Hypoxia inducible factor-1α (HIF-1α) plays a key role in tumour adaptation to the hypoxic microenvironment by stimulating the production of pro-angiogenic factors, such as vascular endothelial growth factor (VEGF) and matrix melalloproteinases MMP-2 and MMP-9, and by inducing the expression of enzymes participating in anaerobic metabolism. Here, MMP9 is linked to neoplasm.