The Epithelial-Mesenchymal Transition and the Estrogen-Signaling in Ovarian Cancer

Epithelial ovarian cancer is the leading cause of death for gynecological cancer in most of the Western world; lethality ensues from the occurrence of occult metastasis within the peritoneal cavity, a process requiring the acquisition of capacity for migration and invasiveness by ovarian tumor cells (metastatic phenotype), and characterized by a complex series of interrelated cellular events. Unlike most carcinomas that dedifferentiate during neoplastic progression with loss of epithelial E-cadherin (epithelial to mesenchymal transition, EMT), ovarian carcinomas undergo transition to a more epithelial phenotype, early in tumor progression, with increased E-cadherin expression. Subsequent reacquisition of mesenchymal features is observed in late-stage tumors, and loss of E-cadherin expression or function is a factor in ovarian cancer progression. Changes in E-cadherin expression are indicative of the phenotypic plasticity that occurs in ovarian cancer, with a variety of signal transduction pathways impinging on the regulation of E-cadherin levels or subcellular distribution. Among them, the Snail transcription family, consisting of members SNAIL and SLUG, is thought to be mainly involved in the repression of E-cadherin expression, leading to EMT. E-cadherin, SNAIL, and SLUG also represent crucial targets of estrogen signaling. In this review, we discuss recent advances in the understanding of the role of estrogen signaling in the complex network underlying the phenotypic plasticity in ovarian cancer. Insight into the mechanisms involved will allow rational drug designs, aimed at the molecules critical to cellular signaling.