HIF1A and breast cancer: Other studies reported that HIF-1α and HIF-2α negatively regulated the transcription of Fas-associated death domain protein (FADD) [22], cystic fibrosis transmembrane conductance regulator [23] and nucleoside transporter 2 [24] in epithelial cells, and of tissue factor pathway inhibitor (TFPI) in endothelial cells [25] and breast cancer MCF-7 cell line [14].