TRANSCRIPTIONAL ACTIVATION OF THE MATRIX METALLOPROTEINASE-9 GENE IN AN H-RAS AND V-MYC TRANSFORMED RAT EMBRYO CELL-LINE

The 92 kd type IV collagenase/gelatinase (MMP-9) is important in media ting basement membrane and extracellular matrix degradation in metasta sis. Because MMP-9 is made in tumor cells, but not in quiescent normal cells, we wished to identify the transcriptional elements responsible for its synthesis in tumor cells. We chose to characterize transcript ional regulation of the MMP-9 gene in a highly metastatic H-ras and v- myc transformed rat embryo cell line which overexpresses MMP-9. Using transient transfection of reporter gene constructs containing either 5 '-deleted or mutated MMP-9 promoter fragments, as well as electrophore tic mobility shift assays, we have demonstrated that multiple transcri ption factor consensus binding motifs in the promoter, including those for NF kappa B, SP-1, Ets, AP-1, and a retinoblastoma binding element , participate in transcriptional regulation of MMP-9 expression in thi s cell line. Also, deletion of an alternating purine-pyrimidine tract in the downstream promoter was found to decrease transcriptional activ ity, suggesting that promoter conformation may be important in MMP-9 r egulation. Thus multiple pathways leading to activation of NF kappa B, SP-1, Ets, AP-1, and retinoblastoma binding factors in tumor cells al l may contribute to MMP-9 transcription and hence to metastasis.