Skeletal and Uterotrophic Effects of Endoxifen in Female Rats.

Abstract

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.

• Authors: Anne Gingery, Urszula T Iwaniec, Malayannan Subramaniam, Russell T Turner, Kevin S Pitel, Renee M McGovern, Joel M Reid, Ronald J Marler, James N Ingle, Matthew P Goetz, John R Hawse
• Journal: Endocrinology (Endocrinology) Vol. 158 Issue 10 Pg. 3354-3368 (10 01 2017) ISSN: 1945-7170 [Electronic] United States
• PMID: 28977607 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, N.I.H., Extramural)
• Copyright: Copyright © 2017 Endocrine Society.

Chemical References

• Estrogen Receptor alpha
• Estrogen Receptor beta
• Selective Estrogen Receptor Modulators
• Tamoxifen
• 4-hydroxy-N-desmethyltamoxifen

Topics

• Animals
• Bone Remodeling (drug effects)
• Bone and Bones (drug effects)
• Breast Neoplasms (drug therapy)
• Cell Proliferation (drug effects)
• Endometrium (drug effects, metabolism, pathology)
• Estrogen Receptor alpha (drug effects, metabolism)
• Estrogen Receptor beta (drug effects, metabolism)
• Female
• Organ Size
• Osteoporosis (chemically induced)
• Ovariectomy
• Rats
• Selective Estrogen Receptor Modulators (adverse effects, pharmacology)
• Tamoxifen (adverse effects, analogs & derivatives, pharmacology)
• Uterus (drug effects, metabolism, pathology)