Abstract
The tyrosine kinase receptor EphB4 is frequently overexpressed in ovarian and other solid tumors and is involved in interactions between tumor cells and the tumor microenvironment, contributing to metastasis. Trans-interaction between EphB4 and its membrane-bound ligand ephrin B2 (EFNB2) mediates bi-directional signaling: forward EFNB2-to-EphB4 signaling suppresses tumor cell proliferation, while reverse EphB4-to-EFNB2 signaling stimulates the invasive and angiogenic properties of endothelial cells. Currently, no small molecule–based, dual-function, EphB4-binding peptides are available. Here, we report our discovery of a bi-directional ephrin agonist peptide, BIDEN-AP which, when selectively internalized via receptor-mediated endocytosis, suppressed invasion and epithelial-mesenchymal transition of ovarian cancer cells. BIDEN-AP also inhibited endothelial migration and tube formation. In vivo, BIDEN-AP and its nanoconjugate CCPM-BIDEN-AP significantly reduced growth of orthotopic ovarian tumors, with CCPM-BIDEN-AP displaying greater antitumor potency than BIDEN-AP. Both BIDEN-AP and CCPM-BIDEN-AP compromised angiogenesis by downregulating epithelial-mesenchymal transition and angiogenic pathways. Thus, we report a novel EphB4-based therapeutic approach against ovarian cancer.
Highlights
EphB4 belongs to the Eph family, the largest family of membrane-bound receptor tyrosine kinases
The dual function of EphB4 as tumor promoter or suppressor associated with its EFNB2 ligand opens a therapeutic window for modulating EphB4 activity in tumor cells[14]
While exploring the effects of structural modifications to the binding affinity of EphB4 antagonist TNYL-RAW peptide[21,22], we unexpectedly found that substitution of L-Tyr-P3 with D-Tyr-P3 led to a functional switch from EphB4 antagonist to EphB4 agonist
Summary
EphB4 belongs to the Eph family, the largest family of membrane-bound receptor tyrosine kinases Both EphB4 and its sole physiologically relevant ligand, ephrin B2 (EFNB2), are membrane bound, and their interaction initiates forward signaling through EphB4 and reverse signaling through EFNB21. Independent of interaction with EFNB2, EphB4 can be activated by ligand-independent pathways to promote proliferation and metastasis, as EphB4 mutants with mutated phosphorylation sites can still promote tumor cell growth and migration[11]. Several groups have shown that the reverse EphB4 to EFNB2 signaling in endothelial cells plays an essential role in initiating angiogenesis and lymphangiogenesis, important processes in supporting tumor growth and metastasis[17,18,19]. Functional studies showed that BIDEN-AP could simultaneously activate EphB4-initiated Abl/Crk[1] tumor-suppressive signaling in tumor cells and inhibit EFNB2-regulated angiogenic signaling in endothelial cells.
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