The small molecule specific EphB4 kinase inhibitor NVP-BHG712 inhibits VEGF driven angiogenesis

Abstract

EphB4 and its cognitive ligand ephrinB2 play an important role in embryonic vessel development and vascular remodeling. In addition, several reports suggest that this receptor ligand pair is also involved in pathologic vessel formation in adults including tumor angiogenesis. Eph/ephrin signaling is a complex phenomena characterized by receptor forward signaling through the tyrosine kinase of the receptor and ephrin reverse signaling through various protein–protein interaction domains and phosphorylation motifs of the ephrin ligands. Therefore, interfering with EphR/ephrin signaling by the means of targeted gene ablation, soluble receptors, dominant negative mutants or antisense molecules often does not allow to discriminate between inhibition of Eph/ephrin forward and reverse signaling. We developed a specific small molecular weight kinase inhibitor of the EphB4 kinase, NVP-BHG712, which inhibits EphB4 kinase activity in the low nanomolar range in cellular assays showed high selectivity for targeting the EphB4 kinase when profiled against other kinases in biochemical as well as in cell based assays. Furthermore, NVP-BHG712 shows excellent pharmacokinetic properties and potently inhibits EphB4 autophosphorylation in tissues after oral administration. In vivo, NVP-BHG712 inhibits VEGF driven vessel formation, while it has only little effects on VEGF receptor (VEGFR) activity in vitro or in cellular assays. The data shown here suggest a close cross talk between the VEGFR and EphR signaling during vessel formation. In addition to its established function in vascular remodeling and endothelial arterio-venous differentiation, EphB4 forward signaling appears to be an important mediator of VEGF induced angiogenesis since inhibition of EphB4 forward signaling is sufficient to inhibit VEGF induced angiogenesis.

Eph receptor tyrosine kinases in cancer stem cells

“…In addition to the identification of inhibitors targeting EphA2, efforts have been devoted to develop selective EphB4 RTK inhibitors (61) due to its prominent role in tumor angiogenesis. Of these, NVP-BHG712 has displayed relative selectivity towards EphB4, inhibiting its kinase activity in the nanomolar range in cell-based assays.…”

Reduced pathological angiogenesis and tumor growth in mice lacking GPR4, a proton sensing receptor

“…The model has been previously described [24][25][26]. Briefly, porous tissue chambers made of perfluoro-alkoxy-Teflon (Teflon Ò -PFA, 21 9 8 mm diameter, 550 ll volume) were filled with 0.8% agar (BBL Ò Nr.…”

“…growth factor implant angiogenesis model [24][25][26]. For this purpose, mice were implanted with Teflon chambers containing either VEGF or bFGF, two well known angiogenic factors, or PBS as a baseline control.…”

Expression of dual angiogenic/neurogenic growth factors in human primary brain tumors

“…In the primary human brain cancers that we studied, the expression of the components of the ephrinB system evaluated did not display a clear relationship with either grade or cancer type, EphrinB2 being the most highly expressed, but anyhow at low level and possibly only in the remaining nontumoral neural cells, reactive astrocytes or remaining neurons, of the cancer tissue. EPHB4 and EphrinB2 are necessary for vascular development, and for tumor angiogenesis, cross-talking with the VEGF system [1,3,19], however the role of EphrinB2 and EPHB4 in cancer cells is complex, paradoxical, and sometimes opposite. It has been shown that EPHB4 on tumor cells interact with EphrinB2 on endothelial cells, promoting angiogenesis, while EPHB4 may be important for tumor cell growth, either increasing or decreasing tumor growth depending on the context; for example, human colorectal cancers lose expression of EphB at the adenoma-carcinoma transition, correlated with cancer progression [20].…”