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Blood disease: Successful gene therapy - treatment with side effects.
(16.09.2010) With the help of gene therapy, the blood disease beta-thalassemia was successfully treated for the first time in a young man. However, there were unexpected side effects that make the future use of the method appear questionable.
Beta-thalassemia is triggered by a genetic defect and leads to red blood cell disease or lack of education and to rapid breakdown of hemoglobin. The result: anemia. As an inherited disorder, beta-thalassemia is particularly common in the Mediterranean and occurs relatively frequently there. Not only is the above-mentioned anemia characteristic of a disease, but the patients usually have an enlarged spleen and liver just a few months after birth. There are also growth disorders, severe damage to internal organs and bone malformations. Sufferers often cannot survive without blood transfusions unless they find a donor for the transplantation of blood stem cells from the bone marrow. The blood transfusions are not only uncomfortable for the patient, but also have a negative impact on their health. Therapy-related iron overload in the course of lifelong blood transfusions is extremely likely, with severe organ damage in the area of the heart, liver and pancreas being the result of such iron poisoning.
Therefore, the news of successful gene therapy offered a glimmer of hope for all those affected, but this was considerably clouded by the serious side effects. For example, the young man described in the British science magazine "Nature" has apparently been successful with gene therapy, but there has been uncontrolled blood stem cell growth that the researchers say can also be a precursor to blood cancer. In 2007, the patient was treated with genetically modified, endogenous cells at the age of 18, whereby the physicians from Harvard University (Boston / USA) used lentiviruses for the genetic manipulation, which were used as gene transporters in the cells. Since 2008, according to Philippe Leboulch from Harvard University, the patient has not had to receive a blood transfusion. With gene therapy, however, there was a potential side effect that, according to the experts, needs to be examined in more detail and may be malignant. Apparently the use of lentiviruses as gene transporters had changed the activity of a gene (HMGA2) that controls the behavior of blood stem cells and stimulated them to uncontrolled growth after therapy. So far, only benign cells have been widespread in the patient, but according to Philippe Leboulch, this could also be a preliminary stage of blood cancer. For example, further studies will investigate which forms the uncontrolled cell growth takes and what treatment success can be achieved with the method in other patients. In the short term, gene therapy definitely helped the patient described a lot. He had had blood transfusions since the age of three and had his spleen removed at the age of 6. (fp)