However, during hypoxia the two enzymes are inactive, thus HIF-1α mediates the transcription of thousands of genes in BC such as MMP-9, VEGF [81], glucose transporter 1 (GLUT-1), TGF-β, CXCR4/its ligand CXCL12, and Bcl-2 [82]. This evidence concerns the gene MMP9 and breast cancer.