[Comparison of background factors relevant to mammary tumorigenesis between DDD/1-Mtv-2/Mtv-2 congenic and DDD/1 mice].

To elucidate the possible participation of the Mtv-2 gene in the background factors relevant to mammary tumorigenesis, DDD/1-Miv-2/Mtv-2 (DDD-Mtv-2) congenic and DDD/1 background mice were compared for endocrine and immune organs, mammary gland development, expression of mouse mammary tumor virus (MMTV)-gp 52 antigen, hyperplastic alveolar nodules (HAN) and mammary tumor incidence. The congenic strain had been established by introducing Mtv-2 from GRS/AJms (GR) into DDD/1 mice by repeated 12 backcrosses. Body, thymus, spleen, uterus, ovary, adrenal and pituitary weights, histology of the ovary and mammary gland development showed no differences ascribable to Mtv-2 between both strains of mice at 4,6 and 12 months of age. In contrast, MMTV-gp 52 antigen expression, HAN and mammary tumor occurred in DDD-Mtv-2 but not in DDD/1 mice. These results showed that the Mtv-2 gene stimulates mammary tumorigenesis by constitutional production of endogenous MMTV which transforms mammary epithelial cells but not by influencing the background factors relevant to mammary tumorigenesis. Furthermore, the expression of Mtv-2 appeared to be lower on the DDD/1 than on the GR background.