OS10.7.A Activation of the CCR8-ACP5 axis by human microglia/macrophage derived CCL18 promotes glioma growth

Background

Glioblastoma multiforme is a highly malignant primary brain tumor with an average survival of 14 months and very limited therapeutic options. Glioma associated microglia and macrophages (GAMs) foster tumor growth by releasing several cytokines, which have only partly been identified. Here, we studied the chemokine (C-C motif) ligand 18 (CCL18), a chemokine which is only expressed in human, but not rodent GAMs, in a novel ex-vivo brain slice model including transplantation of human induced pluripotent stem cells (iPSC) derived human microglia (iMGL) and human glioma cells in to murine brain slices, which had been depleted of intrinsic murine microglia before.

Material and Methods

After establishing the humanized ex-vivo brain slice model, we performed immunohistochemical analysis (IHC) of growth and invasiveness, qrtPCR on glioma cells isolated by magnetic-activated cell sorting (MACS), functional assays measuring invasiveness, proliferation, migration and colony formation of glioma cells in vitro and in slice experiments. Corresponding studies on tumor growth and invasiveness were performed after treatment with a CCL18 neutralizing antibody, a CCR8 neutralizing antibodies and knockdown of CCR8, ACP5 (Acid Phosphatase 5) and PITPNM3 with small interfering RNA (siRNA) and short hairpin RNA (shRNA). QrtPCR, IHC and Westernblot analysis were performed on primary glioma specimens. We also conducted bioinformatic analyses, based on the TCGA GBM, GLIOVIS and GEPIA databases.

Results

We observed that CCL18 was highly expressed in GAMs, whereas CCR8 was only expressed in glioma cells. We identified the chemokine (C-C motif) receptor 8 (CCR8) as a functional receptor for CCL18 and ACP5 as an important down-stream signaling component in glioma cells. Activation of the CCL18/CCR8/ACP5 signaling pathway in human glioblastoma was associated with enhanced tumor growth and invasiveness.

Conclusion

GAMs derived CCL18 promoted glioma growth by activation of the CCR8/ACP5 axis in human glioma cells and therefore is a potential therapeutic target.

P16.05 Implementation of a novel ex-vivo brain slice model to study human glioblastoma and glioma-associated microglia

BACKGROUND

Glioblastoma multiforme is a highly malignant brain tumor with a devastating prognosis. Resection followed by radio-chemotherapy leads to an overall survival of only 15 months. Up to 40% of the tumor mass consist of tumor-associated microglia and macrophages (TAMs). These cells were shown to promote tumor growth and invasiveness in many murine glioma models. The interaction between TAMs and tumor cells is crucial for tumor progression and includes several known pathways. Still, murine glioma models only partially mirror the human tumor microenvironment. Several known genes, which are highly upregulated in human glioma and TAMs are only expressed in human tissue and not in mice. To further investigate some of these genes, we aimed at establishing a humanized ex-vivo brain slice model, in which human TAMs and human glioma cells can be studied in a standardized manner.

MATERIAL AND METHODS

We used 250 micrometer thick murine brain slices, which were depleted of intrinsic microglia by applying clodoronated liposomes. Next, we inoculated human glioma cells (originating from the cell lines mCherryU87, mCherryU251MG, mCherryLN229 and several patient derived cells lines) with or without human microglia derived from induced pluripotent stem cells (iPSCs). Slices were cultivated for 7 to 14 days. Next, we performed a detailed analysis of microglia morphology (sphericity, cell body volume, process length and branching pattern) and tumor volume.

RESULTS

Clodronation efficacy was high, depending on duration of treatment and length of cultivation. iPSCs and tumor cells integrated into the slice very well. The presence of tumor cells led to an increased sphericity of iPSC-dervied microglia and to an increased cell body volume. Branching pattern and process length did not differ between both conditions. Tumor volume was significantly larger when iPSC-derived microglia were present. This was found in various glioma cells lines and also in patient derived cells.

CONCLUSION

The newly established humanized ex-vivo brain slice system was shown to be feasible. The method successfully allows to study the interaction between human TAMs and tumor cells. Microglia foster tumor growth not only in murine glioma models, but also in a human paradigm. The humanized ex-vivo brain slice model therefore is the optimal basis to study the role human-specific genes in TAM-glioma interaction.

Fabrication and characterization of oxygen - diffused titanium using spectroscopy method

A thin native oxide film that forms on the titanium surface makes contact with the bone tissue has been considered to be of great importance to successful osseointegration. The study investigated oxygen-diffused grade 2 titanium obtained by introducing oxygen into the titanium crystal lattice using thermal treatment in fluidized bed performed at 610°C and 640°C in 6, 8, 12h. The thermal treatment at different temperatures and different times led to the formation of a TiO2 rutile film on the titanium surface and a concentration gradient of oxygen into titanium (XRD/GID analyses and GDOS results). Moreover Raman spectroscopy results showed that the TiO2 film on the surface titanium was composed of two oxides (TiO2), i.e. anatase and rutile, for the analyzed variants of heat treatment. The aim of the present study was to establish the optimum conditions for obtaining oxygen-diffused TiO2 film. The results obtained in the study demonstrated that the use of a fluidized bed for titanium oxidation processes allows for obtaining uniform oxide layers with good adhesion to the substrate, thus improving the titanium surface to suit biomedical applications.

Raman spectroscopy of TiO2 thin films formed by hybrid treatment for biomedical applications

The paper presents the results of the investigations of the surface layer obtained after application of the combined hybrid method of oxidation in a fluidized bed (FB) and deposition of the oxide coating by PVD technique. The material used in the study was Ti Grade 2. The process of diffusive saturation was carried out in a fluidized-bed reactor at the temperature of 640°C for 8h in air while the top oxide layer was obtained through PVD method - magnetron sputtering using TiO2 target and argon atmosphere with the pressure of 3×10(-2)mbar and the distance between the substrate to the target of 60mm. In order to determine changes in the properties that occur as a result of modification of the Ti surface, the following examinations were carried out by SEM-EDX, X-ray diffraction methods, Raman spectroscopy, Glow Discharge Optical Spectroscopy (GDOS) and Secondary Ion Mass Spectrometry (SIMS). The coatings obtained were characterized by zonal structure comprising the solution zone of Tiα(O) and oxide zone of TiO2 with modifications of rutile and anatase, depending on the oxidation method. It was found that formation of oxide layers using the hybrid method (FB+PVD) leads to limitation of defects in the oxide layer after fluidized-bed thermal treatment and obtaining a uniform, tight coating with improved corrosion properties which are important from the biomedical standpoint.