Extracellular matrix metalloproteinases (MMPs) are a family of endopeptydases 
which recquire a zinc ion at their active site, for proteolityc activity. There 
are six members of the MMP family: matrilysins, collagenases, stromelysins, 
gelatinases, membrane MMPs and other MMPs. Activity of MMPs is regulated at the 
level of gene transcription, mRNA stability, zymogene proteolitic activation, 
inhibition of an active enzyme and MMP degradation. Tissue inhibitors of 
metalloproteinases (TIMPs) are main intracellular inhibitors of MMPs. Host cells 
can be stimulated by tumor cells to produce MMPs by secreted interleukins, 
interferons, growth factors and an extracellular matrix metalloproteinase 
inducer (EMMPRIN). MMPs are produced by tumor cells, fibroblasts, macrophages, 
mast cells, polimorphonuclear neutrophiles (PMNs) and endothelial cells (ECs). 
MMPs affect many stages of tumor development, facilitating its growth through 
promoting tumor cells proliferation, invasion and migration, new blood vessels 
formation and blocking tumor cells apoptosis. MMPs can promote tumor development 
in several ways. ECM degradation results in release of peptide growth factors. 
Growth factors linked with cell surface or binding proteins can also be 
liberated by MMPs. MMPs can indirectly regulate integrin signalling or cleave 
E-cadherins, facilitating cell migration. MMPs support metastasis inducing an 
epithelial to mesenchymal transition (EMT). MMP also support transendothelial 
migration. MMPs support angiogenesis by releasing pro-angiogenic factors and 
degrading ECM to support ECs migration. Cell surface growth factor receptors are 
also cleaved by MMPs, which results in inhibition of tumor development, so is 
release of anti-angiogenic factors from ECM. 