Hormone-dependent mammary tumors in mice and rats as a model for human breast cancer (review).

Hormone-dependent (HD) mammary tumors can be induced in mice and rats either by endocrine manipulations or by treatment with carcinogens. The tumors metastasize at a low frequency which may be due to immunogenic properties and does not exclude that the tumors are malignant. Hormone deprival may lead to tumor regression. However, regrowth of hormone-independent (HI) tumor cells probably always occur. Estrogens, progesterone, and prolactin are the most important hormones involved in mammary tumor growth, but androgen- and insulin-dependent mammary tumors have also been described. The most important biochemical difference between HD and HI mammary tumors is perhaps the higher hormone receptor content in HD tumors, but high iodide uptake may prove to be the most specific biochemical characteristic of HD tumors. The relevance of rodent mammary tumor models to human breast cancer is discussed.