The Mcchnism Studies Of Endostatin On Both Vascular Endothelial Cell And Hemangioendothelioma

Objective:Hypoxia-inducible factor-1α (HIF-1α) plays a key role in tumor progression and aggressiveness by regulating the expression of a series of genes involved in angiogenesis and anaerobic metabolism. Recent studies reported that the transcription level of HIF-1α can be downregulated by endostatin. However, the molecular mechanism of how endostatin represses HIF-la expression remains obscure. This study elucidates the mechanism by which nuclear-translocated endostatin suppresses HIF-la activation through disrupting Zn(II) homeostasis.Methods:Both qRT-PCR and Westen Blot assay detect HIF-1α expression at both mRNA and protein levels after endostatin treatment. RNA interference and ectopic expression assay verify the fuction of importin al/β1and nucleolin in endostatin nuclear translocation.Co-IP assary verify the function of Zn(II) in the the interaction between CBP/p300and HIF-1α.Results:We reported that endostatin downregulates HIF-1α expression at both mRNA and protein levels. Blockage of endostatin nuclear translocation by RNA interference of importin α1/β1or ectopic expression of mNCLmut (NLS-deficient mutant nucleolin) in HUVECs co-transfected with si-nucleolin compromised endostatin-reduced HIF-1α expression. Nuclear-translocated apo-endostatin, but not holo-endostatin, significantly disrupts the interaction between CBP/p300and HIF-1α through disturbing Zn(Ⅱ) homeostasis, which leads to the transcription inactivation of HIF-1α.Conclusion:Our results reveal mechanistic insights into how nuclear-translocated endostatin downregulates HIF-1α activation and provides a new way to investigate the function of endostatin in endothelia cells. Objective:Hemangioendotheliomas can be repressed by various anti-angiogenic agents in animal models. It is unclear whether the agents target hemangioendothelioma cells directly or indirectly. This study elucidates the mechanism by which endostatin inhibits hemangioendothelioma progression.Methods:Expression of the endostatin receptors nucleolin and integrin α5β1in hemangioendothelioma was assessed by immunohistochemistry. The effects of endostatin on the EOMA cells were evaluated by proliferation and apoptosis assays and by angiogenesis array screening. This revealed the contribution of the chemokine CXCL1to hemangioendothelioma progression, which was explored in vitro and in vivo. The clinical relevance of CXCL1expression in hemangioendothelioma was also evaluated using tissue array.Results:EOMA cells express nucleolin and integrin α5βl and bind endostatin. Endostatin does not alter proliferation or hypoxia-induced apoptosis in EOMA cells but it does impair the pro-angiogenic capacity of the cells. Endothelial cell migration is induced by CXCL1produced by EOMA cells and endostatin downregulates CXCL1production by inactivating its transcriptional factor, NF-κB. In vivo, the knockdown of CXCL1significantly impairs EOMA cell growth in nude mice; endostatin has no effect when CXCL1is overexpressed. A strong correlation was observed between CXCL1levels and hemangioendothelioma occurrence in patients. CXCL1, which is responsible for hemangioendothelioma progression by stimulating angiogenesis, is impaired by endostatin via inactivation of NF-κB in an animal model.Conclusion:In vascular lesions in patients, CXCL1expression is a negative prognostic factor. CXCL1-inhibting agents such as endostatin may constitute a useful approach to treat the malignant or intermediate vascular lesions.