Gene transfer test: so far, so good

Article Abstract:

The first human gene transfer experiment approved by the National Institutes of Health (NIH) has produced preliminary results. Scientists at NIH have revealed results for one of the five patients involved. The experiment's purpose is to fight advanced melanoma, a cancer characterized by dark, melanin-pigmented tumors. Special white blood cells, tumor-infiltrating lymphocytes (TIL cells), were injected into the bloodstream in the hope that they would seek out and destroy the malignant tumor tissue. The single patient for whom results are known did in fact experience dramatic regression (shrinkage) of her tumors. Her own lymphocytes had been removed from fragments of tumor, then labeled with a gene, and injected back into her bloodstream. The gene serves as a marker so that scientists can track the movement of the anticancer TIL cells in the body. The scientists were encouraged by three aspects of the results. First, the gene-labeled TIL cells traveled to the tumors. Second, the anticancer TIL cells were able to survive in the patient's body for at least three weeks. Finally, addition of the marker gene did not interfere with TIL cell activity. For none of the five patients has there been evidence of toxicity from the gene marker, which was derived from bacterial cells. Investigator Steven Rosenberg of the National Cancer Institute emphasizes the preliminary nature of the results from only one patient. Data from the other four patients could contradict the early findings. After all five have been evaluated, adjustments in the experimental procedure may be made and five more patients will then be enrolled. Eventually TIL cells may be used to carry other anticancer substances to tumors, which would constitute gene therapy. Rosenberg's experiment uses the gene as an inert (inactive) marker that has no therapeutic effect; it is, however, the first authorized experiment using human gene transfer.

Physiological aspects, Genetic markers, Tumors, Melanoma, Lymphocytes, Medical genetics, Oncology, Rosenberg, Steven A.

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Gene therapy: into the home stretch

Article Abstract:

Two proposals to use genes to treat cancer recently received approval by the human gene therapy subcommittee of the National Institutes of Health (NIH) and the Recombinant DNA Advisory Committee. This approval is the culmination of years of debate and discussion. Other proposals currently under review by NIH are briefly described. According to Steven Rosenberg's tumor necrosis factor (TNF; a factor that kills cells) protocol, the TNF gene will be inserted into white blood cells known as tumor-infiltrating lymphocytes (TIL) taken from a tumor under laboratory conditions. The modified lymphocytes are then returned to the patient's body. Since TIL ''home'' to the tumor, they carry the deadly TNF into malignant cells, destroying them. Initial results from studies of TIL without TNF indicate that they do, in fact, home to the tumor, where they remain for months. A description of the passage of the TNF proposal through the NIH review process is presented. Concerns were initially raised regarding the safety of TIL that carry genes foreign to the body. In particular, since TNF genes are introduced into TIL via an inactivated retrovirus, reviewers mentioned the finite but real risk that a retrovirus could become activated and itself induce cancer. When such points were made by some committee members, Rosenberg responded by pointing out the dangerous aspects of malignant melanoma (a highly lethal form of skin cancer). One member, R. Scott McIvor, wanted still more data from mouse studies. Toxicity data from more than 900 patients, however, were presented by Rosenberg as a response; but some researchers wanted more animal data. After more debate, the proposal passed. Rosenberg will begin with patients who suffer from malignant melanoma, incurable in its advanced stages. (Consumer Summary produced by Reliance Medical Information, Inc.)

Usage, Tumor necrosis factor

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Gene therapy clears first hurdle

Article Abstract:

Patients with ADA deficiency may become the first human beings to be therapeutically treated with gene therapy. The patients lack a specific enzyme, adenosine deaminase (ADA), which prevents them from developing a functioning immune system. The condition is ideal for gene therapy; in principle, a properly functioning ADA gene may be put into the patient's own bone marrow cells, a task far easier than placing a gene in liver cells or brain cells. In practice, researchers will probably try to place the ADA gene into mature lymphocytes, simply because they are easier to grow in the laboratory than the delicate stem cells from the bone marrow. The severely debilitating nature of the ailment also solves some of the ethical concerns about this somewhat speculative trial procedure. The more devastating the disease, the easier it is to accept risks to combat it. This is the thinking that has led to the approval of the proposal by the National Institutes of Health biosafety committee, the first of several hurdles that the proposal must pass before moving to actual clinical trials. R. Michael Blaese, the principal investigator, must also face review by the NIH Recombinant DNA Advisory Committee and the human gene therapy subcommittee. Then, of course, the director of the NIH and the Food and Drug Administration (FDA) must also approve the proposed experimental treatment. Roughly 15 patients worldwide have a complete deficiency of ADA, so the number of patients is quite limited. Nonetheless, since there is no effective alternative treatment, researchers feel that this is an opportunity to move ahead and try gene therapy on human patients for the first time. (Consumer Summary produced by Reliance Medical Information, Inc.)

Therapeutics, Genetic disorders, Immunodeficiency, Adenosine deaminase deficiency, ADA deficiency, editorial

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