title: Estrogen inhibition of MPA-induced mouse mammary tumor transplants.
abstract: Estrogen compounds were used to treat mice bearing syngeneic transplants of medroxyprogesterone acetate(MPA)-induced BALB/c mammary adenocarcinomas. Both MPA-dependent and MPA-independent tumor lines were used. These lines expressed estrogen (ER) and progesterone receptors (PR). We demonstrate that different doses of estradiol benzoate (EB) and 17-beta-estradiol (E2) inhibit tumor growth and induce tumor regression in both MPA-independent and -dependent tumors, even in the presence of MPA or progesterone (P). EB was unable to induce regression of (ER-) hormone-independent tumor lines. A few MPA-dependent tumors became resistant to the estrogenic treatment; in subsequent passages some of these tumors retained their MPA-responsiveness, although estrogen sensitivity was not recovered.
authors.affiliation: Instituto de Investigaciones Hematológicas, Academia Nacional de Medicina, Buenos Aires, Argentina.
authors.forename: E
authors.initials: E
authors.lastname: Kordon
authors.forename: C
authors.initials: C
authors.lastname: Lanari
authors.forename: A A
authors.initials: AA
authors.lastname: Molinolo
authors.forename: P V
authors.initials: PV
authors.lastname: Elizalde
authors.forename: E H
authors.initials: EH
authors.lastname: Charreau
authors.forename: C
authors.initials: C
authors.lastname: Dosne Pasqualini
mesh_terms: D000230:Adenocarcinoma / Q000139:chemically induced / Q000188:drug therapy* / Q000473:pathology; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D003692:Delayed-Action Preparations; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000188:drug therapy* / Q000473:pathology; D008525:Medroxyprogesterone / Q000031:analogs & derivatives*; D017258:Medroxyprogesterone Acetate; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D011374:Progesterone / Q000494:pharmacology; D011960:Receptors, Estrogen / Q000032:analysis; D011980:Receptors, Progesterone / Q000032:analysis; D012826:Silicone Elastomers; D014185:Transplantation, Isogeneic
chemical_list: D003692:Delayed-Action Preparations; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D012826:Silicone Elastomers; D011374:Progesterone; D004958:Estradiol; D017258:Medroxyprogesterone Acetate; D008525:Medroxyprogesterone