The researchers, from Cleveland Clinic's Lerner Research Institute (Cleveland, OH, USA), discovered that a single vaccination with the antigen a-lactalbumin prevents breast cancer tumors from forming in mice, while also inhibiting the growth of already existing tumors. Human trials could begin within the next year. If successful, it would be the first vaccine to prevent breast cancer.

The research was published online May 30, 2010, and in the June 10, 2010, issue of the journal Nature Medicine. "We believe that this vaccine will someday be used to prevent breast cancer in adult women in the same way that vaccines prevent polio and measles in children,” said Vincent Tuohy, Ph.D., the study's lead investigator and an immunologist in Cleveland Clinic's Lerner Research Institute department of immunology. "If it works in humans the way it works in mice, this will be monumental. We could eliminate breast cancer.”

In the study, genetically cancer-prone mice were vaccinated - half with a vaccine containing a-lactalbumin and half with a vaccine that did not contain the antigen. None of the mice vaccinated with a-lactalbumin developed breast cancer, while all of the other mice did.

The U.S. Food and Drug Administration (FDA) has approved two cancer-prevention vaccines, one against cervical cancer and one against liver cancer. However, these vaccines target viruses--the human papillomavirus (HPV) and the Hepatitis B virus (HBV)--not cancer formation.

In terms of developing a preventive vaccine, cancer presents a dilemma not posed by viruses. Whereas viruses are recognized as foreign invaders by the immune system, cancer is not. Instead, cancer is an overdevelopment of the body's own cells. Trying to vaccinate against this cell overgrowth would effectively be vaccinating against the recipient's own body, destroying healthy tissue.

The solution, according to Dr. Tuohy, is to find a target within the tumor that is not typically found in a healthy individual. In the instance of breast cancer, Dr. Tuohy and colleagues targeted a-lactalbumin--a protein that is found in the majority of breast tumors, but is not found in healthy women, except during lactation. Therefore, the vaccine can jumpstart a woman's immune system to target a-lactalbumin--thereby stopping tumor formation--without damaging healthy breast tissue.

The strategy would be to vaccinate women over 40--when breast cancer risk starts to increase and pregnancy becomes less likely. (If a woman would become pregnant after being vaccinated, she would experience breast soreness and would likely have to choose not to breast feed.) For younger women with an increased risk of breast cancer, the vaccine may be an option to consider instead of prophylactic radical mastectomy.

"Most attempts at cancer vaccines have targeted viruses, or cancers that have already developed,” said Joseph Crowe, M.D., director of the Breast Center at Cleveland Clinic. "Dr. Tuohy is not a breast cancer researcher; he's an immunologist, so his approach is completely different--attacking the tumor before it can develop. It's a simple concept, yet one that has not been explored until now.”

Dr. Tuohy believes that the findings of this study go beyond breast cancer, providing clues into the development of vaccines to prevent other types of cancer. The results demonstrate that the antigen used in a cancer vaccine must meet several criteria: it must be overexpressed in most of the targeted tumors; and it must not be found in normal tissue, except under specific, avoidable conditions (such as lactation).

Related Links:
Cleveland Clinic's Lerner Research Institute