bims-malgli Biomed News
on Biology of malignant gliomas
Issue of 2020‒09‒20
sixteen papers selected by
Oltea Sampetrean
Keio University

  1. Sci Rep. 2020 Sep 16. 10(1): 15195
      Hypoxia inducible factor (HIFs) signaling contributes to malignant cell behavior in glioblastoma (GBM). We investigated a novel HIF2α inhibitor, PT2385, both in vitro, with low-passage patient-derived cell lines, and in vivo, using orthotopic models of glioblastoma. We focused on analysis of HIF2α expression in situ, cell survival/proliferation, and survival in brain tumor-bearing mice treated with PT2385 alone and in combination with standard of care chemoradiotherapy. HIF2α expression increased with glioma grade, with over half of GBM specimens HIF2α positive. Staining clustered in perivascular and perinecrotic tumor regions. Cellular phenotype including proliferation, viability, migration/invasion, and also gene expression were not altered after PT2385 treatment. In the animal model, PT2385 single-agent treatment did improve median overall survival compared to placebo (p = 0.04, n = 21) without a bioluminescence correlate (t = 0.67, p = 0.52). No difference in animal survival was seen in combination treatment with radiation (RT)/temozolomide (TMZ)/PT2385 (p = 0.44, n = 10) or mean tumor bioluminescence (t 1.13, p = 0.32). We conclude that HIF2α is a reasonable novel therapeutic target as expressed in the majority of glioblastomas in our cohort. PT2385 as a single-agent was efficacious in vivo, however, an increase in animal survival was not seen with PT2385 in combination with RT/TMZ. Further study for targeting HIF2α as a therapeutic approach in GBM is warranted.
  2. Oncoimmunology. 2020 Jun 05. 9(1): 1776577
      Currently, human glioma tumors are mostly modeled in immunodeficient recipients; however, lack of interactions with adaptive immune system is a serious flaw, particularly in the era when immunotherapies dominate treatment strategies. Our group was the first to successfully establish the orthotopic transplantation of human glioblastoma (GBM) in immunocompetent mice by inducing immunological tolerance using a short-term, systemic costimulation blockade strategy (CTLA-4-Ig and MR1). In this study, we further validated the feasibility of this method by modeling pediatric diffuse intrinsic pontine glioma (DIPG) and two types of adult GBM (GBM1, GBM551), in mice with intact immune systems and immunodeficient mice. We found that all three glioma models were successfully established, with distinct difference in tumor growth patterns and morphologies, after orthotopic xenotransplantation in tolerance-induced immunocompetent mice. Long-lasting tolerance that is maintained for up to nearly 200 d in GBM551 confirmed the robustness of this model. Moreover, we found that tumors in immunocompetent mice displayed features more similar to the clinical pathophysiology found in glioma patients, characterized by inflammatory infiltration and strong neovascularization, as compared with tumors in immunodeficient mice. In summary, we have validated the robustness of the costimulatory blockade strategy for tumor modeling and successfully established three human glioma models including the pediatric DIPG whose preclinical study is particularly thwarted by the lack of proper animal models.
    Keywords:  Glioma; brain tumor; costimulation blockade; immunocompetent; tolerance
  3. Neuro Oncol. 2020 Sep 14. pii: noaa214. [Epub ahead of print]
      BACKGROUND: Acquired chemoresistance is a major challenge in the clinical treatment of glioblastoma (GBM). Circular RNAs have been verified to play a role in tumor chemoresistance. However, the underlying mechanisms remain unclear. The aim of this study was to elucidate the potential role and molecular mechanism of circASAP1 in temozolomide resistance of GBM.METHODS: We analyzed circRNA alterations in recurrent GBM tissues relative to primary GBM through RNA sequencing. Real-time quantitative reverse transcription PCR (qRT-PCR) verified the expression of circASAP1 in tissues and cells. Knockdown and overexpressed plasmids were used to evaluate the effect of circASAP1 on GBM cell proliferation and temozolomide-induced apoptosis. Mechanistically, fluorescent in situ hybridization, dual-luciferase reporter, and RNA immunoprecipitation assays were performed to confirm the regulatory network of circASAP1/miR-502-5p/NRAS. Intracranial tumors model was used to verify our findings in vivo.
    RESULTS: CircASAP1 expression was significantly up-regulated in recurrent GBM tissues and temozolomide-resistant cell lines. CircASAP1 overexpression enhanced GBM cell proliferation and temozolomide-resistance, which could reduced by circASAP1 knockdown. Further experiments revealed that circASAP1 increasd the expression of NRAS via sponging miR-502-5p. Moreover, circASAP1 depletion effectively restored the sensitivity of temozolomide-resistant xenografts to temozolomide treatment in vivo.
    CONCLUSIONS: Our data demonstrate that circASAP1 exerts regulatory functions in GBM and that ceRNA-mediated microRNA sequestration might be a potential therapeutic strategy for GBM treatment.
    Keywords:  NRAS; circASAP1; glioblastoma; miR-502-5p; temozolomide resistance
  4. Cancers (Basel). 2020 Sep 10. pii: E2583. [Epub ahead of print]12(9):
      Resistance to chemotherapy by temozolomide (TMZ) is a major cause of glioblastoma (GBM) recurrence. So far, attempts to characterize factors that contribute to TMZ sensitivity have largely focused on protein-coding genes, and failed to provide effective therapeutic targets. Long noncoding RNAs (lncRNAs) are essential regulators of epigenetic-driven cell diversification, yet, their contribution to the transcriptional response to drugs is less understood. Here, we performed RNA-seq and small RNA-seq to provide a comprehensive map of transcriptome regulation upon TMZ in patient-derived GBM stem-like cells displaying different drug sensitivity. In a search for regulatory mechanisms, we integrated thousands of molecular associations stored in public databases to generate a background "RNA interactome". Our systems-level analysis uncovered a coordinated program of TMZ response reflected by regulatory circuits that involve transcription factors, mRNAs, miRNAs, and lncRNAs. We discovered 22 lncRNAs involved in regulatory loops and/or with functional relevance in drug response and prognostic value in gliomas. Thus, the investigation of TMZ-induced gene networks highlights novel RNA-based predictors of chemosensitivity in GBM. The computational modeling used to identify regulatory circuits underlying drug response and prioritizing gene candidates for functional validation is applicable to other datasets.
    Keywords:  chemoresistance; glioblastoma; lncRNA; regulatory circuit; temozolomide; transcriptome
  5. Nat Commun. 2020 09 16. 11(1): 4660
      Intratumor spatial heterogeneity facilitates therapeutic resistance in glioblastoma (GBM). Nonetheless, understanding of GBM heterogeneity is largely limited to the surgically resectable tumor core lesion while the seeds for recurrence reside in the unresectable tumor edge. In this study, stratification of GBM to core and edge demonstrates clinically relevant surgical sequelae. We establish regionally derived models of GBM edge and core that retain their spatial identity in a cell autonomous manner. Upon xenotransplantation, edge-derived cells show a higher capacity for infiltrative growth, while core cells demonstrate core lesions with greater therapy resistance. Investigation of intercellular signaling between these two tumor populations uncovers the paracrine crosstalk from tumor core that promotes malignancy and therapy resistance of edge cells. These phenotypic alterations are initiated by HDAC1 in GBM core cells which subsequently affect edge cells by secreting the soluble form of CD109 protein. Our data reveal the role of intracellular communication between regionally different populations of GBM cells in tumor recurrence.
  6. Biochem Biophys Res Commun. 2020 Sep 14. pii: S0006-291X(20)31699-5. [Epub ahead of print]
      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.
    Keywords:  Mesenchymal stromal cells; Mitochondria; Primary GBM cultures; Tunneling nanotubes
  7. Sci Rep. 2020 Sep 17. 10(1): 15286
      Glioblastoma multiforme involves glioma stem cells (GSCs) that are resistant to various therapeutic approaches. Here, we studied the importance of paracrine signaling in the glioma microenvironment by focusing on the celecoxib-mediated role of chemokines C-C motif ligand 2 (CCL2), C-X-C ligand 10 (CXCL10), and their receptors, CCR2 and CXCR3, in GSCs and a GSC-bearing malignant glioma model. C57BL/6 mice were injected with orthotopic GSCs intracranially and divided into groups administered either 10 or 30 mg/kg celecoxib, or saline to examine the antitumor effects associated with chemokine expression. In GSCs, we analyzed cell viability and expression of chemokines and their receptors in the presence/absence of celecoxib. In the malignant glioma model, celecoxib exhibited antitumor effects in a dose dependent manner and decreased protein and mRNA levels of Ccl2 and CxcL10 and Cxcr3 but not of Ccr2. CCL2 and CXCL10 co-localized with Nestin+ stem cells, CD16+ or CD163+ macrophages and Iba-1+ microglia. In GSCs, celecoxib inhibited Ccl2 and Cxcr3 expression in a nuclear factor-kappa B-dependent manner but not Ccr2 and CxcL10. Moreover, Ccl2 silencing resulted in decreased GSC viability. These results suggest that celecoxib-mediated regulation of the CCL2/CCR2 and CXCL10/ CXCR3 axes may partially contribute to glioma-specific antitumor effects.
  8. PLoS One. 2020 ;15(9): e0239325
      Mutation in isocitrate dehydrogenase 1 (IDH1R132H) occurs in various types of cancer, including low and high grade gliomas. Despite high incidence indicating its central role in tumor initiation and progression there are no targeted therapies directed against this oncogene available in the clinic. This is due to the limited understanding of the role of IDH1R132H in carcinogenesis, which is further propagated by the lack of appropriate experimental models. Moreover, proper in vitro models for analysis of gliomagenesis are required. In this study, we employed a Tet On system to generate human induced neural stem cells with doxycycline-inducible IDH1R132H. Equivalent expression of both forms of IDH1 in the presented model remains similar to that described in tumor cells. Additional biochemical analyses further confirmed tightly controlled gene regulation at protein level. Formation of a functional mutant IDH1 enzyme was supported by the production of D-2-hydroxyglutarate (D2HG). All samples tested for MGMT promoter methylation status, including parental cells, proved to be partially methylated. Analysis of biological effect of IDH1R132H revealed that cells positive for oncogene showed reduced differentation efficiency and viability. Inhibition of mutant IDH1 with selective inhibitor efficiently suppressed D2HG production as well as reversed the effect of mutant IDH1 protein on cell viability. In summary, our model constitutes a valuable platform for studies on the molecular basis and the cell of origin of IDH-mutant glioma (e.g. by editing P53 in these cells and their derivatives), as well as a reliable experimental model for drug testing.
  9. Sci Adv. 2020 May;pii: eaaz4125. [Epub ahead of print]6(22):
      Although tumor invasiveness is known to drive glioblastoma (GBM) recurrence, current approaches to treatment assume a fairly simple GBM phenotype transition map. We provide new analyses to estimate the likelihood of reaching or remaining in a phenotype under dynamic, physiologically likely perturbations of stimuli ("phenotype stability"). We show that higher stability values of the motile phenotype (Go) are associated with reduced patient survival. Moreover, induced motile states are capable of driving GBM recurrence. We found that the Dormancy and Go phenotypes are equally represented in advanced GBM samples, with natural transitioning between the two. Furthermore, Go and Grow phenotype transitions are mostly driven by tumor-brain stimuli. These are difficult to regulate directly, but could be modulated by reprogramming tumor-associated cell types. Our framework provides a foundation for designing targeted perturbations of the tumor-brain environment, by assessing their impact on GBM phenotypic plasticity, and is corroborated by analyses of patient data.
  10. Nat Commun. 2020 Sep 18. 11(1): 4709
      Glioblastoma cancer-stem like cells (GSCs) display marked resistance to ionizing radiation (IR), a standard of care for glioblastoma patients. Mechanisms underpinning radio-resistance of GSCs remain largely unknown. Chromatin state and the accessibility of DNA lesions to DNA repair machineries are crucial for the maintenance of genomic stability. Understanding the functional impact of chromatin remodeling on DNA repair in GSCs may lay the foundation for advancing the efficacy of radio-sensitizing therapies. Here, we present the results of a high-content siRNA microscopy screen, revealing the transcriptional elongation factor SPT6 to be critical for the genomic stability and self-renewal of GSCs. Mechanistically, SPT6 transcriptionally up-regulates BRCA1 and thereby drives an error-free DNA repair in GSCs. SPT6 loss impairs the self-renewal, genomic stability and tumor initiating capacity of GSCs. Collectively, our results provide mechanistic insights into how SPT6 regulates DNA repair and identify SPT6 as a putative therapeutic target in glioblastoma.
  11. Rev Physiol Biochem Pharmacol. 2020 Sep 16.
      Brain tumors come in many types and differ greatly in outcome. They are classified by the cell of origin (astrocytoma, ependymoma, meningioma, medulloblastoma, glioma), although more recently molecular markers are used in addition to histology. Brain tumors are graded (from I to IV) to measure their malignancy. Glioblastoma, one of the most common adult primary brain tumors, displays the highest malignancy (grade IV), and median survival of about 15 months. Main reasons for poor outcome are incomplete surgical resection, due to the highly invasive potential of glioblastoma cells, and chemoresistance that commonly develops during drug treatment. An important role in brain tumor malignancy is played by ion channels. The Ca2+-activated K+ channels of large and intermediate conductance, KCa3.1 and KCa1.1, and the volume-regulated anion channel, whose combined activity results in the extrusion of KCl and osmotic water, control cell volume, and in turn migration, invasion, and apoptotic cell death. The transient receptor potential (TRP) channels and low threshold-activated Ca (T-type) channels have equally critical role in brain tumor malignancy, as dysregulated Ca2+ signals heavily impact on glioma cell proliferation, migration, invasion. The review provides an overview of the current evidence involving these channels in brain tumor malignancy, and the application of these insights in the light of future prospects for experimental and clinical practice.
    Keywords:  Apoptosis; Brain tumor; Ca2+ signaling; Ca2+-activated K channels; Cell migration; Cell proliferation; Cell volume regulation; Cl channels; Glioma; T-type Ca Channels; TRP Channels
  12. Neuro Oncol. 2020 Sep 14. pii: noaa212. [Epub ahead of print]
    Keywords:  Glioma; IDH1 mutation; temozolomide
  13. Cancer Res. 2020 Sep 14. pii: canres.1233.2020. [Epub ahead of print]
      Muscleblind-like-proteins (MBNL) belong to a family of tissue-specific regulators of RNA metabolism that control pre-messenger RNA-splicing (AS). Inactivation of MBNL causes an adult-to-fetal AS transition, resulting in the development of myotonic dystrophy. We have previously shown that the aggressive brain cancer glioblastoma (GBM) maintains stem-like features (GSC) through hypoxia-induced responses. Accordingly, we hypothesize here that hypoxia-induced responses in GBM might also include MBNL-based AS to promote tumor progression. When cultured in hypoxia, GSC rapidly exported MBNL1 out of the nucleus, resulting in significant inhibition of MBNL1 activity. Notably, hypoxia-regulated inhibition of MBNL1 also resulted in evidence of adult-to-fetal alternative splicing transitions. Forced expression of a constitutively active isoform of MBNL1 inhibited GSC self-renewal and tumor initiation in orthotopic transplantation models. Induced expression of MBNL1 in established orthotopic tumors dramatically inhibited tumor progression, resulting in significantly prolonged survival. This study reveals that MBNL1 plays an essential role in GBM stemness and tumor progression, where hypoxic responses within the tumor inhibit MBNL1 activity, promoting stem-like phenotypes and tumor growth. Reversing these effects on MBNL1 may therefore yield potent tumor suppressor activities, uncovering new therapeutic opportunities to counter this disease.
  14. Cancers (Basel). 2020 Sep 15. pii: E2628. [Epub ahead of print]12(9):
      The glioma microenvironment is a critical regulator of tumor progression. It contains different cellular components such as blood vessels, immune cells, and neuroglial cells. It also contains non-cellular components, such as the extracellular matrix, extracellular vesicles, and cytokines, and has certain physicochemical properties, such as low pH, hypoxia, elevated interstitial pressure, and impaired perfusion. This review focuses on a particular type of cells recently identified in the glioma microenvironment: glioma-associated stromal cells (GASCs). This is just one of a number of names given to these mesenchymal stromal-like cells, which have phenotypic and functional properties similar to those of mesenchymal stem cells and cancer-associated fibroblasts. Their close proximity to blood vessels may provide a permissive environment, facilitating angiogenesis, invasion, and tumor growth. Additional studies are required to characterize these cells further and to analyze their role in tumor resistance and recurrence.
    Keywords:  cancer-associated fibroblasts; gliomas; mesenchymal stem cells; microenvironment
  15. Cancer Cell. 2020 Sep 14. pii: S1535-6108(20)30423-2. [Epub ahead of print]38(3): 311-313
      Glioblastoma is heterogeneous in the molecular subtypes based on transcriptomic classification. In this issue of Cancer Cell, Wang et al. define a cell-lineage-based stratification model for glioblastoma, highlighting how the cell of origin generates distinct molecular landscapes and therapeutic vulnerabilities from identical driver mutations.
  16. Oncoimmunology. 2020 May 13. 9(1): 1757360
      Recent advances in novel immune strategies, particularly chimeric antigen receptor (CAR)-bearing T-cells, have shown limited efficacy against glioblastoma (GBM) in clinical trials. We currently have an incomplete understanding of how these emerging therapies integrate with the current standard of care, specifically radiation therapy (RT). Additionally, there is an insufficient number of preclinical studies monitoring these therapies with high spatiotemporal resolution. To address these limitations, we report the first longitudinal fluorescence-based intravital microscopy imaging of CAR T-cells within an orthotopic GBM preclinical model to illustrate the necessity of RT for complete therapeutic response. Additionally, we detail the first usage of murine-derived CAR T-cells targeting the disialoganglioside GD2 in an immunocompetent tumor model. Cell culture assays demonstrated substantial GD2 CAR T-cell-mediated killing of murine GBM cell lines SB28 and GL26 induced to overexpress GD2. Complete antitumor response in advanced syngeneic orthotopic models of GBM was achieved only when a single intravenous dose of GD2 CAR T-cells was following either sub-lethal whole-body irradiation or focal RT. Intravital microscopy imaging successfully visualized CAR T-cell homing and T-cell mediated apoptosis of tumor cells in real-time within the tumor stroma. Findings indicate that RT allows for rapid CAR T-cell extravasation from the vasculature and expansion within the tumor microenvironment, leading to a more robust and lasting immunologic response. These exciting results highlight potential opportunities to improve intravenous adoptive T-cell administration in the treatment of GBM through concurrent RT. Additionally, they emphasize the need for advancements in immunotherapeutic homing to and extravasation through the tumor microenvironment.
    Keywords:  Chimeric antigen receptor (CAR); glioblastoma; imaging; immunotherapy; intravital microscopy