Expression of matrix metalloproteinase genes in transformed rat cell lines of high and low metastatic potential.

The enzymes that comprise the family of matrix metalloproteinases (MMPs) share the capacity to degrade extracellular matrix components. A large body of evidence indicates that certain members of this metalloproteinase gene family play critical roles in determining the malignant phenotype of solid tumors. We previously have derived transformed cell lines with vastly different metastatic potentials by transfecting different combinations of oncogenes into primary rat embryo cells. Conditioned medium from those cell lines was assayed by Western blot analysis for the production of four separate matrix metalloproteinases to see whether a correlation could be found between protease expression and the metastatic phenotype. The transformed rat embryo cell lines with high metastatic potential were found to produce high levels of the stromelysin 1 (MMP-3) and stromelysin 2 (MMP-10) proteases, while the nonmetastatic lines produced low or undetectable levels of these two enzymes. No correlation was seen between the metastatic phenotype of the cell lines and the level of expression of two other matrix metalloproteinases, the M(r) 72,000 type IV collagenase (MMP-2) and the M(r) 92,000 gelatinase (MMP-9). These data suggest that the differential regulation of the stromelysin proteases may contribute to the difference seen in the metastatic potential of these cell lines.