bims-malgli Biomed News
on Biology of malignant gliomas
Issue of 2021‒06‒20
seventeen papers selected by
Oltea Sampetrean
Keio University

  1. Nat Commun. 2021 06 17. 12(1): 3720
      Low levels of reactive oxygen species (ROS) are crucial for maintaining cancer stem cells (CSCs) and their ability to resist therapy, but the ROS regulatory mechanisms in CSCs remains to be explored. Here, we discover that prohibitin (PHB) specifically regulates mitochondrial ROS production in glioma stem-like cells (GSCs) and facilitates GSC radiotherapeutic resistance. We find that PHB is upregulated in GSCs and is associated with malignant gliomas progression and poor prognosis. PHB binds to peroxiredoxin3 (PRDX3), a mitochondrion-specific peroxidase, and stabilizes PRDX3 protein through the ubiquitin-proteasome pathway. Knockout of PHB dramatically elevates ROS levels, thereby inhibiting GSC self-renewal. Importantly, deletion or pharmacological inhibition of PHB potently slows tumor growth and sensitizes tumors to radiotherapy, thus providing significant survival benefits in GSC-derived orthotopic tumors and glioblastoma patient-derived xenografts. These results reveal a selective role of PHB in mitochondrial ROS regulation in GSCs and suggest that targeting PHB improves radiotherapeutic efficacy in glioblastoma.
  2. Neurooncol Adv. 2021 Jan-Dec;3(1):3(1): vdab065
      Background: Clinical outcomes in high-grade glioma (HGG) have remained relatively unchanged over the last 3 decades with only modest increases in overall survival. Despite the validation of biomarkers to classify treatment response, most newly diagnosed (ND) patients receive the same treatment regimen. This study aimed to determine whether a prospective functional assay that provides a direct, live tumor cell-based drug response prediction specific for each patient could accurately predict clinical drug response prior to treatment.Methods: A modified 3D cell culture assay was validated to establish baseline parameters including drug concentrations, timing, and reproducibility. Live tumor tissue from HGG patients were tested in the assay to establish response parameters. Clinical correlation was determined between prospective ex vivo response and clinical response in ND HGG patients enrolled in 3D-PREDICT ( Identifier: NCT03561207). Clinical case studies were examined for relapsed HGG patients enrolled on 3D-PREDICT, prospectively assayed for ex vivo drug response, and monitored for follow-up.
    Results: Absent biomarker stratification, the test accurately predicted clinical response/nonresponse to temozolomide in 17/20 (85%, P = .007) ND patients within 7 days of their surgery, prior to treatment initiation. Test-predicted responders had a median overall survival post-surgery of 11.6 months compared to 5.9 months for test-predicted nonresponders (P = .0376). Case studies provided examples of the clinical utility of the assay predictions and their impact upon treatment decisions resulting in positive clinical outcomes.
    Conclusion: This study both validates the developed assay analytically and clinically and provides case studies of its implementation in clinical practice.
    Keywords:  3D culture; drug response prediction; ex vivo; glioblastoma; glioma
  3. J Clin Invest. 2021 Jun 17. pii: 142116. [Epub ahead of print]
      Glioblastoma, the most aggressive brain cancer, recurs because glioblastoma stem cells (GSCs) are resistant to all standard therapies. We showed that GSCs, but not normal astrocytes, are sensitive to lysis by healthy allogeneic natural killer (NK) cells in vitro. Mass cytometry and single cell RNA sequencing of primary tumor samples revealed that glioblastoma-infiltrating NK cells acquired an altered phenotype associated with impaired lytic function relative to matched peripheral blood NK cells from glioblastoma patients or healthy donors. We attributed this immune evasion tactic to direct cell-cell contact between GSCs and NK cells via integrin-mediated TGF-β activation. Treatment of GSC-engrafted mice with allogeneic NK cells in combination with inhibitors of integrin or TGF-β signaling, or with TGFBR2 gene-edited allogeneic NK cells prevented GSC-induced NK cell dysfunction and tumor growth. These findings revealed an important mechanism of NK cell immune evasion by GSCs and implicated the integrin-TGF-β axis as a potentially useful therapeutic target in glioblastoma.
    Keywords:  Brain cancer; Cancer immunotherapy; Immunology; NK cells
  4. Nat Commun. 2021 06 14. 12(1): 3615
      Glioblastoma is considered one of the most aggressive malignancies in adult and pediatric patients. Despite decades of research no curative treatment is available and it thus remains associated with a very dismal prognosis. Although recent pre-clinical and clinical studies have demonstrated the feasibility of chimeric antigen receptors (CAR) T cell immunotherapeutic approach in glioblastoma, tumor heterogeneity and antigen loss remain among one of the most important challenges to be addressed. In this study, we identify p32/gC1qR/HABP/C1qBP to be specifically expressed on the surface of glioma cells, making it a suitable tumor associated antigen for redirected CAR T cell therapy. We generate p32 CAR T cells and find them to recognize and specifically eliminate p32 expressing glioma cells and tumor derived endothelial cells in vitro and to control tumor growth in orthotopic syngeneic and xenograft mouse models. Thus, p32 CAR T cells may serve as a therapeutic option for glioblastoma patients.
  5. Oncogene. 2021 Jun 15.
      Mini-chromosome maintenance (MCM) proteins are critical components of DNA-replication-licensing factors. MCM8 is an MCM protein that exhibits oncogenic functions in several human malignancies. However, the role of MCM8 in glioblastomas (GBMs) has remained unclear. In the present study, we investigated the biological functions and mechanisms of MCM8 in glioma stem cells (GSCs). The clinical relevance of MCM8 mRNA expression was explored via TCGA and REMBRANDT datasets. The effects of MCM8 on the self-renewal and tumorigenicity of GSCs were examined both in vitro and in vivo. The regulation of MCM8 expression and its interacting proteins were also evaluated. We found that the expression of MCM8 was elevated in high-grade gliomas and classical molecular subtypes and was inversely correlated with patient prognosis. GSCs had a significantly higher expression of MCM8 compared with that in normal glioma cells. Silencing of MCM8 induced G0/G1 arrest and apoptosis, as well as inhibited the proliferation and self-renewal of GSCs. Forced expression of MCM8 enhanced clonogenicity of GSCs both in vitro and in vivo. MCM8 expression was regulated by EGFR signaling, which was mediated by NF-κB (p65). MCM8 interacted with DNA-replication-initiating factors-including EZH2, CDC6, and CDCA2-and influenced these factors to associate with chromatin. In addition, MCM8 knockdown increased the sensitivity of GSCs to radiation and TMZ treatments. Our findings suggest that MCM8, regulated by the EGFR pathway, maintains the clonogenic and tumorigenic potential of GSCs through interaction with DNA-replication-initiating factors; hence, MCM8 may represent a novel therapeutic target in GBMs.
  6. Brain Tumor Pathol. 2021 Jun 14.
      Two hot spot mutations (C228T, C250T) in the telomerase reverse transcriptase (TERT) gene are frequently identified in glioblastoma and oligodendroglioma. TERT mutations predicts an aggressive clinical course in isocitrate dehydrogenase (IDH) wild-type astrocytic tumors. Therefore, it is important to accurately detect TERT promoter mutations in glioma. Sanger DNA sequencing is the currently standard method for analyzing TERT mutations. However, PCR amplification in the first step of the sequencing has proven technically difficult because of the high GC content around the TERT mutation. In this report, we described a novel droplet digital PCR (ddPCR) assay to evaluate TERT hot spot mutations in fresh frozen and formalin-fixed paraffin-embedded (FFPE) specimens of glioma and verified the difference in results from the Sanger DNA sequencing results. We obtained the mutant allele fraction for TERT mutations of in a single ddPCR run in all cases, including the micro-dissected FFPE sections. On the contrary, up to twice the DNA sequences were required from fresh frozen tissue to obtain the results, consistent with ddPCR assay. When FFPE specimens were used, more time was required to evaluate TERT mutations through DNA sequencing. DdPCR is an effective and sensitive assay compared to the conventional standard Sanger DNA sequencing.
    Keywords:  Digital PCR; Glioma; TERT promoter mutation
  7. Genomics. 2021 Jun 09. pii: S0888-7543(21)00231-7. [Epub ahead of print]113(4): 2623-2633
      Gamma-glutamyltransferase (GGT) and keratins (KRT) are key factors in regulating tumor progression rely on emerging evidence. However, the prognostic values of GGT and KRT isoforms and their regulation patterns at transcriptional and post-transcriptional levels have been rarely studied. In this study, we aimed to identify cooperative prognostic biomarker signature conducted by GGT and KRT genes for overall survival prediction and discrimination in patients with low-grade glioma (LGG) and glioblastoma multiforme (GBM). To this end, we employed a differential expression network analysis on LGG-NORMAL, GBM-NORMAL, and LGG-GBM datasets. Then, all the differentially expressed genes related to a GO term "GGT activity" were excluded. After that, for obtained potential biomarkers genes, differentially expressed lncRNAs were used to detect cis-regulatory elements (CREs) and trans-regulatory elements (TREs). To scrutinize the regulation on the cytoplasm, potential interactions between these biomarker genes and DElncRNAs were predicted. Our analysis, for the first time, revealed that GGT6, KRT33B, and KRT75 in LGG, GGT2, and KRT75 in GBM and KRT75 for LGG to GBM transformation tumors can be novel cooperative prognostic biomarkers that may be applicable for early detection of LGG, GBM, and LGG to GBM transformation tumors. Consequently, KRT75 was the most important gene being regulated at both transcriptional and post-transcriptional levels significantly. Furthermore, CREs and their relative genes were coordinative up-regulated or down-regulated suggesting CREs as regulation points of these genes. In the end, up-regulation of most DElncRNAs that had physical interaction with target genes pints out that the transcripted genes may have obstacles for translation process.
    Keywords:  Cis and trans regulatory elements; Gamma-glutamyltransferase; Keratin; Transcription and post transcription regulation; mRNA-lncRNA interaction
  8. Commun Biol. 2021 Jun 10. 4(1): 718
      Recently, we involved the carbohydrate-binding protein Galectin-3 (Gal-3) as a druggable target for KRAS-mutant-addicted lung and pancreatic cancers. Here, using glioblastoma patient-derived stem cells (GSCs), we identify and characterize a subset of Gal-3high glioblastoma (GBM) tumors mainly within the mesenchymal subtype that are addicted to Gal-3-mediated macropinocytosis. Using both genetic and pharmacologic inhibition of Gal-3, we showed a significant decrease of GSC macropinocytosis activity, cell survival and invasion, in vitro and in vivo. Mechanistically, we demonstrate that Gal-3 binds to RAB10, a member of the RAS superfamily of small GTPases, and β1 integrin, which are both required for macropinocytosis activity and cell survival. Finally, by defining a Gal-3/macropinocytosis molecular signature, we could predict sensitivity to this dependency pathway and provide proof-of-principle for innovative therapeutic strategies to exploit this Achilles' heel for a significant and unique subset of GBM patients.
  9. Front Immunol. 2021 ;12 679954
      Extracellular vesicle (EV) secretion is a ubiquitous cellular process with both physiologic and pathologic consequences. EVs are small lipid bilayer vesicles that encompass both microvesicles and exosomes and which are secreted by virtually all cells including cancer cells. In this review, we will focus on the roles of EVs in mediating the crosstalk between glioblastoma (GBM) cells and innate and adaptive immune cells and the potential impact on glioma progression. Glioma-derived EVs contain many bioactive cargoes that can broaden and amplify glioma cell mediated immunosuppressive functions and thereby contribute to shaping the tumor microenvironment. We will discuss evidence demonstrating that the low oxygen (hypoxia) in the GBM microenvironment, in addition to cell-intrinsic effects, can affect intercellular communication through EV release, raising the possibility that properties of the tumor core can more widely impact the tumor microenvironment. Recent advances in glioma-derived EV research have shown their importance not only as message carriers, but also as mediators of immune escape, with the capacity to reprogram tumor infiltrating immune cells. Exploring EV function in cancer-immune crosstalk is therefore becoming an important research area, opening up opportunities to develop EV monitoring for mechanistic studies as well as novel diagnostic glioma biomarker applications. However, robust and reproducible EV analysis is not always routinely established, whether in research or in clinical settings. Taking into account the current state of the art in EV studies, we will discuss the challenges and opportunities for extending the many exciting findings in basic research to a better interpretation of glioma and its response to current and future immunotherapies.
    Keywords:  biomarkers; extracellular vesicles; glioma; hypoxia; immunosuppression; tumor microenvironment
  10. Oncogene. 2021 Jun 14.
      Although radiotherapy is a well-known effective non-surgical treatment for malignant gliomas, the therapeutic efficacy is severely limited due to the radioresistance of tumor cells. Previously, we demonstrated that Yes-associated protein (YAP) promotes glioma malignant progression. However, whether YAP plays a role in radioresistance and its potential value in cancer treatment are still unclear. In this study, we found that high YAP expression is associated with poor prognosis in malignant glioma patients undergoing radiotherapy. Research in immortalized cell lines and primary cells from GBM patients revealed that YAP exhibited a radioresistant effect on gliomas via promoting DNA damage repair. Mechanistically, after radiation, YAP was translocated into the nucleus, where it promoted the expression and secretion of FGF2, leading to MAPK-ERK pathway activation. FGF2 is a novel target gene of YAP. Inhibition of YAP-FGF2-MAPK signaling sensitizes gliomas to radiotherapy and prolongs the survival of intracranial cell-derived and patient-derived xenograft models. These results suggest that YAP-FGF2-MAPK is a key mechanism of radioresistance and is an actionable target for improving radiotherapy efficacy.
  11. Neurooncol Adv. 2021 Jan-Dec;3(1):3(1): vdab062
      Background: Glioma-associated microglia/macrophages (GAMs) markedly influence glioma progression. Under the influence of transforming growth factor beta (TGFB), GAMs are polarized toward a tumor-supportive phenotype. However, neither therapeutic targeting of GAM recruitment nor TGFB signaling demonstrated efficacy in glioma patients despite efficacy in preclinical models, underscoring the need for a comprehensive understanding of the TGFB/GAM axis. Spontaneously occurring canine gliomas share many features with human glioma and provide a complementary translational animal model for further study. Given the importance of GAM and TGFB in human glioma, the aims of this study were to further define the GAM-associated molecular profile and the relevance of TGFB signaling in canine glioma that may serve as the basis for future translational studies.Methods: GAM morphometry, levels of GAM-associated molecules, and the canonical TGFB signaling axis were compared in archived samples of canine astrocytomas versus normal canine brain. Furthermore, the effect of TGFB on the malignant phenotype of canine astrocytoma cells was evaluated.
    Results: GAMs diffusely infiltrated canine astrocytomas. GAM density was increased in high-grade tumors that correlated with a pro-tumorigenic molecular signature and upregulation of the canonical TGFB signaling axis. Moreover, TGFB1 enhanced the migration of canine astrocytoma cells in vitro.
    Conclusions: Canine astrocytomas share a similar GAM-associated immune landscape with human adult glioma. Our data also support a contributing role for TGFB1 signaling in the malignant phenotype of canine astrocytoma. These data further support naturally occurring canine glioma as a valid model for the investigation of GAM-associated therapeutic strategies for human malignant glioma.
    Keywords:  canine; glioma; microglia; transforming growth factor beta 1
  12. Neuro Oncol. 2021 Jun 12. pii: noab142. [Epub ahead of print]
      Accounting for approximately 8% of the human genome, Human Endogenous Retroviruses (HERVs) have been implicated in a variety of cancers including gliomas. In normal cells, tight epigenetic regulation of HERVs prevent aberrant expression; however, in cancer cells, HERVs expression remains pervasive, suggesting a role of HERVs in oncogenic transformation. HERVs may contribute to oncogenesis in several ways including insertional mutagenesis, chromosomal rearrangements, proto-oncogene formation, and maintenance of stemness. On the other hand, recent data has suggested that reversing epigenetic silencing of HERVs may induce robust anti-tumor immune responses, suggesting HERVs' potential therapeutic utility in gliomas. By reversing epigenetic modifications that silence HERVs, DNA methyltransferase and histone deacetylase inhibitors may stimulate a viral-mimicry cascade via HERV-derived dsRNA formation that induce interferon-mediated apoptosis. Leveraging this anti-tumor autoimmune response may be a unique avenue to target certain subsets of epigenetically-dysregulated gliomas. Nevertheless, the role of HERVs in gliomas as either arbitrators of oncogenesis or forerunners of the innate anti-tumor immune response remains unclear. Here, we review the role of HERVs in gliomas, their potential dichotomous function in propagating oncogenesis and stimulating the anti-tumor immune response and identify future directions for research.
    Keywords:  etiology; glioma; human endogenous retrovirus; viral mimicry
  13. Neurooncol Adv. 2021 Jan-Dec;3(1):3(1): vdab060
      Background: Determining failure to anti-angiogenic therapy in recurrent glioblastoma (GBM) (rGBM) remains a challenge. The purpose of the study was to assess treatment response to bevacizumab-based therapy in patients with rGBM using MR spectroscopy (MRS).Methods: We performed longitudinal MRI/MRS in 33 patients with rGBM to investigate whether changes in N-acetylaspartate (NAA)/Choline (Cho) and Lactate (Lac)/NAA from baseline to subsequent time points after treatment can predict early failures to bevacizumab-based therapies.
    Results: After stratifying based on 9-month survival, longer-term survivors had increased NAA/Cho and decreased Lac/NAA levels compared to shorter-term survivors. ROC analyses for intratumoral NAA/Cho correlated with survival at 1 day, 2 weeks, 8 weeks, and 16 weeks. Intratumoral Lac/NAA ROC analyses were predictive of survival at all time points tested. At the 8-week time point, 88% of patients with decreased NAA/Cho did not survive 9 months; furthermore, 90% of individuals with an increased Lac/NAA from baseline did not survive at 9 months. No other metabolic ratios tested significantly predicted survival.
    Conclusions: Changes in metabolic levels of tumoral NAA/Cho and Lac/NAA can serve as early biomarkers for predicting treatment failure to anti-angiogenic therapy as soon as 1 day after bevacizumab-based therapy. The addition of MRS to conventional MR methods can provide better insight into how anti-angiogenic therapy affects tumor microenvironment and predict patient outcomes.
    Keywords:  MR spectroscopy; bevacizumab; biomarker; brain tumor; lactate
  14. Nat Commun. 2021 06 15. 12(1): 3621
      Chromatin structure and accessibility, and combinatorial binding of transcription factors to regulatory elements in genomic DNA control transcription. Genetic variations in genes encoding histones, epigenetics-related enzymes or modifiers affect chromatin structure/dynamics and result in alterations in gene expression contributing to cancer development or progression. Gliomas are brain tumors frequently associated with epigenetics-related gene deregulation. We perform whole-genome mapping of chromatin accessibility, histone modifications, DNA methylation patterns and transcriptome analysis simultaneously in multiple tumor samples to unravel epigenetic dysfunctions driving gliomagenesis. Based on the results of the integrative analysis of the acquired profiles, we create an atlas of active enhancers and promoters in benign and malignant gliomas. We explore these elements and intersect with Hi-C data to uncover molecular mechanisms instructing gene expression in gliomas.
  15. JCI Insight. 2021 Jun 15. pii: 145875. [Epub ahead of print]
      The blood-brain barrier (BBB) prevents antibodies from penetrating the CNS and limits conventional antibody-based approaches to brain tumors. We now show that ENT2, a transporter that regulates nucleoside flux at the BBB, may offer an unexpected path to circumventing this barrier to allow targeting of brain tumors with an anti-DNA autoantibody. Deoxymab-1 (DX1) is a DNA-damaging autoantibody that localizes to tumors and is synthetically lethal to cancer cells with defects in the DNA damage response. We find DX1 penetrates brain endothelial cells and crosses the BBB, and mechanistic studies identify ENT2 as the key transporter. In efficacy studies DX1 crosses the BBB to suppress orthotopic glioblastoma and breast cancer brain metastases. ENT2-linked transport of autoantibodies across the BBB has potential to be exploited in brain tumor immunotherapy, and its discovery raises new hypotheses on actionable mechanisms of CNS penetration by neurotoxic autoantibodies in CNS lupus.
    Keywords:  Autoimmunity; Brain cancer; Breast cancer; Immunoglobulins; Oncology
  16. Neuro Oncol. 2021 Jun 16. pii: noab138. [Epub ahead of print]
      Pediatric low-grade gliomas (pLGGs) are the most common brain tumor in children, and are associated with life-long clinical morbidity. Relative to their high-grade adult counterparts or other malignant childhood brain tumors, there is a paucity of authenticated preclinical models for these pediatric low-grade gliomas and an incomplete understanding of their molecular and cellular pathogenesis. While large scale genomic profiling efforts have identified the majority of pathogenic driver mutations, which converge on the MAPK/ERK signaling pathway, it is now appreciated that these events may not be sufficient by themselves for gliomagenesis and clinical progression. In light of the recent World Health Organization reclassification of pLGGs, and pilocytic astrocytoma (PA) in particular, we review our current understanding of these pediatric brain tumors, provide a conceptual framework for future mechanistic studies, and outline the challenges and pressing needs for the pLGG clinical and research communities.
    Keywords:  BRAF; MEK; cellular senescence; low-grade glioma; neurofibromatosis type 1; pediatric brain tumor; pilocytic astrocytoma; tumor microenvironment