Primary Glioblastoma Cultures Research Articles

KRAS is a molecular determinant of platinum responsiveness in glioblastoma

BackgroundKRAS is the undisputed champion of oncogenes, and despite its prominent role in oncogenesis as mutated gene, KRAS mutation appears infrequent in gliomas. Nevertheless, gliomas are considered KRAS-driven cancers due to its essential role in mouse malignant gliomagenesis. Glioblastoma is the most lethal primary brain tumor, often associated with disturbed RAS signaling. For newly diagnosed GBM, the current standard therapy is alkylating agent chemotherapy combined with radiotherapy. Cisplatin is one of the most effective anticancer drugs and is used as a first-line treatment for a wide spectrum of solid tumors (including medulloblastoma and neuroblastoma) and many studies are currently focused on new delivery modalities of effective cisplatin in glioblastoma. Its mechanism of action is mainly based on DNA damage, inducing the formation of DNA adducts, triggering a series of signal-transduction pathways, leading to cell-cycle arrest, DNA repair and apoptosis.MethodsLong-term cultures of human glioblastoma, U87MG and U251MG, were either treated with cis-diamminedichloroplatinum (cisplatin, CDDP) and/or MEK-inhibitor PD98059. Cytotoxic responses were assessed by cell viability (MTT), protein expression (Western Blot), cell cycle (PI staining) and apoptosis (TUNEL) assays. Further, gain-of-function experiments were performed with cells over-expressing mutated hypervariable region (HVR) KRASG12V plasmids.ResultsHere, we studied platinum-based chemosensitivity of long-term cultures of human glioblastoma from the perspective of KRAS expression, by using CDDP and MEK-inhibitor. Endogenous high KRAS expression was assessed at transcriptional (qPCR) and translational levels (WB) in a panel of primary and long-term glioblastoma cultures. Firstly, we measured immediate cellular adjustment through direct regulation of protein concentration of K-Ras4B in response to cisplatin treatment. We found increased endogenous protein abundance and involvement of the effector pathway RAF/MEK/ERK mitogen-activated protein kinase (MAPK) cascade. Moreover, as many MEK inhibitors are currently being clinically evaluated for the treatment of high-grade glioma, so we concomitantly tested the effect of the potent and selective non-ATP-competitive MEK1/2 inhibitor (PD98059) on cisplatin-induced chemosensitivity in these cells. Cell-cycle phase distribution was examined using flow cytometry showing a significant cell-cycle arrest in both cultures at different percentage, which is modulated by MEK inhibition. Cisplatin-induced cytotoxicity increased sub-G1 percentage and modulates G2/M checkpoint regulators cyclins D1 and A. Moreover, ectopic expression of a constitutively active KRASG12V rescued CDDP-induced apoptosis and different HVR point mutations (particularly Ala 185) reverted this phenotype.ConclusionThese findings warrant further studies of clinical applications of MEK1/2 inhibitors and KRAS as ‘actionable target’ of cisplatin-based chemotherapy for glioblastoma.

P2X7 receptor antagonism by AZ10606120 significantly reduced in vitro tumour growth in human glioblastoma

Glioblastomas are highly aggressive and deadly brain tumours, with a median survival time of 14–18 months post-diagnosis. Current treatment modalities are limited and only modestly increase survival time. Effective therapeutic alternatives are urgently needed. The purinergic P2X7 receptor (P2X7R) is activated within the glioblastoma microenvironment and evidence suggests it contributes to tumour growth. Studies have implicated P2X7R involvement in a range of neoplasms, including glioblastomas, although the roles of P2X7R in the tumour milieu remain unclear. Here, we report a trophic, tumour-promoting role of P2X7R activation in both patient-derived primary glioblastoma cultures and the U251 human glioblastoma cell line, and demonstrate its inhibition reduces tumour growth in vitro. Primary glioblastoma and U251 cell cultures were treated with the specific P2X7R antagonist, AZ10606120 (AZ), for 72 h. The effects of AZ treatment were also compared to cells treated with the current first-line chemotherapeutic drug, temozolomide (TMZ), and a combination of both AZ and TMZ. P2X7R antagonism by AZ significantly depleted glioblastoma cell numbers compared to untreated cells, in both primary glioblastoma and U251 cultures. Notably, AZ treatment was more effective at tumour cell killing than TMZ. No synergistic effect between AZ and TMZ was observed. AZ treatment also significantly increased lactate dehydrogenase release in primary glioblastoma cultures, suggesting AZ-induced cellular cytotoxicity. Our results reveal a trophic role of P2X7R in glioblastoma. Importantly, these data highlight the potential for P2X7R inhibition as a novel and effective alternative therapeutic approach for patients with lethal glioblastomas.

CNSC-23. NEURONAL ORIGIN INFLUENCES SPONTANEOUS NETWORK ACTIVITY IN GLIOBLASTOMA-NEURON COCULTURES

Abstract Neuronal activity is emerging as a driver of cancer initiation and proliferation. Several models have been developed to recapitulate cancer-neuron interactions within the tumor microenvironment; however, there is substantial diversity of neuronal subtypes within the murine and human cortex. Differences in the neuronal microenvironment may influence glioma cell behavior and fail to recapitulate in vivo mechanisms. Here, we investigate the electrophysiological properties of cortical neurons and activity-regulated paracrine signaling across co-culture conditions using microelectrode arrays (MEA). Cortical neurons were obtained from three conditions, (1) human prenatal tissues, (2) murine embyronic tissue (E18), and (3) murine postnatal tissue (P1.5), then co-cultured with primary patient-derived glioblastoma cultures. Neuronal activity was assessed using weighted mean firing rate (WMFR; spike rate multiplied by number of active electrodes) and network burst synchrony index. Characterization of the activity-dependent paracrine signaling was performed using proteomics. Initiation of spontaneous firing activity differed across neuronal conditions, with activity occurring earlier in postnatal P1.5 cultures (day in vitro [DIV] 7), whereas E18 and human prenatal cultures demonstrated delayed patterns of activity (DIV 14 and DIV 21, respectively). Glioblastoma cells were added on the first day of consistent spiking. All neuronal co-culture conditions demonstrated glioma-induced hyper-activity (increased WMFR), however in different patterns. E18 co-cultures exhibited glioma-induced hyperexcitability within 24 hours with a subsequent decrease in activity over 14 days with minimal synchrony. P1.5 demonstrated no glioma-induced hyper-excitability at 24 hours; however, WMFR peaked by 7 days and remained elevated through co-culture day 14 (including concurrent increase in synchrony). Human postnatal neurons demonstrated a steady and consistent increase in WMFR as early as 24 hours post co-culture and remained active through day 14 with no synchrony change. Our data suggest that careful consideration should go into selecting neuronal co-culture conditions for mechanistic studies.

Enhanced Natural Killers with CISH and B2M Gene Knockouts Reveal Increased Cytotoxicity in Glioblastoma Primary Cultures

Enhanced Natural Killers with CISH and B2M Gene Knockouts Reveal Increased Cytotoxicity in Glioblastoma Primary Cultures

P17.16.B Additional antitumoral activity of TTFields stimulation and Chloride Intracellular Channel 1 inhibition in human glioblastoma primary culture

Abstract Background Glioblastoma relapse inevitably occurs in the majority of patients after surgery. Chemo- and radiotherapy are in most cases ineffective, while Tumor Treating Fields (TTFields) therapy delays average tumor recurrence by a few months. It is widely accepted that tumor reappearance is a result of the proliferation of residual glioblastoma stem cell (GSC) subpopulation, which escaped surgery. Previous experiments demonstrated that inhibition of the membrane form of Chloride Intracellular Channel 1 (tmCLIC1) is particularly efficient to hit GSCs in glioblastoma human primary cultures. tmCLIC1 is an ideal target as it is express only in the tumor cell membranes. tmCLIC1 blockage slowdown GSC cell cycle at G1/S transition. On the contrary, TTFields act mainly during G2/M progression. The objective of our study is to test the therapeutic potential of combining TTFields exposure with the inhibition of the protein transmembrane Chloride Intracellular Channel 1 (tmCLIC1), which is crucial for GSCs proliferation. Material and Methods Cell preparation: human primary culture from patients’ biopsies. Stimulation device: NOVOCURE Inovitro system®. Stimulation procedure: long-term TTFields stimulation in in-vitro experiments mimics glioblastoma cells’ recrudescence. Analysis: cytofluorimetry for stem cell recognition, cell-cycle progression, and cell count. Results Cell growth is inhibited after the first three days of TTFields exposure. However, despite the chronic presence of TTFields stimulation in prolonged experiments, glioblastoma cells reestablish the ability to proliferate. At the end of twelve days, exponentially growing cells show an increase in stemness markers, a drop in the membrane resistance with a related increase of membrane current, and an average depolarized membrane potential. Twelve days of TTFields treatment resulted in a progressive increase in GSCs in the tumor cell population from 10% to more than 30%. Thus, experiments have been designed to combine TTFields stimulation with tmCLIC1 inhibition. This would include in the treatment of the vast majority of the glioblastoma cell population. After twelve days, the parallel antiproliferative activities show a complete impairment in cell proliferation. Conclusion The additive effect of TTFields stimulation and tmCLIC1 ion channel inhibition could represent an efficacious step forward to optimize an antitumoral therapy against glioblastoma expansion.

Abstract 3560: Towards personalized oncolytic virotherapy: Differential response of four oncolytic viruses in primary glioblastoma cultures

Abstract Background: The brain tumor glioblastoma (GBM) is one of the most aggressive forms of cancer. The dismal prognosis of these patients, with a median survival of less than 15 months despite maximal therapy makes the need for new therapeutic approaches urgent. Clinical trials employing oncolytic viruses (OVs) have shown encouraging results, however, it appears that for each OV only a small group of patients responds to treatment. As inter- and intra-tumoral heterogeneity is a hallmark of GBM, we hypothesized that fresh patient-derived GBM cell cultures will reflect this inter-tumoral variability in response and allow identification of potential biomarkers of susceptibility to specific OVs. Furthermore, we established a co-culture system of primary GBM cultures with autologous peripheral blood mononuclear cells (PBMCs) to capture the degree of OV-induced oncolysis in conjunction with subsequent immune activation. Using these model systems, we attempt to develop tools which may guide future personalized trials of OV treatment for GBM. Methods: We tested the oncolytic potency of four OVs derived from different viral families (DNX2401, rQnestin34.5 V1, wild type Reovirus, lentogenic NDV-f0-GFP) on a panel of 19 molecularly characterized GBM cultures and calculated the half maximal effective concentration (EC50) for each virus on each cell culture. Quantitative PCR was performed to assess cytokine expression in tumor cells after infection with the 4 different OVs. OV-induced changes in the gene and protein expression of immune associated genes were assessed in co-cultures of GBM cells with PBMCs using Nanostring nCounter System and Elisa. Results: Screening of the 4 OVs on the panel of patient-derived GBM cell cultures revealed great inter-tumoral variability in oncolysis and cytokine response to the 4 different OVs with some degree of OV specific cytokine response profiles. Correlation analysis of transcriptome data with susceptibility to the four OVs shows that genes involved in distinct pathways are related to specific OV-sensitivity. In particular, cell cycle and immune related biological processes discriminate responders and non-responders. The co-culture of OV-infected glioma cells with PBMCs suggests that infection with different OVs leads to expression of distinct sets of genes and proteins in PBMCs; indicating that each OV mounts a specific immune response. Conclusion: Heterogeneity in OV sensitivity is demonstrated in primary GBM cultures, in terms of oncolysis, cytokine induction and in virus-specific changes in gene and protein expression in OV-infected tumor cells/PBMCs co-cultures. These results support the hypothesis that improving the response rates in oncolytic virotherapy for GBM may require a personalized approach. Citation Format: Eftychia Stavrakaki, Anne Kleijn, Wouter B. van den Bossche, Rutger K. Balvers, Lisette B. Vogelezang, Jie Ju, Andrew Stubbs, Yunlei Li, Dana Mustafa, Federica Fabro, Bernadette van den Hoogen, Rob Hoeben, William F. Goins, Hiroshi Nakashima, E. Antonio Chiocca, Clemens M. Dirven, Martine L. Lamfers. Towards personalized oncolytic virotherapy: Differential response of four oncolytic viruses in primary glioblastoma cultures [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3560.

Abstract 2315: Synergic antitumoral activity of TTFields stimulation and Chloride Intracellular Channel 1 (CLIC1) inhibition in human glioblastoma primary culture

Abstract Glioblastoma relapse inevitably occurs in the majority of patients after surgery. Chemo- and radio- therapy are in most cases ineffective, while Tumor Treating Fields (TTFields) therapy delays average tumor recurrence by a few months. It is widely accepted that tumor reappearance is a result of the proliferation of residual glioblastoma stem cell (GSC) subpopulation, which escaped surgery. Long-term TTFields stimulation in in vitro experiments mimic glioblastoma cells recrudescence. After the first three days of TTFields exposure, cell growth is totally inhibited. However, in prolonged experiments, despite the chronic presence of TTFields stimulation, glioblastoma cells reestablish the ability to proliferate, even if at low rate. At the end of twelve days, exponentially growing cells show an increase of stemness markers, a drop of the membrane resistance with a related increase of membrane current, and an average depolarized membrane potential. Twelve days of TTFields treatment resulted in progressive increase in GSCs in the tumor cell population from 10% to more than 30%. Our long-term goal is to improve TTFields antitumoral activity by linking brain stimulation with a pharmacological strategy targeting GSC proliferation. The objective of our study is to test the therapeutic potential of combining TTFields exposure with the inhibition of the protein transmembrane Chloride Intracellular Channel 1 (tmCLIC1), which is crucial for GSCs proliferation. tmCLIC1 activity increases under oxidative stress conditions. Preliminary experiments using the INOVITRO-LIVE system showed a cytoplasmic oxidation increase under acute TTFields stimulation. tmCLIC1 impairment by ion channel specific antagonists affected the G1/S checkpoint and hence, tumor cell proliferation. Targeting synergically different glioblastoma cell cycle checkpoints, G2/M with TTFields stimulation and G1/S with tmCLIC1 inhibition, would include the vast majority of glioblastoma cell population. Combination TTFields exposure and tmCLIC1 ion channel inhibition could represent an efficacious step forward in the treatment of glioblastoma. Citation Format: Michele Mazzanti, Stefania Castiglione, Matteo Ranucci, Gaetano Cannavale, Francesca Cianci, Ivan Verduci. Synergic antitumoral activity of TTFields stimulation and Chloride Intracellular Channel 1 (CLIC1) inhibition in human glioblastoma primary culture [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2315.

Enhanced Natural Killers with CISH and B2M Gene Knockouts Reveal Increased Cytotoxicity in Glioblastoma Primary Cultures

In an experimental study using the CRISPR/Cas9 system, "enhanced" NK cell lines with knockout of CISH, the gene for the CIS protein (a negative regulator of NK cytotoxicity), as well as two lines with a knocked-out β2-microglobulin gene, which provides membrane exposure of MHC class I, were obtained from two parental lines of human natural killers (YT wild type and YT-VAV1^(+) overexpressing the VAV1 cytotoxicity enhancing protein). The knockout efficiency was determined by real-time PCR as well as by flow cytometry with specific antibodies. The resulting CISH^(-/-) or B2M^(-/-) knockout lines were tested for cytotoxicity in primary monolayer cultures of human glioblastoma multiforme. The cytotoxicity of the lines was assessed using a cell analyzer that records the cell index based on cell impedance. YT-CISH^(-/-) has been shown to be significantly more effective than wild-type YT in eliminating primary glioblastoma cells in an in vitro cell monolayer experiment. The cytotoxicity of the YT-VAV1^(+)-CISH^(-/-) and YT-VAV1^(+)B2M^(-/-) lines against glioblastoma cells was the highest, but overall, it did not significantly differ from the initially increased cytotoxicity of the YT-VAV1^(+) line. The lines of NK-like cells obtained may serve as a prototype for the creation of "enhanced" allogeneic and autologous NK- and CAR-NK cells for the immunotherapy of glioblastoma multiforme.

Histone Deacetylase Inhibitors Impair Glioblastoma Cell Motility and Proliferation.

Simple SummaryGlioblastoma (GBM) is considered the deadliest brain tumor; with patients displaying a high incidence of relapse and a 3-year survival of only 3–5%. For these reasons, investigation of the molecular basis of the disease could provide novel targets for therapy and improve patient prognoses. Based on our previous data, demonstrating that high levels of the transcription factor TCF4 (TCF7L2) sustain the aggressiveness and the stem cell features of these tumors, in this study we tested the ability of the histone deacetylase inhibitors (HDI) Trichostatin-A and Vorinostat to suppress TCF4 levels. We demonstrated that HDI treatment impairs proliferation and viability of GBM cells. Moreover, molecular analysis of HDI effects disclosed their ability to counteract tumor cell motility by affecting the RhoA-GTPase and the interferon pathways, supporting their further characterization as potential anti-GBM agents.Despite being subjected to high-dose chemo and radiotherapy, glioblastoma (GBM) patients still encounter almost inevitable relapse, due to the capability of tumor cells to disseminate and invade normal brain tissues. Moreover, the presence of a cancer stem cell (CSC) subpopulation, already demonstrated to better resist and evade treatments, further frustrates potential therapeutic approaches. In this context, we previously demonstrated that GBM is characterized by a tightly-regulated balance between the β-catenin cofactors TCF1 and TCF4, with high levels of TCF4 responsible for sustaining CSC in these tumors; thus, supporting their aggressive features. Since histone deacetylase inhibitors (HDI) have been reported to strongly reduce TCF4 levels in colon cancer cells, we hypothesized that they could also exert a similar therapeutic action in GBM. Here, we treated primary GBM cultures with Trichostatin-A and Vorinostat, demonstrating their ability to strongly suppress the Wnt-dependent pathways; thus, promoting CSC differentiation and concomitantly impairing GBM cell viability and proliferation. More interestingly, analysis of their molecular effects suggested a prominent HDI action against GBM cell motility/migration, which we demonstrated to rely on the inhibition of the RhoA-GTPase and interferon intracellular cascades. Our results suggest HDI as potential therapeutic agents in GBM, through their action on multiple cancer hallmarks.

TAMI-10. CHARACTERIZATION OF CANCER-ASSOCIATED FIBROBLASTS IN GBM AND DEFINING THEIR PRO-TUMORAL EFFECTS

Abstract Cancer-associated fibroblasts (CAFs) constitute a key component of the tumor microenvironment. While pro-tumoral CAFs have been identified in some cancers, CAFs had been presumed absent in glioblastoma given the lack of brain fibroblasts. We found that serial trypsinization of primary glioblastoma cultures yields cells that morphologically resemble fibroblasts and transcriptomically resemble CAFs as shown by bulk RNA-seq and single-cell RNA-seq. Moreover, Single-cell RNA-seq from patient GBMs showed a mesenchymal lineage for CAFs. We demonstrate that Glioblastoma CAFs are chemotactically attracted to glioblastoma stem cells (GSCs) and CAFs enriched GSCs. To identify CAF/GSC interaction mediators, we created a resource of inferred crosstalk by mapping the expression of receptors to their cognate ligands/agonists. This analysis suggested PDGF-b and TGF-b as mediators of GSC recruitment and proliferation of CAFs, and osteopontin and hepatocyte growth factor (HGF) as mediators of CAF-induced GSC enrichment, hypothesis confirmed by blocking antibodies. Glioblastoma CAFs also induce hypertrophied vessels and M2 macrophage polarization, the latter through unique CAF production of the EDA fibronectin variant which binds macrophage toll-like receptor 4 (TLR4) in a targetable manner. Glioblastoma CAFs were enriched in the subventricular zone which houses the neural stem cells that produce GSCs. Depleting CAFs in GSC-derived xenografts slowed their in vivo growth. These findings are among the first to identify glioblastoma CAFs and reveal their involvement with GSCs, making them an intriguing target.

Exploring the efficacy of tumor electric field therapy against glioblastoma: An in vivo and in vitro study.

AimsTumor electric fields therapy (TTFields) is emerging as a novel anti‐cancer physiotherapy. Despite recent breakthroughs of TTFields in glioma treatment, the average survival time for glioblastoma patients with TTFields is <2 years, even when used in conjugation with traditional anti‐cancer therapies. To optimize TTFields‐afforded efficacy against glioblastoma, we investigated the cancer cell‐killing effects of various TTFields paradigms using in vitro and in vivo models of glioblastoma.MethodsFor in vitro studies, the U251 glioma cell line or primary cell cultures prepared from 20 glioblastoma patients were treated with the tumor electric field treatment (TEFT) system. Cell number, volume, and proliferation were measured after TEFT at different frequencies (100, 150, 180, 200, or 220 kHz), durations (24, 48, or 72 h), field strengths (1.0, 1.5, or 2.2V/cm), and output modes (fixed or random sequence output). A transwell system was used to evaluate the influence of TEFT on the invasiveness of primary glioblastoma cells. For in vivo studies, the therapeutic effect and safety profiles of random sequence electric field therapy in glioblastoma‐transplanted rats were assessed by calculating tumor size and survival time and evaluating peripheral immunobiological and blood parameters, respectively.ResultsIn the in vitro settings, TEFT was robustly effective in suppressing cell proliferation of both the U251 glioma cell line and primary glioblastoma cell cultures. The anti‐proliferation effects of TEFT were frequency‐ and “dose” (field strength and duration)‐dependent, and contingent on the field sequence output mode, with the random sequence mode (TEFT‐R) being more effective than the fixed sequence mode (TEFT‐F). Genetic tests were performed in 11 of 20 primary glioblastoma cultures, and 6 different genetic traits were identified them. However, TEFT exhibited comparable anti‐proliferation effects in all primary cultures regardless of their genetic traits. TEFT also inhibited the invasiveness of primary glioblastoma cells in transwell experiments. In the in vivo rat model of glioblastoma brain transplantation, treatment with TEFT‐F or TEFT‐R at frequency of 200 kHz and field strength of 2.2V/cm for 14 days significantly reduced tumor volume by 42.63% (TEFT‐F vs. control, p = 0.0002) and 63.60% (TEFT‐R vs. control, p < 0.0001), and prolonged animal survival time by 30.15% (TEFT‐F vs. control, p = 0.0415) and 69.85% (TEFT‐R vs. control, p = 0.0064), respectively. The tumor‐bearing rats appeared to be well tolerable to TEFT therapies, showing only moderate increases in blood levels of creatine and red blood cells. Adverse skin reactions were common for TEFT‐treated rats; however, skin reactions were curable by local treatment.ConclusionTumor electric field treatment at optimal frequency, strength, and output mode markedly inhibits the cell viability, proliferation, and invasiveness of primary glioblastoma cells in vitro independent of different genetic traits of the cells. Moreover, a random sequence electric field output confers considerable anti‐cancer effects against glioblastoma in vivo. Thus, TTFields are a promising physiotherapy for glioblastoma and warrants further investigation.

OS06.9A Diversity of cellular communication in glioblastoma

Abstract BACKGROUND Owing to recent advances in understanding of the active functional states exhibited within glioblastoma (GBM), intra-tumoral cellular signaling has moved into focus of neuro-oncological research. In our study, we aim to explore the diversity of transcellular signaling and investigate correlations to transcriptional dynamics and cellular behavior. MATERIAL AND METHODS Electrophysiological mapping of primary GBM cultures was performed by planar microelectrodes, in conjunction with calcium imaging in a human neocortical section based GBM model. Exposure to conditions that are physiologically present within the tumor was carried out to identify specific signaling cells of interest and signaling diversity presented as response to specific environmental conditions. Transcriptional dynamics and plasticity were examined by means of scRNA-sequencing with CRISPR based perturbation, spatial transcriptomics and deep long-read RNA-sequencing. RESULTS Electrophysiological profiles of primary GBM cell lines revealed highly variable network activity. Despite these different characteristics, all profiled primary cell-lines exhibited characteristics of scale-free networks, confirmed in a human neocortical GBM model. When the GBM was allowed to grow in “in-vivo” like environment, basal activity was significantly increased, owing to interactions with elements within the neural environment. Cellular signaling was directly correlated to changes in the environment, like hypoxia or glutamatergic activation, and total inhibition of electrical signaling was achieved only with a combination of both gap junction and synaptic inhibitors. Using single-cell sequencing and proteomics, we identified several genes related to synaptogenesis that plays a crucial role in network formation and consequently transcellular signaling. CRISPR based perturbation of these genes resulted in alterations in cellular morphology and decreased cellular connectivity, with electrical signaling being significantly attenuated. Single-cell sequencing of perturbed tumor cells in the GBM model revealed a loss of developmental lineages and significant reduction of cellular stress response state. CONCLUSION Our findings highlight the role of electrical signaling in glioblastoma. Cellular stressors induce intercellular signaling, leading to transcriptional adaptation suggesting that there exists a highly complex and powerful mechanism for dynamic transcriptional state adaptation.

Abstract 1200: Long-duration term TTFields treatment of glioblastoma cells induces cell death

Abstract Glioblastoma is the most aggressive among brain tumors. Radiotherapy and chemotherapy, as adjuvanttreatments after surgical removal of the tumor mass, are often accompanied by undesirable symptoms. Evenwith these available treatment options, patient prognosis is extremely poor. The only approved treatmentoption demonstrating improved life expectancy in the last twenty years has been the application of TumorTreating Fields (TTFields). However, despite different therapeutic actions, tumor relapse occurs inexorably inmost patients. It is essentially unanimously agreed upon that tumor recurrence is due to a small populationof cells named glioblastoma stem cells (GSCs). GSCs represent a restricted cellular subpopulation in the tumormass composed mainly of bulk cells. The main characteristic of GSCs is their tumorigenic capacity even if asmall number of cells are left after surgery. Our working hypothesis is based on evidence that TTFieldsexposure destabilizes the mitotic spindle of rapidly dividing cells to elicit cell death. Thus, TTFields stimulationshould preferentially target bulk cells due to their higher proliferation rates compared to GSCs. Preliminaryexperiments performed using glioblastoma primary cultures obtained from patients' biopsies demonstratedthe presence of two different cell populations. In glioblastoma primary cultures maintained in stem-cellselective medium, more than 90% of glioblastoma cells did not exhibit stemness characteristics. After 72hours of TTFields stimulation, cell death was ascertained in approximately 50% of cells. The remaining viablecells were more than 20% positive for three different stemness markers. Long duration TTFields treatmentexperiments (144 and 288 hours) showed that TTFields at 200 kHz is able to increase the percentage of GSCin glioblastoma cells, yet did exhibit a propensity to reestablish cellular proliferation.In conclusion, long duration TTFields (200 kHz) treatment demonstrated efficacy by inducing cell death anddelaying glioblastoma cell expansion. However, to prevent glioblastoma relapse it is important to combineTTFields with different combination partners that specifically target glioblastoma stem cells. Citation Format: Stefania Castiglione, Matteo Ranucci, Gaetano Cannavale, Francesca Cianci, Ivan Verduci, Michele Mazzanti. Long-duration term TTFields treatment of glioblastoma cells induces cell death [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1200.

The Leloir Cycle in Glioblastoma: Galactose Scavenging and Metabolic Remodeling.

Simple SummaryProliferation of glioblastoma (GBM) depends on access to extracellular nutrients. Inadequate tumor perfusion creates a short supply of the most common nutrients, such as glucose (Glc) and glutamine. As a result, GBMs undergo metabolic remodeling and scavenge alternative nutrients from the tumor microenvironment for their growth and proliferation. GBM expresses sugar transporters, such as Glut3 and Glut14. Galactose (Gal) is a good substrate for Glut3/Glut14, and GBM cells can scavenge Gal from the circulation/extracellular space. The Leloir pathway allows GBM to transport and metabolize Gal at physiologic Glc concentrations, providing GBM cells with an alternate energy source. GBM cultures proliferated when grown solely on Gal. GBMs metabolize Gal via the Leloir pathway, glycolysis, and pentose phosphate pathway (PPP) to optimize ATP production, while the mitochondrial metabolism of Gal in GBM is limited. The selective targeting of the Leloir/PPP pathway may provide new treatment strategies for GBM.Background: Glioblastoma (GBM) can use metabolic fuels other than glucose (Glc). The ability of GBM to use galactose (Gal) as a fuel via the Leloir pathway is investigated. Methods: Gene transcript data were accessed to determine the association between expression of genes of the Leloir pathway and patient outcomes. Growth studies were performed on five primary patient-derived GBM cultures using Glc-free media supplemented with Gal. The role of Glut3/Glut14 in sugar import was investigated using antibody inhibition of hexose transport. A specific inhibitor of GALK1 (Cpd36) was used to inhibit Gal catabolism. Gal metabolism was examined using proton, carbon and phosphorous NMR spectroscopy, with 13C-labeled Glc and Gal as tracers. Results: Data analysis from published databases revealed that elevated levels of mRNA transcripts of SLC2A3 (Glut3), SLC2A14 (Glut14) and key Leloir pathway enzymes correlate with poor patient outcomes. GBM cultures proliferated when grown solely on Gal in Glc-free media and switching Glc-grown GBM cells into Gal-enriched/Glc-free media produced elevated levels of Glut3 and/or Glut14 enzymes. The 13C NMR-based metabolic flux analysis demonstrated a fully functional Leloir pathway and elevated pentose phosphate pathway activity for efficient Gal metabolism in GBM cells. Conclusion: Expression of Glut3 and/or Glut14 together with the enzymes of the Leloir pathway allows GBM to transport and metabolize Gal at physiological glucose concentrations, providing GBM cells with an alternate energy source. The presence of this pathway in GBM and its selective targeting may provide new treatment strategies.

ИССЛЕДОВАНИЕ МИКРОСАТЕЛЛИТНОЙ НЕСТАБИЛЬНОСТИ В ПЕРВИЧНЫХ КЛЕТОЧНЫХ ЛИНИЯХ НИЗКОДИФФЕРЕНЦИРОВАННЫХ ГЛИАЛЬНЫХ ОПУХОЛЕЙ

Glial tumors, in particular those composed of astrocytes, are the most common group of primary brain tumors. The most common glial tumor is astrocytoma. The biology of glial tumors was routinely studied on immortalized cell lines. However, multiple passages result in a loss of cellular heterogeneity. Therefore, more and more scientific laboratories in their research are beginning to use primary cell lines obtained directly from the patient’s native postoperative material. The question of the timing of the genetic stability of primary cell lines remains open. A special type of genetic instability is microsatellite instability, which affects microsatellites found throughout the genome. Microsatellites have several alleles, which are determined by changes in the number of repetitions of a motif unit. Microsatellite instability is of great importance in the oncogenesis of malignant neoplasms. The aim of this work was to study the microsatellite instability of primary cell lines of poorly differentiated glial tumors at different passages in comparison with the patient’s primary tumor material. Tumor cells of primary cultures of anaplastic astrocytoma and glioblastoma at different passages were used as material for the study. Formalin-fixed paraffin wax (FFPE) slides were used as a microsatellite control. Microsatellite analysis was performed on primary cultures of anaplastic astrocytoma and glioblastoma using the following markers: D17S250, D2S123, D5S346, NR21, NR24, NR27, BAT25, BAT26 by PCR. Microsatellite analysis has shown that primary glioblastoma cell lines are genetically more stable than primary anaplastic astrocytoma cell lines.

Differential Effects of IGF-1R Small Molecule Tyrosine Kinase Inhibitors BMS-754807 and OSI-906 on Human Cancer Cell Lines.

Simple SummaryWe have tested the effects of IGF-1R tyrosine kinase inhibitors BMS-754807 (BMS) and OSI-906 (OSI) on human colon, pancreatic carcinoma cell, and glioblastoma cell lines and primary cultures. Although OSI and BMS are able to inhibit IGF-1R activity at low doses, the differential effect on cell proliferation and cell-cycle phase distribution shown by both compounds probes that many effects observed are mediated by BMS off-target interactions. Using MAPKs ELISAs and phospho-RTK array analysis, we have identified several BMS regulated putative kinases able to mediate BMS off-target effects. Interestingly, molecular docking assays suggest that BMS could affect these kinases not only by blocking their ATP-binding domain, but also by means of allosteric interactions. Since BMS has an important antineoplastic effect on these poor prognosis types of cancer, these compounds could be taken in consideration for treatment independently of IGF-1R status.We have determined the effects of the IGF-1R tyrosine kinase inhibitors BMS-754807 (BMS) and OSI-906 (OSI) on cell proliferation and cell-cycle phase distribution in human colon, pancreatic carcinoma, and glioblastoma cell lines and primary cultures. IGF-1R signaling was blocked by BMS and OSI at equivalent doses, although both inhibitors exhibited differential antiproliferative effects. In all pancreatic carcinoma cell lines tested, BMS exerted a strong antiproliferative effect, whereas OSI had a minimal effect. Similar results were obtained on glioblastoma primary cultures, where HGUE-GB-15, -16 and -17 displayed resistance to OSI effects, whereas they were inhibited in their proliferation by BMS. Differential effects of BMS and OSI were also observed in colon carcinoma cell lines. Both inhibitors also showed different effects on cell cycle phase distribution, BMS induced G2/M arrest followed by cell death, while OSI induced G1 arrest with no cell death. Both inhibitors also showed different effects on other protein kinases activities. Taken together, our results are indicative that BMS mainly acts through off-target effects exerted on other protein kinases. Given that BMS exhibits a potent antiproliferative effect, we believe that this compound could be useful for the treatment of different types of tumors independently of their IGF-1R activation status.

Mitochondria transfer from tumor-activated stromal cells (TASC) to primary Glioblastoma cells

The tumor microenvironment (TME) controls many aspects of cancer development but little is known about its effect in Glioblastoma (GBM), the main brain tumor in adults. Tumor-activated stromal cell (TASC) population, a component of TME in GBM, was induced in vitro by incubation of MSCs with culture media conditioned by primary cultures of GBM under 3D/organoid conditions. We observed mitochondrial transfer by Tunneling Nanotubes (TNT), extracellular vesicles (EV) and cannibalism from the TASC to GBM and analyzed its effect on both proliferation and survival. We created primary cultures of GBM or TASC in which we have eliminated mitochondrial DNA [Rho 0 (ρ0) cells]. We found that TASC, as described in other cancers, increased GBM proliferation and resistance to standard treatments (radiotherapy and chemotherapy). We analyzed the incorporation of purified mitochondria by ρ0 and ρ+ cells and a derived mathematical model taught us that ρ+ cells incorporate more rapidly pure mitochondria than ρ0 cells.

Epigenetic preconditioning with decitabine sensitizes glioblastoma to temozolomide via induction of MLH1

IntroductionTo improve the standard treatment paradigm for glioblastoma (GBM), efforts have been made to explore the efficacy of epigenetic agents as chemosensitizers. Recent data suggest possible synergy between decitabine (DAC), a DNA hypomethylating agent, and temozolomide (TMZ) in GBM, but the mechanism remains unclear. The objective of this study was to determine the effects of DAC on TMZ sensitization in a consecutively derived set of primary GBM cultures, with a focus on mismatch repair (MMR) proteins.MethodsHalf maximal inhibitory concentrations (IC50) of TMZ were calculated in eleven consecutive patient-derived GBM cell lines before and after preconditioning with DAC. MMR protein expression changes were determined by quantitative immunoblots and qPCR arrays. Single-molecule real-time (SMRT) sequencing of bisulfite (BS)-converted PCR amplicons of the MLH1 promoter was performed to determine methylation status.ResultsTMZ IC50 significantly changed in 6 of 11 GBM lines of varying MGMT promoter methylation status in response to DAC preconditioning. Knockdown of MLH1 after preconditioning reversed TMZ sensitization. SMRT-BS sequencing of the MLH1 promoter region revealed higher levels of baseline methylation at proximal CpGs in desensitized lines compared to sensitized lines.ConclusionsDAC enhances TMZ cytotoxicity in a subset of GBM cell lines, comprising lines both MGMT methylated and unmethylated tumors. This effect may be driven by levels of MLH1 via E2F1 transcription factor binding. Using unbiased long-range next-generation bisulfite-sequencing, we identified a region of the proximal MLH1 promoter with differential methylation patterns that has potential utility as a clinical biomarker for TMZ sensitization.

A Simple and Reliable Protocol for the Preparation and Culturing of Fresh Surgically Resected Human Glioblastoma Tissue.

Glioblastoma is a heterogeneous glial cell malignancy with extremely high morbidity and mortality. Current treatment is limited and provide minimal therapeutic efficacy. Previous studies were reliant on cell lines that do not accurately reflect the heterogeneity of the glioma microenvironment. Developing reliable models of human glioblastoma is therefore essential. Direct culture of human brain tumours is often difficult and there is a limited number of protocols available. Hence, we have developed an effective method for the primary culture of human glioblastoma samples obtained during surgical resection. Culturing tumour tissue direct from human brain is advantageous in that cultures (1) more closely resemble true human disease, relative to the use of cell lines; (2) comprise a range of cellular components present in the natural tumour microenvironment; and (3) are free of added antibodies and reagents. Additionally, primary glioblastoma cultures are valuable in studies examining the effects of anti-cancer pharmaceuticals and therapeutic agents, and can be further used in live cell imaging, immunocytochemistry, flow cytometry and immunoassay experiments. Via this protocol, cells are maintained in supplemented medium at 37 °C (5% CO2) and are expected to achieve sufficient confluency within 7 days of initial culture.

NKG2D Controls Natural Reactivity of Vγ9Vδ2 T Lymphocytes against Mesenchymal Glioblastoma Cells

Cellular immunotherapies are currently being explored to eliminate highly invasive and chemoradioresistant glioblastoma (GBM) cells involved in rapid relapse. We recently showed that concomitant stereotactic injections of nonalloreactive allogeneic Vγ9Vδ2 T lymphocytes eradicate zoledronate-primed human GBM cells. In the present study, we investigated the spontaneous reactivity of allogeneic human Vγ9Vδ2 T lymphocytes toward primary human GBM cells, in vitro and in vivo, in the absence of any prior sensitization. Through functional and transcriptomic analyses, we extensively characterized the immunoreactivity of human Vγ9Vδ2 T lymphocytes against various primary GBM cultures directly derived from patient tumors. We evidenced that GBM cells displaying a mesenchymal signature are spontaneously eliminated by allogeneic human Vγ9Vδ2 T lymphocytes, a reactivity process being mediated by γδ T-cell receptor (TCR) and tightly regulated by cellular stress-associated NKG2D pathway. This led to the identification of highly reactive Vγ9Vδ2 T lymphocyte populations, independently of a specific TCR repertoire signature. Moreover, we finally provide evidence of immunotherapeutic efficacy in vivo, in the absence of any prior tumor cell sensitization. By identifying pathways implicated in the selective natural recognition of mesenchymal GBM cell subtypes, accounting for 30% of primary diagnosed and 60% of recurrent GBM, our results pave the way for novel targeted cellular immunotherapies.