Expression of receptor tyrosine kinase EphB4 and its ligand ephrin-B2 is associated with malignant potential in endometrial cancer.

The protein kinases includes many oncogenes and growth-factor receptors, as well as genes that are involved in cell cycle regulation. EphB4 receptors are a subfamily of receptor tyrosine kinases that are activated by ephrin-B2 ligands and are thought to play an important role in the development and oncogenesis of various tissues. However, very little experimental evidence exists to support this hypothesis. To elucidate the involvement of EphB4 and ephrin-B2 in endometrial carcinogenesis, we used fluorescent immunohistochemistry to analyze serial frozen sections of 20 endometrial carcinomas and 20 normal endometria for EphB4 and ephrin-B2 protein expression. We analyzed the relationship between the patient's characteristics and the percentages of EphB4- and ephrin-B2-stained cells. EphB4 expression was significantly associated with histological grade (p < 0.001) and certain clinical stages. Ephrin-B2 Expression was significantly associated with the presence of invasion to > 1/2 myometrium (p = 0.002). Our results demonstrate that increased EphB4 and ephrin-B2 expression may reflect or induce in endometrial carcinomas increased potential for growth and tumorigenicity. Furthermore, these results suggest that EphB4 receptor kinase may modulate the biological behavior of endometrial carcinomas through autocrine and/or paracrine activation, which is caused by ephrin-B2 ligands that are expressed in the same or neighbouring cells by immunohistochemistry.