Epithelial ovarian cancer (EOC) is the most lethal gynecological malignancy and the fifth common cause of tumor-related death in women in the United States. The survival rates for advanced stage of the disease that have not changed in several decades [
1,
2]. Lack of specific symptoms of the disease in its early stages is a significant factor contributing to the high mortality rate. Consequently, most patients have reached advanced stage at the time of diagnosis [
3]. Despite new diagnostic and surgical advances, and development of chemotherapeutic regimens, the overall 5-year survival for women with advanced stage epithelial ovarian cancer has remained approximately 12% over the past 40 years [
4]. Ovarian serous carcinoma (OSC) is a common ovarian epithelial malignancy, which has traditionally been graded as high, moderately, and poorly differentiated, indicating that it is a homogeneous disease in the position of pathogenesis. More recently, a 2-tier grading system has been proposed, in which ovarian serous carcinomas are subdivided into low-grade and high-grade. Seminal clinicopathologic and molecular genetic studies have revealed that this approach is simplistic, reproducible, and on the basis of underlying morphologic and molecular genetic differences between low-grade and high-grade tumors [
5]. The progression to invasive carcinoma is a slow step-wise process. Low-grade tumors are indolent and have better outcome than high-grade tumors [
6]. Notwithstanding the enormous effort, the etiopathogenesis of epithelial ovarian cancers are still unknown. The development of more effective therapeutic strategies highlight the need to better understand the molecular mechanisms of ovarian cancer.
The Eph (Erythropoietin-producing human hepatocellular carcinoma cell) family of receptors and ligands is the largest group of tyrosine kinase receptor-ligand systems, which is involved in many physiological roles including axon guidance, neural plasticity, angiogenesis, cell migration and tissue segmentation [
7,
8]. Based on the structural homology and the binding affinities, The Eph receptors and their ephrin ligands are classified into two groups, A and B. Ephrin-A ligands generally bind to EphA receptors via a glycosylphosphatidylinositol anchor on the cell membrane, whereas ephrin-B ligands bind to EphB receptors via a transmembrane domain [
9]. Eph receptors have been implicated in mediating developmental events, particularly in the nervous system. The roles of the Eph receptors and ephrin ligands in cell adhesion, migration, formation of the borders of compartments, regulation of cell proliferation in various tumors and angiogenesis are also well documented [
10,
11]. EphA5 (also known as REK7, Ehk-1, Bsk) is a member of the Eph receptor tyrosine kinase subfamily, originally identified as a nervous-system-specific orphan receptor expressed in embryonic rats at high levels and in the adult brain at lower levels [
12]. The function of the EphA5 receptor is well established as an axon guidance molecule during neural system development [
13]. However, the potential role of EphA5 in human carcinogenesis has not been well addressed. Fu et al. revealed that increased methylation of EphA5 is correlated with decreased expression in primary breast cancer [
14]. Giaginis et al. found that pancreatic adenocarcinoma cases with enhanced EphA5 expression presented significantly increased tumor cells proliferative capacity [
15]. To date, there have been no published reports describing the role of EphA5 expression in epithelial ovarian carcinoma. Here, we evaluated the expression of EphA5 protein in a set of normal fallopian tube, benign epithelial ovarian tumors, ovarian serous borderline tumors, and ovarian serous carcinomas samples to explore its roles in ovarian serous carcinoma.