MMP9 and cancer: Among all metalloproteinases, the gelatinase group, consisting of MMP-2 (gelatinase A) and MMP-9 (gelatinase B), is considered to play an important role in malignant tumour development due to their ability to degrade extracellular matrix components, including collagens types IV, V, VII, X, XI and XIV, elastin, proteoglycans and fibronectin [20,21,22].