title: Decreasing hormonal promotion is key to breast cancer prevention.
abstract: An early full-term pregnancy in women is highly protective against breast cancer. This protection can be mimicked by short-term treatment with estradiol plus progesterone in nulliparous rats. We determined the effect of long-term hormonal promotion following the protective short-term estradiol and progesterone treatment that mimics parity protection against mammary tumors. Rats were treated with N-methyl-N-nitrosourea before or after protective hormone treatment. In brief, the animals could be broadly classified into three categories. First, the controls that received no protective hormone treatment, second, the short-term protective hormone treated rats, and third, rats which received the short-term protective hormone treatment plus continuous treatment with estradiol or progesterone or a combination of estradiol and progesterone. Different doses of hormones were used for short-term protective and long-term promotion treatments. The experiments were terminated 9 months post carcinogen treatment. Mammary tumor incidence in all the short-term estradiol- plus progesterone-treated rats was significantly lower compared with controls. Short-term hormone treatment followed by long-term promotion resulted in an increased mammary tumor incidence compared with animals that received only the short-term treatment. Overall, the results demonstrate the importance of the promotional environment in mammary carcinogenesis indicating that the decreased promotional environment could be the reason for protection against mammary carcinogenesis.
authors.affiliation: Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, 5001 El Paso Drive, El Paso, TX, 79905, USA. rajkumar.lakshmanaswamy@ttuhsc.edu
authors.forename: Lakshmanaswamy
authors.initials: L
authors.lastname: Rajkumar
authors.forename: Amy
authors.initials: A
authors.lastname: Canada
authors.forename: David
authors.initials: D
authors.lastname: Esparza
authors.forename: Katherine
authors.initials: K
authors.lastname: Collins
authors.forename: Enrique
authors.initials: E
authors.lastname: Moreno
authors.forename: Huyen
authors.initials: H
authors.lastname: Duong
mesh_terms: D000818:Animals; D002273:Carcinogens; D004958:Estradiol / Q000008:administration & dosage* / Q000097:blood; D005260:Female; D015674:Mammary Neoplasms, Animal / Q000139:chemically induced / Q000517:prevention & control*; D008770:Methylnitrosourea; D011374:Progesterone / Q000008:administration & dosage*; D051381:Rats; D011917:Rats, Inbred Lew; D013997:Time Factors
chemical_list: D002273:Carcinogens; D011374:Progesterone; D004958:Estradiol; D008770:Methylnitrosourea