By Margaret A. Varnell
ATLANTA, Jun 13 (Reuters Health) - Recent technological developments and a
better understanding of the body's immune system have heralded a new era in
which vaccines for breast cancer may actually be possible.
Two studies presented at the recent "Era of Hope" Department of Defense
Breast Cancer Research Program Meeting in Atlanta demonstrate that vaccines for
treatment as well as prevention of recurrence are effective, and small scale
clinical trials are now under way in human subjects.
The first study, presented by Dr. Mary L. Disis, associate professor of
medicine at the University of Washington in Seattle, showed that it is possible
to stimulate an immune response toward HER-2/neu, a cancer protein.
"The problem with HER-2/neu is that it is a self-protein, which means it is
produced by the body, and the immune system doesn't want to respond and attack a
part of itself," Disis told Reuters Health.
She and her colleagues decided to break the HER-2/neu protein into small
protein segments, called peptides, and challenge the bodies of women who had
completed treatment for advanced breast cancer, ovarian cancer or lung cancer.
The investigators theorized that the immune system might not recognize the
smaller peptides when injected as a vaccine. If the body would respond and
attack the peptide as if it were a new invader, it would most likely also attack
the cancer at the same time.
Disis prepared three versions of the HER-2/neu protein vaccine and recruited
64 women to test their theory. Thirty-eight women received six monthly
injections of the new vaccine.
Ninety percent of the women who received all six vaccines had an immune
system response. Four of these women have maintained this immune system response
for more than 2 years since receiving the initial six injections. "There were no
differences among the three preparations, all of the women completing the series
of injections responded well," said Disis. "One very exciting point to note is
that the vaccine was totally nontoxic."
The second trial presented at the meeting reported on a new technique of
injecting dendritic cells directly into the tumor itself. Dendritic cells are
immune system cells that play a crucial role in helping the body identify and
attack tumors. "We gave four injections to 25 mice over the course of several
weeks," said Dr. Christopher J. Kirk, research fellow in the tumor immunology
program at the University of Michigan Medical Center in Ann Arbor. "In five of
the mice, the tumors regressed completely and new tumor grafts into the animals
did not grow. The remaining 20 of the mice reduced their tumor growth by
two-thirds." This treatment also had no apparent toxic side effects.
Encouraged by their success, the Michigan researchers have begun recruiting
women for a phase 1 study and hope to have preliminary data by the end of the
year.
They are also continuing their mice studies. Kirk and his colleagues have
injected 10 more cancerous mice with dendritic cells and added a protein called
tumor necrosis factor alpha that is known to kill breast cancer cells.
"We wanted to determine if there would be a beneficial synergistic effect of
combining the two, and there was," Kirk said. Having documented that the
dendritic cell vaccine can be successfully combined with other known
cancer-fighting drugs, the Michigan researchers are now searching for the most
effective breast cancer-fighting treatment options.
"These two studies really complement each other," said Dr. Anna D. Barker,
president and CEO of BIO-NOVA, Inc. "Because of technology, we can now isolate
these types of cells in the quantities that make clinical trials possible and
are able to take this kind of research from the laboratory to clinical setting
for testing. This is very exciting early data."
