Adaptive adhesion systems mediate glioma cell invasion in complex environments.

Diffuse brain invasion by glioma cells prevents effective surgical or molecular-targeted therapy and underlies a detrimental outcome. Migrating glioma cells are guided by complex anatomical brain structures but the exact mechanisms remain poorly defined. To identify adhesion receptor systems and matrix structures supporting glioma cell invasion into brain-like environments we used 2D and 3D organotypic invasion assays in combination with antibody-, peptide- and RNA-based interference. Combined interference with ß1 and αV integrins abolished the migration of U-251 and E-98 glioma cells on reconstituted basement membrane; however, invasion into primary brain slices or 3D astrocyte-based scaffolds and migration on astrocyte-deposited matrix was only partly inhibited. Any residual invasion was supported by vascular structures, as well as laminin 511, a central constituent of basement membrane of brain blood vessels. Multi-targeted interference against ß1, αV and α6 integrins expressed by U-251 and E-98 cells proved insufficient to achieve complete migration arrest. These data suggest that mechanocoupling by integrins is relatively resistant to antibody- or peptide-based targeting, and cooperates with additional, as yet unidentified adhesion systems in mediating glioma cell invasion in complex brain stroma.