TUESDAY, June 3 (HealthDay News) -- When scientists first began
looking into using the body's own immune system to target
malignancies, it was hoped that the therapy would be able to zero
in on a specific cancer without affecting healthy tissue.
While the original theory is still worth pursuing, researchers
have found some potentially harmful side effects.
The findings, published in the June 10 issue of the
Proceedings of the National Academy of Sciences, concluded
that a skin cancer immunization therapy created a dangerous
consequence.
"The ultimate lesson to be learned from this report is that all
treatments have potential side effects, and we have to be very
thoughtful about potential side effects," said Dr. Louis M. Weiner,
director of the Lombardi Comprehensive Cancer Center at Georgetown
University in Washington, D.C. "We have to be very thoughtful about
how we apply those treatments, who we apply those treatments for,
and how we follow the patients we treat to assure appropriate
safety."
Cancer vaccines are developed to stimulate the body's own immune
system to fight off deadly cancers. Ideally, the target of the
vaccine will be very specific to the tumor, but this is not always
the case: Antigens, or molecules that provoke antibody production,
that are found only on the tumor are usually found also only in
individual patients. Other antigens are shared between patients but
are also found in normal cells, leading to the possibility that the
vaccine will kill healthy cells along with malignant ones.
The investigators on this study, from the National Cancer
Institute, plucked T-cells from the bloodstream of mice, cultured
the cells in the lab to mount a response against a melanoma-related
target, GP10, then re-injected the T-cells into the mice to fight
the cancer. Melanoma is a particularly lethal form of cancer that
starts on the skin.
Such a therapy can cause depigmentation of the skin and,
sometimes, attacks on the thyroid.
"Those problems tend to be irritating but not life-threatening,
and if they are the price that one has to pay for a cure or highly
effective treatment for a highly deadly disease, most patients are
willing to pay the price," Weiner said.
But in this particular investigation, the eye also became a
target. "That carries with it more profound consequences, although
they could inject steroids into the eye that would kill the T-cells
in the eye," Weiner said. (This would produce a local effect only
and would not affect the melanoma treatment itself.)
"As we develop increasingly more effective immune therapy
strategies that are capable of attacking self, be it a self-tumor
or self-normal organ, there may well be potentially surprising
prices to pay in terms of toxicities," Weiner said. "The authors
suggest that understanding the consequences of new immunotherapies
for cancer should help researchers guide future treatments and
anticipate and treat side effects, thus preventing healthy cells
from getting caught in the crossfire."
More information
Learn more about cancer vaccines at the
National Cancer Institute.
