[Carcinogenesis induced by the neonatal administration of 5-bromo-2'-deoxyuridine and subsequent exposure to estradiol benzoate in female BALB/c mice].

Female BALB/c mice were given 1 mg 5-bromo-2'-deoxyuridine (BDU) subcutaneously on days 1, 3 and 7 after birth or 5 mg estradiol benzoate (EB) 15 times weekly starting at the age of 3 months or both. Combined application of BDU and EB potentiated the carcinogenic effect of each agent on breast tissue: breast cancer occurred in 80.6% of animals as compared to 15.8, 9.7 and 0% in groups treated with EB or BDU alone and controls, respectively (p < 0.001). Treatment with BDU induced a slightly (but significantly, p < 0.02) higher overall tumor occurrence as well as higher occurrence of primary multiple and malignant tumors and breast cancer as compared to controls. It is suggested that BDU-induced accumulation of DNA errors contributes to initiation of neoplastic changes in the cell and cancer development which is further stimulated by EB.