and humans.9
Potential Side Effects of Gene Therapy
Some studies have shown that there are health risks associated with different gene therapies.12 Because gene therapy is so new, scientists and researchers don’t yet know all the potential side effects. If you are considering gene therapy, it’s important to discuss the potential benefits and risks with your doctor.
Additional Resources on Gene Therapy
- Genetics Home Reference
What is gene therapy? - American Society of Gene & Cell Therapy
Gene Therapy 101
References
Gene Therapy Basics. American Society of Gene & Cell Therapy. https://www.asgct.org/education/gene-therapy-basics. Accessed April 18, 2019.
What is a gene? National Institutes of Health. Genetics Home Reference. https://ghr.nlm.nih.gov/primer/basics/gene. Published March 19, 2019. Accessed March 28, 2019.
What are proteins and what do they do? National Institutes of Health. Genetics Home Reference. https://ghr.nlm.nih.gov/primer/howgeneswork/protein. Published March 19, 2019. Accessed March 28, 2019.
What is a gene mutation and how do mutations occur? National Institutes of Health. Genetics Home Reference. https://ghr.nlm.nih.gov/primer/mutationsanddisorders/genemutation. Published March 19, 2019. Accessed March 28, 2019.
University of Utah. Approaches to Gene Therapy. Learn. Genetics. Genetic Science Learning Center. https://learn.genetics.utah.edu/content/genetherapy/approaches/. Accessed March 28, 2019.
Vachani, Carolyn. What is Gene Therapy?. Abramson Cancer Center of the University of Pennsylvania. https://www.oncolink.org/cancer-treatment/immunotherapy/what-is-gene-therapy. Updated June 7, 2018. Accessed March 28, 2019.
What is a cell? Genetics Home Reference. https://ghr.nlm.nih.gov/primer/basics/cell. Accessed April 18, 2019.
Wang D, Gao G. Discov Med 2014;18(98):151-161.
What are genome editing and CRISPR-Cas9? National Institutes of Health. Genetics Home Reference. https://ghr.nlm.nih.gov/primer/genomicresearch/genomeediting. Accessed April 15, 2019.
How does gene therapy work? National Institutes of Health. Genetics Home Reference. https://ghr.nlm.nih.gov/primer/therapy/procedures. Published March 19, 2019. Accessed March 28, 2019.
American Society of Gene & Cell Therapy. Gene Therapy 101. https://www.asgct.org/education/different-approaches. Accessed March 28, 2019.
Is gene therapy safe? National Institutes of Health. Genetics Home Reference. https://ghr.nlm.nih.gov/primer/therapy/safety. Accessed April 15, 2019.
