New Vaccine Fights Breast Cancer Tumors
DNA Vaccination Kills Herceptin-Resistant Breast Tumors
Sept. 15, 2008 -- An experimental breast cancer vaccine makes
mice reject tumors -- even cancers no longer sensitive to Herceptin.
The vaccine targets breast cancers that grow wildly in response to a growth
factor called HER-2. About 25% of women with breast cancer have HER-2 positive
Herceptin, a man-made antibody approved for the treatment of breast cancer,
targets these cancers. But after a while, tumor cells often become resistant to
The new vaccine elicits immune responses that kill HER-2 positive breast
tumors in mice, whether or not they've become Herceptin resistant, says Wei-Zen
Wei, PhD, professor of immunology at Detroit's Karmanos Cancer Institute.
"Regardless of whether tumor cells are resistant, if immune cells are
properly primed by immunization we can destroy
these cells," Wei tells WebMD.
The vaccine developed by Wei's team uses DNA that carries the genetic code
for a key piece of the HER-2 molecule. After injection of the DNA into the
skin, a small electric pulse is administered to help cells take up the DNA and
produce the protein that elicits immune responses.
Mice given the vaccine made anti-HER-2 antibodies. The vaccine also primed
cellular immune responses that attacked breast cancer tumors. These cellular
responses alone were enough to kill HER-2 positive cells in mice unable to make
A version of the vaccine is now undergoing human safety tests.
a different HER-2 vaccine made headlines when it halved the number of
deaths in women with HER-2 positive breast cancer. The vaccine also slowed
breast cancer recurrence.
However, researchers at San Antonio's Brooke Army Medical Center found that
26 months after vaccination, there was no significant difference in cancer
recurrence between vaccinated and unvaccinated women.
Gary Yang, MD, associate professor of radiation medicine at Roswell Park
Cancer Institute in Buffalo, N.Y., says these human studies are a major step
"These studies accomplished a lot -- but we need to find out why the
immune system cannot sustain this efficacy," Yang tells WebMD.
Yang says that is why Wei's team's work is so important. What's learned in
the lab must be tested in patients -- and then more lab work is needed to
answer questions raised by human studies.
"The clinical research into breast cancer vaccines is not going to be a
home run," he says.
Wei is convinced that in the long run, vaccines will prove to be powerful
"Ultimately, we will be using the best defense we have to fight cancer
-- the human immune system," she says. "It is a very challenging thing
to do. We hope we have reached a point where we can make it useful to
Wei and colleagues report their findings in the Sept. 15 issue of Cancer