Glioblastoma is refractory to therapy and presents a significant oncological challenge. Promising immunotherapies have not shown the promise observed in other aggressive cancers. The reasons for this include the highly immuno-suppressive tumour microenvironment controlled by the glioblastoma cells and heterogeneous phenotype of the glioblastoma cells. Here, we wanted to better understand which glioblastoma phenotypes produced the regulatory cytokines, particularly those that are implicated in shaping the immune microenvironment. In this study, we employed nanoString analysis of the glioblastoma transcriptome, and proteomic analysis (proteome profiler arrays and cytokine profiling) of secreted cytokines by different glioblastoma phenotypes. These phenotypes were cultured to reflect a spectrum of glioblastoma cells present in tumours, by culturing an enhanced stem-like phenotype of glioblastoma cells or a more differentiated phenotype following culture with serum. Extensive secretome profiling reveals that there is considerable heterogeneity in secretion patterns between serum-derived and glioblastoma stem-like cells, as well as between individuals. Generally, however, the serum-derived phenotypes appear to be the primary producers of cytokines associated with immune cell recruitment into the tumour microenvironment. Therefore, these glioblastoma cells have considerable importance in shaping the immune landscape in glioblastoma and represent a valuable therapeutic target that should not be ignored.

Glioblastoma is considered the most aggressive and lethal form of brain cancer. Glioblastoma tumours are complex, comprising a spectrum of oncogenically transformed cells displaying distinct phenotypes. These can be generated in culture and are called differentiated-glioblastoma cells and glioblastoma stem cells. These cells are phenotypically and functionally distinct, where the stem-like glioblastoma cells give rise to and perpetuate the tumour. Electric cell-substrate impedance sensing (ECIS) is a real-time, label-free, impedance-based method for the analysis of cellular behaviour, based on cellular adhesion. Therefore, we asked the question of whether ECIS was suitable for, and capable of measuring the adhesion of glioblastoma cells. The goal was to identify whether ECIS was capable of measuring glioblastoma cell adhesion, with a particular focus on the glioblastoma stem cells. We reveal that ECIS reliably measures adhesion of the differentiated glioblastoma cells on various array types. We also demonstrate the ability of ECIS to measure the migratory behaviour of differentiated glioblastoma cells onto ECIS electrodes post-ablation. Although the glioblastoma stem cells are adherent, ECIS is substantially less capable at reliably measuring their adhesion, compared with the differentiated counterparts. This means that ECIS has applicability for some glioblastoma cultures but much less utility for weakly adherent stem cell counterparts.

Background/Objectives: Brain cancers offer poor prognoses to patients accompanied by symptoms that drastically impact the patient and their family. Brain tumours recruit local non-transformed cells to provide trophic support and immunosuppression within the tumour microenvironment, supporting tumour progression. Given the localisation and supportive role of pericytes at the brain vasculature, we explored the potential for brain pericytes to contribute to the brain cancer microenvironment. Methods: To investigate this, primary brain pericytes were treated with factors commonly upregulated in brain cancers. Immunofluorescent labelling identified changes to brain pericyte cell signalling, cytometric bead array measured inflammatory secretion, and flow cytometry investigated brain pericyte phagocytosis. Results: The TGFβ superfamily cytokines TGFβ and GDF-15 activated SMAD2/3 and inhibited C/EBP-δ, revealing a potential mechanism behind the pleiotropic action of TGFβ on brain pericytes. IL-17 induced secretion of IL-6 without activating NFκB, STAT1, SMAD2/3, or C/EBP-δ signalling pathways. IL-27 and IFNγ induced STAT1 signalling and significantly reduced brain pericyte phagocytosis. The remaining brain cancer-derived factors did not induce a measured response, indicating that these factors may act on other cell types or require co-stimulation with other factors to produce significant effects. Conclusions: We identify several brain cancer-secreted factors which alter relevant brain pericyte functions. This reveals mechanisms through which brain tumours may regulate brain pericyte activity and these data start to uncover the supportive role these cells may play in brain cancers.

The overall goal of this work was to assess the ability of Natural Killer cells to kill cultures of patient-derived glioblastoma cells. Herein we report impressive levels of NK-92 mediated killing of various patient-derived glioblastoma cultures observed at ET (effector: target) ratios of 5:1 and 1:1. This enabled direct comparison of the degree of glioblastoma cell loss across a broader range of glioblastoma cultures. Importantly, even at high ET ratios of 5:1, there are always subpopulations of glioblastoma cells that prove very challenging to kill that evade the NK-92 cells. Of value in this study has been the application of ECIS (Electric Cell–Substrate Impedance Sensing) biosensor technology to monitor the glioblastoma cells in real-time, enabling temporal assessment of the NK-92 cells. ECIS has been powerful in revealing that at higher ET ratios, the glioblastoma cells are acutely sensitive to the NK-92 cells, and the observed glioblastoma cell death is supported by the high-content imaging data. Moreover, long-term ECIS experiments reveal that the surviving glioblastoma cells were then able to grow and reseed the culture, which was evident 300–500 h after the addition of the NK-92 cells. This was observed for multiple glioblastoma lines. In addition, our imaging provides evidence that some NK-92 cells appear to be compromised early, which would be consistent with potent evasive mechanisms by the glioblastoma tumour cells. This research strongly highlights the potential for NK-92 cells to kill glioblastoma tumour cells and provides a basis to identify the mechanism utilised by the surviving glioblastoma cells that we now need to target to achieve maximal cytolysis of the resistant glioblastoma cells. It is survival of the highly resistant glioblastoma clones that results in tumour relapse.

Brain cancers offer poor prognoses to patients accompanied by symptoms that drastically impact the patient and their family. Brain tumours recruit local non-transformed cells to provide trophic support and immunosuppression within the tumour microenvironment, supporting tumour progression. Given the localization and supportive role of pericytes at the brain vasculature, we explored the potential for brain pericytes to contribute to the brain cancer microenvironment. To investigate this, primary brain pericytes were treated with factors commonly upregulated in brain cancers. Changes to brain pericyte cell signalling, inflammatory secretion, and phagocytosis were investigated. The TGFβ superfamily cytokines TGFβ and GDF-15 activated SMAD2/3 and inhibited C/EBP-δ, revealing a potential mechanism behind the pleiotropic action of TGFβ on brain pericytes. IL-17 induced secretion of IL-6 without activating NFκB, STAT1, SMAD2/3, or C/EBP-δ signalling pathways. IL-27 and IFNγ induced STAT1 signalling and significantly reduced pericyte phagocytosis. The remaining brain cancer-derived factors did not induce a measured response, indicating that these factors may act on other cell types or require co-stimulation with other factors to produce significant effects. Together, these findings show potential mechanisms by which brain pericytes contribute to aspects of inflammation and starts to uncover the supportive role brain pericytes may play in brain cancers.