HIF1A and neoplasm: Inhibits VEGF expression via promoting HIF-1α proteasome degradation pathway and blocks VEGFR-2 activation and the transduction of its downstream signaling in human umbilical vein endothelial cells (HUVECs), MCF-7 cells and MDA-MB-231 cells and in vivo tumor xenograft of MDA-MB-231 cells