Gene Therapy to Treat Disease

The doctors are injecting Ashanti s own blood cells into her arm. The blood cells have been treated in a lab with a virus related 

More than 15 years and hundreds of clinical trials later, the FDA has not yet approved any gene therapy product. It has not been for lack of trying. By 2004, there were more than 600 hmnan 

The challenge is to get the genetic construct into the appropriate cell, and have it settle down in the cell to be copied faithfully every time the cell divides. Most importantly, it must be placed where it would direct the production of the correct protein so that the protein would be produced in the right amount and in the proper location within the cell. So far, gene therapy has not had much success. 

The system used to deliver the desired gene into the cells, called the gene therapy vector, may be a virus, a plasmid, or even just the naked DNA. The choice of vector is based on the difficulty of getting the gene into the cell, the amount of DNA the vector can carry, the size of the gene sequence needed to provide the correct protein, and the effects the vector may have on the body. Each type of vector has advantages and disadvantages. 

Viruses are very important as gene therapy vectors. Over the millennia of their existence, they have evolved to be very good at 

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Gene Therapy to Treat Disease 95 Stop and Consider... 

Although simple in concept, the application of gene therapy to treat/cure genetic diseases has, thus far, made little impact in practice. The slow progress in this regard is likely due to a number of factors. These include ... 

Another form of gene therapy to treat cancer involves oncolytic virotherapy. This involves the use of oncolytic vectors, which are virus-designed to home and kill the tumor cells without harming the normal cells in the body. The cancer cells are killed by cell lysis as a result of the production of cytotoxic proteins or due to the propagation of the virus itself. The viruses that have been used to produce oncolytic vectors include adenovirus, vaccinia, reovirus, HSV-1 and Newcastle disease virus. 

Alderuccio, R, Siatskas, C., Chan, J., Field, J., Murphy, K., Nasa, Z. and Toh, B. H. (2006). Haematopoietic stem cell gene therapy to treat autoimmune disease. Curr. Stem Cell Res. Ther. 1 279-287. 

This chapter will review the potential of gene therapy to treat a range of diseases as well as the technology that is currently available to achieve this. 

Researchers must overcome many technical challenges before gene therapy will be a practical approach to treating disease. For example, scientists must find better ways to deliver genes and target them to particular cells. They must also ensure that new genes are precisely controlled by the body. 

Gene therapy is under study to determine whether it could be used to treat disease. Current research is evaluating the safety of gene therapy future studies will test whether it is an effective treatment option. Several studies have already shown that this approach can have very serious health risks, such as toxicity, inflammation, and cancer. Because the techniques are relatively new, some of the risks may be unpredictable however, medical researchers, institutions, and regulatory agencies are working to ensure that gene therapy research is as safe as possible. 

Many diseases, such as hereditary metabolic defects and tumors, can still not be adequately treated. About 10 years ago, projects were therefore initiated that aimed to treat diseases of this type by transferring genes into the affected cells (gene therapy). The illustration combines conceivable and already implemented approaches to gene therapy for metabolic defects (left) and tumors (right). None of these procedures has yet become established in clinical practice. 

The gene delivery systems presented in this section represent those with the most information regarding characterization and application. Each system has advantages and disadvantages. For this reason, there may be a disease application for one type of system that is not suitable for another. A few years ago, gene therapy was criticized for the number of clinical trials that had been completed with little or no success. Only in the past few years have demonstrations of benefit been realized to validate the concept. The question is no longer will this form of therapy be employed to treat disease, but when it will be employed. 

In general, adenoviral vectors are known to infect the target cells effectively, but it is noteworthy to keep in mind that safety always comes first because some adverse side effects could be critical to the health of patients. Other types of viral vectors, such as adeno-associated virus, also are used for gene therapy in many diseases, even though more studies on safety, as well as efficacy, still remain until successful human clinical use can be expected. As demonstrated by clinical reports, fusion of knowledge on the molecular biology of viral vectors and the diseases to be treated holds promises for the future of medicine. 

The idea behind gene therapy is to treat diseases caused by defective genes by inserting the normal form of the gene into a patient s cells. If gene therapy could work, it could provide a cure for many diseases that are hard to treat. 

Steroid hormones can increase and decrease the level and/or activity of a large number of proteins in eukaryotes. Steroid hormones were first discovered in humans, where they play essential roles in development, differentiation, homeostasis, and endocrine therapies. However, current interest in steroid hormones is increasing because they constitute excellent model systems for examining the control of gene expression. Many human pathologies result from the inappropriate expression of protein(s). Thus, to treat disease states, it is critical to understand the normal processes governing how, when, and how much of the information encoded in the DNA of cells is transcribed to mRNAs and eventually into proteins, which perform most of the functions of cells. Steroid hormones provide excellent model systems with which to address these clinically relevant questions. 

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