Vaccine study for HER2-positive breast cancer moves forward

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Researchers hope the vaccine combined with trastuzumab can help prevent breast cancer recurrence.

Treating breast cancer has long involved addressing two problems: the elimination of cancer cells from the tumor and potential disease recurrence. The key may be to harness the full capabilities of the body's immune system to do both jobs.

On Mayo Clinic's campus in Florida, a team of researchers has a new anti-cancer vaccine in the works to help the body resist the return of human epidermal growth factor receptor 2 (HER2)-positive breast cancer. The vaccine is intended to be used in combination with trastuzumab (Herceptin), an immune-stimulating drug given after HER2 tumor removal surgery.

If it works, the vaccine could help prevent the return of the breast cancer, which can be hard to treat once it spreads to other parts of the body. Mayo Clinic researchers recently received a grant of $11 million from the Department of Defense to push the next studies of the vaccine ahead and help address this unmet patient need.

Photo of Keith L. Knutson, Ph.D.
Keith L. Knutson, Ph.D.

The combination approach will engage two types of immune cells. Trastuzumab works by activating the immune system's B cells, which look for and attack breast tumor cells with HER2 proteins on the surface. The new vaccine also stimulates another group of cells in the immune system — long-lasting T cells that remember the proteins and promote resistance to recurrence.

"The vaccine provides a prevention strategy to deter cancer reformation," said Keith L. Knutson, Ph.D., an immunologist at Mayo Clinic in Florida who is principal investigator of the study. "The body's T cells and B cells synergize with each other for a strong, durable immune response."

In previous Mayo Clinic studies, the team investigated the physical effects of the vaccine and whether it stimulated an immune response. They found that the vaccine promoted mild responses typical of any vaccination, such as fatigue. They also found that the vaccine promotes a measurable immune response to the HER2 protein in patients.

Future research to be conducted at Mayo Clinic and in collaboration with other medical centers will determine if the vaccine is effective against the recurrence of HER2-positive breast cancer. This research is expected to determine how long immunity lasts and whether booster shots are necessary to help the immune system continue identifying the cancerous cells. In addition, the research will help identify specific tumor subtypes that are good candidates for vaccine treatments.

"The standard approaches to treating cancer address the existing disease," Dr. Knutson said. "Our goal is to develop a strategy to address recurrence. We have good drugs, like trastuzumab, that can interfere with the recurrence of HER2-positive breast cancer. Our hope is that a vaccine that engages multiple aspects of the body's own immune system will build on those successes."


This article was originally published in Forefront, Mayo Clinic Cancer Center's online magazine, which ceased publication in December 2020.