TUMOR-CELL CONTACT MEDIATED TRANSCRIPTIONAL ACTIVATION OF THE FIBROBLAST MATRIX METALLOPROTEINASE-9 GENE - INVOLVEMENT OF MULTIPLE TRANSCRIPTION FACTORS INCLUDING ETS AND AN ALTERNATING PURINE-PYRIMIDINE REPEAT

The 92-kDa type IV collagenase (MMP-9) is a metalloproteinase frequent ly localized in both tumor stroma and in tumor cells, particularly at the tumor invasion front. To explore the factors regulating transcript ional activation of MMP-9 in stromal cells, we used a model system in which fibroblast MMP-9 expression can be upregulated by cell-cell cont act with metastatic transformed rat embryo cells. Using transient tran sfection of reporter gene constructs containing 5'-deleted or mutated MMP-9 promoter fragments, as well as electrophoretic mobility shift as says, the upstream NF kappa B, SP-1, and Ets sites and the downstream AP-1 site and retinoblastoma binding element were shown to be necessar y for basal transcriptional activity of fibroblast MMP-9. In contrast only Ets or SP-1 appeared to be involved in contact-mediated induction of MMP-9. Mutation of the upstream AP-1 site increased both basal and contact-stimulated promoter activation. Deletion of the alternating p urine-pyrimidine repeat in the downstream promoter decreased transcrip tional activity. Together these findings suggest that Ets and SP-1 are the central transcriptional activators of MMP-9 gene expression in fi broblasts specifically responding to tumor cell contact, and that prom oter conformation may regulate MMP-9 expression. (C) 1998 Rapid Scienc e Ltd.