Mesothelioma Treatment - Gene Therapy

While more conventional therapies such as radiation and chemotherapy are commonly used to treat mesothelioma, experimental treatments such as gene therapy are becoming more common (most often in clinical trials that test how effective such treatments might be in fighting asbestos-caused cancer).

What is Gene Therapy?

Genes are DNA sequences that are located on chromosomes. They provide living organisms with genetic instructions for creating an enormous variety of proteins. If a gene is defective, the protein it produces is also defective, and this may cause the development of a genetic disease. Hemophilia, muscular dystrophy, and color blindness are all examples of disorders that are caused by faulty genes.

Gene therapy is a largely experimental medical treatment that seeks to correct the problems caused by a defective gene by using genetic techniques to replace the defective copy of a gene with a copy that functions correctly.

In most cases, this is done by genetically altering a virus so that it carries a normal copy of the gene. Viruses are an ideal way of transporting genes into cells because their normal method of action is to enter cells and take over the cell's genetic machinery to produce viral proteins.

In gene therapy, a patient is "infected" with a virus that has been genetically altered with a copy of a normal gene, which has been treated to prevent it from causing infection. The virus enters target cells, and causes those cells to produce normal proteins instead of defective ones.

Gene Therapy for Mesothelioma Treatment

Gene therapy was originally conceived of as a means of treating inherited genetic diseases such as hemophilia. Throughout the last decade, gene therapy research has concentrated mainly on developing potential treatments for various types of cancer. In terms of mesothelioma treatment, gene therapy involves the use of genetic material to target cancer cells and make them vulnerable to chemotherapeutic drugs.

One of the most promising types of gene therapy for the treatment of mesothelioma is called "suicide gene therapy." This involves the targeting of tumor cells with a virus that has been genetically altered. The virus carries a gene that produces a protein which converts a non-toxic drug into a drug that can kill those cells.

When this genetically-altered virus is administered to a patient, the virus infects only tumor cells. After a short waiting period, the patient is subsequently treated with a drug that is not toxic to normal cells, but toxic to cancer cells.

Suicide gene therapy has experienced some success in patients enrolled in clinical trials. In one such clinical trial at the University of Pennsylvania Medical Center, 34 patients were treated with varying doses of genetically altered Adenovirus. Of these 34 patients, four achieved considerable tumor regression, and two patients from this group achieved complete regression of tumors for more than seven years after treatment.

Other types of gene therapy for mesothelioma treatment include the application of genetically altered viruses to deliver immune system molecules called cytokines to target cells. Cytokines are proteins that control and direct the immune response. When delivered using gene therapy, cytokines can help the immune system mount an attack against cancer cells.

Side Effects of Gene Therapy

Because gene therapy involves infection with a genetically modified virus, it is common for recipients of the treatment to experience symptoms of infection such as chills and fever. More serious side effects are possible, but for those suffering with mesothelioma the potential benefits far outweigh the risks.

Potential Complications with Gene Therapy

Currently, gene therapy is available only to patients who qualify for clinical trials, as the FDA has not yet approved gene therapy for widespread public use. Researchers continue to address concerns in regards to how a patient's immune system responds to the genetically altered virus. A negative response can reduce the efficacy of the treatment and will make it difficult to repeat treatments.

Another significant concern regarding gene therapy is the difficulties involved in delivering the virus to target cancer cells in a way that ensures the therapeutic gene will be able to produce the protein once it is inside cancer cells.

Until these two issues are aptly addressed, gene therapy will continue to provide some short term benefits, but the therapeutic genes will not be able to provide a permanent cure.

Sources:

http://www.ornl.gov/sci/techresources/Human_Genome/medicine/genetherapy.shtml
http://marf.org/Documents/SymSlides/Steven%20Albelda,%20MD%20WM.pdf
http://www.cancer.org/downloads/PUB/DOCS/SECTION28/89.pdf

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