SUNDAY, June 19 (HealthDay News) -- Preliminary research shows
that an experimental vaccine may cure prostate cancer in mice.
Unlike previous cancer vaccine attempts, the new prostate cancer
vaccine appears to be smart enough to outfox prostate cancer
tumors, but experts caution that the research is still in its
infancy and has yet to be tested in humans.
The hunt for effective cancer treatment vaccines has been going
on for decades with varying degrees of success early on, but the
new prostate cancer vaccine takes a markedly different
Instead of aiming at a few cancer-causing proteins or antigens
on the tumor, the new vaccine casts a much a wider net. The goal of
a cancer vaccine is to trick the body's immune system into
recognizing the tumor as an invader and attacking it. This is
typically done using a virus as a host.
The researchers developed a library of genetic material (DNA)
from healthy human prostate tissue cells and then inserted them
into a virus. The end product was intravenously injected into the
mice, which recognized the antigens and launched a potent immune
response, according to a report on the findings, published online
June 19 in
The study reported no side effects, and none of the mice
developed autoimmune diseases, which had been reported in previous
cancer vaccine trials.
"Many cancer vaccines display one, two or few antigens and, although this is successful in alerting the immune system to the cancer, the tumor eventually outsmarts the vaccine and adapts," explained the study's lead author, Richard Vile, an immunologist and professor at the Mayo Clinic in Rochester, Minn.
Vile said he hopes that the new approach is smarter than the
tumor. If the tumor adapts to the antigen, he explained, the
vaccine launches a second wave of attacks.
The approach also makes the development easier, he said, as
scientists don't have to identify specific antigens or targets. "We
clone them all and let the immune system select which is most
important," Vile said.
But, this may also prove to be a hurdle in getting U.S. Food and
Drug Administration approval to study the vaccine in humans. "The
FDA requires that the active proteins be well characterized, and we
don't know which the active proteins are," Vile said.
Even so, he said, "we hope to try to put this vaccine into
patients within the next three to five years."
Dr. J. Leonard Lichtenfeld, deputy chief medical officer for the
American Cancer Society in Atlanta, said that news of the study
"certainly holds out hope that this may represent a true
He cautioned, though, that "we have been looking to vaccines for
cancer for many decades and have not yet seen a vaccine or immune
therapy make the leap from interesting concept to something
effective in the clinic."
That said, the approach outlined in the new paper is "very
different," Lichtenfeld said, adding that he remains cautiously
optimistic about the vaccine.
"We have been excited in the past by some of these reports, and the success has not panned out," he said. "There is still a ways to go before we can get excited and say it will have benefit for patients with prostate cancer."
Willem W. Overwijk, a cancer vaccine researcher at the
University of Texas MD Anderson Cancer Center in Houston, agreed.
"We have to wait and see if it will work in people," he said. "They
are inducing a broad immune response at many targets on the tumor,
which makes it harder for the tumor to escape. [If it does], they
make a new vaccine targeting the recurring tumor."
But the bottom line remains: "We have to see if this works the
same way in people with prostate cancer," Overwijk said. "Stay
The U.S. National Cancer Institute has more on
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