Tissue inhibitor of metalloproteinase-1 inhibits apoptosis of human breast epithelial cells.

The signaling pathways critical for cell survival are mediated in part by the composition and integrity of the extracellular matrix and the action of its components on specific cell adhesion receptors. Withdrawal of anchorage-dependent epithelial cells from their association with ECM results in apoptotic cell death. Consistently, the matrix metalloproteinases (MMPs) or their inhibitors (TIMPs) have been suggested to regulate apoptosis. In this report, we investigated whether bcl-2 inhibition of apoptosis involves regulation of TIMP expression. We have found that bcl-2 overexpression induces TIMP-1 expression in breast epithelial cell lines (MCF10A, MCF10AneoT.TG3B, and MCF-7), whereas it has no effect on TIMP-2 expression. We demonstrated that TIMP-1 inhibits cell death induced by hydrogen peroxide, Adriamycin, or X-ray irradiation. In addition, TIMP-1 overexpression inhibits apoptosis after the loss of cell adhesion (anoikis) in MCF10A cells, suggesting that the antiapoptotic activity of TIMP-1 does not depend on its ability to stabilize cell-matrix interactions. We also showed that TIMP-1 overexpression is associated with constitutive activation of focal adhesion kinase, a signaling molecule known to be critical for the cell survival pathway.