Yamanda Shinsuke, Ebihara Satoru, Asada Masanori, Okazaki Tatsuma, Niu Kaijun, Ebihara Takae, Koyanagi Akemi, Yamaguchi Noriko, Yagita Hideo, Arai Hiroyuki
Department of Geriatrics and Gerontology, Institute of Development, Aging and Cancer, Tohoku University, Aoba-ku, Sendai, Japan.
Blood. 2009 Apr 9;113(15):3631-9. doi: 10.1182/blood-2008-07-170381. Epub 2009 Feb 13.
Delta-like 4 (DLL4) is one of the Notch ligands and plays an important role in vascular development. DLL4 blockade inhibits tumor growth by promoting nonproductive angiogenesis, which is characterized by an increase in vascular density and decrease in tissue perfusion. However, a detailed mechanism remains unclear. In this study, newly developed neutralizing antibodies against mouse and human DLL4 were used to investigate the possible involvement of VEGF-DLL4-ephrinB2 cascade in nonproductive angiogenesis caused by DLL4 blockade. DLL4 blockade and soluble ephrinB2 treatment suppressed tumor growth and induced nonproductive angiogenesis. DLL4 was expressed in subcutaneous tumors, and DLL4 blockade suppressed ephrinB2 expression in the tumors. DLL4 blockade significantly promoted human umbilical vein endothelial cell (HUVEC) proliferation in vitro, and the effect was additive to that of VEGF. Both DLL4 blockade and VEGF significantly increased cord length and branch points in a tubular formation assay. Expression of ephrinB2 in HUVECs was enhanced by VEGF alone, and the enhancement was inhibited by DLL4 blockade. Moreover, when we studied the effect of ephrinB2 RNA interference on HUVEC tubular formation, knockdown of ephrinB2 mimicked the effect of DLL4. These results suggest that ephrinB2 plays a crucial role in nonproductive angiogenesis caused by DLL4 blockade.
Delta样蛋白4（DLL4）是Notch配体之一，在血管发育中起重要作用。DLL4阻断通过促进无效血管生成抑制肿瘤生长，其特征是血管密度增加和组织灌注减少。然而，具体机制仍不清楚。在本研究中，使用新开发的针对小鼠和人类DLL4的中和抗体来研究VEGF-DLL4-ephrinB2级联反应在DLL4阻断引起的无效血管生成中的可能作用。DLL4阻断和可溶性ephrinB2处理抑制肿瘤生长并诱导无效血管生成。DLL4在皮下肿瘤中表达，DLL4阻断抑制肿瘤中ephrinB2的表达。DLL4阻断在体外显著促进人脐静脉内皮细胞（HUVEC）增殖，且该作用与VEGF的作用具有相加性。在管状形成试验中，DLL4阻断和VEGF均显著增加了条索长度和分支点。单独的VEGF可增强HUVEC中ephrinB2的表达，而DLL4阻断可抑制这种增强。此外，当我们研究ephrinB2 RNA干扰对HUVEC管状形成的影响时，ephrinB2的敲低模拟了DLL4的作用。这些结果表明，ephrinB2在DLL4阻断引起的无效血管生成中起关键作用。
