gms | German Medical Science

Objective: Despite multimodal treatment survival in primary glioblastoma still remains poor. One of the main difficulties treating these tumors is caused by invasion of glioblastoma cells into surrounding and distant brain tissue. The aim of this study is to determine whether glioblastoma cells can enlist exosome-mediated processes to influence extracellular matrix deposition by surrounding glial cells in a way that might influence infiltrative invasion of the tumor and the resulting morbidity of the disease.

Methods: Two patient derived stem cell enriched primary glioblastoma cell lines and CRISPR-engineered murine neural stem cells displaying characteristic hallmarks of glioblastoma were used. All cell lines show distinct growth patterns and invasive behavior when orthotopically implanted in CD1-nude mice. Exosomes from these cell lines were isolated using differential centrifugation and characterized by Nanosight technology. Subsequently, astrocytes isolated from rats or mice were treated with these exosomes. Astrocytes were then either re-plated to assess migration via time lapse microscopy or used to generate extracellular matrices (ECMs). After decellularizing these astrocyte-derived ECMs, glioblastoma cells were replated on these and migration was assessed using time lapse microscopy.

Results: Glioblastoma exosomes change migratory speed of astrocytes in a manner corresponding to the invasive behavior of the donor cells. Moreover, the ECM generated by glioblastoma exosome-treated astrocytes facilitated glioma cell migration in similar manner. Integrin trafficking, which is known to influence ECM deposition, is controlled by a Rab GTPase regulated pathway which requires the lipid kinase, diacylglycerol kinase-α (DGKα). Indeed, the ability of glioblastoma exosomes to influence ECM deposition was opposed by treatment of astrocytes with an inhibitor of DGKα, indicating that glioblastoma exosomes can regulate integrin trafficking in astrocytes to influence ECM deposition.

Conclusion: Glioblastoma cells are able to influence ECM deposition by surrounding astrocytes in a way that can support infiltrative invasion of tumor cells in a DGKα-dependent manner unveiling a possible target for adjuvant therapies.