INDUCTION OF FIBROBLAST 92 KDA GELATINASE TYPE-IV COLLAGENASE EXPRESSION BY DIRECT-CONTACT WITH METASTATIC TUMOR-CELLS

Previous studies have correlated release of the 92 kDa type IV collage nase/gelatinase by tumor cells in culture with metastatic potential. W e have now demonstrated that the ability of tumor cells that do not ex press the 92 kDa gelatinase to induce release of this metalloproteinas e from normal fibroblasts may also be associated with the metastatic p henotype. A transformed rat embryo cell line, 2.8, failed to release t he 92 kDa gelatinase alone in culture, but gave rise to metastatic tum ors whose explants contained the 92 kDa gelatinase. In contrast, a non -metastatic transformed cell line, RA3, did not express the 92 kDa gel atinase alone in culture or in tumor explants. To explore the mechanis ms that might govern host-tumor cell interactions in this system, we h ave studied the effects of co-culture of these transformed cell lines with rat embryo fibroblasts (REF) in culture. 92 kDa gelatinase expres sion was induced by coculture of 2.8 with REF, but co-culture of the n on-metastatic line RA3 with REF did not result in induction of the 92 kDa gelatinase. The 92 kDa gelatinase in these co-cultures was release d by the fibroblasts; methanol-fixed 2.8 cells induced 92 kDa gelatina se expression in REF, but fixed REF cells did not induce enzyme expres sion in 2.8 cells. This suggested that cell contact was required for i nduction, which was confirmed by showing that 92 kDa gelatinase induct ion in co-culture was abolished by separating REF from 2.8 by solute-p ermissive membranes. In addition, REF could not be stimulated to produ ce the 92 kDa gelatinase by 2.8-derived conditioned medium, by 2.8-der ived extracellular matrix, or by isolated matrix components. These dat a indicate that metastatic tumor cells can induce 92 kDa gelatinase ex pression in fibroblasts through a mechanism dependent upon cell contac t. In situ hybridization of nude mouse tumors derived from these trans formed cell lines revealed 92 kDa gelatinase expression in the stroma of tumors from 2.8, but not in tumors from RA3. Therefore, the experim ents based on in vitro co-culture of tumor cells and fibroblasts, toge ther with the in situ localization of mRNA to host cells, suggest that host production of the 92 kDa gelatinase may occur in response to dir ect contact with metastatic tumor cells.