BACKGROUND:Tissue inhibitor of metalloproteinases (TIMPs) can restrain the tumor growth by their protein property and matrix metalloproteinases (MMPs) inhibition. There are currently four known TIMP family members-TIMP-1, 2, 3, 4. We determined whether increasing levels of TIMP-3 expression could suppress the malignant phenotype of human hepatocarcinoma cell line HCC-7721. METHODS:A recombinant expression vector, which contained full-length cDNA of human TIMP-3, was constructed and transfected into the human hepatocarcinoma cell line HCC-7721 by the lipofectamine technique. In vitro and in vivo tests such as Western blotting, immunohistochemistry as well as xenografting in nude mice were used to analyze expression levels of TIMP and MMP, and changes in malignant phenotype after the gene transfection. RESULTS:TIMP-3 expression in TIMP-3 gene-transfected HCC-7721 cells was upregulated as assessed by Western blotting. The ability of in vitro invasion through a Boyden chamber was signiifcantly decreased compared to controls. Following subcutaneous injection into nude mice, the TIMP-3 transfected cells suppressed primary tumor growth, as characterized by reduced tumor weight, size and microvasculature as well as maintaining the extracellular matrix. CONCLUSION:The results suggest that upregulation of TIMP-3 expression in HCC-7721 cells inhibits invasion capacity in vitro as well as tumorigenic and metastatic potential in nude mice.