HIF1A and neoplasm: In oxygenated tumor cells and endothelial cells, pyruvate stably oxidizes HIF-1α, thereby activating HIF-1 and triggering the transcription of vascular endothelial growth factor A (VEGF-A) in tumor cells and VEGF receptor 2 (VEGFR2) as well as basic fibroblast growth factor (bFGF) in endothelial cells (4).