Prototype Vaccine to Prevent Breast Cancer

Researchers at Cleveland Clinic's Lerner Research Institute say they have developed prototype vaccine to prevent breast cancer. The research can lead to prevention in women over age 40 and those at high risk. The vaccine has shown favorable results in animal models.

The researchers found 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.

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.

In terms of developing a preventive vaccine, cancer presents a quandary not posed by viruses. While viruses are recognised 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 Vincent Tuohy, the study's principal investigator and an immunologist, says is to find a target within the tumor that is not typically found in a healthy person.

In the case of breast cancer, Dr. Tuohy targeted a-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 a-lactalbumin - thus stopping tumor 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. For younger women with a heightened risk of breast cancer, the vaccine may be an option to consider instead of prophylactic radical mastectomy.

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 tumors; and it must not be found in normal tissue, except under specific, avoidable conditions (such as lactation).