Research could lead to first vaccine to prevent breast cancer formation in women over age 40 and women at high risk

A first-of-its-kind vaccine to prevent breast cancer has shown overwhelmingly favourable results in animal models, according to a study by researchers at Cleveland Clinic's Lerner Research Institute.

The researchers found that a single vaccination with the antigen α-lactalbumin prevents breast cancer tumours from forming in mice, while also inhibiting the growth of already existing tumours. 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 in Nature and in the June 10 issue of 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 Dr. Vincent Tuohy, the study's principal 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 α-lactalbumin and half with a vaccine that did not contain the antigen.

None of the mice vaccinated with α-lactalbumin developed breast cancer, while all of the other mice did.

The US Food and Drug Administration 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 quandary not posed by viruses. While viruses are recognized as foreign invaders by the immune system, cancer is not. Rather, cancer is an over-development of the body's own cells. Trying to vaccinate against this cell over-growth would effectively be vaccinating against the recipient's own body, destroying healthy tissue.

The key, Dr. Tuohy said, is to find a target within the tumour that is not typically found in a healthy person. In the case of breast cancer, Dr. Tuohy and his research team targeted α-lactalbumin - a protein that is found in the majority of breast cancers, but is not found in healthy women, except during lactation. Therefore, the vaccine can rev up a woman's immune system to target α-lactalbumin - thus stopping tumour formation - without damaging healthy breast tissue.

The strategy would be to vaccinate women over 40 - when breast cancer risk begins 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 a heightened 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 Dr. Joseph Crowe, 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 tumour 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 insight into the development of vaccines to prevent other types of cancer. The results show that the antigen used in a cancer vaccine must meet several criteria: it must be over-expressed in the majority of targeted tumours; and it must not be found in normal tissue, except under specific, avoidable conditions (such as lactation).

Source: Cleveland Clinic's Lerner Research Institute