489P - Interfering with the tumor microenvironment of glioblastoma: An in vitro study

Background

Glioblastoma multiforme (GBM) is the most aggressive primary brain cancer characterized by an extensive intra-tumor and inter-patient heterogeneity. While glioma stem cells (GSCs) are considered responsible for GBM recurrences, the crosstalk between tumor cells and tumor microenvironment (TME) strongly influences tumor behavior. Glioma associated stem cells (GASCs) are representative of the TME since they are not tumorigenic, but, in vitro, they increase the biological aggressiveness of tumor cells through the release of exosomes (EXOs). Here we aimed at evaluating the efficacy of selected compounds, acting on the TME, to blunt its tumor supporting ability, taking advantage of a patient-derived in vitro model of TME, represented by GASCs and released exosomes.

Methods

We selected 3 drugs: bacitracin, a₅b₁ integrin antibody and ciclopirox, known to inhibit migration and invasion of tumor cells. Three lines of GASC were treated, first to select the maximum dose and the timing of treatments, and then to evaluate a possible reduction in the activated phenotype of the TME, in vitro. To this aim, proliferation, motility and anchorage-independent growth of treated GASCs were evaluated. Moreover, GASCs supernatants (SN) were collected to evaluate the effect of GASC-SN, and EXOs isolated from GASC-SN, on U87 MG glioblastoma cells in terms of proliferation, cell motility, anchorage-independent growth, migration and invasion.

Results

Drugs were able to reduce the activated phenotype of GASCs, inhibiting proliferation, cell motility and anchorage-independent growth. GASC SN collected from control cells was able to support proliferation and motility of U87 cells, while SNs derived from GASCs, treated with drugs, were able to inhibit cell proliferation and motility, confirming the ability of the drugs to reverse the tumor support function. U87s, conditioned with EXOs isolated from treated GASC-SN, showed reduced motility, proliferation, migration, invasion and anchorage-independent growth.

Conclusions

We confirmed the important supporting role, mediated by exosomes, of the TME on tumor cells behavior and we demonstrated that the 3 selected compounds can efficiently revert its activated phenotype.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

University of Udine.

Funding

Regione Autonoma Friuli Venezia Giulia.

Disclosure

All authors have declared no conflicts of interest.