Transforming growth factor-beta1 modulates matrix metalloproteinase-9 production through the Ras/MAPK signaling pathway in transformed keratinocytes.

Mouse transformed keratinocytes cultured in the presence of transforming growth factor-beta1 (TGF-beta1) acquire a set of morphological and functional properties giving rise to a more motile phenotype that expresses mesenchymal markers. In this work, we present evidence showing that TGF-beta1 stimulates cellular production of MMP-9 (Gelatinase B), a metalloproteinase that plays an important role in tumoral invasion. Our results demonstrate that TGF-beta1stimulates MMP-9 production and MMP-9 promoter activity in a process that depends of the activation of the Ras-ERK1,2 MAP kinase pathway. The latter was demonstrated by cellular transfection of TGF-beta1-sensitive cells with a RasN17 mutant gene, using PD 098059, a MEK 1,2 inhibitor, and treating cells with anti-sense oligodeoxinucleotides. The enhanced MMP-9 production proved to be an important factor in the acquisition of migratory and invasive properties as shown by the use of a specific inhibitor of MMP-9 (GM6001) that inhibits the TGF-beta1-stimulated invasive and migratory properties of these transformed keratinocytes.