The effects of intermittent progesterone upon tamoxifen inhibition of tumor growth in the 7,12-dimethylbenzanthracene rat mammary tumor model.
The development of endometrial cancer is a potential risk during long-term tamoxifen therapy for breast cancer. In order to protect the uterus, progestin treatment has been proposed for these patients. However, within the 7,12-dimethylbenzanthracene-induced rat mammary model, progesterone is known to reverse the antitumor effects of tamoxifen. This study shows that progesterone administered intermittently still reverses the antitumor effects of tamoxifen in this model. This effect of progesterone is not due to a decrease in the tissue levels of tamoxifen, and may be direct, via the progesterone receptor.
Gibson
D F
DF
Department of Human Oncology, University of Wisconsin Comprehensive Cancer Center, Madison 53792.
Johnson
D A
DA
Langan-Fahey
S M
SM
Lababidi
M K
MK
Wolberg
W H
WH
Jordan
V C
VC
D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000188:drug therapy* / Q000473:pathology; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013629:Tamoxifen / Q000627:therapeutic use*; D014599:Uterus / Q000187:drug effects
D013629:Tamoxifen; D011374:Progesterone; D015127:9,10-Dimethyl-1,2-benzanthracene