Abstract
EphB4 is a membrane-bound receptor tyrosine kinase (RTK) commonly over-produced by many epithelial cancers but with low to no expression in most normal adult tissues. EphB4 over-production promotes ligand-independent signaling pathways that increase cancer cell viability and stimulate migration and invasion. Several studies have shown that normal ligand-dependent signaling is tumour suppressive and therefore novel therapeutics which block the tumour promoting ligand-independent signaling and/or stimulate tumour suppressive ligand-dependent signaling will find application in the treatment of cancer. An EphB4-specific polyclonal antibody, targeting a region of 200 amino acids in the extracellular portion of EphB4, showed potent in vitro anti-cancer effects measured by an increase in apoptosis and a decrease in anchorage independent growth. Peptide exclusion was used to identify the epitope targeted by this antibody within the cysteine-rich region of the EphB4 protein, a sequence defined as a potential ligand interacting interface. Addition of antibody to cancer cells resulted in phosphorylation and subsequent degradation of the EphB4 protein, suggesting a mechanism that is ligand mimetic and tumour suppressive. A monoclonal antibody which specifically targets this identified extracellular epitope of EphB4 significantly reduced breast cancer xenograft growth in vivo confirming that EphB4 is a useful target for ligand-mimicking antibody-based anti-cancer therapies.
Highlights
EphB4 is a member of the largest family of receptor tyrosine kinases and is an important regulator of fundamental physiological and pathophysiological processes such as tissue patterning during development, angiogenesis and tumour progression [1]
A clear increase in fluorescence of the MCF10A-B4 when compared with the MCF10A cells shows that the H200 polyclonal antibody (Ab) is binding to surface expressed EphB4 in the MCF10A–B4 cells (Figure 1B)
The increased green fluorescence in the MCF10A-B4 cells when compared with MCF10A-VO cells indicates that the H200 pAb recognizes over-expressed EphB4 protein
Summary
EphB4 is a member of the largest family of receptor tyrosine kinases and is an important regulator of fundamental physiological and pathophysiological processes such as tissue patterning during development, angiogenesis and tumour progression [1]. Despite significant promiscuity between other Eph family members and the ephrin ligands, the single physiologically-relevant ligand of the EphB4 receptor is ephrin-B2 [2]. Both the receptor and the ligand are membrane-bound but usually expressed on neighbouring cells. Through EphB4, and reverse signaling, through ephrin-B2, requires heterotetramerisation of two receptors on one cell with two ligands on a neighbouring cell [3] This normal interaction between EphB4 and ephrin-B2 requires direct cell-cell contact and induces forward signaling of the receptor that leads to tumour suppression and reverse signaling through the ligand that stabilizes cell-cell adhesion and can stimulate angiogenesis if the ephrin-B2 expressing cell is an endothelial cell [3].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
