The vaccine uses the men's own dendritic cells, extracted white blood cells that activate the immune system by snagging substances that trigger an immune attack. These dendritic cells contain genetic information or RNA, a derivative of DNA, from a substance secreted by the prostate gland called prostate specific antigen. PSA levels increase in prostate cancer patients. These dendritic cells are then injected under the patient's skin to trigger immune system to destroy the tumor.

Patients received three doses of the vaccine at increased levels each time. Vieweg said four men developed flu-like symptoms and fever and four men experienced inflammation at the injection site, but overall, the vaccine was well tolerated. Tumors make it difficult to immune system cells to find them, Vieweg explained to United Press International. So the object of a cancer vaccine is to expose the tumor to the body's own natural defense mechanisms.

"To uncloak, sort of, the mystery of the tumor," Vieweg said. "The RNA technique has really opened up new avenues of cancer vaccination." This was a Phase I clinical trial, the first of three phases in drug testing, which is meant to establish safety so research can continue. However, Vieweg said the vaccine not only proved safe, but also effective in igniting an immune response. One risk researchers face is over-activating a vaccine, which could adversely trigger the immune system to not only attack the tumor but also healthy tissue. Whether the patients' tumors shrank in this study is not known since it was not designed to evaluate what happened to the tumors, Vieweg said. Vieweg points out this vaccine could have applications in other cancers, particularly kidney and skin cancer.

"The beauty of this concept is broad use of this vaccine," he said, "not just among prostate cancer patients, but all cancer patients." The findings are published in the February issue of Journal of Clinical Investigations. In the past few years, there has been great interest among scientists in developing a cancer vaccine, though the United States is years away from having such a cancer treatment federally approved for use. Dr. Robert Dillman, medical director of the Hoag Cancer Center at Hoag Memorial Hospital Presbyterian in Newport Beach, Calif., told UPI current cancer vaccine research is all over the map in terms of approaches, with some scientists using the patients' own cells and some using cells created in the lab. Researchers are examining various techniques and are still a ways off from narrowing the field to a handful of effective approaches, he said. "At this point, it's hard to know which approach is the best approach," Dillman said. "The jury is still out.”

He acknowledged, however, "there's been a lot of enthusiasm in recognition role dendritic cells play" in cancer vaccine research. Dillman also cautioned against too much enthusiasm on the results of a study only in its first phase and based on 13 people.