The effect of tamoxifen on IGF signaling pathway in the mouse ovary

Abstract

Tamoxifen (TAM) is one of selective estrogen receptor modulators used in breast cancer treatment and prevention. The objective of this study was to determine whether or not insulin-like growth factor-I (IGF-1) and its receptor (IGF-1R), has any role in the effect mechanism of TAM on the ovary. Experimentally, animals were divided into three groups as control group (n=20), low dose TAM treatment group (0.5 mg/mouse/day, n=20) and high dose TAM treatment group (1.5 mg/mouse/day, n=20). TAM was injected 0.5 and 1.5 mg/mouse/day for 5 days. Ovarian sections were used to examine the general structure by trichrome staining method and to determine IGF-1 and IGF-1R expressions by immunohistochemical staining method. After the experiment, the presence of atretic follicles and small cystic structures in the TAM-treated animals was determined. Also, antral follicles and the corpus luteum were much less in the high dose TAM group than in the control. TAM did not change the expression of IGF-1 in granulosa cells, but increased the expression of IGF-1R. In TAM groups, IGF-1 and IGF-1R expression were increased in oocytes of follicles and in interstitial cells depending on TAM doses. However, while IGF-1 expression was unchanged in the corpus luteum, decreased in treatment group. TAM generally stimulated IGF-1 and IGF-1R expression in a dose-dependent manner. The results suggest that IGF-1 signaling pathway is involved in the mechanism of action of TAM on the ovary. We may assert that it may be useful to use IGF-1 signaling pathway regulators to adjust the effects of TAM on the ovary.