Artikel
Influence of the tumour microenvironment on the therapeutic response of residual tumour cells after GBM resection
Einfluss der Tumor-Mikroumgebung auf die Therapieresponsivität von residuellen Tumorzellen nach einer GBM-Resektion
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Veröffentlicht: | 25. Mai 2022 |
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Gliederung
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Objective: Glioblastoma (GBM) is the most malignant brain tumor in adults. Despite the standard therapy including surgical resection and adjuvant combined radio/chemotherapy, the average survival of GBM patients is still poor. Since the crosstalk between residual tumor cells and the surrounding healthy brain cells is having a strong influence on the therapeutic outcome after surgical resection of the solid tumor mass, the present study evaluates the intra- and intercellular effects of a sequential therapy with TMZ combined with the alternative compound AT101 on two GBM primary cultures in an in vitro co-culture model mimicking an incomplete GBM resection.
Methods: The analyses comprised cytotoxicity assays, a fluorescence real-time apoptosis detection assay, the investigation of changes in signaling pathways and on the gene expression level, as well as the role of extracellular vesicles (EVs) using nanoparticle-tracking analysis (NTA) and western blotting. The analysis for both the intra- and intercellular effects of the sequential therapy were compared between mono- and co-culture of two GBM primary cultures.
Results: GBM cells were found to exhibit different apoptotic states over time upon sequential treatment when comparing mono- vs. co-culture conditions. Co-culture conditions were protectively influencing the death rates of GBM cells and were characterized by an increase of early-apoptotic cells (reversible event) with only little numbers of dead cells, whereas the mono-culture showed the opposite behavior, indicating a regulatory effect of healthy brain cells on the apoptotic cell death mechanisms. In addition, the MAP-kinases ERK1/2, GSK3β, mTOR, as well as β-Catenin were found to be activated upon treatment and the activation appeared to be differentially regulated in mono- vs. co-cultured GBM cells. Moreover, genes associated with dormancy and stemness were found to be upregulated under co-culture conditions upon treatment. Furthermore, NTA of isolated EVs revealed a shift in the size distribution of particles towards smaller sizes and a change in the total number of EVs in the samples that underwent the sequential treatment.
Conclusion: Our results indicate a complex role of the tumor microenvironment for the therapeutic outcome of GBMs. Understanding the mechanisms how healthy brain cells influence the response of residual GBM cells to a treatment and how the cellular crosstalk via EVs is involved might help to develop a more effective treatment strategy.