Harnessing the immune system to target cancer has long resided on doctors’ wish lists, with very little promise of becoming reality. The risk of directing cancer cells to die is high because they are not normal cells and can mutate.
However, immunotherapy has made it possible to develop powerful drugs that help the immune cells distinguish cancer cells from healthy cells. Researchers are currently testing whether this can train the immune system to identify and kill breast cancer cells the way viruses and bacteria do.
G. Thomas Budd is a staff physician at Cleveland Clinic Taussig Cancer Center and leads a groundbreaking study on a breast-cancer vaccine. This could allow women to produce antibodies or other immune cells that can protect them against getting the disease. This vaccine will target triple-negative breast cancer, which is the most aggressive and has limited treatment options. Triple negative cancer lacks the molecular flags—for estrogen, progesterone or HER2—that common breast cancer drugs target.
The first phase of the study will focus on safety and include 18 to 24 women who have already been diagnosed with triple negative breast cancer and treated with standard therapies, which include chemotherapy, surgery and DNA-interfering drugs that inhibit cancer cells’ ability to copy their genes and grow. Budd will give them three doses each of an experimental vaccine. Budd and his colleagues will examine the side effects to determine if the participant’s immune system is able to target the cancer targets. Budd’s team will also see if the women’s cancer returns.
Ultimately, he says, if this early phase indicates the vaccine is safe and shows promise in triggering an anti-cancer immune response, the study will expand to include women at high risk of developing triple negative cancer, but who haven’t been diagnosed yet, to see if immunizing them could help prevent the cancer from occurring in the first place. BRCA1 mutation-positive women, as well as Black women and Hispanic women, are at greater risk for developing triple negative cancers. The vaccine’s effectiveness will be demonstrated by including them in the research.
“I would say this could be game changing,” says Budd of the approach. While others have tried to develop breast cancer vaccines, targeted against some of the more common features of breast cancer cells like the HER2 receptor, those efforts haven’t led to dramatic success yet. The vaccine is toxic to breast cancer cells and not healthy cells. This makes it less effective in stopping them from growing.
Budd’s vaccine is based upon work done by Vincent Tuohy, a Cleveland Clinic immunologist. This vaccine targets alpha lactalbumin which is a new breast cancer protein. It can only be expressed in breast cells when the woman is breastfeeding. If she’s no longer lactating, the gene for the protein goes silent, and the protein isn’t produced. The immune system can target this protein because 70% of triple-negative breast carcinomas actually produce it. Tuohy’s studies on mice showed that making the immune system recognize this protein and using a vaccine to prevent tumors from developing in these animals slowed the growth of the existing breast tumors.
These data convinced Food and Drug Administration (FDA) to approve Budd’s first study in humans. His team has received funding from the Department of Defense and is currently recruiting triple-negative breast cancer patients who are now in remission. They will be treating these women to determine if the vaccine can protect them and prevent future complications.
Budd is confident that the vaccine can be used to protect against disease and recurrence. His team is hoping that after the first safety trial, he will soon begin vaccinations of healthy women with high-risk for developing triple-negative breast carcinoma. “I do think the [target] we are using makes a difference, and the major lesson from previous vaccine trials shows that ultimately we ought to move more to the prevention setting than the treatment setting,” he says.
This trial may be an important step in the establishment of immuno-based treatments for breast cancer. Some immunotherapy drugs that manipulate the immune system and make it easier for immune cells to target breast tumors have demonstrated some anti-cancer activity, but it’s not enough. “Those showed us the bear can dance, and we’d like to teach it new steps,” says Budd about the vaccine strategy.