EXPRESSION OF STROMELYSIN-1 IN HUMAN ASTROCYTOMA CELL-LINES

In a wide variety of tumor types, the expression of stromelysin 1 whic h is one of the matrix metalloproteinases (MMPs) has been shown to cor relate with tumor invasion. However, little is known about the distrib ution of stromelysin in human brain tumors. We have previously shown t hat a correlation exists between the type IV collagenases, tissue inhi bitor of metalloproteinase (TIMP)-1 and TIMP-2 transcripts and in vitr o invasiveness among 7 human astrocytoma cell lines. In the present st udy, we analyzed the expression of stromelysin 1 among the same panel of human astrocytoma cell lines and human fibroblasts by northern blot analyses and in situ hybridization. Northern blot analysis demonstrat ed that SF-126 and U87 MG expressed high level stromelysin 1 transcrip ts. Following heat shock stimulation, the stromelysin 1 transcript was up-regulated in U87 MG astrocytoma cells. In situ hybridization analy sis showed specific intracytoplasmic localization bf mRNA for stromely sin in these astrocytoma cell lines. By casein zymography, we have det ermined that both SF-126 and U87 MG secreted stromelysin 1 protein. We conclude that stromelysin 1 is expressed by certain human astrocytoma cell lines, and this study confirms the importance of continuing to c haracterize the proteolytic enzyme profile of these tumors to fully un derstand the molecular mechanisms involved in astrocytoma invasiveness .