Malignant gliomas are the most common primary brain tumors in adults and the second most common tumor in children. Gliomas are associated high morbidity and mortality because these tumors are highly invasive into surrounding brain tissue, making complete surgical resection impossible. Glial cell line-derived neurotrophic factor (GDNF) has been identified as a potent neurotrophic factor in a variety of neuronal cell populations. However, the molecular mechanisms and pathologic roles underlying GDNF-induced glioma migration remain unclear. In this study, we found that application of recombinant human GDNF enhances the migration of U87 and U251 cells but not C6 cells. In addition, we found that the expression of matrix metalloproteinase-13 (MMP-13) mRNA, protein and secretion increase in response to GDNF stimulation. The GDNF-induced increase in cell migration was antagonized by MMP-13 neutralizing antibody or silencing MMP-13. We then examined the involvement of mitogen-activated protein kinases (MAPKs) in glioma cell migration induced by GDNF. GDNF-induced MMP-13 expression and glioma migration were attenuated by MEK/extracellular signal-regulating kinase (ERK) and c-Jun N-terminal protein kinase (JNK) inhibitors, as well as ERK and JNK dominant-negative mutants. Treatment with GDNF-induced MEK/ERK and JNK/c-Jun activation and increased AP-1 DNA binding activity in a time-dependent manner. Treatment with AP-1 inhibitors (tanshinone IIA and curcumin) also reduced GDNF-induced glioma cell migration. In migration-prone sublines, cells with greater migration ability had higher GDNF expression. These results indicate that GDNF enhances migration of glioma cells through the increase of MMP-13 production and is mainly regulated by the MEK/ERK and JNK, c-Jun and AP-1 pathways.
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