HIF1a may decrease the expression of VEGF, then inhibit the angiogenesis. The researcher Vuorela using immunohistochemical method analysis found that patients with missed abortion had less expression of VEGF in trophoblast. Our study also demonstrated the expression of VEGF was statistically reduced and HIF-1a was negatively correlated with VEGF in missed abortion. When VEGF affects endothelial is tessellated among endothelial cells in the vessel area, where activation of angiogenesis takes place, the tip-cell specific characteristics are preferably acquired by endothelia cells devoid of Notch1 expression. It appears that the signaling system Dll4/Notch plays a key role in the regulation of angiogenesis.The mechanism of the Dll4/Notch associated signaling cascade that determines the differing behavior of endothelial cells is evidently connected with the intracellular signal transduction stimulated by VEGF. In hypoxic tissue, Dll4 signaling by tip cells suppress VEGFR2 expression in neighboring stalk cells via Notch pathway activation, inhibiting tip cell phenotype and ectopic sprout formation. The interplay of VEGFR2 and Notch signaling controls the angiogenic sprouting. Consistently, our study found that in induced abortion, there were positive correlations between HIF-1a, Dll4, Notch, and VEGFR2. These indicated that the low-oxygen environment, with the high expression of HIF-1a, leads to up-regulation of the ligand Dll4, while Dll4-mediated activation of Notch1 receptors in a neighboring cell activate VEGFR2 expression then promote the angiogenesis. Other Notch ligands or receptors may take part in the interaction with VEGF in the process of placental angiogenesis. However, in missed abortion, there were no correlations between Dll4 and VEGF/VEGFR1/VEGFR2, which indicated that the positive AbMole Gemifloxacin mesylate feedback between Dll4/Notch and HIF-1a-VEGF might be destroyed. In order to confirm the interaction of Dll4/Notch and VEGF pathway, HUVECs cultured on dishes were transfected with Dll4expressing plasmid. Compared with HUVECs transfected with GFP control plasmid, Dll4, Notch1 and VEGFR1 were upregulated while VEGF and VEGFR2 were down-regulated in Dll4 transfected HUVECs. In conclusion, our findings support the hypothesis that the association of HIF-1a-VEGF and Dll4/Notch1 may have a role in missed abortion. Further functional study will be necessary to determine the mechanisms of missed abortion. Neuroblastoma is a common childhood malignant tumor of neural crest origin, arising in the paravertebral sympathetic ganglia and the adrenal medulla. The clinical characteristics of neuroblastoma are heterogeneity, metastasis and high malignancy, resulting in lower survival rates in patients. During the past 15 years, treatment of NB has included high-dose 
chemotherapy accompanied by autologous stem cell transplantation. Once the NB recurrence the possibility survival of patients was very small.