gms | German Medical Science

Objective: Glioblastomas (GBM) are heterogeneous tumors, consisting of different cell types like glioma cells and recruited host cells. Yet, the underlying complex interactions of adhesion/migration of these cells within the tumor environment are widely unknown. Integrins are involved in these mechanisms and characterized by their ability for inside-out and outside-in signalling. Here, we analyzed expression of integrins as well as the functional impact of integrin-inhibition (INT-INH) on glial tumor cells and mesenchymal stem like cells.

Method: Tumor cells from malignant glioma (U87) and mesenchymal stem like cells derived from the bone marrow (bmMSC) of healthy donors were analyzed for expression of integrin alpha v beta 3 (αvβ3) and integrin-subunit b5 by immunocytochemistry and Western Blot. To determine if INT-INH impairs cell adhesion or proliferation, INT-INH were administered simultaneously (before seeding) or delayed (after seeding and adhesion of cells) to cell cultures of U87 and bmMSC with or without conditioned tumor medium.

Results: Both cell lines, U87 and bmMSC showed expression of integrin subunits αv, β3 and β5. Only integrin subunit av did show significantly higher expression in bmMSC compared to U87 (p<0.05). Regarding functional impact, simultaneous addition of INT-INH with cell seeding led to a dose-dependent loss of adhesion in bmMSC. Yet, delayed addition of INT-INH did not lead to a significant loss of adhesion in these cells. Interestingly, U87 cell cultures displayed loss of adhesion already with significantly smaller dosages. Moreover, almost complete loss of adhesion could be found in U87 independently if INT-INH were administered simultaneously with or delayed after seeding. Surprisingly, addition of tumor-conditioned medium completely reversed loss of adhesion in bmMSC treated simultaneously with INT-INH. For bmMSC cell cultures reduced proliferation rates could be detected already at 24 h to 48 h after addition of INT-INH, whereas INT-INH displayed no influence to proliferation rates in U87 cells.

Conclusions: Integrin expression alone does not sufficiently predict response to INT-INH per se. Moreover, glioma secreted factors seem to exhibit antagonistic effects against INT-INH in bone marrow stem cells. Differential response of GBM to INT-INH treatment should be interpreted on the background of intercellular crosstalk between tumor and recruited host cells.