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The Notch signaling pathway and the delta-like 4 ligand (DLL4) play key roles in embryonic vascular development. Many of the pathways involved in embryonic vascular development also play important roles in tumor angiogenesis. In this study, we assessed the expression of DLL4 in primary renal cancer and investigated the biological function of DLL4 in primary endothelial cells. Using real-time quantitative PCR and in situ hybridization, we showed that the expression of DLL4 was up-regulated within the vasculature of clear cell-renal cell carcinoma almost 9-fold more than normal kidney and was correlated with the expression of vascular endothelial growth factor (VEGF). The expression of DLL4 in endothelial cells was up-regulated by VEGF and basic fibroblast growth factor synergistically, and by hypoxia through hypoxia-inducible factor 1alpha. Down-regulation of DLL4 expression with RNA interference led to decreased expression of HEY1 and EphrinB2, and the inhibition of endothelial cell proliferation, migration, and network formation, all of which are important processes in tumor angiogenesis. The inhibition of proliferation occurred via the induction of cell cycle arrest in G0-G1 by increased expression of p21 and decreased phosphorylation of retinoblastoma. We conclude that an optimal window of the DLL4 expression is essential for tumor angiogenesis and that selective modulation of the DLL4 expression within human tumors may represent a potential novel antiangiogenic therapy.

Original publication

DOI

10.1158/0008-5472.CAN-05-1208

Type

Journal article

Journal

Cancer Res

Publication Date

01/10/2005

Volume

65

Pages

8690 - 8697

Keywords

Blood Proteins, Cell Growth Processes, Cell Hypoxia, Cell Movement, Endothelial Cells, Endothelium, Vascular, Humans, In Situ Hybridization, Intercellular Signaling Peptides and Proteins, Kidney Neoplasms, Neovascularization, Pathologic, RNA, Small Interfering, Umbilical Veins, Up-Regulation