Send to

Choose Destination
Endocrinology. 2017 Oct 1;158(10):3354-3368. doi: 10.1210/en.2016-1871.

Skeletal and Uterotrophic Effects of Endoxifen in Female Rats.

Author information

Division of Orthopedic Research, Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota 55905.
Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905.
Skeletal Biology Laboratory, School of Biological and Population Health Sciences, Oregon State University, Corvallis, Oregon 97331.
Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota 55905.
Department of Oncology, Mayo Clinic, Rochester, Minnesota 55905.
Department of Comparative Medicine, Mayo Clinic, Scottsdale, Arizona 85259.


Endoxifen, the primary active metabolite of tamoxifen, is currently being investigated as a novel endocrine therapy for the treatment of breast cancer. Tamoxifen is a selective estrogen receptor modulator that elicits potent anti-breast cancer effects. However, long-term use of tamoxifen also induces bone loss in premenopausal women and is associated with an increased risk of endometrial cancer in postmenopausal women. For these reasons, we have used a rat model system to comprehensively characterize the impact of endoxifen on the skeleton and uterus. Our results demonstrate that endoxifen elicits beneficial effects on bone in ovary-intact rats and protects against bone loss following ovariectomy. Endoxifen is also shown to reduce bone turnover in both ovary-intact and ovariectomized rats at the cellular and biochemical levels. With regard to the uterus, endoxifen decreased uterine weight but maintained luminal epithelial cell height in ovariectomized animals. Within luminal epithelial cells, endoxifen resulted in differential effects on the expression levels of estrogen receptors α and β as well as multiple other genes previously implicated in regulating epithelial cell proliferation and hypertrophy. These studies analyze the impact of extended endoxifen exposure on both bone and uterus using a Food and Drug Administration-recommended animal model. Although endoxifen is a more potent breast cancer agent than tamoxifen, the results of the present study demonstrate that endoxifen does not induce bone loss in ovary-intact rats and that it elicits partial agonistic effects on the uterus and skeleton in ovariectomized animals.

[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Silverchair Information Systems Icon for PubMed Central
Loading ...
Support Center