Glioblastoma (GB), a highly hypoxic brain tumor (Bekaert et al. 2017), is characterized by a massive macrophage (MΦ) infiltration (Lapa et al. 2015). Hypoxia triggers a shift to a pro-tumoral M2 phenotype in GB (Leblond et al. 2016). Thus, strategies aiming to reduce hypoxia could promote an anti-tumoral M1 phenotype. Among these reoxygenation strategies, we recently developed a new approach with zeolites nanoparticles. These zeolites are able to carry hyperoxic/hypercapnic gases and release them according to a hypoxic gradient. We have demonstrated that the charge balancing cation changes affinity to the gases but also the ability to track zeolite with MRI. Our objective is to study the reoxygenation efficacy of zeolites specifically in the GB and to evaluate their impact on tumor associated MΦ with in vitro and in vivo studies.
Faujasite zeolites (FAU, ∼20nm of diameter) were used and modified by ion exchange with various cations (Fe, Gd, Cu, Ag). GB model was obtained by orthotopic glioblastoma cells implantation (U251) in nude rats (ONCOModels/Unicaen). 7T MRI (Bruker/Cyceron) was used to follow zeolites after intravenous injection and for oxygen measurement. Murine bone marrow derived MΦ were prepared and polarized to M1 and M2 using LPS/IFNg or IL4 as previously described (Leblond et al. 2016). Zeolites were added in MΦ medium and their impact on MΦ were evaluated by crystal violet dye assay, flow cytometry (Plateau ICORE/Unicaen) and polarization assays.
Our results show that zeolites are able to accumulate and release the carried gases specifically in the brain tumor leading to tumor reoxygenation. Regarding the effect on MΦ, our preliminary results show, in vitro, the safety of as-prepared zeolites or Fe, Gd or Cu dopped zeolites on M0, M1 and M2 MΦ cultures. Similarly, no alteration of the cell cycle was observed. As a positive control of cell death, the presence of Ag-dopped zeolites dramatically decreased M0 and M1 MΦ viability.
Zeolites can deliver oxygen to the brain tumor and may improve the effectiveness of conventional treatments. Zeolites do not exhibit toxicity on primary cultures of MΦ. Additional studies are underway to evaluate the effect of zeolites on the polarization of MΦ, both in vitro and in vivo.
Région Normandie, CNRS, Université de Caen Normandie, Ministère de l'Enseignement Supérieur et de la Recherche, European Union-Fonds Européen de Développement Régional (FEDER), HABIONOR European project, co-funded by the Normandy County Council, the French State in the framework of the interregional development Contract “Vallée de la Seine” 2015-2020, ARCHADE, Fédération pour la Recherche sur le Cerveau (FRC) et INCa (INCA-11699).
The authors.
Région Normandie, CNRS, Université de Caen Normandie, Ministère de l’Enseignement Supérieur et de la Recherche, European Union-Fonds Européen de Développement Régional (FEDER), HABIONOR European project, co-funded by the Normandy County Council, the French State in the framework of the interregional development Contract “Vallée de la Seine” 2015-2020, ARCHADE, Fédération pour la Recherche sur le Cerveau (FRC) et INCa (INCA-11699).
All authors have declared no conflicts of interest.