Researcher Pilar Nava-Parada, MD, PhD, of the Mayo Clinic in Rochester, Minn., says some of the mice were essentially cured.
The research was presented at the annual meeting of the American Association for Cancer Research.
How the Vaccine Works
Unlike flu and many other vaccines, most cancer vaccines under development are not intended to be given to healthy people to prevent disease. Rather, they help sick patients bolster their immune system to better fight the cancer.
In this case, the goal is to re-educate the immune system to recognize breast cancer cells as foreign invaders that need to be attacked and annihilated, Nava-Parada tells WebMD.
Usually, breast cancer cells fly under the radar of the immune system, evading the body's surveillance mechanisms, she explains.
To overcome that obstacle, the injectable vaccine uses a bacteria-type substance that is altered to contain the gene HER2/neu, which is associated with extremely aggressive breast tumors, as well as antibodies that jack up the immune system.
The body launches an immediate response to the bacteria, and revved-up immune cells go on the offensive, patrolling the body and attacking and wiping out cells that contain HER2/neu.
"Any cell that expressed HER2/neu in high amounts is killed," Nava-Parada says.
Immune-Boosting Vaccine a Promising Approach
Ronald A. DePinho, MD, professor of medicine and genetics at Harvard Medical School and chairman of the committee that chose which studies to highlight at the meeting, says that similar approaches show promise in people with pancreatic and skin cancers.
"As cancer develops, the immune system finds a way to sequester itself. The idea with all these studies is to jack up the immune system so it will recognize cancer cells as foreign," he tells WebMD. "It's a very promising approach."
Nava-Parada cautions that a lot more study is needed before the vaccine is ready for prime time. If it does pan out, she says, it would only work for women whose breast cancers overexpress HER2/neu -- about 15% to 25% of breast cancers, according to the American Cancer Society.