TIMP3 (tissue inhibitor of metalloproteinases 3), along with family members TIMP1, TIMP2, and TIMP4, are inhibitors of the matrix metalloproteinases (MMPs), a group of peptidases involved in degradation of the extracellular matrix (ECM). An imbalance between MMPs and the associated TIMPs may play a significant role in the invasive phenotype of malignant tumors. TIMP's inhibit the proteolytic invasiveness of tumor cells and normal placental trophoblast cells. TIMP-3 may be involved in regulating trophoblastic invasion of the uterus as well as in regulating remodeling of the extracellular matrix during the folding of epithelia, and in the formation, branching and expansion of epithelial tubes.