Abstract
TIMP-3 is one of four tissue inhibitors of matrix metalloproteinases, the endogenous inhibitors of the matrix metalloproteinase enzymes. These enzymes have an important role in metastasis, in the invasion of cancer cells through the basement membrane and extracellular matrix. TIMP-1, -2 and -4 both promote and inhibit tumour development, in a context-dependent manner, however TIMP-3 is consistently anti-tumourigenic. TIMP-3 is also the only insoluble member of the family, being either bound to the extracellular matrix or the low density lipoprotein-related protein-1, through which it can be endocytosed. Levels of TIMP-3 have also been shown to be regulated by micro RNAs and promoter hypermethylation, resulting in frequent silencing in many tumour types, to the extent that its expression has been suggested as a prognostic marker in some tumours, being associated with lower levels of metastasis, or better response to treatment. TIMP-3 has been shown to have anti-metastatic effects, both through inhibition of matrix metalloproteinases and ADAM family members and downregulation of angiogenesis. This occurs via interactions with receptors including VEGF, via modulation of signaling pathways and due to protease inhibition. TIMP-3 has also been shown to reduce tumour growth rate, most often by inducing apoptosis by stabilisation of death receptors. A number of successful mechanisms of delivery of TIMP-3 to tumour or inflammatory sites have been investigated in vitro or in animal studies. It may therefore be worthwhile further exploring the use of TIMP-3 as a potential anti-metastatic or anti-tumorigenic therapy for many tumour types.