Influence of diet on mammary cancer in transgenic mice bearing an oncogene expressed in mammary tissue.

Breast cancer is one of the most common cancers in women. The laboratory rat treated with strong carcinogen is the most commonly used animal model for study of breast cancer. Transgenic mouse lines with homologues of human breast cancer oncogenes have been developed. The transgenic mouse line TG.NK with c-neu, the human breast cancer oncogene homologue of erbB2, was evaluated to determine its suitability for study of intervention strategies to delay/prevent the development of breast cancer. There were no palpable mammary tumor masses up to 22-weeks of age, and almost all mice fed a purified diet developed palpable mammary tumors by 28-weeks of age. Nonpurified diets decreased the incidence and multiplicity, and delayed the development of mammary tumors as compared to a purified diet. Increasing the fiber content of nonpurified diet decreased the tumor incidence further. There is approximately a 19-week interval between weaning and development of palpable mammary masses to evaluate intervention strategies to delay or prevent the development of mammary cancer in the TG.NK mouse model. Fiber from nonpurified cereal ingredients appears to be highly beneficial in delaying the development of mammary cancer in TG.NK mice, and this observation is in agreement with human epidemiological findings. Therefore, the TG.NK transgenic mouse with oncogene c-neu (erbB2), appears to be a useful animal model for evaluation of dietary intervention strategies.