bims-malgli Biomed News
on Biology of malignant gliomas
Issue of 2020‒10‒11
twelve papers selected by
Oltea Sampetrean
Keio University

  1. Nat Commun. 2020 10 05. 11(1): 4997
      Despite a deeper molecular understanding, human glioblastoma remains one of the most treatment refractory and fatal cancers. It is known that the presence of macrophages and microglia impact glioblastoma tumorigenesis and prevent durable response. Herein we identify the dual function cytokine IL-33 as an orchestrator of the glioblastoma microenvironment that contributes to tumorigenesis. We find that IL-33 expression in a large subset of human glioma specimens and murine models correlates with increased tumor-associated macrophages/monocytes/microglia. In addition, nuclear and secreted functions of IL-33 regulate chemokines that collectively recruit and activate circulating and resident innate immune cells creating a pro-tumorigenic environment. Conversely, loss of nuclear IL-33 cripples recruitment, dramatically suppresses glioma growth, and increases survival. Our data supports the paradigm that recruitment and activation of immune cells, when instructed appropriately, offer a therapeutic strategy that switches the focus from the cancer cell alone to one that includes the normal host environment.
  2. J Exp Clin Cancer Res. 2020 Oct 07. 39(1): 208
      High-grade gliomas (HGGs), including glioblastoma and diffuse intrinsic pontine glioma, are amongst the most fatal brain tumors. These tumors are associated with a dismal prognosis with a median survival of less than 15 months. Radiotherapy has been the mainstay of treatment of HGGs for decades; however, pronounced radioresistance is the major obstacle towards the successful radiotherapy treatment. Herein, tumor hypoxia is identified as a significant contributor to the radioresistance of HGGs as oxygenation is critical for the effectiveness of radiotherapy. Hypoxia plays a fundamental role in the aggressive and resistant phenotype of all solid tumors, including HGGs, by upregulating hypoxia-inducible factors (HIFs) which stimulate vital enzymes responsible for cancer survival under hypoxic stress. Since current attempts to target tumor hypoxia focus on reducing oxygen demand of tumor cells by decreasing oxygen consumption rate (OCR), an attractive strategy to achieve this is by inhibiting mitochondrial oxidative phosphorylation, as it could decrease OCR, and increase oxygenation, and could therefore improve the radiation response in HGGs. This approach would also help in eradicating the radioresistant glioma stem cells (GSCs) as these predominantly rely on mitochondrial metabolism for survival. Here, we highlight the potential for repurposing anti-parasitic drugs to abolish tumor hypoxia and induce apoptosis of GSCs. Current literature provides compelling evidence that these drugs (atovaquone, ivermectin, proguanil, mefloquine, and quinacrine) could be effective against cancers by mechanisms including inhibition of mitochondrial metabolism and tumor hypoxia and inducing DNA damage. Therefore, combining these drugs with radiotherapy could potentially enhance the radiosensitivity of HGGs. The reported efficacy of these agents against glioblastomas and their ability to penetrate the blood-brain barrier provides further support towards promising results and clinical translation of these agents for HGGs treatment.
    Keywords:  Anti-parasitic drugs; Glioma stem cells; HIFs; High-grade gliomas; Hypoxia; Metabolism; Mitochondria; Radioresistance
  3. J Clin Invest. 2020 Oct 05. pii: 127916. [Epub ahead of print]
      Glioblastoma multiforme (GBM) heterogeneity causes a greater number of deaths than any other brain tumor, despite the availability of alkylating chemotherapy. GBM stem-like cells (GSCs) contribute to GBM complexity and chemoresistance, but it remains challenging to identify and target GSCs or factors that control their activity. Here, we identified a specific GSC subset and show that activity of these cells is positively regulated by stabilization of methyl CpG binding domain 3 (MBD3) protein. MBD3 binds to CK1A and to BTRCP E3 ubiquitin ligase, triggering MBD3 degradation, suggesting that modulating this circuit could antagonize GBM recurrence. Accordingly, xenograft mice treated with the CK1A activator pyrvinium pamoate (Pyr-Pam) showed enhanced MBD3 degradation in cells expressing high levels of O6-methylguanine-DNA methyltransferase (MGMT) and in GSCs, overcoming temozolomide chemoresistance. Pyr-Pam blocked recruitment of MBD3 and the repressive nucleosome remodeling and deacetylase (NuRD) complex to neurogenesis-associated gene loci and increased acetyl-histone H3 activity and GSC differentiation. We conclude that CK1A/BTRCP/MBD3/NuRD signaling modulates GSC activation and malignancy, and that targeting this signaling could suppress GSC proliferation and GBM recurrence.
    Keywords:  Brain cancer; Drug therapy; Epigenetics; Oncology; Stem cells
  4. Cancer Discov. 2020 Oct 06. pii: CD-20-0331. [Epub ahead of print]
      Glioblastoma is a universally lethal cancer driven by glioblastoma stem cells (GSCs). Here, we interrogated N6-methyladenosine (m6A) mRNA modifications in GSCs by methyl RNA-immunoprecipitation followed by sequencing (meRIP-seq) and transcriptome analysis, finding transcripts marked by m6A often upregulated compared to normal neural stem cells (NSCs). Interrogating m6A regulators, GSCs displayed preferential expression, as well as in vitro and in vivo dependency, of the m6A reader, YTHDF2, in contrast to NSCs. While YTHDF2 has been reported to destabilize mRNAs, YTHDF2 stabilized MYC and VEGFA transcripts in GSCs in an m6A-dependent manner. We identified IGFBP3 as a downstream effector of the YTHDF2-MYC axis in GSCs. The IGF1/IGF1R inhibitor, linsitinib, preferentially targeted YTHDF2-expressing cells, inhibiting GSC viability without affecting NSCs and impairing in vivo glioblastoma growth. Thus, YTHDF2 links RNA epitranscriptomic modifications and GSC growth, laying the foundation for the YTHDF2-MYC-IGFBP3 axis as a specific and novel therapeutic target in glioblastoma.
  5. Sci Transl Med. 2020 Oct 07. pii: eabb2311. [Epub ahead of print]12(564):
      Glioblastoma is a poorly immunogenic cancer, and the successes with recent immunotherapies in extracranial malignancies have, so far, not been translated to this devastating disease. Therefore, there is an urgent need for new strategies to convert the immunologically cold glioma microenvironment into a hot one to enable effective antitumor immunity. Using the L19 antibody, which is specific to a tumor-associated epitope of extracellular fibronectin, we developed antibody-cytokine fusions-immunocytokines-with interleukin-2 (IL2), IL12, or tumor necrosis factor (TNF). We showed that L19 accumulated in the tumor microenvironment of two orthotopic immunocompetent mouse glioma models. Furthermore, intravenous administration of L19-mIL12 or L19-mTNF cured a proportion of tumor-bearing mice, whereas L19-IL2 did not. This therapeutic activity was abolished in RAG-/- mice or upon depletion of CD4 or CD8 T cells, suggesting adaptive immunity. Mechanistically, both immunocytokines promoted tumor-infiltrating lymphocytes and increased the amounts of proinflammatory cytokines within the tumor microenvironment. In addition, L19-mTNF induced tumor necrosis. Systemic administration of the fully human L19-TNF fusion protein to patients with glioblastoma (NCT03779230) was safe, decreased regional blood perfusion within the tumor, and was associated with increasing tumor necrosis and an increase in tumor-infiltrating CD4 and CD8 T cells. The extensive preclinical characterization and subsequent clinical translation provide a robust basis for future studies with immunocytokines to treat malignant brain tumors.
  6. Cancers (Basel). 2020 Oct 04. pii: E2860. [Epub ahead of print]12(10):
      Advances in functional imaging are supporting neurosurgery and radiotherapy for glioblastoma, which still remains the most aggressive brain tumor with poor prognosis. The typical infiltration pattern of glioblastoma, which impedes a complete surgical resection, is coupled with a high rate of invasiveness and radioresistance, thus further limiting efficient therapy, leading to inevitable and fatal recurrences. Hypoxia is of crucial importance in gliomagenesis and, besides reducing radiotherapy efficacy, also induces cellular and molecular mediators that foster proliferation and invasion. In this review, we aimed at analyzing the biological mechanism of glioblastoma invasiveness and radioresistance in hypoxic niches of glioblastoma. We also discussed the link between hypoxia and radiation-induced radioresistance with activation of SRC proto-oncogene non-receptor tyrosine kinase, prospecting potential strategies to overcome the current limitation in glioblastoma treatment.
    Keywords:  Glioblastoma; SRC tyrosine kinase; hypoxia; invasion; radioresistance; targeted therapy
  7. Mol Oncol. 2020 Oct 05.
      The concept of polypharmacology involves the interaction of drug molecules with multiple molecular targets. It provides a unique opportunity for the repurposing of already-approved drugs to target key factors involved in human diseases. Herein, we used an in silico target prediction algorithm to investigate the mechanism of action of mebendazole, an anti-helminthic drug, currently repurposed in the treatment of brain tumors. First, we confirmed that mebendazole decreased the viability of glioblastoma cells in vitro (IC50 values ranging from 288 nM to 2.1 µM). Our in silico approach unveiled 21 putative molecular targets for mebendazole, including 12 proteins significantly up-regulated at the gene level in glioblastoma as compared to normal brain tissue (fold change > 1.5; p < 0.0001). Validation experiments were performed on three major kinases involved in cancer biology: ABL1, MAPK1/ERK2 and MAPK14/p38α. Mebendazole could inhibit the activity of these kinases in vitro in a dose-dependent manner, with a high potency against MAPK14 (IC50 = 104 +/- 46 nM). Its direct binding to MAPK14 was further validated in vitro and inhibition of MAPK14 kinase activity was confirmed in live glioblastoma cells. Consistent with biophysical data, molecular modeling suggested that mebendazole was able to bind to the catalytic site of MAPK14. Finally, gene silencing demonstrated that MAPK14 is involved in glioblastoma tumor spheroid growth and response to mebendazole treatment. This study thus highlighted the role of MAPK14 in the anticancer mechanism of action of mebendazole and provides further rationale for the pharmacological targeting of MAPK14 in brain tumors. It also opens new avenues for the development of novel MAPK14/p38α inhibitors to treat human diseases.
    Keywords:  MAPK14; Mebendazole; cancer; drug target prediction; glioblastoma; polypharmacology
  8. Mol Cancer Res. 2020 Oct 07. pii: molcanres.0420.2020. [Epub ahead of print]
      Signaling from multiple receptor tyrosine kinases (RTKs) contributes to therapeutic resistance in glioblastoma (GBM). Heparan sulfate (HS), present on cell surfaces and in the extracellular matrix, regulates cell signaling via several mechanisms. To investigate the role for HS in promoting RTK signaling in GBM, we generated neural progenitor cells deficient for heparan sulfate (HS) by knockout of the essential HS-biosynthetic enzyme Ext1, and studied tumor initiation and progression. HS-null cells had decreased proliferation, invasion, and reduced activation of multiple RTKs compared to control. In vivo tumor establishment was significantly decreased and rate of tumor growth reduced with HS deficient cells implanted in an HS-poor microenvironment. To investigate if HS regulates RTK activation through platelet-derived growth factor receptor α (PDGFRα) signaling, we removed cell surface HS in patient-derived GBM lines and identified reduced cell surface PDGF-BB ligand. Reduced ligand levels were associated with decreased phosphorylation of PDGFRα suggesting HS promotes ligand-receptor interaction. Using human GBM tumorspheres and a murine GBM model, we show that ligand-mediated signaling can partially rescue cells from targeted RTK inhibition and that this effect is regulated by HS. Indeed, tumor cells deficient for HS had increased sensitivity to EGFR inhibition in vitro and in vivo. Implications: Our study shows that HS expressed on tumor cells and in the tumor microenvironment regulates ligand-mediated signaling, promoting tumor cell proliferation and invasion, and these factors contribute to decreased tumor cell response to targeted RTK inhibition.
  9. Br J Cancer. 2020 Oct 06.
      BACKGROUND: The aetiology of glioma is poorly understood. Summary data from genome-wide association studies (GWAS) can be used in a Mendelian randomisation (MR) phenome-wide association study (PheWAS) to search for glioma risk factors.METHODS: We performed an MR-PheWAS analysing 316 phenotypes, proxied by 8387 genetic variants, and summary genetic data from a GWAS of 12,488 glioma cases and 18,169 controls. Causal effects were estimated under a random-effects inverse-variance-weighted (IVW-RE) model, with robust adjusted profile score (MR-RAPS), weighted median and mode-based estimates computed to assess the robustness of findings. Odds ratios per one standard deviation increase in each phenotype were calculated for all glioma, glioblastoma (GBM) and non-GBM tumours.
    RESULTS: No significant associations (P < 1.58 × 10-4) were observed between phenotypes and glioma under the IVW-RE model. Suggestive associations (1.58 × 10-4 < P < 0.05) were observed between leukocyte telomere length (LTL) with all glioma (ORSD = 3.91, P = 9.24 × 10-3) and GBM (ORSD = 4.86, P = 3.23 × 10-2), but the association was primarily driven by the TERT variant rs2736100. Serum low-density lipoprotein cholesterol and plasma HbA1C showed suggestive associations with glioma (ORSD = 1.11, P = 1.39 × 10-2 and ORSD = 1.28, P = 1.73 × 10-2, respectively), both associations being reliant on single genetic variants.
    CONCLUSIONS: Our study provides further insight into the aetiological basis of glioma for which published data have been mixed.
  10. Sci Rep. 2020 Oct 09. 10(1): 16900
      Gliomas grow and invade along white matter fiber tracts. This study assessed the effects of motor cortex gliomas on the cerebral white matter fiber bundle skeleton. The motor cortex glioma group included 21 patients, and the control group comprised 14 healthy volunteers. Both groups underwent magnetic resonance imaging-based 3.0 T diffusion tensor imaging. We used tract-based spatial statistics to analyze the characteristics of white matter fiber bundles. The left and right motor cortex glioma groups were analyzed separately from the control group. Results were statistically corrected by the family-wise error rate. Compared with the controls, patients with left motor cortex gliomas exhibited significantly reduced fractional anisotropy and an increased radial diffusivity in the corpus callosum. The alterations in mean diffusivity (MD) and the axial diffusivity (AD) were widely distributed throughout the brain. Furthermore, atlas-based analysis showed elevated MD and AD in the contralateral superior fronto-occipital fasciculus. Motor cortex gliomas significantly affect white matter fiber microstructure proximal to the tumor. The range of affected white matter fibers may extend beyond the tumor-affected area. These changes are primarily related to early stage tumor invasion.
  11. Mol Cancer Ther. 2020 Oct 08. pii: molcanther.0420.2020. [Epub ahead of print]
      We previously reported the in vitro and in vivo efficacy of N,N-bis(2-chloroethyl)-2-(1-methyl-1,2,3,6-tetrahydropyridin-4-yl)propenamide, a prodrug that targeted the mitochondria of glioblastoma (GBM). The mitochondrial enzyme monoamine oxidase B (MAOB) is highly expressed in GBM and oxidizes an uncharged methyl-tetrahydropyridine (MP-) moiety into the mitochondrially-targeted cationic form, methyl-pyridinium (P+-). Coupling this MAOB-sensitive group to a nitrogen mustard produced a prodrug that damaged GBM mitochondria and killed GBM cells. Unfortunately, the intrinsic reactivity of the nitrogen-mustard group and low solubility of MP-MUS precluded clinical development. In our second generation prodrug, MP-Pt(IV) we coupled the MP-group to an unreactive cisplatin precursor. The enzymatic conversion of MP-Pt(IV) to P+-Pt(IV) was tested using recombinant human MAOA and rhMAOB. The generation of cisplatin from Pt(IV) by ascorbate was studied optically and using mass-spectroscopy. Efficacy toward primary GBM cells and tumors was studied in vitro and in an intracranial patient-derived xenograft mice GBM model. Our studies demonstrate that MP-Pt(IV) is selectively activated by MAOB. MP-Pt(IV) is highly toxic toward GBM cells in vitro. MP-Pt(IV) toxicity against GBM is potentiated by elevating mitochondrial ascorbate and can be arrested by MAOB inhibition. In in vitro studies, sub-lethal MP-Pt(IV) doses elevated mitochondrial MAOB levels in surviving GBM cells. MP-Pt(IV) is a potent chemotherapeutic in intracranial patient-derived xenograft mouse models of primary GBM and potentiates both temozolomide (TMZ) and TMZ-chemoradiation therapies. MP-Pt(IV) was well tolerated and is highly effective against GBM in both in vitro and in vivo models.
  12. Sci Rep. 2020 Oct 05. 10(1): 16512
      Desorption electrospray ionisation mass spectrometry (DESI-MS) can image hundreds of molecules in a 2D tissue section, making it an ideal tool for mapping tumour heterogeneity. Tumour lipid metabolism has gained increasing attention over the past decade; and here, lipid heterogeneity has been visualised in a glioblastoma xenograft tumour using 3D DESI-MS imaging. The use of an automatic slide loader automates 3D imaging for high sample-throughput. Glioblastomas are highly aggressive primary brain tumours, which display heterogeneous characteristics and are resistant to chemotherapy and radiotherapy. It is therefore important to understand biochemical contributions to their heterogeneity, which may be contributing to treatment resistance. Adjacent sections to those used for DESI-MS imaging were used for H&E staining and immunofluorescence to identify different histological regions, and areas of hypoxia. Comparing DESI-MS imaging with biological staining allowed association of different lipid species with hypoxic and viable tissue within the tumour, and hence mapping of molecularly different tumour regions in 3D space. This work highlights that lipids are playing an important role in the heterogeneity of this xenograft tumour model, and DESI-MS imaging can be used for lipid 3D imaging in an automated fashion to reveal heterogeneity, which is not apparent in H&E stains alone.