Influence of bcl-2-related proteins on matrix metalloproteinase expression in a rat glioma cell line

The expression of bcl-2-related proteins has been shown to be a key element in tumoral malignancy. The degradation of the extracellular matrix (ECM) by specialized matrix metalloproteinases (MMPs) is another major step in tumor invasion and metastasis. We have examined, in a rat glioma cell line A15A5, the effect of the stable transfection of human bcl-2, bax and bcl-xl on MMPs expression. Using a zymographic assay, we found that all transfected cell lines expressed a gelatinase activity which is predominantly associated with MMP-9. In bcl-2 and bcl-xl transfected cells, the transcription of MMP-9 was decreased compared to that of control or bax transfected cells. In addition, in bax transfected A15A5, we observed a down regulation of TIMP-1, the inhibitor of MMP-9. These results suggest that the ratio between MMP-9 and its inhibitor TIMP-1 is tightly controlled in cells overexpressing bcl-2 related proteins (i.e., high ratio in bax transfected A15A5 and low ratio in bcl-2 transfected A15A5). However, MMPs secreted by bcl-2 transfected cells were still capable of hydrolyzing FasL present on human lymphocytes. Our results suggest that the expression of bcl-2 related proteins could participate in the regulation of MMP-9/TIMP-1 in gliomas.