MMP9 and central nervous system cancer: Our current study used glioma cell lines expressing intermediate levels of endogenous Bmi-1 as an experimental model, and by examining the effect of knocking down endogenous Bmi-1, or overexpressing ectopic Bmi-1, on the phenotype of glioma cells, we have identified that Bmi-1 activates NF-kappaB and subsequently upregulates MMP-9 expression, leading to increased migration and invasion of glioma cells.