INDUCTION OF M(R)-92,000 TYPE-IV COLLAGENASE EXPRESSION IN A SQUAMOUS-CELL CARCINOMA CELL-LINE BY FIBROBLASTS

A previous investigation (Matsumoto et al., J. Oral Pathol. Med., Ig: 498-501, 1989) has shown that the in vitro invasion of a collagen gel by squamous cell carcinoma can be substantially augmented in the prese nce of fibroblasts. Therefore, we undertook a study to determine if th e production of collagenase(s) by a squamous cell carcinoma cell line, UMSCC-1, was up-regulated by fibroblasts. Cocultivation of UM-SCC-I c ells with MDA-TU-138 fibroblasts, both established from the oral cavit y, resulted in a dose-dependent increase in the activity of a M(r) 92, 000 gelatinase as shown by zymography. Augmented M(r) 92,000 gelatinas e activity was a consequence of the stimulation of the UM-SCC-1 cells by a soluble, fibroblast-derived factor since this effect could be rep roduced with fibroblast-conditioned medium but not with glutaraldehyde -fixed fibroblasts. The increased M(r) 92,000 gelatinolytic activity c ould be accounted for by an increase in M(r) 92,000 type IV collagenas e (MMP-9) protein, as demonstrated by Western blotting for this metall oproteinase. Trypsin treatment of the fibroblast-conditioned medium ab olished its ability to increase, MMP-9 secretion by UM-SCC-1 cells. Fu rthermore, fractionation of the fibroblast-conditioned medium revealed a M(r) 3,000-10,000 soluble factor(s) which was responsible for the a ugmented production of MMP-9 by UM-SCC-1 cells. To determine if the in creased production of MMP-9, in response to the fibroblasts, was a con sequence of increased promoter activity, UM-SCC-1 cells were transient ly transfected with a chloramphenicol acetyltransferase reporter drive n by the MMP-9 promoter and plated on plastic or on a monolayer of MDA -TU-138 fibroblasts. A 4-5-fold stimulation of MMP-9 promoter activity was observed with UM-SCC-1 cells plated with the MDA-TU-138 fibroblas ts, when compared with similarly transfected cells recultured on plast ic. In conclusion, we have demonstrated that MMP-9 expression in a squ amous cell carcinoma cell line is augmented by a fibroblast-derived pr otein(s). This finding indicates a role for stromal cells in the regul ation of MMP-9 expression in squamous cell carcinoma. The ability of f ibroblasts to regulate MMP-9 expression in tumor cells in vitro may ex plain the observation that the amount of M(r) 92,000 type IV collagena se mRNA in tumor cells is highest at the tumor:stromal interface of re sected squamous cell carcinoma.