bims-malgli Biomed News
on Biology of malignant gliomas
Issue of 2021‒01‒24
seventeen papers selected by
Oltea Sampetrean
Keio University

  1. Acta Neuropathol Commun. 2021 Jan 19. 9(1): 16
      Cancer cells optimize nutrient utilization to supply energetic and biosynthetic pathways. This metabolic process also includes redox maintenance and epigenetic regulation through nucleic acid and protein methylation, which enhance tumorigenicity and clinical resistance. However, less is known about how cancer cells exhibit metabolic flexibility to sustain cell growth and survival from nutrient starvation. Here, we find that serine and glycine levels were higher in low-nutrient regions of tumors in glioblastoma multiforme (GBM) patients than they were in other regions. Metabolic and functional studies in GBM cells demonstrated that serine availability and one-carbon metabolism support glioma cell survival following glutamine deprivation. Serine synthesis was mediated through autophagy rather than glycolysis. Gene expression analysis identified upregulation of methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) to regulate one-carbon metabolism. In clinical samples, MTHFD2 expression was highest in the nutrient-poor areas around "pseudopalisading necrosis." Genetic suppression of MTHFD2 and autophagy inhibition caused tumor cell death and growth inhibition of glioma cells upon glutamine deprivation. These results highlight a critical role for serine-dependent one-carbon metabolism in surviving glutamine starvation and suggest new therapeutic targets for glioma cells adapting to a low-nutrient microenvironment.
    Keywords:  Glioblastoma multiforme; Glutamine starvation; One-carbon metabolism; Serine synthesis
  2. Autophagy. 2021 Jan 19. 1-20
      Increasing evidence suggests that induction of lethal macroautophagy/autophagy carries potential significance for the treatment of glioblastoma (GBM). In continuation of previous work, we demonstrate that pimozide and loperamide trigger an ATG5- and ATG7 (autophagy related 5 and 7)-dependent type of cell death that is significantly reduced with cathepsin inhibitors and the lipid reactive oxygen species (ROS) scavenger α-tocopherol in MZ-54 GBM cells. Global proteomic analysis after treatment with both drugs also revealed an increase of proteins related to lipid and cholesterol metabolic processes. These changes were accompanied by a massive accumulation of cholesterol and other lipids in the lysosomal compartment, indicative of impaired lipid transport/degradation. In line with these observations, pimozide and loperamide treatment were associated with a pronounced increase of bioactive sphingolipids including ceramides, glucosylceramides and sphingoid bases measured by targeted lipidomic analysis. Furthermore, pimozide and loperamide inhibited the activity of SMPD1/ASM (sphingomyelin phosphodiesterase 1) and promoted induction of lysosomal membrane permeabilization (LMP), as well as release of CTSB (cathepsin B) into the cytosol in MZ-54 wild-type (WT) cells. Whereas LMP and cell death were significantly attenuated in ATG5 and ATG7 knockout (KO) cells, both events were enhanced by depletion of the lysophagy receptor VCP (valosin containing protein), supporting a pro-survival function of lysophagy under these conditions. Collectively, our data suggest that pimozide and loperamide-driven autophagy and lipotoxicity synergize to induce LMP and cell death. The results also support the notion that simultaneous overactivation of autophagy and induction of LMP represents a promising approach for the treatment of GBM. Abbreviations: ACD: autophagic cell death; AKT1: AKT serine/threonine kinase 1; ATG5: autophagy related 5; ATG7: autophagy related 7; ATG14: autophagy related 14; CERS1: ceramide synthase 1; CTSB: cathepsin B; CYBB/NOX2: cytochrome b-245 beta chain; ER: endoplasmatic reticulum; FBS: fetal bovine serum; GBM: glioblastoma; GO: gene ontology; HTR7/5-HT7: 5-hydroxytryptamine receptor 7; KD: knockdown; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LAP: LC3-associated phagocytosis; LMP: lysosomal membrane permeabilization; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MTOR: mechanistic target of rapamycin kinase; RB1CC1: RB1 inducible coiled-coil 1; ROS: reactive oxygen species; RPS6: ribosomal protein S6; SMPD1/ASM: sphingomyelin phosphodiesterase 1; VCP/p97: valosin containing protein; WT: wild-type.
    Keywords:  Acid sphingomyelinase; autophagy-dependent cell death; brain tumors; cholesterol metabolism; drug repurposing; er stress; lysophagy
  3. Cell Death Discov. 2021 Jan 22. 7(1): 21
      Significant advance has been made towards understanding glioblastoma metabolism through global metabolomic profiling. However, hitherto little is known about the role by which altered metabolism plays in driving the aggressive glioma phenotype. We have previously identified hypotaurine as one of the top-ranked metabolites for differentiating low- and high-grade tumors, and that there is also a strong association between the levels of intratumoral hypotaurine and expression of its biosynthetic enzyme, cysteamine (2-aminoethanethiol) dioxygenase (ADO). Using transcription profiling, we further uncovered that the ADO/hypotaurine axis targets CCL20 secretion through activating the NF-κB pathway to drive the self-renewal and maintenance of glioma 'cancer stem cells' or glioma cancer stem-like cells. Conversely, abrogating the ADO/hypotaurine axis using CRISPR/Cas9-mediated gene editing limited glioblastoma cell proliferation and self-renewal in vitro and tumor growth in vivo in an orthotopical mouse model, indicating that this metabolic pathway is a potential key therapeutic target. Collectively, our results unveil a targetable metabolic pathway, which contributes to the growth and progression of aggressive high-grade gliomas, as well as a novel predictive marker for glioblastoma diagnosis and therapy.
  4. Brain. 2021 Jan 22. pii: awaa408. [Epub ahead of print]
      As the clinical failure of glioblastoma treatment is attributed by multiple components, including myelin-associated infiltration, assessment of the molecular mechanisms underlying such process and identification of the infiltrating cells have been the primary objectives in glioblastoma research. Here, we adopted radiogenomic analysis to screen for functionally relevant genes that orchestrate the process of glioma cell infiltration through myelin and promote glioblastoma aggressiveness. The receptor of the Nogo ligand (NgR1) was selected as the top candidate through Differentially Expressed Genes (DEG) and Gene Ontology (GO) enrichment analysis. Gain and loss of function studies on NgR1 elucidated its underlying molecular importance in suppressing myelin-associated infiltration in vitro and in vivo. The migratory ability of glioblastoma cells on myelin is reversibly modulated by NgR1 during differentiation and dedifferentiation process through deubiquitinating activity of USP1, which inhibits the degradation of ID1 to downregulate NgR1 expression. Furthermore, pimozide, a well-known antipsychotic drug, upregulates NgR1 by post-translational targeting of USP1, which sensitizes glioma stem cells to myelin inhibition and suppresses myelin-associated infiltration in vivo. In primary human glioblastoma, downregulation of NgR1 expression is associated with highly infiltrative characteristics and poor survival. Together, our findings reveal that loss of NgR1 drives myelin-associated infiltration of glioblastoma and suggest that novel therapeutic strategies aimed at reactivating expression of NgR1 will improve the clinical outcome of glioblastoma patients.
    Keywords:  glioblastoma; myelin-associated infiltration; nogo receptor; radiogenomics
  5. Cancers (Basel). 2021 Jan 14. pii: E289. [Epub ahead of print]13(2):
      Tumor suppressor microRNAs (miRNAs) have been explored as agents to target cancer stem cells. Most strategies use a single miRNA mimic and present many disadvantages, such as the amount of reagent required and the diluted effect on target genes. miRNAs work in a cooperative fashion to regulate distinct biological processes and pathways. Therefore, we propose that miRNA combinations could provide more efficient ways to target cancer stem cells. We have previously shown that miR-124, miR-128, and miR-137 function synergistically to regulate neurogenesis. We used a combination of these three miRNAs to treat glioma stem cells and showed that this treatment was much more effective than single miRNAs in disrupting cell proliferation and survival and promoting differentiation and response to radiation. Transcriptomic analyses indicated that transcription regulation, angiogenesis, metabolism, and neuronal differentiation are among the main biological processes affected by transfection of this miRNA combination. In conclusion, we demonstrated the value of using combinations of neurogenic miRNAs to disrupt cancer phenotypes and glioma stem cell growth. The synergistic effect of these three miRNA amplified the repression of oncogenic factors and the effect on cancer relevant pathways. Future therapeutic approaches would benefit from utilizing miRNA combinations, especially when targeting cancer-initiating cell populations.
    Keywords:  glioblastoma; miR-124; miR-128; miR-137; miRNA; neuroblastoma
  6. Cancers (Basel). 2021 Jan 19. pii: E361. [Epub ahead of print]13(2):
      (1) Background: Despite the indisputable effectiveness of dexamethasone (DEXA) to reduce inflammation in glioblastoma (GBM) patients, its influence on tumour progression and radiotherapy response remains controversial. (2) Methods: We analysed patient data and used expression and cell biological analyses to assess effects of DEXA on GBM cells. We tested the efficacy of tyrosine kinase inhibitors in vitro and in vivo. (3) Results: We confirm in our patient cohort that administration of DEXA correlates with worse overall survival and shorter time to relapse. In GBM cells and glioma stem-like cells (GSCs) DEXA down-regulates genes controlling G2/M and mitotic-spindle checkpoints, and it enables cells to override the spindle assembly checkpoint (SAC). Concurrently, DEXA up-regulates Platelet Derived Growth Factor Receptor (PDGFR) signalling, which stimulates expression of anti-apoptotic regulators BCL2L1 and MCL1, required for survival during extended mitosis. Importantly, the protective potential of DEXA is dependent on intact tyrosine kinase signalling and ponatinib, sunitinib and dasatinib, all effectively overcome the radio-protective and pro-proliferative activity of DEXA. Moreover, we discovered that DEXA-induced signalling creates a therapeutic vulnerability for sunitinib in GSCs and GBM cells in vitro and in vivo. (4) Conclusions: Our results reveal a novel DEXA-induced mechanism in GBM cells and provide a rationale for revisiting the use of tyrosine kinase inhibitors for the treatment of GBM.
    Keywords:  PDGFR; dexamethasone; glioblastoma; mitosis checkpoint; sunitinib
  7. Cancer Res. 2021 Jan 22. pii: canres.1785.2020. [Epub ahead of print]
      The tumor microenvironment plays an essential role in supporting glioma stemness and radioresistance. Following radiotherapy, recurrent gliomas form in an irradiated microenvironment. Here we report that astrocytes, when pre-irradiated, increase stemness and survival of co-cultured glioma cells. Tumor-naïve brains increased reactive astrocytes in response to radiation, and mice subjected to radiation prior to implantation of glioma cells developed more aggressive tumors. Extracellular matrix derived from irradiated astrocytes were found to be a major driver of this phenotype and astrocyte-derived transglutaminase 2 (TGM2) were identified as a promoter of glioma stemness and radioresistance. TGM2 levels increased after radiation in vivo and in recurrent human glioma, and TGM2 inhibitors abrogated glioma stemness and survival. These data suggest that irradiation of the brain results in the formation of a tumor-supportive microenvironment. Therapeutic targeting of radiation-induced, astrocyte-derived extracellular matrix proteins may enhance the efficacy of standard-of-care radiotherapy by reducing stemness in glioma.
  8. Semin Cancer Biol. 2021 Jan 13. pii: S1044-579X(20)30262-5. [Epub ahead of print]
      Glioblastoma (GBM) and other malignant tumours consist of heterogeneous cancer cells, including GBM-initiating cells (GICs). This heterogeneity is likely to arise from the following: different sets of genetic mutations and epigenetic modifications, which GICs gain in the transformation process; differences in cells of origin, such as stem cells, precursor cells or differentiated cells; and the cancer microenvironment, in which GICs communicate with neural cells, endothelial cells and immune cells. Furthermore, considering that various types of GICs can be generated at different time points of the transformation process, GBM very likely consists of heterogeneous GICs and their progeny. Because cancer cell heterogeneity is responsible for therapy resistance, it is crucial to develop methods of reducing such heterogeneity. Here, I summarize how GIC heterogeneity is generated in the transformation process and present how cell heterogeneity in cancer can be addressed based on recent findings.
    Keywords:  Dihydroorotate dehydrogenase (DHODH); GBM-initiating cells (GICs); Glioblastoma (GBM); Heterogeneity; Temozolomide (TMZ)
  9. Neuro Oncol. 2021 Jan 20. pii: noab009. [Epub ahead of print]
      BACKGROUND: DIPG is associated with transcriptional dysregulation driven by H3K27 mutation. The super elongation complex (SEC) is required for transcriptional elongation through release of RNA polymerase II (Pol II). Inhibition of transcription elongation by SEC disruption can be an effective therapeutic strategy of H3K27M-mutant diffuse intrinsic pontine glioma (DIPG). Here, we tested the effect of pharmacological disruption of the SEC in H3K27M-mutant DIPG to advance understanding of the molecular mechanism and as a new therapeutic strategy for DIPG.METHODS: Short hairpin RNAs (shRNAs) were used to suppress the expression of AF4/FMR2 4 (AFF4), a central SEC component, in H3K27M-mutant DIPG cells. A peptidomimetic lead compound KL-1 was used to disrupt a functional component of SEC. Cell viability assay, colony formation assay, and apoptosis assay were utilized to analyze the effects of KL-1 treatment. RNA- and ChIP-sequencing were used to determine the effects of KL-1 on gene expression and chromatin occupancy. We treated mice bearing human H3K27M-mutant DIPG xenografts with KL-1. Intracranial tumor growth was monitored by bioluminescence image and therapeutic response was evaluated by animal survival.
    RESULTS: Depletion of AFF4 significantly reduced the cell growth of H3K27M-mutant DIPG. KL-1 increased genome-wide Pol II occupancy and suppressed transcription involving multiple cellular processes that promote cell proliferation and differentiation of DIPG. KL-1 treatment suppressed DIPG cell growth, increased apoptosis, and prolonged animal survival with human H3K27M-mutant DIPG xenografts.
    CONCLUSIONS: SEC disruption by KL-1 increased therapeutic benefit in vitro and in vivo, supporting a potential therapeutic activity of KL-1 in H3K27M-mutant DIPG.
    Keywords:  H3K27M-mutant DIPG; RNA polymerase II (Pol II); patient-derived xenograft (PDX); super elongation complex (SEC); transcriptional elongation
  10. Oncotarget. 2021 Jan 05. 12(1): 8-9
    Keywords:  glioblastoma; glioma; immunoediting; immunotherapy; resistance
  11. iScience. 2021 Jan 22. 24(1): 101968
      Dopamine (DA) plays many roles in the brain, especially in movement, motivation, and reinforcement of behavior; however, its role in regulating innate immunity is not clear. Here, we show that DA can induce DNA-based extracellular traps in primary, adult, human microglia and BV2 microglia cell line. These DNA-based extracellular traps are formed independent of reactive oxygen species, actin polymerization, and cell death. These traps are functional and capture fluorescein (FITC)-tagged Escherichia coli even when reactive oxygen species production or actin polymerization is inhibited. We show that microglial extracellular traps are present in Glioblastoma multiforme. This is crucial because Glioblastoma multiforme cells are known to secrete DA. Our findings demonstrate that DA plays a significant role in sterile neuro-inflammation by inducing microglia extracellular traps.
    Keywords:  Cell Biology; Cellular Neuroscience; Immunology; Molecular Biology
  12. Cancers (Basel). 2021 Jan 19. pii: E356. [Epub ahead of print]13(2):
      Aldehyde dehydrogenase 1A3 (ALDH1A3) belongs to an enzymatic superfamily composed by 19 different isoforms, with a scavenger role, involved in the oxidation of a plethora of aldehydes to the respective carboxylic acids, through a NAD+-dependent reaction. Previous clinical studies highlighted the high expression of ALDH1A3 in cancer stem cells (CSCs) correlated to a higher risk of cancer relapses, chemoresistance and a poor clinical outcome. We report on the structural, biochemical, and cellular characterization of NR6, a new selective ALDH1A3 inhibitor derived from an already published ALDH non-selective inhibitor with cytotoxic activity on glioblastoma and colorectal cancer cells. Crystal structure, through X-Ray analysis, showed that NR6 binds a non-conserved tyrosine residue of ALDH1A3 which drives the selectivity towards this isoform, as supported by computational binding simulations. Moreover, NR6 shows anti-metastatic activity in wound healing and invasion assays and induces the downregulation of cancer stem cell markers. Overall, our work confirms the role of ALDH1A3 as an important target in glioblastoma and colorectal cells and propose NR6 as a promising molecule for future preclinical studies.
    Keywords:  aldehyde dehydrogenases; biochemistry; cancer stem cells; cancer therapy; glioblastoma; structural biology; target validation
  13. Nat Commun. 2021 01 19. 12(1): 444
      Glioblastoma multiforme (GBM) is the most common and aggressive form of primary brain cancer, for which effective therapies are urgently needed. Chimeric antigen receptor (CAR)-based immunotherapy represents a promising therapeutic approach, but it is often impeded by highly immunosuppressive tumor microenvironments (TME). Here, in an immunocompetent, orthotopic GBM mouse model, we show that CAR-T cells targeting tumor-specific epidermal growth factor receptor variant III (EGFRvIII) alone fail to control fully established tumors but, when combined with a single, locally delivered dose of IL-12, achieve durable anti-tumor responses. IL-12 not only boosts cytotoxicity of CAR-T cells, but also reshapes the TME, driving increased infiltration of proinflammatory CD4+ T cells, decreased numbers of regulatory T cells (Treg), and activation of the myeloid compartment. Importantly, the immunotherapy-enabling benefits of IL-12 are achieved with minimal systemic effects. Our findings thus show that local delivery of IL-12 may be an effective adjuvant for CAR-T cell therapy for GBM.
  14. Aging (Albany NY). 2021 Jan 05. 13(1): 1510-1527
      Despite a growing proportion of aged individuals at risk for developing cancer in the brain, the prognosis for these conditions remains abnormally poor due to limited knowledge of underlying mechanisms and minimal treatment options. While cancer metabolism in other organs is commonly associated with upregulated glycolysis (i.e. Warburg effect) and hyperactivation of PIK3/AKT/mTOR (PAM) pathways, the unique bioenergetic demands of the central nervous system may interact with these oncogenic processes to promote tumor progression in aging. Specifically, constitutive glycolysis and PIK3/AKT/mTOR signaling in glia may be dysregulated by age-dependent alterations in neurometabolic demands, ultimately contributing to pathological processes otherwise associated with PIK3/AKT/mTOR induction (e.g. cell cycle entry, impaired autophagy, dysregulated inflammation). Although several limitations to this theoretical model exist, the consideration of aberrant PIK3/AKT/mTOR signaling in glia during aging elucidates several therapeutic opportunities for brain tumors, including non-pharmacological interventions.
    Keywords:  aging; bioenergetics; glioma