|Paper title||GBM bioreactors enable preclinical testing of combinatorial tumor targeting and microenvironment modulation|
|Form of presentation||Poster|
Glioblastoma (GBM) is a fatal brain tumor. Standard of care consists of gross total resection and chemo-radiation resulting in an overall survival of only 14 months. Recently, strategies harnessing the immune tumor microenvironment (TME) have gained headwind. The TME of GBM consists partly of macrophages and microglia (termed as TAMs). To evaluate the effect of microglia/macrophage modulating therapies in combination with tumor targeting approaches in a realistic setting, we generated patient-derived, region-specific 3D GBM perfusion bioreactors with intact microenvironment. We aimed at simulating the combinatorial effect of temozolomide (TMZ) and a microglia modulator (CSF1r inhibitor BLZ495) on the immune microenvironment to predict therapeutic synergy.
GBM tissue from tumor center and periphery (according to neuronavigation and 5-ALA fluorescence intensity) was processed, placed into collagen scaffolds, and transferred to perfusion bioreactors (Cellec Biotek AG). 3D cultures were perfused with GBM stem cell medium supplemented with 5% human serum for two weeks. Cultures were treated with TMZ, BLZ945 and in combination. Control conditions included static cultures of the same tumor. Tissue was harvested for histology, flow cytometry, and quantitative real-time PCR analysis.
Viable GBM tumors with intact microenvironment in bioreactors were cultured for up to two weeks. Histology confirmed presence of TAMs in the TME and proliferating tumor cells in both center and periphery compared to disrupted histoarchitecture in static samples. Combination treatment induced a TAM polarization shift indicated by a novel population of CD11highCD80highCx3cr1+CD49d+ cells in perfused center, but not in periphery samples. BLZ945 or TMZ treatment alone did not mediate this effect indicating potential benefit of combined tumor and macrophage targeting. Tumor cell viability was reduced when subjected to combination therapy compared to monotherapy.
In our preliminary data, we demonstrated that GBM bioreactors might serve as valid tools to stratify responses of tumor- and microglia/macrophage modulating drugs. We found differential TAM responses based on the location of the tumor biopsy. We are currently refining and extending the methodology, and will employ multiplexed histology (Codex), flowcytometry, and cytokine analysis to pinpoint the effect of different combinations of microglia modulators and tumor targeting approaches in vivo.