title: Changes in the parous rat mammary gland environment are involved in parity-associated protection against mammary carcinogenesis.
abstract: Parity in rats results in protection from methylnitrosourea (MNU)-induced mammary cancer. Our goal was to determine if systemic alterations in the mammary gland environment after a full-term pregnancy rendered the parous rat an inadequate host for promotion of initiated mammary epithelial cells to become cancerous. Lewis rat MNU-treated mammary epithelial cells were transplanted into uniparous (UP), age-matched virgin (AMV) (both 130-150 d), or young virgin (YV) (50-60 d) syngeneic hosts to examine if differences in the systemic environments of the three hosts had an effect on hyperplasia and cancer formation. More transplants in YV and AMV hosts contained hyperplasias and adenocarcinomas as compared to transplants in UP hosts. In addition, UP host transplants had significantly fewer numbers of hyperplastic lesions than transplants from the virgin hosts. The evidence presented here shows that the uniparous host environment is less supportive than that of the virgin host for hyperplasia and cancer development.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley 94720, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Abrams
authors.forename: R C
authors.initials: RC
authors.lastname: Guzman
authors.forename: S M
authors.initials: SM
authors.lastname: Swanson
authors.forename: G
authors.initials: G
authors.lastname: Thordarson
authors.forename: F
authors.initials: F
authors.lastname: Talamantes
authors.forename: S
authors.initials: S
authors.lastname: Nandi
mesh_terms: D000818:Animals; D002273:Carcinogens; D018890:Chemoprevention; D005260:Female; D006965:Hyperplasia; D008321:Mammary Glands, Animal / Q000166:cytology / Q000473:pathology / Q000502:physiology*; D008325:Mammary Neoplasms, Experimental / Q000473:pathology* / Q000517:prevention & control; D008770:Methylnitrosourea; D009368:Neoplasm Transplantation; D010298:Parity; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D051381:Rats; D011917:Rats, Inbred Lew; D013997:Time Factors; D014185:Transplantation, Isogeneic
chemical_list: D002273:Carcinogens; D008770:Methylnitrosourea