An angiogenic role of E-cadherin-positive exosomes in ovarian cancer

Abstract

Angiogenesis, the induction of vasculature, is a vital step for metastasis. Loss of E-cadherin is a well-established marker for tumor metastasis. In ovarian cancer, a highly metastatic tumor that is rapidly lethal, we and others have previously shown the deregulated pattern of E-cadherin and its close association with tumor progression. Although E-cadherin is synthesized as a transmembrane molecule, it can be shed from the cell surface (sE-cad) which accounts for a rapid removal of functional E-cadherin. Here, in addition to ectodomain shedding, we show for the first time that sE-cad can be actively released from ovarian cancer cells in the form of exosomes. These sE-cad-positive exosomes play a critical role in angiogenesis which stimulated the migration, permeability, and tubulogenesis of human umbilical vein endothelial cells in vitro, and promoted functional neovascularization in vivo. In search of the underlying mechanisms by which sE-cad-positive exosomes might regulate angiogenic endothelial cells, which lack E-cadherin, we showed that a novel heterophilic crosstalk between sE-cad and VE-cadherin. Moreover, such angiogenic effect was mediated through activation of the phosphatidylinositol 3-kinase/Akt-beta-catenin signaling cascade. These results uncover a new angiogenic function for sE-cad and a novel paradigm for sE-cad production which may have potential clinical implications (This study was supported by RGC grant HKU781013). ©2015 American Association for Cancer Research.