Primary Glioblastoma Cells Research Articles

Involvement of the tumour necrosis factor receptor system in glioblastoma cell death induced by palbociclib-heptamethine cyanine dye conjugate

Glioblastoma is the most common and aggressive primary brain tumour in adults. The development of anti-brain cancer agents are challenged by the blood-brain barrier and the resistance conferred by the local tumour microenvironment. Heptamethine cyanine dyes (HMCDs) are a class of near-infrared fluorescence compounds that have recently emerged as promising agents for drug delivery. We conjugated palbociclib, a cyclin-dependent kinase (CDK) 4/6 inhibitor, to an HMCD, MHI-148, and conducted drug activity analysis on primary patient-derived glioblastoma cell lines. In addition to the expected cytostatic activity, our in vitro studies revealed that palbociclib-MHI-148 conjugate resulted in an almost 100-fold increase in cytotoxicity compared to palbociclib alone. This shift of palbociclib from cytostatic to cytotoxic when conjugated to MHI-148 was due to increased DNA damage, as indicated by an increase in γH2AX foci, followed by an increased expression of key extrinsic apoptosis genes, including TP53, TNFR1, TRAIL, FADD and caspase 8. In addition, we observed a time-dependent increase in the cell surface expression of TNFR1, consistent with an observed increase in the secretion TNFα, followed by TNFR1 endocytosis at 48 h. The treatment of patient GBM cells with the palbociclib-MHI-148 conjugate prevented TNFα-induced NFκB translocation, suggesting conjugate-induced TNFR1 signalling favoured the TNFR1-mediated apoptotic response rather than the pro-inflammatory response pathway. Notably, pharmacological inhibition of endocytosis of TNFR1, and siRNA-knockdown of TNFR1 reversed the palbociclib-MHI-148-induced cell death. These results show a novel susceptibility of glioblastoma cells to TNFR1-dependent apoptosis, dependent on inhibition of canonical NFκB signalling using our previously reported palbociclib-HMCD conjugate.9u5DmcuTyYJ7m7Hnyrq7sRVideo

Effect of Oxygen Tension on Glioblastoma Cell Growth

Background and Hypothesis:Glioblastoma (GBM) is an aggressive primary malignancy of the CNS with a dismal prognosis (~15-20 months) despite standard of care therapies. The poor prognosis of GBM despite ongoing research may be due to inaccuracies in preclinical models of the disease. Cell lines typically used to study GBM are exposed to ambient air containing 21% oxygen (normoxia compared to physiologic oxygen tension, physoxia, ~5%). In extracranial tumors, exposure to the oxygen in ambient air triggers epigenetic changes that alter cell growth, metabolism, and treatment responsiveness. The aim of this study is to obtain preliminary data on the impact ofphysiologic oxygen tensions on primary glioma cell growth in vitro.
 Experimental Design:Growth of primary glioma cell lines (GB43, GB10, GB001) and one immortalized cell line (293T HEK) was assessed in normoxia and physoxia. All cell lines were plated at 10,000 cells per well. Cells were harvested and counted in triplicate on days 2, 4, 6, 8, 10, 12. On each day the cells were counted, the media in the remaining wells was changed. This experiment was repeated three times. Wound healing assays with all cell lines were also performed at normoxia and physoxia.
 Results:Cells line growth curves were plotted and showed consistent exponential growth after counting on day two. From these graphs, the cell doubling time was calculated over a period of four days during which the cells were undergoing exponential growth.
 Conclusions:Current results indicated that primary glioblastoma cell lines grow at different rates at differing oxygen tensions. In ongoing studies, we are exploring the effect of low oxygen tensions on functional assays such as wound-healing. Future work will assess rates of growth and functional consequence of physoxia in tumor samples never exposed to ambient air to most accurately recapitulate the in-situ environment.

Selenoprotein P expression in glioblastoma as a regulator of ferroptosis sensitivity: preservation of GPX4 via the cycling-selenium storage

Glioblastoma (GBM) is one of the most aggressive and deadly brain tumors; however, its current therapeutic strategies are limited. Selenoprotein P (SeP; SELENOP, encoded by the SELENOP gene) is a unique selenium-containing protein that exhibits high expression levels in astroglia. SeP is thought to be associated with ferroptosis sensitivity through the induction of glutathione peroxidase 4 (GPX4) via selenium supplementation. In this study, to elucidate the role of SeP in GBM, we analyzed its expression in GBM patients and found that SeP expression levels were significantly higher when compared to healthy subjects. Knock down of SeP in cultured GBM cells resulted in a decrease in GPX1 and GPX4 protein levels. Under the same conditions, cell death caused by RSL3, a ferroptosis inducer, was enhanced, however this enhancement was canceled by supplementation of selenite. These results indicate that SeP expression contributes to preserving GPX and selenium levels in an autocrine/paracrine manner, i.e., SeP regulates a dynamic cycling-selenium storage system in GBM. We also confirmed the role of SeP expression in ferroptosis sensitivity using patient-derived primary GBM cells. These findings indicate that expression of SeP in GBM can be a significant therapeutic target to overcome anticancer drug resistance.

Alkoxy-functionalised dihydropyrimido[4,5-b]quinolinones enabling anti-proliferative and anti-invasive agents.

In this communication, we explored the synthesis of novel alkoxy-functionalised dihydropyrimido[4,5-b]quinolinones using a microwave-assisted multicomponent reaction. All the synthesized molecules were screened for anti-proliferative and anti-invasive activity against glioblastoma cells. 5c shows the most potent anti-proliferative activity with a half maximal effective concentration of less than 3 μM against primary patient-derived glioblastoma cells. 5c effectively inhibited invasion and tumor growth of 3D primary glioma cultures in a basement membrane matrix. This suggests that the novel compounds could inhibit both the proliferation and invasive spread of glioma and they were selected for further study.

One-pot synthesis of tetrahydropyrimidinecarboxamides enabling in vitro anticancer activity: a combinative study with clinically relevant brain-penetrant drugs.

In this study, we describe a one-pot three-component synthesis of bioactive tetrahydopyrimidinecarboxamide derivatives employing lanthanum triflate as a catalyst. Out of the synthesized compounds, 4f had the most potent anti-cancer activity and impeded cell cycle progression effectively. Anti-cancer bioactivity was observed in 4f against liver, breast, and lung cancers as well as primary patient-derived glioblastoma cell lines. Compound 4f effectively inhibited the 3D neurosphere formation in primary patient-derived glioma stem cells. Specifically, 4f exhibited synergistic cytotoxicity with the EGFR inhibitor that is the clinical epidermal growth factor receptor inhibitor osimertinib. 4f does not exhibit anti-kinase activity and is cytostatic in nature, and further work is needed to understand the true molecular target of 4f and its derivatives. Through our current work, we establish a promising tetrahydopyrimidinecarboxamide-based lead compound with anti-cancer activity, which may exhibit potent anti-cancer activity in combination with specific clinically relevant small molecule kinase inhibitors.

CRISPR-Cas9 library screening combined with an exosome-targeted delivery system addresses tumorigenesis/TMZ resistance in the mesenchymal subtype of glioblastoma.

Rationale: The large-scale genomic analysis classifies glioblastoma (GBM) into three major subtypes, including classical (CL), proneural (PN), and mesenchymal (MES) subtypes. Each of these subtypes exhibits a varying degree of sensitivity to the temozolomide (TMZ) treatment, while the prognosis corresponds to the molecular and genetic characteristics of the tumor cell type. Tumors with MES features are predominantly characterized by the NF1 deletion/alteration, leading to sustained activation of the RAS and PI3K-AKT signaling pathways in GBM and tend to acquire drug resistance, resulting in the worst prognosis compared to other subtypes (PN and CL). Here, we used the CRISPR/Cas9 library screening technique to detect TMZ-related gene targets that might play roles in acquiring drug resistance, using overexpressed KRAS-G12C mutant GBM cell lines. The study identified a key therapeutic strategy to address the chemoresistance against the MES subtype of GBM. Methods: The CRISPR-Cas9 library screening was used to discover genes associated with TMZ resistance in the U87-KRAS (U87-MG which is overexpressed KRAS-G12C mutant) cells. The patient-derived GBM primary cell line TBD0220 was used for experimental validations in vivo and in vitro. Chromatin isolation by RNA purification (ChIRP) and chromatin immunoprecipitation (ChIP) assays were used to elucidate the silencing mechanism of tumor suppressor genes in the MES-GBM subtype. The small-molecule inhibitor EPIC-0412 was obtained through high-throughput screening. Transmission electron microscopy (TEM) was used to characterize the exosomes (Exos) secreted by GBM cells after TMZ treatment. Blood-derived Exos-based targeted delivery of siRNA, TMZ, and EPIC-0412 was optimized to tailor personalized therapy in vivo. Results: Using the genome-wide CRISPR-Cas9 library screening, we found that the ERBIN gene could be epigenetically regulated in the U87-KRAS cells. ERBIN overexpression inhibited the RAS signaling and downstream proliferation and invasion effects of GBM tumor cells. EPIC-0412 treatment inhibited tumor proliferation and EMT progression by upregulating the ERBIN expression both in vitro and in vivo. Genome-wide CRISPR-Cas9 screening also identified RASGRP1(Ras guanine nucleotide-releasing protein 1) and VPS28(Vacuolar protein sorting-associated protein 28) genes as synthetically lethal in response to TMZ treatment in the U87-KRAS cells. We found that RASGRP1 activated the RAS-mediated DDR pathway by promoting the RAS-GTP transformation. VPS28 promoted the Exos secretion and decreased intracellular TMZ concentration in GBM cells. The targeted Exos delivery system encapsulating drugs and siRNAs together showed a powerful therapeutic effect against GBM in vivo. Conclusions: We demonstrate a new mechanism by which ERBIN is epigenetically silenced by the RAS signaling in the MES subtype of GBM. Restoration of the ERBIN expression with EPIC-0412 significantly inhibits the RAS signaling downstream. RASGRP1 and VPS28 genes are associated with the promotion of TMZ resistance through RAS-GDP to RAS-GTP transformation and TMZ efflux, as well. A quadruple combination therapy based on a targeted Exos delivery system demonstrated significantly reduced tumor burden in vivo. Therefore, our study provides new insights and therapeutic approaches for regulating tumor progression and TMZ resistance in the MES-GBM subtype.

Dual-Responsive Nanorobot-Based Marsupial Robotic System for Intracranial Cross-Scale Targeting Drug Delivery.

Nanorobots capable of active movement are an exciting technology for targeted therapeutic intervention. However, the extensive motion range and hindrance of the blood-brain barrier impeded their clinical translation in glioblastoma therapy. Here, a marsupial robotic system constructed by integrating chemical/magnetic hybrid nanorobots (child robots) with a miniature magnetic continuum robot (mother robot) for intracranial cross-scale targeting drug delivery is reported. For primary targeting on macroscale, the continuum robot enters the cranial cavity through a minimally invasive channel (e.g., Ommaya device) in the skull and transports the nanorobots to pathogenic regions. Upon circumventing the blood-brain barrier, the released nanorobots perform secondary targeting on microscale to further enhance the spatial resolution of drug delivery. In vitro experiments against primary glioblastoma cells derived from different patients are conducted for personalized treatment guidance. The operation feasibility within organisms is shown in ex vivo swine brain experiments. The biosafety of the treatment system is suggested in in vivo experiments. Owing to the hierarchical targeting method, the targeting rate, targeting accuracy, and treatment efficacy have improved greatly. The marsupial robotic system offers a novel intracranial local therapeutic strategy and constitutes a key milestone in the development of glioblastoma treatment platforms.

EXTH-78. CRISPROFF EPIGENOME EDITING AND FUNCTIONAL GENOMICS DEFINE MEDIATORS OF CHEMOTHERAPY RESISTANCE IN GLIOBLASTOMA

Abstract Alkylating chemotherapies exhibit survival benefit for patients with glioblastoma (GBM). CRISPRoff is a programmable epigenetic memory writer that stably and heritably silences genes through DNA methylation. Epigenetic silencing of MGMT via promoter methylation predicts response to chemotherapy and is prognostic for overall survival. Here, we performed epigenome editing using CRISPRoff to stably silence MGMT through induced promoter methylation as a therapeutically tractable approach for potentiating GBM to chemotherapy. We then used genome-wide CRISPR interference (CRISPRi) screens to broadly define novel chemosensitizing targets of GBM cells. Epigenome editing was performed through electroporation of CRISPRoff mRNA and sgRNAs into MGMT hypomethylated GBM cell lines (LN18 and T98G) and primary GBM cells. Whole genome bisulfite sequencing, RT-qPCR, and western blot assessed gene silencing. Cell viability assays measured drug sensitivity. GBM xenografts with CRISPRoff-induced silencing of MGMT were intracranially transplanted in mice and treated with temozolomide. Genome-wide functional genomics screens were performed using CRISPR interference. CRISPRoff against MGMT reduced MGMT mRNA and protein levels by 99.97%, generating up to 150-fold sensitization to temozolomide and 9-fold sensitization to lomustine in GBM cells. Silencing remained stable and heritable in clonally isolated GBM cells at 145 days after transient delivery of CRISPRoff, and gene repression and drug sensitization were equivalent to Cas9-mediated homozygous deletion of MGMT in vitro and in vivo. CRISPRoff of MGMT in intracranial xenografts exhibited significant reduction in tumor growth with temozolomide treatment compared to temozolomide treatment with control CRISPRoff (p = 0.0047). CRISPRi screens validated MGMT and defined 266 and 238 additional modifiers of temozolomide and lomustine response, respectively, including the ATR (BRCA2), DNA repair (REV1), cell cycle (PSMD13), and Fanconi anemia pathways (FANCI, FANCD2). In summary, we integrate targeted epigenome editing with unbiased genome-wide approaches to establish a novel discovery and therapeutic platform against glioblastoma.

STEM-17. IMPLICATING ASTROCYTE PROGENITOR SIGNATURES FROM THE DEVELOPING HUMAN SUBVENTRICULAR ZONE IN GLIOBLASTOMA PROGRESSION AND RECURRENCE

Abstract Although astrocyte-like progenitors in the adult subventricular zone (SVZ) have been put forward as the glioblastoma (GBM) cell of origin, the mechanisms that trigger astrogenesis in the developing SVZ are poorly understood. We previously reconstructed astrocyte lineages using computational tools and identified PDGFRβ+ astrogenesis-committed radial glia (RG-A) and EGFR+ gliogenic intermediate progenitor cells (gIPCs). We have, however, yet to identify the transcription factors (TFs) that drive the differentiation of these progenitors in the pre- and postnatal SVZ. As malignant cells are known to co-opt neurodevelopmental pathways, the exploitation of TF driver vulnerabilities in malignant cells could bring novel therapeutic strategies to hinder GBM progression or recurrence. Here, we integrated single nucleus RNA- (snRNA-seq) and ATAC-sequencing (snATAC-seq) datasets from 1) surgically resected GBMs (n = 5), 2) the subventricular zone and neocortex from non-pathological adult cortices (n = 3) and 3) the corresponding germinal matrix and cortical plate of non-pathological cortices ranging from 17 to 41 gestational weeks (n = 17) and 21 to 301 postnatal days in age (n = 9). To prioritize candidate drivers of astrogenesis computationally, we correlated motif enrichment with gene expression over pseudotime in gIPC and RG-A lineages. Subsequently, we projected transcriptional signatures from non-pathological neocortices onto GBMs. Interestingly, we observed high proportions of tumor cells with preferentially enriched prenatal gIPC-like signature in EGFR amplified GBMs and with preferentially enriched postnatal RG-A-like signature in GBMs with PFGFRα or FGFR3 amplification. As tumor recurrence is associated with a mesenchymal-like switch, we were intrigued to find that RG-A-like cells exhibited a mesenchymal-like phenotype in a recurrent GBM. Currently, we are developing an in vitro assay to manipulate the expression of astrogenic drivers and force the differentiation of patient-derived, primary GBM cells into astrocytes; a strategy that we will later apply in patient-derived xenograft models.

CNSC-29. NKCC1 SIGNALING IN GLIOBLASTOMA REGULATES NEURONAL HYPEREXCITABILITY THROUGH GABAERGIC TONE

Abstract Over 90% of patients with glioma experience tumor-associated epilepsy, however first-line treatment fails to control seizures in most patients. Thus, there is a critical need to identify novel drivers of glioblastoma-induced neuronal hyperexcitability. We therefore used high-density electrode arrays to record local field potentials in vivo from gliomas. We then developed cerebral organoid and mouse models using primary glioblastoma cells from patients and neurons derived from induced pluripotent stem cells. Single-cell RNA sequencing (13,730 cells analyzed) in this system identified genes elevated in glioma-intrinsic neurons, including the sodium-potassium-chloride co-transporter 1 (NKCC1), which mediates chloride (Cl-) influx into cells. This elevated NKCC1 expression and subsequent increase of intracellular Cl- sets the reversal potential of GABAAR-mediated currents promoting depolarizing excitatory GABAergic responses. Electrophysiological analysis of glioma-neuron co-cultures using multi-electrode array and live-cell calcium imaging demonstrated increased network burst synchrony in the presence of NKCC1-high expressing tumor cells. Single-nucleus sequencing (54,000 cells analyzed) of embryonic neurons in co-culture with GBM cells further confirmed the elevated expression of circuit assembly genes including neuronal NKCC1. Live-cell imaging of iPSC-induced neuron organoids co-cultured with NKCC1-high-and low-GBM cells revealed increased migration and integration of NKCC1-elevated tumor cells. Mechanistic and functional studies validating therapeutic vulnerabilities to NKCC1 silencing by shRNA knockdown and by the FDA-approved diuretic drug, bumetanide was performed in vitro. The reduction in neuronal synchrony induced by NKCC1 downregulation correlated with a decrease in extracellular GABA and glutamate, suggesting a strong association between excitatory GABAergic and glutamate signaling with neuronal hypersynchrony in glioblastoma. Patient-derived xenograft in vivo experiments evaluated the effect of NKCC1 on tumor growth and progression and NKCC1-high GBM cells exhibited greater tumor burden compared to control mice. Collectively, these findings reveal a novel mechanism driving neuronal hyperactivity in glioblastoma and identifies potential therapeutic vulnerabilities for the treatment of glioma-associated epilepsy.

CNSC-26. GLIOBLASTOMA-NEURONAL CIRCUIT INTEGRATION IS MODULATED BY INTERLEUKIN-6

Abstract The pleiotropic cytokine interleukin-6 (IL-6) is known to be involved in both pro- and anti-inflammatory signaling cascades. In glioblastoma studies using animal and human models, IL-6 promotes immunosuppression and tumor progression and is negatively associated with survival. Intriguingly, IL-6 also contributes to increased synaptogenesis during development and following focal brain injury. Glioblastoma remodeling of neuronal circuits influences patient survival; therefore, it is possible that IL-6 has mechanistic significance. Here, we investigated IL-6 as a driver of activity-dependent glioblastoma proliferation using patient-derived xenograft (PDX) mouse and human glioblastoma models. We assessed neuronal activity by microelectrode arrays and in vitro calcium imaging using weighted mean firing rate (WMFR), network burst frequency (NBF), and synchrony index. Next, we used bulk and single-cell RNA sequencing on 13,731 cells from ten tumors including pair-matched samples to identify differentially expressed genes in intratumoral regions with elevated functional connectivity and found IL6 to be highly upregulated. Mouse embryonic cortical neurons and cerebral organoids co-cultured with primary patient-derived glioblastoma cells demonstrated concentration-dependent neuronal hyperexcitability (increased WMFR and NBF) in IL-6-overexpressing conditions compared to the neuron-only condition. Pharmacological inhibition using the humanized IL-6 receptor antibody tocilizumab reduced network synchrony across models. These findings suggest that IL-6-induced glioma-neuronal hyperexcitability may be inhibited by the FDA-approved tocilizumab, thereby providing preclinical support for its use to treat activity-dependent mechanisms of glioblastoma proliferation. Future studies are needed to uncover mechanisms and clinical efficacy.

RBIO-09. HMGB2 INHIBITION RADIO-SENSITIZES GLIOBLASTOMA CELLS INDEPENDENTLY OF THEIR TP53-MUTATION STATUS

Abstract Alterations in TP53 are major drivers of radiation resistance in gliomas. High Mobility Group Box 2 (HMGB2) has been implicated in resistance to temozolomide through p53-phosphorylation during DNA double-strand break repair and in silico analysis suggests its involvement in the p53-p21-RB signaling pathway. Nevertheless, the role of HMGB2 in radiation response has not been fully explored in gliomas. While HMGB2 is virtually not expressed in the normal adult brain, increasing expression with histopathological glioma grade correlates with poor patient survival. We confirmed increased HMGB2 expression in grade 3 compared to grade 2 gliomas using ClariomD and observed spatial heterogeneous HMGB2 expression in glioblastomas (GBMs) in histopathology-targeted supervised proteomic analysis employing liquid chromatography tandem mass spectroscopy (LC-MS-MS). Here, we aimed to study HMGB2 effects in cell proliferation and response to radiation in a set of molecularly distinct genetically engineered GBM cell lines (IDHwt). Using an established U87 GBM cell line and isogenic primary GBM cell lines GBM3359 TP53wt and CRISPR/Cas9-engineered mutant TP53 (R248W) generated in our laboratory, we successfully produced clones with either HMGB2 shRNA knockdown (KD – over 70% reduction) or HMGB2 lentiviral-mediated overexpression (OE – 3-76x higher expression). HMGB2-KD reduced cell proliferation (10% in U87; 20-25% in isogenic GBM3359 cell lines) and colony formation (more than 50% reduction), which was further rescued with HMGB2 OE in all cell lines. Half maximal inhibitory concentration (IC50) for radiation was determined by methylene blue cell proliferation and clonogenic assays, which showed that HMGB2-KD decreased the IC50 while rescued HMGB2 OE increased RT resistance of all clones. Taken together, our data suggest that HMGB2 inhibition may improve radiation response independently of TP53 status in gliomas. Further mechanistic studies to elucidate the relationship between HMGB2 and TP53 are underway to unfold the contribution of heightened HMGB2 expression to radiation resistance mechanisms in gliomas.

STEM-16. PROMOTING THE CANCER STEM CELL SUBPOPULATION AND PHENOTYPE IN GLIOBLASTOMA VIA EXTRACELLULAR VESICLE CROSS-TALK

Abstract INTRODUCTION Extracellular vesicles (EVs) released from cancer cells contain bioactive molecules that have been long implicated in tumorigenesis. In glioblastoma (GBM), there is mounting evidence that EVs play a role in critical processes including angiogenesis, immune suppression, and invasion. GBM secreted EVs have also been demonstrated to promote a cancer stem cell (CSC) phenotype by transporting stemness markers and proteins (I.e. Notch-1) involved in stem-cell activating pathways. Understanding the maintenance of CSCs, which contributes to tumor proliferation, treatment resistance, and re-expansion of the tumor bulk, can offer insight into new therapeutic drug targets that can disrupt this subpopulation. METHODS EVs were isolated from patient-derived primary GBM cell lines maintained as adherent cultures and free floating spheres (n = 3) using a staged ultracentrifugation technique. Normal astrocytes were used as the control group (n = 1). Protein expression profiles were then generated via high-throughput mass spectrometry for both EVs and whole cell lysate samples from the same cell line and compared against each other. RESULTS EGF-containing fibulin extracellular matrix protein 1 (EFEMP1) was shown to be upregulated in GBM derived EVs compared to control. Further analysis shows that EFEMP1 is enhanced in adherent cultures compared to free floating sphere cultures. CONCLUSION EFEMP1 is an extracellular matrix protein that has been identified as an oncogenic protein in GBM by activating Notch-1, Akt, and NF-Kb signaling pathways resulting in increased Temozolomide resistance, cellular proliferation, and invasion, all of which are hallmark characteristics of CSCs. EFEMP1 is also a downstream effector in the HIF-1 pathway, which has been strongly correlated in the maintenance of CSCs. Our results therefore demonstrate a possible EV mediated mechanism for the maintenance of the CSC population and phenotype in GBM.

Retraction Note: Dissecting the role of novel EZH2 inhibitors in primary glioblastoma cell cultures: effects on proliferation, epithelialmesenchymal transition, migration, and on the pro-inflammatory phenotype

Retraction Note: Dissecting the role of novel EZH2 inhibitors in primary glioblastoma cell cultures: effects on proliferation, epithelialmesenchymal transition, migration, and on the pro-inflammatory phenotype

The Signaling of Neuregulin-Epidermal Growth Factor Receptors and Its Impact on the Nervous System

The activation of members of the Epidermal Growth Factor Receptor (EGFR) family (including ErbB) triggers pathways that have significant effects on cellular processes and have profound consequences both in physiological and pathological conditions. Within the nervous system, the neuregulin (NRG)/ErbB3 signaling plays a crucial role in promoting the formation and maturation of excitatory synapses. Noteworthy is ErbB3, which is actively involved in the process of cerebellar lamination and myelination. All members of the ErbB-family, in particular ErbB3, have been observed within the nuclei of various cell types, including both full-length receptors and alternative variants. One of these variants was detected in Schwann cells and in glioblastoma primary cells where it showed a neuregulin-dependent expression. It binds to promoters’ chromatin associated with genes, like ezrin, involved in the formation of Ranvier’s node. Its nucleolar localization suggests that it may play a role in ribosome biogenesis and in cell proliferation. The regulation of ErbB3 expression is a complex and dynamic process that can be influenced by different factors, including miRNAs. This mechanism appears to play a significant role in glioblastoma and is often associated with a poor prognosis. Altogether, the targeting of ErbB3 has emerged as an active area of research in glioblastoma treatment. These findings highlight the underappreciated role of ErbB3 as a significant receptor that can potentially play a pivotal role in diverse pathologies, implying the existence of a shared and intricate mechanism that warrants further investigation.

Ribosomal S6 protein kinase 4 promotes resistance to EZH2 inhibitors in glioblastoma.

Glioblastoma (GBM) is a highly malignant type of brain tumor with limited treatment options. Recent research has focused on epigenetic regulatory factors, such as Enhancer of Zeste Homolog 2 (EZH2), which plays a role in gene expression through epigenetic modifications. EZH2 inhibitors have been developed as potential therapeutic agents for GBM, but resistance to these inhibitors remains a considerable challenge. This study aimed to investigate the role of ribosomal S6 protein kinase 4 (RSK4) in GBM and its association with resistance to EZH2 inhibitors. We first induced drug resistance in primary GBM cell lines by treatment with an EZH2 inhibitor and observed increases in the expression of stemness markers associated with glioblastoma stem cells (GSCs) in the drug-resistant cells. We also found high expression of RSK4 in GBM patient samples and identified the correlation of high RSK4 expression with poor prognosis and GSC marker expression. Further experiments showed that knocking down RSK4 in drug-resistant GBM cells restored their sensitivity to EZH2 inhibitors and decreased the expression of GSC markers, thus reducing their self-renewal capacity. From a mechanistic perspective, we discovered that RSK4 directly phosphorylates EZH2, activating the EZH2/STAT3 pathway and promoting resistance to EZH2 inhibitors in GBM. We also found that combining EZH2 inhibitors with an RSK4 inhibitor called BI-D1870 had better inhibitory effects on GBM occurrence and progression in both in vitro and in vivo experiments. In conclusion, this study demonstrates that RSK4 enhances cancer stemness and mediates resistance to EZH2 inhibitors in GBM. Combination treatment with EZH2 inhibitors and RSK4 inhibitors is a promising potential therapeutic strategy for GBM. Collectively, our results strongly demonstrate that RSK4 regulates the EZH2/STAT3 pathway to promote GSC maintenance and EZH2i resistance in a PRC2-independent manner, indicating that RSK4 is a promising therapeutic target for GBM.

Formulation of multicomponent inclusion complex of cyclodextrin-amino acid with Chrysin: Physicochemical characterization, cell viability and apoptosis assessment in human primary glioblastoma cell line

Chrysin (CR) is a water-insoluble drug reported for different therapeutic effects. The microwave irradiation method was used in this study to create a multicomponent inclusion complex (CR-MC) containing CR (drug) and carrier hydroxyl propyl beta cyclodextrin (HP β CD) and L-arginine (LA). The prepared inclusion complex (CR-MC) was evaluated for dissolution study and results were compared with chrysin physical mixture (CR-PM). Further, the samples were assessed for infra-red (IR), nuclear magnetic resonance (NMR), differential scanning calorimeter (DSC), scanning electron microscope (SEM) and molecular docking. Finally, the cell viability, reactive oxygen species and flow cytometer studies were also assessed to check the potential of the prepared inclusion complex on the human primary glioblastoma cell line (U87-MG cell). The phase solubility findings revealed a stability constant (773 mol L−1) as well as a complexation efficiency of 0.027. The dissolution study displayed a significant increase in CR release from CR-MC (99.03 ± 0.39%) > CR-PM (70.58 ± 1.16%) > pure CR (35.29 ± 1.55%). NMR and IR spectral data revealed no interaction between CR and carriers. SEM and DSC study results revealed the conversion into amorphous form. The molecular docking results illustrated a high docking score, which supports the findings of complex formation. The cell viability, reactive oxygen species, and flow cytometry studies results showed enhanced activity from CR-MC against the tested human primary glioblastoma cell line. From the results it has been observed that chrysin solubility significantly increased after complexation and there in vitro activity also enhanced against cancer cell line.

Anticancer Activity of Measles-Mumps-Rubella MMR Vaccine Viruses against Glioblastoma.

Oncolytic viruses (OVs) have been utilized since 1990s for targeted cancer treatment. Our study examined the Measles-Mumps-Rubella (MMR) vaccine's cancer-killing potency against Glioblastoma (GBM), a therapy-resistant, aggressive cancer type. We used GBM cell lines, primary GBM cells, and normal mice microglial cells, to assess the MMR vaccine's efficacy through cell viability, cell cycle analysis, intracellular viral load via RT-PCR, and Transmission Electron Microscopy (TEM). After 72 h of MMR treatment, GBM cell lines and primary GBM cells exhibited significant viability reduction compared to untreated cells. Conversely, normal microglial cells showed only minor changes in viability and morphology. Intracellular viral load tests indicated GBM cells' increased sensitivity to MMR viruses compared to normal cells. The cell cycle study also revealed measles and mumps viruses' crucial role in cytopathic effects, with the rubella virus causing cell cycle arrest. Herein the reported results demonstrate the anti-cancer activity of the MMR vaccine against GBM cells. Accordingly, the MMR vaccine warrants further study as a potential new tool for GBM therapy and relapse prevention. Therapeutic potential of the MMR vaccine has been found to be promising in earlier studies as well.

Antiproliferative effect of boldine on neural progenitor cells and on glioblastoma cells.

The subventricular zone (SVZ) is a brain region that contains neural stem cells and progenitor cells (NSCs/NPCs) from which new neurons and glial cells are formed during adulthood in mammals. Recent data indicate that SVZ NSCs are the cell type that acquires the initial tumorigenic mutation in glioblastoma (GBM), the most aggressive form of malignant glioma. NSCs/NPCs of the SVZ present hemichannel activity whose function has not yet been fully elucidated. In this work, we aimed to analyze whether hemichannel-mediated communication affects proliferation of SVZ NPCs and GBM cells. For that purpose, we used boldine, an alkaloid derived from the boldo tree (Peumus boldus), that inhibits connexin and pannexin hemichannels, but without affecting gap junctional communication. Boldine treatment (50 μM) of rat SVZ NPCs grown as neurospheres effectively inhibited dye uptake through hemichannels and induced a significant reduction in neurosphere diameter and in bromodeoxyuridine (BrdU) incorporation. However, the differentiation pattern was not modified by the treatment. Experiments with specific blockers for hemichannels formed by connexin subunits (D4) or pannexin 1 (probenecid) revealed that probenecid, but not D4, produced a decrease in BrdU incorporation similar to that obtained with boldine. These results suggest that inhibition of pannexin 1 hemichannels could be partially responsible for the antiproliferative effect of boldine on SVZ NPCs. Analysis of the effect of boldine (25-600 μM) on different types of primary human GBM cells (GBM59, GBM96, and U87-MG) showed a concentration-dependent decrease in GBM cell growth. Boldine treatment also induced a significant inhibition of hemichannel activity in GBM cells. Altogether, we provide evidence of an antimitotic action of boldine in SVZ NPCs and in GBM cells which may be due, at least in part, to its hemichannel blocking function. These results could be of relevance for future possible strategies in GBM aimed to suppress the proliferation of mutated NSCs or glioma stem cells that might remain in the brain after tumor resection.

Aloe-Emodin Overcomes Anti-Cancer Drug Resistance to Temozolomide and Prevents Colony Formation and Migration in Primary Human Glioblastoma Cell Lines NULU and ZAR.

Glioblastoma, the most dangerous and aggressive type of CNS tumor, appears resistant to many chemotherapy drugs. In the patient-derived glioma cell lines NULU and ZAR, which exhibit drug-resistant phenotypes, we investigated the effect of combined AE (Aloe-emodin) and TMZ (temozolomide) and found a significant additive inhibitory effect on cell growth and a promising cytotoxic effect on both cell lines compared to treatment with single agents. We also examined the effect of combined AE and TMZ treatment on the drug-resistance protein MGMT. The results suggest that using AE combined with traditional drugs restores drug resistance in both primary resistant cell lines (NULU and ZAR). Furthermore, migration assays and scratch tests showed that the combined use of AE and TMZ can slow down the colony formation and migration of glioblastoma cells. These convincing results suggest that AE could be a natural adjuvant agent to potentiate the effects of traditional drugs (TMZ) and overcome drug resistance in glioblastoma cells.