Protective effects of progesterone and tamoxifen in estrogen-induced mammary carcinogenesis in ovariectomized W/Fu rats

Jpn J Cancer Res. 1985 Aug;76(8):699-704.

Abstract

The protective effect of progesterone or tamoxifen, an antiestrogenic agent, was investigated in estrogen-induced mammary carcinogenesis. Multiple mammary tumors (MT) of tubular or medullary carcinoma type developed at a high rate following prolonged treatment of ovariectomized W/Fu rats with diethylstilbestrol or 17 beta-estradiol. All MTs were located adjacent to the nipple and were slow-growing. The induction rate, multiplicity and size of estrogen-induced MTs were reduced by the simultaneous administration of either progesterone or tamoxifen. The estrogen-induced pituitary tumorigenesis was effectively inhibited by tamoxifen treatment, but it was not affected by progesterone. The results indicated that the inhibitory effect of progesterone or tamoxifen in estrogen-induced carcinogenesis is attributable to interference with the binding of estrogen to the estrogen receptors on the target cells.

MeSH terms

  • Adenoma / chemically induced
  • Adenoma / pathology
  • Animals
  • Carcinoma / analysis
  • Carcinoma / chemically induced*
  • Carcinoma / pathology
  • Diethylstilbestrol
  • Estradiol
  • Estrogens / pharmacology*
  • Female
  • Mammary Glands, Animal / pathology
  • Mammary Neoplasms, Experimental / analysis
  • Mammary Neoplasms, Experimental / chemically induced*
  • Mammary Neoplasms, Experimental / pathology
  • Ovariectomy
  • Pituitary Neoplasms / chemically induced
  • Pituitary Neoplasms / pathology
  • Progesterone / pharmacology*
  • Rats
  • Rats, Inbred WF
  • Receptors, Estrogen / analysis
  • Tamoxifen / pharmacology*

Substances

  • Estrogens
  • Receptors, Estrogen
  • Tamoxifen
  • Progesterone
  • Estradiol
  • Diethylstilbestrol