Glioblastoma (GBM) is known to be the most common and lethal primary malignant brain tumor. Therapies against this neoplasia have a high percentage of failure, associated with the survival of ...self-renewing glioblastoma stem cells (GSCs), which repopulate treated tumors. In addition, despite new radical surgery protocols and the introduction of new anticancer drugs, protocols for treatment, and technical advances in radiotherapy, no significant improvement in the survival rate for GBMs has been realized. Thus, novel antitarget therapies could be used in conjunction with standard radiochemotherapy approaches. Targeted therapy, indeed, may address specific targets that play an essential role in the proliferation, survival, and invasiveness of GBM cells, including numerous molecules involved in signal transduction pathways. Significant cellular heterogeneity and the hierarchy with GSCs showing a therapy-resistant phenotype could explain tumor recurrence and local invasiveness and, therefore, may be a target for new therapies. Therefore, the forced differentiation of GSCs may be a promising new approach in GBM treatment. This article provides an updated review of the current standard and experimental therapies for GBM, as well as an overview of the molecular characteristics of GSCs, the mechanisms that activate resistance to current treatments, and a new antitumor strategy for treating GSCs for use as therapy.
Successful treatment of glioblastoma multiforme (GBM), an aggressive form of primary brain neoplasm, mandates the need to develop new therapeutic strategies. In this study, we investigated the ...potential of PBI-05204 in targeting GBM stem cells (GSCs) and the underlying mechanisms. Treatment with PBI-05204 significantly reduced both the number and size of tumor spheres derived from patient-derived GSCs (GBM9, GSC28 and TS543), and suppressed the tumorigenesis of GBM9 xenografts. Moreover, PBI-05204 treatment led to a significant decrease in the expression of CD44 and NANOG, crucial markers of progenitor stem cells, in GBM9 and GSC28 GSCs. This treatment also down-regulated GRP78 expression in both GSC types. Knocking down GRP78 expression through GRP78 siRNA transfection in GBM9 and GSC28 GSCs also resulted in reduced spheroid size and CD44 expression. Combining PBI-05204 with GRP78 siRNA further decreased spheroid numbers compared to GRP78 siRNA treatment alone. PBI-05204 treatment led to increased expression of pRIP1K and pRIP3K, along with enhanced binding of RIPK1/RIPK3 in GBM9 and GSC28 cells, resembling the effects observed in GRP78-silenced GSCs, suggesting that PBI-05204 induced necroptosis in these cells. Furthermore, oleandrin, a principle active cardiac glycoside component of PBI-05204, showed the ability to inhibit the self-renewal capacity in GSCs. These findings highlight the potential of PBI-05204 as a promising candidate for the development of novel therapies that target GBM stem cells.
Glioblastoma therapies have remained elusive due to limitations in understanding mechanisms of growth and survival of the tumorigenic population. Using CRISPR-Cas9 approaches in patient-derived GBM ...stem cells (GSCs) to interrogate function of the coding genome, we identify actionable pathways responsible for growth, which reveal the gene-essential circuitry of GBM stemness and proliferation. In particular, we characterize members of the SOX transcription factor family, SOCS3, USP8, and DOT1L, and protein ufmylation as important for GSC growth. Additionally, we reveal mechanisms of temozolomide resistance that could lead to combination strategies. By reaching beyond static genome analysis of bulk tumors, with a genome-wide functional approach, we reveal genetic dependencies within a broad range of biological processes to provide increased understanding of GBM growth and treatment resistance.
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•Genome-wide CRISPR-Cas9 screens in patient-derived glioblastoma stem cells•Identification of regulators of stemness governing glioblastoma stem cell growth•Multiple stress response pathways are genetic vulnerabilities in glioblastoma•Identification of modulators of sensitivity to standard of care chemotherapy
MacLeod et al. describe genome-wide CRISPR-Cas9 screens identifying genetic vulnerabilities across a panel of patient-derived glioblastoma stem cell cultures. Regulators of stemness (SOX2, SOX9, DOT1L, and SOCS3) and stress response (ufmylation and ERAD pathways) govern the growth of glioblastoma stem cells. Chemogenomic screens using temozolomide identify modulators of sensitivity to chemotherapy.
Epidermal Growth Factor Receptor variant III (EGFRvIII) is an active mutant form of EGFR that drives tumor growth in a subset of glioblastoma (GBM). It occurs in over 20% of GBMs, making it a ...promising receptor for small molecule targeted therapy. We hypothesize that poor penetration of the blood-brain barrier by previously tested EGFR-tyrosine kinase inhibitors (EGFR-TKIs) such as afateninb, erlotinib, gefitinib, and lapatinib played a role in their limited efficacy. The present study examined the effects of osimertinib (previously known as AZD9291) on EGFRvIII+ GBM models, both
in vitro
and
in vivo
. Therefore, a panel of six GBM stem cells (GSCs) expressing EGFRvIII+ was evaluated. The EGFRvIII+ GSC differed in the expression of EGFRvIII and other key genes. The GSC line D317, which expresses high levels of EGFRvIII and has robust tyrosine kinase activity, was selected for assessing osimertinib’s efficacy. Herein, we report that osimertinib inhibits the constitutive activity of EGFRvIII tyrosine kinase with high potency (<100 nM) while also inhibiting its downstream signaling. Further, osimertinib inhibited D317’s growth
in vitro
and in both heterotopic and orthotopic xenograft models. Additional preclinical studies are warranted to identify EGFRvIII+ GBM’s molecular signature most responsive to osimertinib.
Diverse genetic, epigenetic, and developmental programs drive glioblastoma, an incurable and poorly understood tumor, but their precise characterization remains challenging. Here, we use an ...integrative approach spanning single-cell RNA-sequencing of 28 tumors, bulk genetic and expression analysis of 401 specimens from the The Cancer Genome Atlas (TCGA), functional approaches, and single-cell lineage tracing to derive a unified model of cellular states and genetic diversity in glioblastoma. We find that malignant cells in glioblastoma exist in four main cellular states that recapitulate distinct neural cell types, are influenced by the tumor microenvironment, and exhibit plasticity. The relative frequency of cells in each state varies between glioblastoma samples and is influenced by copy number amplifications of the CDK4, EGFR, and PDGFRA loci and by mutations in the NF1 locus, which each favor a defined state. Our work provides a blueprint for glioblastoma, integrating the malignant cell programs, their plasticity, and their modulation by genetic drivers.
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•Four cellular states drive glioblastoma malignant cells heterogeneity•In vivo single-cell lineage tracing supports plasticity between these four states•Genetics and the microenvironment influence the frequency of cells in each state•TCGA subtypes reflect the highest-frequency malignant states and the microenvironment
Single-cell analyses of glioblastoma samples reveal multiple cellular states, their plasticity and the genetic underpinnings of state proportions in a given tumor.
Glioblastoma stem cells (GSCs) exert a crucial influence on glioblastoma (GBM) development, progression, resistance to therapy, and recurrence, making them an attractive target for drug discovery. ...UTX, a histone H3K27 demethylase, participates in regulating multiple cancer types. However, its functional role in GSCs remains insufficiently explored. This study aims to investigate the role and regulatory mechanism of UTX on GSCs. Analysis of TCGA data revealed heightened UTX expression in glioma, inversely correlating with overall survival. Inhibiting UTX suppressed GBM cell growth and induced apoptosis. Subsequently, we cultured primary GSCs from three patients, observing that UTX inhibition suppressed cell proliferation and induced apoptosis. RNA‐seq was performed to analyze the gene expression changes after silencing UTX in GSCs. The results indicated that UTX‐mediated genes were strongly correlated with GBM progression and regulatory tumor microenvironment. The transwell co‐cultured experiment showed that silencing UTX in the transwell chamber GSCs inhibited the well plate cell proliferation. Protein–protein interaction analysis revealed that periostin (POSTN) played a role in the UTX‐mediated transcriptional regulatory network. Replenishing POSTN reversed the effects of UTX inhibition on GSC proliferation and apoptosis. Our study demonstrated that UTX inhibition hindered POSTN expression by enhancing the H3K27me2/3 level, eventually resulting in inhibiting proliferation and promoting apoptosis of patient‐derived GSCs. Our findings may provide a novel and effective strategy for the treatment of GBM.
Glioblastoma stem cells (GSCs) are crucial in glioblastoma (GBM) progression, making them a drug discovery target. Our research unveiled that UTX (a histone H3K27 demethylase) inhibition hindered POSTN expression by enhancing the H3K27me2/3 level, ultimately regulating proliferation and apoptosis in GSCs. These findings suggest a promising strategy for GBM treatment.
Despite advances in neurosurgical techniques and radio-/chemotherapy, the treatment of brain tumors remains a challenge. This is particularly true for the most frequent and fatal adult brain tumor, ...glioblastoma (GB). Upon diagnosis, the average survival time of GB patients remains only approximately 15months. The alkylating drug temozolomide (TMZ) is routinely used in brain tumor patients and induces apoptosis, autophagy and unfolded protein response (UPR). Here, we review these cellular mechanisms and their contributions to TMZ chemoresistance in brain tumors, with a particular emphasis on TMZ chemoresistance in glioma stem cells and GB.
Glioblastoma (GBM) remains the most lethal and common primary brain tumor, even after treatment with multiple therapies, such as surgical resection, chemotherapy, and radiation. Although great ...advances in medical development and improvements in therapeutic methods of GBM have led to a certain extension of the median survival time of patients, prognosis remains poor. The primary cause of its dismal outcomes is the high rate of tumor recurrence, which is closely related to its resistance to standard therapies. During the last decade, glioblastoma stem cells (GSCs) have been successfully isolated from GBM, and it has been demonstrated that these cells are likely to play an indispensable role in the formation, maintenance, and recurrence of GBM tumors, indicating that GSCs are a crucial target for treatment. Herein, we summarize the current knowledge regarding GSCs, their related signaling pathways, resistance mechanisms, crosstalk linking mechanisms, and microenvironment or niche. Subsequently, we present a framework of targeted therapy for GSCs based on direct strategies, including blockade of the pathways necessary to overcome resistance or prevent their function, promotion of GSC differentiation, virotherapy, and indirect strategies, including targeting the perivascular, hypoxic, and immune niches of the GSCs. In summary, targeting GSCs provides a tremendous opportunity for revolutionary approaches to improve the prognosis and therapy of GBM, despite a variety of challenges.
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