Thrombin induces increased expression and secretion of angiopoietin-2 from human umbilical vein endothelial cells.
Angiogenesis is required for tumor growth and metastasis. It has recently been suggested that thrombin is a potent promoter of angiogenesis. We therefore examined the possibility that thrombin could be inducing the expression of angiopoietin-2 (Ang-2), necessary for remodeling. Human umbilical vein endothelial cells were incubated with or without thrombin (1 U/mL) for 1 to 24 hours and then examined for messenger RNA (mRNA) by Northern analysis. Enhanced mRNA expression (about 4-fold over baseline) was noted at 4 hours. Enhanced expression of Ang-2 mRNA was secondary to enhanced transcription (about 4-fold), with no effect on stabilization. Enhanced Ang-2 mRNA transcription was inhibited by H7 and PD98059, indicating the requirement of serine/threonine kinases as well as the mitogen-activated protein kinase pathway. Up-regulation of mRNA was associated with enhanced Ang-2 protein synthesis and secretion as assayed by immunoblot. Thrombin-induced secreted Ang-2 inhibited the binding of recombinant (35)S-Ang-1 to its Tie-2-Fc receptor, demonstrating functionality. Hirudin reversed this effect, demonstrating thrombin specificity. Thus, thrombin-induced tumorigenesis and metastasis is associated with enhanced Ang-2 protein synthesis and secretion via enhanced transcription of Ang-2. This could help explain how thrombin promotes angiogenesis.
Huang
Yao-Qi
YQ
Department of Medicine and Kaplan Cancer Center, New York University Medical School, New York, NY 10016, USA. huangy02@med.nyu.edu
Li
Jian-Jun
JJ
Hu
Liang
L
Lee
Merlin
M
Karpatkin
Simon
S
D042702:Angiopoietin-2; D003029:Coagulants / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D009389:Neovascularization, Pathologic / Q000209:etiology; D010770:Phosphotransferases / Q000037:antagonists & inhibitors / Q000502:physiology; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects; D013917:Thrombin / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects; D014471:Umbilical Veins / Q000166:cytology; D015854:Up-Regulation / Q000187:drug effects
D042702:Angiopoietin-2; D003029:Coagulants; D004791:Enzyme Inhibitors; D011506:Proteins; D012333:RNA, Messenger; D010770:Phosphotransferases; D013917:Thrombin