Novartis Institutes for Biomedical Research, Expertise Platform Kinases, Novartis Campus, Fabrikstrasse 16, WJS152.1.72.2, 4056 Basel, Switzerland.
Angiogenesis. 2010 Sep;13(3):259-67. doi: 10.1007/s10456-010-9183-z. Epub 2010 Aug 29.
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.
EphB4 及其认知配体 EphrinB2 在胚胎血管发育和血管重塑中发挥着重要作用。此外，有几项报告表明，该受体配体对在包括肿瘤血管生成在内的成人病理性血管形成中也有涉及。Eph/ephrin 信号是一种复杂的现象，其特征是通过受体的酪氨酸激酶进行受体正向信号传递，以及通过 Ephrin 配体的各种蛋白-蛋白相互作用域和磷酸化模体进行 Ephrin 的反向信号传递。因此，通过靶向基因敲除、可溶性受体、显性负突变体或反义分子来干扰 EphR/ephrin 信号，通常不能区分 Eph/ephrin 正向和反向信号的抑制。我们开发了 EphB4 激酶的一种特异性小分子激酶抑制剂 NVP-BHG712，该抑制剂在细胞测定中以低纳摩尔范围抑制 EphB4 激酶活性，在生化和基于细胞的测定中对其他激酶进行分析时，表现出对 EphB4 激酶的高选择性。此外，NVP-BHG712 表现出优异的药代动力学特性，并在口服给药后在组织中强烈抑制 EphB4 自身磷酸化。在体内，NVP-BHG712 抑制 VEGF 驱动的血管形成，而在体外或细胞测定中对 VEGFR 活性仅有很小的影响。这里显示的数据表明在血管形成过程中 VEGFR 和 EphR 信号之间存在密切的串扰。除了 EphB4 在血管重塑和内皮动静脉分化中的既定功能外，EphB4 正向信号传递似乎是 VEGF 诱导的血管生成的重要介质，因为抑制 EphB4 正向信号传递足以抑制 VEGF 诱导的血管生成。
