Accelerated mammary cancer development by fetal salivary mesenchyma isografted to adult mouse mammary epithelium.

: Transplantation of fetal salivary mesenchyma into adult mammary glands resulted in atypical outgrowths from the mammary duct system. These duct-alveolus nodules (DAN) were distinguishable from hyperplastic alveolar nodules (HAN) that arose from normal mammary duct systems in mice infected with murine mammary tumor virus (MuMTV). DAN displayed a type of ductal branching characteristic of salivary gland rather than of mammary gland, reflecting a tissue-specific perturbation of epithelium-mesenchyma in DAN in milk-transmitted MuMTV-infected C3H/HeN mice and in MuMTV-negative BALB/c mice given 7,12-dimethylbenz[a]anthracene (DMBA) subsequent to transplantation of fetal salivary mesenchyma. Mammary cancers were not increased in milk-transmitted MuMTV-free C3H/HeN and GRS/A mice that received salivary mesenchyma transplants. Salivary mesenchyma accelerated mammary carcinogenesis by increasing the mammary epithelial cell population responsive to MuMTV and DMBA.