BALTIMORE (AP) - A team of Johns Hopkins Oncology Center researchers has developed a vaccine that helps strengthen the body's immune system against prostate cancer, according to a study published in the journal Cancer Research.
The study, released Tuesday, showed a vaccine can trigger the immune system to fight cancer in the manner that it fights infection, said Dr. Jonathan Simons, who led the study.
``For years, people have said there is no way to turn the immune system against prostate cancer,'' he said. ``We were astounded to find that every part of the immune system was alerted and turned on.''
Researchers injected 11 prostate cancer patients with a genetically engineered vaccine. The patients had their prostates removed prior to the clinical trials, but their cancer was still spreading.
Tumor shrinkage occurred in eight of the 11 patients, according to study.
``We reeducated the immune system to recognize prostate cancer cells as a potential infection and attack them,'' said Simons.
The experiment produced not only the release of T-cells as researchers had hoped, but also the production of antibodies against cancer, Simons said. Both are key weapons of the immune system.
Simons cautioned that it is too early to draw any conclusions from the study.
Dr. William J. Catalona, director of urologic surgery at Washington University School of Medicine in St. Louis, said the results seem promising, but cancer patients shouldn't hang their hopes on such vaccines in the near future.
``You don't want to have a person who might live in Peoria uproot themselves and travel halfway across the country in hopes that there's going to be a treatment that's going to cure them, when it's really in its development stages,'' said Catalona, who was not involved in the study.
Roughly 330,000 men in the United States develop prostate cancer each year and 40,000 die annually from the illness. It is the fourth-leading cancer killer in the nation.
In the Hopkins study, scientists removed tumors from each of the 11 patients, chopped up the tissue and grew them on laboratory culture dishes.
A gene called GMF-CSF, which produces a protein that alerts tissues to the presence of foreign substances, was inserted into the cancer cells.
The vaccine was then irradiated to prevent any further cancerous growth and injected into the patients' thighs, like a flu shot.
``The gene we used to turn on the immune system is so good that it activates everything,'' said Dr. William Nelson, who was part of the study.
Researchers have used the technique on many different types of cancer, but the new study represents the first time researchers have been able to activate the entire human immune system.
Johns Hopkins researchers will now begin recruiting patients with advanced prostate cancer for larger trials of the vaccine, a university spokeswoman said today.
The study was funded by the National Cancer Institute, the Department of Defense Prostate Cancer Initiative and the CaP Cure Foundation, founded by financier Michael Milken.
