Activation of the receptor protein tyrosine kinase EphB4 in endometrial hyperplasia and endometrial carcinoma

Abstract

Members of the Eph family of tyrosine kinases have been implicated in embryonic pattern formation and vascular development; however, little is known about their role in the adult organism. We have observed estrogen-dependent EphB4 expression in the normal breast suggesting its implication in the hormone-controlled homeostasis of this organ. Since the endometrium is a similarly hormone dependent organ and endometrial carcinoma is thought to result from estrogenic stimulation, we have investigated EphB4 expression in normal human endometrium and during its carcinogenesis. EphB4 expression was analyzed immunohistochemically in 26 normal endometrium specimens, 15 hyperplasias and 102 endometrioid adenocarcinomas and correlated with clinical and prognostic tumor characteristics. In normal endometrial tissue no EphB4 protein was detected. Strikingly, we observed a drastic increase (P <0.0001) in the number of EphB4 protein-expressing glandular epithelial cells in the majority of hyperplasias and carcinomas. Moreover, we found a statistically highly significant positive correlation between EphB4 expression and post-menopausal stage of the patient (P = 0.007). These findings indicate that in the endometrium, EphB4 is an early indicator of malignant development and, thus, EphB4 may represent a potent tool for diagnosis and therapeutic intervention.