Modulation of phorbol ester-induced regulation of matrix metalloproteinases and tissue inhibitors of metalloproteinases by SB203580, a specific inhibitor of p38 mitogen-activated protein kinase.

OBJECT: Expression of matrix metalloproteinases (MMPs) has been postulated to play a central role in brain tumor invasion; however, its underlying mechanism is not yet fully understood. In the present study, by assessing the effect of a specific p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, on the secretion of MMPs and in vitro invasion of various glioma cells, the authors attempt to define the role of the p38 MAPK pathway in the regulation of MMPs and tissue inhibitors of metalloproteinases (TIMPs) activated by phorbol ester (phorbol-12-myristate-13-acetate [PMA]) in the D54 human glioblastoma cell line.

METHODS: The activation of MAPKs was determined using Western blot analysis after addition of phospho-specific antibodies against these kinases, the status of MMPs and TIMPs was analyzed using gelatin zymography and Western blot analysis, and the invasion rate of D54 cells and other glioma cells was analyzed using a modified Boyden chamber assay. Treatment of D54 cells with PMA activated two distinct MAPKs, extracellular signal-regulated kinase (ERK) 1/2 and p38 MAPK, but not c-Jun N-terminal kinase/stress-activated protein kinase. Induction of MMP-9 production and MMP-2 activation by PMA were blocked by SB203580, a specific inhibitor of p38 MAPK, but not by PD98059, a specific inhibitor of ERK 1/2. In addition, PMA-induced downregulation of TIMP-1 and TIMP-2 secretion and upregulation of the membrane type I MMP, a major activator of MMP-2 on the cell surface, were reversed by SB203580 in these cells; the PMA-induced increase of invasion in vitro decreased when SB203580 was added to the top compartment of a modified Boyden chamber; and the inhibitor also reduced the MMP secretion and PMA-induced in vitro invasion in various glioma cell lines.

CONCLUSIONS: These results indicate that activation of p38 MAPK by PMA plays a central role in the regulation of MMPs and TIMPs in D54 cells, which has a major influence in tumor invasion and metastasis. Furthermore, inhibition of p38 MAPK by SB203580 blocked the secretion of MMPs and in vitro invasion of various glioma cells, underscoring a possible role of p38 MAPK inhibitors as antiinvasive and/or antimetastatic agents of malignant gliomas.