Ezrin-dependent promotion of glioma cell clonogenicity, motility, and invasion mediated by BCL-2 and transforming growth factor-beta 2

Ezrin belongs to the ezrin-radixin-moesin family proteins, which cross-link actin cytoskeleton and plasma membrane. Malignant glioma cells are paradig matic for their strong migratory and invasive properties. Here, we report t hat the expression of dominant-negative ezrins inhibits clonogenicity, migr ation, and invasiveness of human malignant glioma cells. Furthermore, domin ant-negative ezrins block hepatocyte growth factor (HGF)-mediated stimulati on of clonogenicity and migration, without altering HGF-induced protein kin ase B/Akt and focal adhesion kinase phosphorylation. Glioma cells expressin g dominant-negative ezrins exhibit a shift of the BCL-2/BAX rheostat toward apoptosis, reduced alpha (v)beta (3) integrin expression and reduced matri x metalloproteinase (MMP) expression and activity. These changes are associ ated with a dramatic loss of transforming growth factor beta (2) (TGF-beta (2)) release. Exogenous supplementation of TGF-beta (2) overcomes the inhib itory effects of dominant-negative ezrins on migration and clonogenicity. A neutralizing TGF-beta (2) antibody mimics the effects of dominant-negative ezrins on clonogenicity and migration. Exogenous HGF markedly induces TGF- beta (2) protein levels, and a neutralizing TGF-beta (2) antibody abolishes the HGF-mediated increase in glioma cell motility. Finally, TGF-beta (2) d oes not modulate BCL-2 or BAX expression, but BCL-2 gene transfer increases the levels of latent and active TGF-beta (2). Intracranial xenografts of U 87MG glioma cells transfected with the dominant-negative ezrins in athymic mice grow to significantly smaller volumes, and the median survival of thes e mice is 50 d compared with 28 d in the control group. These data define a novel pathway for HGF-induced glioma cell migration and invasion, which re quires ezrin, changes in the BCL-2/BAX rheostat, and the induction of TGF-b eta (2) expression in vitro, and underscore the important role of HGF signa ling in vivo.