Gene therapy study takes aim at prostate cancer
Sep 26, 2006 - 10:40:37 PM
Researchers at Baylor College of Medicine (BCM) are hoping a new gene therapy that takes a gene called RTVP-1 directly into the prostate tumor will prove effective in preventing recurrence of the disease.
The first phase of the study is designed to test the safety of the treatment and determine the proper dosage of gene, said Dr. Dov Kadmon, professor of urology at BCM. It will be carried out in the department of urology at BCM as well as at Ben Taub General Hospital, The Methodist Hospital and Michael E. DeBakey Veterans Affairs Medical Center.
"We are treating patients who are scheduled for a prostatectomy (prostate removal) but who also have a high risk that their disease will recur (or come back)," said Kadmon. "The operation itself is highly successful in eradicating local tumors (in the prostate)."
The design of the study is simple, said Kadmon.
"One injection into the prostate that should take no more than 10 minutes, although patients will be monitored in a special unit of the hospital for 23 hours to make sure there are no side effects. After that, they come to the unit for a check-up once a week."
After about 30 days, the subjects undergo their surgery, which has already been scheduled, he said. He said the hope is that the gene therapy will reduce the risk that cancer will recur at or near the site of the tumor as well as in distant points in the body.
"We hope that by generating a systemic immune response, we are enabling the body to destroy prostate cancer cells that have moved elsewhere," he said. Kadmon and his colleagues plan to test six different doses of the gene.
The gene therapy involves attaching an inactivated adenovirus (related to viruses that cause respiratory infections) to the RTVP-1 gene. As the virus infects the tumor cells, it will introduce the gene into the cells as well. (RTVP stands for related to testes-specific, vespid and pathogenesis proteins.) The RTVP-1 gene was isolated in the laboratory of Dr. Timothy Thompson, also a professor of urology at BCM.
As Thompson began to study the gene, he found that it was a target for a tumor suppressor gene called p53, which is a major controller of cell activity in prostate and other cancers. He found that the human form of the gene is normally present in benign prostate or low grade tumor but is lost as the tumors become more malignant. "This characterized it as a tumor suppressor gene that is active in the prostate," said Kadmon.
When the gene is introduced into the tumors of animals lacking RTVP-1, it suppresses the formation of new blood vessels. It causes what is known as "apoptosis" or programmed cell death in prostate cancer cells and also activates the immune system to fight cancer cells.
"We are proceeding carefully, step-by-step," said Kadmon. He said they do not think the study presents a significant risk.
They will inject the virus-gene compound directly into the prostate. While there is a risk of infection with the injection, he said patients will receive antibiotics. Most patients will have some fever after the injection, but it can probably be handled with Tylenol.
Doctors will monitor patients after their surgery to determine the effect of the gene therapy on their disease.
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