Cancer immunoprevention posits that the enhancement of immune defenses in healthy individuals could control
tumor onset. Immunoprevention of viral
tumors is already implemented at the population level for human hepatocellular and cervical
carcinomas. Altogether,
viral vaccines could prevent more than 10% of all human
tumors. The big question is whether immunoprevention can be applied to nonviral
tumors, including
breast cancer. Promising results were obtained in preclinical models, in particular in HER-2/neu transgenic mice, which are prone to mammary
carcinoma development, using
vaccines against HER-2/neu
oncoprotein p185. The life expectancy of vaccinated mice was more than doubled. Protective immune mechanisms elicited by effective
vaccines were mainly based on helper T cell
cytokines, in particular γ-
interferon, and anti-p185
antibodies. The term "oncoantigens" was coined to define those antigenic molecules that, like HER-2, are indispensable for
tumor growth, thus representing the best class of targets for
cancer immunoprevention. The study of immunopreventive
vaccines against subsequent phases of neoplastic progression showed a dramatic loss of efficacy against established mammary
carcinomas, whereas the prevention of
micrometastasis growth was successful. Preclinical results provide useful indications for the translation of
cancer immunoprevention to humans, and useful hints for
cancer immunotherapy.