Estrogen regulation of lactoferrin expression in human endometrium

PROBLEM: Lactoferrin is an iron-binding glycoprotein that has been shown to be overexpressed in human endometrial carcinomas. The purpose of our present study is to investigate the possible role of estradiol in the expression of lactoferrin. METHOD OF STUDY: We investigated 1) serum levels of lactoferrin in five women during normal ovulatory cycles, 2) serum levels of lactoferrin during ten human menopausal gonadotropin induced cycles when estradiol levels are high, and 3) lactoferrin expression in five proliferative and five secretory phase endometrium by immunohistochemical studies. The serum concentrations of lactoferrin were measured by a peroxidase-based enzyme-linked immunosorbent assay. RESULTS: In normal ovulatory cycles, the mean serum lactoferrin concentration during the proliferative phase (0.4013 ± 0.0242 μg/mL) was significantly higher (P<0.02) than in the secretory phase (0.3468 ± 0.0209 μg/mL). In induced cycles, there was gradual increase in lactoferrin levels with increasing estradiol concentrations. Peak lactoferrin levels in induced cycles (0.7495 ± 0.1148 μg/mL) were significantly higher (P<0.003) than the midcycle levels (0.423 ± 0.0424 μg/mL) in normal cycles. Immunohistochemical analysis of the endometrium revealed greater expression of lactoferrin in proliferative endometrium (50.7 ± 13%, range 28-72%) than in secretory endometrium (19.2 ± 4%, range 7-31%). CONCLUSION: These results indicate that estradiol may play a role in the regulation of lactoferrin expression in human endometrium.