Mary Pintea – News Editor
mvp5879@psu.edu

Breast cancer is one of the leading causes of death in women, but scientists may have found a
way to squash these numbers.
Researchers at the University of Washington School of Medicine in Seattle have developed a
vaccine that treats different types of breast cancer, which would certainly change the landscape
of cancer related treatments and care. The vaccine targets a key tumor protein—the HER2
gene—formulating an immune response that protects the body.
Lead author Dr. Mary “Nora” L. Disis states in an interview, ““Because this was not a
randomized clinical trial, the results should be considered preliminary, but the findings are
promising enough that the vaccine will now be evaluated in a larger, randomized clinical trial.”
HER2 is found on the surface of many cells, but those of over 30-percent of breast cancer
survivors produce as much as one hundred times the amount seen in normal cells. HER2-positive
cancers are often more aggressive and likely to reappear, but shockingly, create an immune
reaction that can be very beneficial.
Patients with HER2-positive breast cancers gain a specific immune response called cytotoxic—
cell killing—immunity, which actually reduces the recurrence of cancer post-treatment. These
survivors also tend to survive longer than those who do not harbor an immune response.
To stimulate this kind of response, Dr. Disis and her colleagues created a DNA vaccine, which
contains the DNA instructions for the target protein. Once introduced to the bloodstream, the
protein encoded in the vaccines DNA will begin production. The cells will then present the
protein to the immune system, which then gives rise to a stronger, cytotoxic immune response.
The vaccine used in this trial contained instructions for the part of HER2 that is typically located
inside of the cell, possessing the strongest cytotoxic immune responses.
Sixty-six women who had metastatic breast cancer were enrolled in the initial study. All of the
women had completed the standard course of radiation and chemotherapy and were either in total
remission or only had slow-growing tumor left in their bone. The participants were divided into
three groups, with each individual receiving three injections. One group received injections at a
low-dose, another at an intermediate-dose, and the last at a high-dose. Regardless of dosage
strength, each participant received the immune-stimulating drug granulocyte-macrophage
colony-stimulating factor (GM-CSF), which promotes cytotoxic immunity.
Researchers followed up the participants for three to 13 years, with the average length of time
nearly 10 years. The long-follow up was important because HER2 is found on many other cell
types, which could potentially trigger an autoimmune response against other healthy cells and
tissues.
“The results showed that the vaccine was very safe,” Disis said. “In fact, the most common side
effects that we saw in about half the patients were very similar to what you see with COVID
vaccines: redness and swelling at the injection site and maybe some fever, chills and flu-like

symptoms.” The vaccine successfully stimulated desired cytotoxic immune response without
triggering any severe side effects, with he strongest immune response present in the group that
received an intermediate dose. Although the study was not designed to see if the vaccine could
slow or prevent progression of breast cancer, researchers noticed that participants are doing
much better than they would have without the vaccine.
While most women with HER2-positive breast cancer would have died within five years of
treatment, the study has followed women well into 10 years past treatment—with 80% of the
participants still alive.
If the results continue to show promise in a randomized-controlled phase II trial, the vaccine will
move forward to a phase III trial, which is now recruiting patients.