NEW YORK, Oct 21 (Reuters Health) -- By injecting prostate cancer patients with a genetically engineered 'vaccine,' researchers have activated the immune system to do battle against the disease.
The technique "could have implications in the treatment of many kinds of cancer," according to a statement issued by Johns Hopkins Oncology Center in Baltimore, Maryland, where the research team is based.
"Such a complete and thorough activation of the immune system against prostate cancer has never before been seen," said study senior author Dr. William G. Nelson, of the Johns Hopkins University School of Medicine. His team published their findings in the October 15th issue of the journal Cancer Research.
Prostate cancer is the second leading cancer killer of men after lung cancer, taking the lives of over 40,000 US men each year. Conventional prostate cancer treatment usually involves radiation therapy, surgery, or hormone therapy.
In their study, the Johns Hopkins researchers focused on eight prostate cancer patients whose cancers had spread throughout the body despite surgical removal of the prostate.
Using cells taken from these patients, the researchers grew prostate cancer cells in the laboratory. They then injected a potent anti-cancer gene, GM-CSF, into these cells. Finally, they reintroduced the cancer cells back into the patient, 'piggybacked' onto an inactivated, harmless retrovirus. The cells were irradiated prior to injection to eliminate the possibility that they might trigger new cancers.
According to the authors, within a month after injection, the cancer 'vaccine' had placed each patient's immune T-cells on 'high alert' against prostate cancer cells.
The researchers "were not surprised to see T-cell activation," Nelson explained in the Johns Hopkins statement, since this T-cells are naturally 'turned on' by the presence of retroviruses such as the one carrying the vaccine.
More surprising was the fact that the vaccine "also stimulated new high-level antibody production," he said. These antibodies, produced by immune cells called B-cells, targeted roving prostate cancer cells, while T-cells attacked tumors.
The investigators are continuing to study the effectiveness of the technique in treating prostate cancer patients. They note that side effects were minimal, mostly itching at the injection site and flu-like symptoms, and that the therapy does not require hospitalization.
The authors believe the therapy holds promise as a new method of attacking metastatic (spreading) cancers. "Using gene therapy, we re-educated the immune system to recognize prostate cancer cells as a potential infection and attack," explained study lead author Dr. Jonathan Simons. He believes that genetically-engineered vaccines "could make a real difference when used as (secondary) therapy to 'mop up' microscopic cancer cells left behind following surgery, chemotherapy, and radiation therapy."
Larger trials focused on the use of vaccines obtained without the need for surgery are currently underway.
