Why it's done

Gene therapy is used to correct defective genes in order to cure a disease or help your body better fight disease.

Researchers are investigating several ways to do this, including:

• Replacing mutated genes. Some cells become diseased because certain genes work incorrectly or no longer work at all. Replacing the defective genes may help treat certain diseases. For instance, a gene called p53 normally prevents tumor growth. Several types of cancer have been linked to problems with the p53 gene. If doctors could replace the defective p53 gene, that might trigger the cancer cells to die.
• Fixing mutated genes. Mutated genes that cause disease could be turned off so that they no longer promote disease, or healthy genes that help prevent disease could be turned on so that they could inhibit the disease.
• Making diseased cells more evident to the immune system. In some cases, your immune system doesn't attack diseased cells because it doesn't recognize them as intruders. Doctors could use gene therapy to train your immune system to recognize the cells that are a threat.