EXPERIMENTALLY-INDUCED MAMMARY-TUMORS IN RATS

Among the multiple experimental animal models employed for analyzing t he various aspects of mammary carcinogenesis, the induction of mammary tumors in rats by chemical carcinogens is one of the models most util ized. Experimentally-induced mammary tumors in rodents have proven to constitute useful tools for the study of the pathogenesis of cancer an d of the molecular mechanisms involved in the initiation and progressi on of the neoplastic process. In vivo experimental animal models provi de information not available in human populations; they are adequate f or hazard identification, dose-response modeling, exposure assessment, and risk characterization, the four required steps for quantifying th e estimated risk of cancer development associated with toxic chemical exposure. Using the DMBA rat mammary model, we have been able to demon strate that the carcinogen acts on the intermediate cell of the termin al end bud (TEE), and that this structure is the one that evolves to i ntraductal proliferation, carcinoma in situ, and invasive carcinoma. T here are several factors that regulate the susceptibility of the TEE; some of them are: a) topographic location of the mammary gland, b) age of the animal, and c) reproductive history. The understanding of the mechanisms that modulate tumorigenesis will further our knowledge and understanding in the prevention of the disease, as a result of the dev elopment of strategies for stopping the progression of the initiated c ells.