BCL-2-induced glioma cell invasiveness depends on furin-like proteases

Migration and invasion are prerequisites for the neoplastic phenotype of malignant glioma. Ectopic expression of BCL-2 enhances migration and invasion of glioma cells and promotes their synthesis of transforming growth factor-β2 (TGF-β2). We here report that BCL-2-expressing cells show enhanced expression and activity of the proprotein convertase, furin, which processes metalloproteinases (MMP) and TGF-β. Consistent with a biological role for a BCL-2-dependent increase in furin-like protease (FLP) activity, BCL-2-expressing cells exhibit enhanced MMP activity. Both a pseudosubstrate furin inhibitor, decanoyl-Arg-Val-Lys-Arg-chloromethylketone (dec-RVKR-cmk), or alpha 1-anti-trypsin Portland (PDX), a recombinant furin-inhibitory protein, suppress constitutive and BCL-2-mediated MMP activity and invasion. This inhibition is not overcome by TGF-β or hepatocyte growth factor (HGF). A neutralizing TGF-β antibody attenuates, but not abrogates, the invasive properties conferred by exogenous expression of BCL-2, whereas the MMP inhibitor o-phenantroline (o-PA) abolishes the pro-invasive action of BCL-2. Exogenous HGF results in enhanced, and expression of dominant-negative ezrin in reduced, FLP activity, and dec-RVKR-cmk blunts the HGF-induced expression of mature TGF-β2. Consequently, HGF and BCL-2 family proteins use a furin-dependent pathway to promote invasion via TGF-β and MMP in human malignant glioma cells and the pro-invasive properties of TGF-β require furin- dependent MMP activity.