The p38 SAPK Pathway Regulates the Expression of the MMP-9 Collagenase via AP-1-Dependent Promoter Activation

• DOI: 10.1006/excr.2001.5374
• Publication Date: 2002-10-06T19:48:37Z
• Authors: Christian Simon; Matthias Simon; Goran Vucelic; M.John Hicks; Peter Karl Plinkert; Assen Koitschev; Hans Peter Zenner
• Keywords: 0301 basic medicine; Base Sequence; Proto-Oncogene Proteins c-jun; Pyridines; Imidazoles; MAP Kinase Kinase 6; Protein Structure, Tertiary; Gene Expression Regulation, Neoplastic; 03 medical and health sciences; Matrix Metalloproteinase 9; Genes, Reporter; Neoplasms; Calcium-Calmodulin-Dependent Protein Kinases; Mutation; Carcinogens; Humans; Protein Isoforms; Neoplasm Invasiveness; Enzyme Inhibitors; Mitogen-Activated Protein Kinases; Promoter Regions, Genetic; Signal Transduction

The invasive phenotype of cancers critically depends on the expression of proteases such as the M(R) 92,000 type IV collagenase (MMP-9). Several growth factors and oncogenes were found to increase promoter activity and as a consequence protease expression. This frequently requires the activation of the transcription factor AP-1 by signal transduction cascades such as the ERK and JNK pathways. We have previously demonstrated that the tumor promoter TPA can induce MMP-9 expression via a third signaling cascade, the p38 pathway. Considering that TPA is a potent activator of AP-1, we hypothesized that this transcription factor might also be required for p38 pathway-dependent MMP-9 regulation. While dominant negative p38 and MKK-6 mutants reduced MMP-9 promoter activity in CAT assays, a construct encoding an activating mutation in the MKK-6 protein potently stimulated it. This was mediated via 144 bp of the 5'flanking region of the wild-type promoter, which contains an AP-1 site at -79. Both point mutations in this motif and the expression of a c-jun protein lacking its transactivation domain and therefore acting as a dominant negative AP-1 mutant abrogated MKK-6-dependent promoter stimulation. Finally SB 203580, a specific p38 pathway inhibitor, reduced MMP-9 expression/secretion and in vitro invasion of cancer cells. Thus, our results provide evidence that also the third SAPK/MAPK signaling cascade, the p38 signal transduction pathway, stimulates MMP-9 expression in an AP-1-dependent fashion.