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Duchenne muscular dystrophy: Severe muscle deterioration leads to the individual dying by the third decade of life. A trial of gene replacement in all three of these conditions has been unsuccessful. Another novel way of managing diseases caused by defective genes is to find a gene that’s active during fetal life (but becomes dormant later on) and that can replace the activity of the defective gene if it can be made to express itself. A prime candidate for this treatment is sickle cell disease. In this disease, abnormal hemoglobin (hemoglobin is the chemical in red cells that carries oxygen to the tissues of the body) leads to the early loss of red blood cells, which become sickled (crescent shaped) in appearance and can block blood flow to tissues, causing great pain. A gene active during fetal life produces fetal hemoglobin, which doesn’t sickle. If this gene can be turned on during adult life, it can replace the defective hemoglobin made by the patient. Scientists are looking for the drug that may be able to turn this gene on. Cancer treatment has seen a lot of activity in the area of gene therapy. Gene therapy can treat cancer of the thyroid in a number of ways, including the following: Inserting a gene that increases the sensitivity of the cancer to a drug, or inserting a poison into cells that are injected directly into the tumor. Inserting a gene that increases the activity of the patient’s immune system. Inserting a new gene into blood cells to restore tumor-suppressor activity. This treatment works because some tumors arise when the activity of tumor suppressors (chemicals in the body that suppress the growth of tumors) declines. Using a virus to introduce a gene into a thyroid cancer cell. The virus causes the DNA to change so that the cell takes up radioactive iodine, which can kill the cell. (This approach is the newest cancer treatment and is outlined in a paper in Thyroid in June 2004.) All these treatments have seen some success, but no one has yet been cured of cancer with gene therapy. Scientists are also attempting to increase a tumor’s immune response by modifying the tumor so that it provokes body cells against it. Scientists perform this technique by inserting genes into the tumor that cause it to produce new antigens that the body can fight against. Tumors like malignant melanoma and colon cancer have been the target of this type of therapy. A similar technique involves inserting a gene directly into a tumor that activates a cancer-killing agent, which is subsequently injected. These techniques have led to some decrease in tumor size but, so far, no cures of cancer. Interestingly, gene therapy isn’t limited to tumors brought on by faulty genes but

Thyroid for dummies  
Thyroid for dummies  
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