T-antigen inhibits metalloproteinase expression and invasion in human placental cells transformed with temperature-sensitive Simian virus 40

Cellular transformation frequently induces invasive behavior in cells. The effects of simian virus (SV) 40 T-antigen on the relationship between metalloproteinase expression and cell invasion were tested in human placental trophoblast-like cells transformed with a temperature-sensitive form of the SV40 virus, tsA 30. As a comparison, metalloproteinase expression was also tested in human fibroblasts transformed with wild-type SV40 T-antigen. When tsA 30.1 cells were cultured at the nonpermissive temperature for T-antigen expression, 40 degrees C, they expressed abundant metalloproteinases, including the 72 kDa gelatinase A (MMP-2), the 92 kDa gelatinase B (MMP-9) and stromelysin-1 (MMP-3). In contrast, tsA30.1 cells cultured at the permissive temperature of 33 degrees C produced T-antigen and showed markedly decreased amounts of these proteinases. A similar suppression was seen in the human fibroblasts transformed with wild-type T-antigen. The tsA 30 cells cultured at either temperature expressed a similar amount of tissue inhibitor of metalloproteinases-1 and -2. Cell invasion assays were performed to determine whether the altered ratio of proteinases to inhibitors under these conditions affected the extracellular matrix-degrading and invasive characteristics of the cells. In their differentiated state at the nonpermissive temperature for T-antigen expression, tsA 30.1 cells were highly invasive, whereas at the permissive temperature they were not invasive. Therefore, the expression of T-antigen suppressed metalloproteinase production and changed the cells from an invasive to a noninvasive phenotype. We conclude that in tsA30.1 cells, SV40 T-antigen expression suppresses metalloproteinase production, thereby decreasing the rate of degradation of the extracellular matrix. Taken together, these data indicate that invasive behavior is related to proteinase gene expression rather than to transformation by T-antigen. Function-blocking antibody to beta(1) integrins did not affect adhesion of tsA 30.1 cells but inhibited invasion at the nonpermissive temperature, even though they continued to secrete proteinases. This observation indicates that beta(1) integrin-mediated cell migration is required along with proteinases for cells to be invasive.