Inhibition of invasion and induction of apoptotic cell death of cancer cell lines by overexpression of TIMP-3

Dysregulation of matrix degrading metalloproteinase enzymes (MMPs) leads to increased extracellular matrix turnover, a key event in the local invasion and metastasis of many tumours, The tissue inhibitors of metalloproteinase s (TIMPs) limit the activity of MMPs, which suggests their use in gene ther apy. We have previously shown that overexpression of TIMP-1, 2 or -3 inhibi ts vascular smooth muscle and melanoma cell invasion, while TIMP-3 uniquely promotes apoptosis. We have therefore sought to determine whether TIMP-3 c an inhibit invasion and promote apoptosis in other cancer cell types, Adeno viral-mediated overexpression of TIMP-3 inhibited invasion of HeLa and HT10 80 cells through artificial basement membrane to similar levels as that ach ieved by TIMP-1 and -2. However, TIMP-3 uniquely promoted cell cycle entry and subsequent death by apoptosis. Apoptosis was confirmed by morphological analysis, terminal dUTP nick end labelling (TUNEL) and flow cytometry, The apoptotic phenotype was mimicked by addition of exogenous recombinant TIMP -3 to uninfected cultures demonstrating that the death signal is initiated extracellularly and that a bystander effect exists. These results show that TIMP-3 inhibits invasion in vitro and promotes apoptosis in cancer cell ty pe of differing origin. This clearly identifies the potential of TIMP-3 for gene therapy of multiple cancer types.