HIF1A and neoplasm: However, arterial occlusion in tumor tissues may trigger hypoxia and hence contribute to the over-expression of hypoxia-inducible factor 1 (HIF-1α) and vascular endothelial growth factor (VEGF) [29, 30].While the over-expression of HIF-1α could cause tumor progression, invasion and metastasis [31, 32], VEGF inhibits the apoptosis of vessel endothelial cells and promotes proliferation [33, 34] and it triggers tumor progression by stimulating the formation of blood vessels [35].