Breast Cancer Vaccine Safely Generates Anti-Tumor Immunity

Breast cancer is the most commonly diagnosed form of cancer in the world. Despite many new treatments and advancements in various therapies, relapse and metastasis are an ongoing challenge for patients and the medical community. As such, researchers continue to look into new treatments and search for breakthroughs.

One promising new study from the Washington School of Medicine has shown that applying vaccines in combination with anti-HER2 monoclonal antibodies or immune checkpoint blockade can effectively and safely treat different types of breast cancer.

Background: Cancer Vaccine Research

Researchers have been studying the possibility of vaccines as a treatment for breast cancer for decades. The vaccines typically focus on treatment and prevention, and trials span the stages of basic immunobiology research, clinical trials, and clinical translation.

Researchers at the Mayo Clinic are currently studying:

  • Triple-negative breast cancer: This breast cancer subset accounts for about 10-15% of all cases, but it doesn’t have any of the receptors typically found in breast cancer. While it can be treated with chemotherapy and radiation, there are no targeted therapies for it, which is why vaccine research is so important.
  • Early breast lesions: At this point, doctors cannot differentiate between precancerous breast lesions that are cancerous and those that may lead to cancer, so all instances of ductal carcinoma in situ are treated with traditional therapies. Researchers are working on a vaccine to replace these therapies and prevent breast cancer development and recurrence. 
  • Advanced metastatic breast cancer: Researchers are developing a vaccine that targets six proteins that are found to be overexpressed in breast cancer patients. The goal is to prevent three types of breast cancer — estrogen receptor (ER) positive, HER2 positive, and triple negative.
  • Breast and ovarian cancer: Another vaccine in development would prevent breast and ovarian cancers from developing and stop their recurrence in patients who already had them.
  • Ovarian cancer: Ovarian cancer vaccines work via immunotherapy, which girds the body’s innate immune system to attack cancer cells. Researchers are trying to use the same technology to train the immune system to always attack cancer cells, thereby preventing recurrence.
  • Other cancers: Researchers are also exploring immunotherapy for vaccines against other types of cancer, including lung, bladder, pancreatic, blood, and more.

A Promising New Vaccine for Breast Cancer

A recent article published by University of Washington School of Medicine researchers in JAMA Oncology details the results of phase I of an experimental vaccine for breast cancer. Researchers studied the long-term effects of a DNA breast cancer vaccine to determine its safety, and the results were largely positive.

The scientists at the University of Washington created a vaccine that targets a protein called human epidermal growth factor receptor 2 (HER2), found on the surface of many cells. In up to 30% of breast cancer, HER2 is significantly overproduced. These cancers are often more aggressive and more likely to recur.

In some cases, the overproduction of HER2 can trigger cytotoxic immunity in breast cancer patients. This is considered a good reaction, since those who experience a cytotoxic response are less likely to have a recurrence and have a higher rate of survival.

The vaccine contains the DNA instructions for the target protein — in this case, HER2. It targets HER2 with the goal of carrying instructions to generate a strong cytotoxic immune response.

Sixty-six women with metastatic cancer participated in the study. The women had already completed a standard course of therapy and were in complete or partial remission. They were divided into three groups, each of which received a different dose of the vaccine along with granulocyte-macrophage colony-stimulating factor (GM-CSF), an immune-stimulating drug that promotes cytotoxic immunity.

The goal of the study was not to measure the vaccine’s efficacy but to see if it was safe in both the long and short run. Toward this end, researchers followed the women for three to 13 years (with a median of 10 years) and results showed an overall safe vaccine.

Additionally, the study found that the vaccine was successful in its initial task: stimulating a cytotoxic immune response without producing significantly negative side effects. In fact, 80% of the women who received the vaccine 10 years ago were still alive, which was not their original prognosis.

The next step of the trial is phase II, which will help researchers move toward a clinical trial, which is crucial for any new cancer treatment. The results of the current phase I trial are positive, but considered preliminary until researchers move on to the next phase.

What do the trial results mean?

The trial results are not cause for celebration just yet, but they are certainly a step in the right direction. Cancer researchers around the world are hailing the study as an important step forward in vaccine research and even a breakthrough that can help researchers achieve successful clinical results more rapidly and effectively.