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    New Vaccine Fights Breast Cancer Tumors

    DNA Vaccination Kills Herceptin-Resistant Breast Tumors
    WebMD Health News
    Reviewed by Louise Chang, MD

    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 tumors.

    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 Herceptin.

    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 antibodies.

    A version of the vaccine is now undergoing human safety tests.

    Last April, 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 forward.

    "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.

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