P17.40GLIOMA ASSOCIATED MICROGLIAL MMP9 EXPRESSION IS UP REGULATED BY TLR2 SIGNALLING AND SENSITIVE TO MINOCYCLINE

OBJECTIVE: The invasiveness of malignant gliomas is one of the major obstacles in glioma therapy and the reason for the poor survival of patients. Glioma cells infiltrate into the brain parenchyma and thereby escape surgical resection. Glioma—associated microglia/macrophages (GAMs) support glioma infiltration into the brain parenchyma by increased expression and activation of extracellular matrix degrading proteases such as maxtrix—metalloprotease (MMP)—2, MMP—9 and MT1—MMP. METHODS: Using in vitro, ex vivo, and in vivo techniques, we identified TLR2 as the main TLR controlling microglial MMP9 expression and promoting microglia assisted glioma expansion. RESULTS: In this work we demonstrate that MMP—9 is predominantly expressed by GAMs in mouse and human glioma tissue but not by the glioma cells. Supernatant from glioma cells induced the expression of MMP—9 in cultured microglial cells. Using mice deficient for different toll—like receptors (TLRs) we identified TLR2/6 as the signalling pathway for the glioma induced upregulation of microglial MMP—9. Also in an experimental mouse glioma model, TLR2 deficiency attenuated the upregulation of microglial MMP—9. Moreover, glioma supernatant triggered an upregulation of TLR2 expression in microglia. Both, the upregulation of MMP—9 and TLR2 were attenuated by the antibiotic minocycline and a p38 MAPK antagonist in vitro. Minocycline also extended the survival rate of glioma bearing mice when given to the drinking water. CONCLUSIONS: Thus glioma cells change the phenotype of GAMs in a complex fashion using TLR2 as an important signalling pathway and minocycline further proved to be a potential candidate for adjuvant glioma therapy.