The expression of insulin-like growth factor and its binding protein mRNA in the endometrium of postmenopausal patients with breast cancer receiving tamoxifen.

Abstract

Insulin-like growth factor I (IGF-I) is known to mediate estrogen effect in the uterus, whereas IGF binding proteins (IGFBPs) modulate the biologic effects of IGF-I. Tamoxifen may act via the IGF-IGFBP system in the postmenopausal endometrium. Endometrial samples were collected from 16 postmenopausal women with breast cancer of whom 9 received tamoxifen and the remaining 7 received no hormonal treatment. The expression of messenger RNA for IGF-I, IGF-II, and the IGFBPs 1-6 was studied using dot blot and Northern blot techniques. Expression of mRNA for IGF-I, IGFBP-2, -3, -4, and -6 was present in endometrial specimens. The expression of IGF-I mRNA was similar in the tamoxifen-treated and control patients, whereas mRNA expression for IGF-II was not detected. The expression of IGFBP-2 and -4 mRNA predominated in the endometrium of patients who received tamoxifen. These findings demonstrate that the IGF-IGFBP system is present in the postmenopausal endometrium and may be modulated by tamoxifen.