Philinopside E, a new sulfated saponin from sea cucumber, blocks the interaction between kinase insert domain-containing receptor (KDR) and α_vβ₃ integrin via binding to the extracellular domain of KDR

Vascular endothelial growth factor (VEGF) signaling pathway is essential for tumor angiogenesis and has long been recognized as a promising target for cancer therapy. Current view holds that physical interaction between α_vβ₃ integrin and kinase insert domain-containing receptor (KDR) is important in regulating angiogenesis and tumor development. We have reported previously that a new marine-derived compound, philinopside E (PE), exhibited the antiangiogenic activity via inhibition on KDR phosphorylation and downstream signaling. Herein, we have further demonstrated that PE specifically interacts with KDR extracellular domain, which is distinct from conventional small-molecule inhibitors targeting cytoplasmic kinase domain, to block its interaction with VEGF and the downstream signaling. We also noted that PE markedly suppresses α_vβ ₃ integrin-driven downstream signaling as a result of disturbance of the physical interaction between KDR and α_vβ₃ integrin in HMECs, followed by disruption of the actin cytoskeleton organization and decreased cell adhesion to vitronectin. All of these findings substantiate PE to be an unrecognized therapeutic class in tumor angiogenesis and, more importantly, help appeal the interest of the therapeutic potential in angiogenesis and cancer development via targeting integrin-KDR interaction in the future.