bims-malgli Biomed News
on Biology of malignant gliomas
Issue of 2020‒12‒06
nineteen papers selected by
Oltea Sampetrean
Keio University

  1. Cancers (Basel). 2020 Nov 25. pii: E3505. [Epub ahead of print]12(12):
      Glioblastoma (GBM) is the most common primary brain malignancy in adults, with a 100% recurrence rate and 21-month median survival. Our lab and others have shown that GBM contains a subpopulation of glioma stem cells (GSCs) that expand during chemotherapy and may contribute to therapeutic resistance and recurrence in GBM. To investigate the mechanism behind this expansion, we applied gene set expression analysis (GSEA) to patient-derived xenograft (PDX) cells in response to temozolomide (TMZ), the most commonly used chemotherapy against GBM. Results showed significant enrichment of cancer stem cell and cell cycle pathways (False Discovery Rate (FDR) < 0.25). The ligand of numb protein 1 (LNX1), a known regulator of Notch signaling by targeting negative regulator Numb, is strongly upregulated after TMZ therapy (p < 0.0001) and is negatively correlated with survival of GBM patients. LNX1 is also upregulated after TMZ therapy in multiple PDX lines with concomitant downregulations in Numb and upregulations in intracellular Notch1 (NICD). Overexpression of LNX1 results in Notch1 signaling activation and increased GSC populations. In contrast, knocking down LNX1 reverses these changes, causing a significant downregulation of NICD, reduction in stemness after TMZ therapy, and resulting in more prolonged median survival in a mouse model. Based on this, we propose that during anti-GBM chemotherapy, LNX1-regulated Notch1 signaling promotes stemness and contributes to therapeutic resistance.
    Keywords:  LNX1; Notch1; glioblastoma; glioma stem cell; therapeutic resistance
  2. Neuro Oncol. 2020 Nov 29. pii: noaa264. [Epub ahead of print]
      BACKGROUND: Glioblastomas (GBMs) are the most common primary brains tumors in adults with almost 100% recurrence rate. Patients with lateral ventricle proximal GBMs (LV-GBMs) exhibit worse survival compared to distal locations for reasons that remain unknown. One potential explanation is the proximity of these tumors to the cerebrospinal fluid (CSF) and its contained chemical cues that can regulate cellular migration and differentiation. We therefore investigated the role of CSF on GBM gene expression and the role of a CSF-induced gene, SERPINA3, in GBM malignancy in vitro and in vivo.METHODS: We utilized patient-derived CSF and primary cultures of GBM brain tumor initiating cells (BTICs). We determined the impact of SERPINA3 expression in glioma patients using TCGA database. SERPINA3 expression changes were evaluated at both the mRNA and protein levels. The effects of knockdown (KD) and overexpression (OE) of SERPINA3 on cell behavior were evaluated by transwell assay (for cell migration), and alamar blue and Ki67 (for viability and proliferation respectively). Stem cell characteristics on KD cells were evaluated by differentiation and colony formation experiments. Tumor growth was studied by intracranial and flank injections.
    RESULTS: GBM CSF induced a significant increase in BTIC migration accompanied by upregulation of the SERPINA3 gene. In patient samples and TCGA data we observed SERPINA3 to correlate directly with brain tumor grade and indirectly with GBM patient survival. Silencing of SERPINA3 induced a decrease in cell proliferation, migration, invasion, and stem cell characteristics, while SERPINA3 overexpression increased cell migration. In vivo, mice orthotopically-injected with SERPINA3 KD BTICs showed increased survival.
    CONCLUSIONS: SERPINA3 plays a key role in GBM malignancy and its inhibition results in a better outcome using GBM preclinical models.
    Keywords:  Alpha 1-antichymotrypsin; Glioblastoma; SERPINA3; brain tumor; cerebrospinal fluid
  3. Neuro Oncol. 2020 Nov 29. pii: noaa265. [Epub ahead of print]
      BACKGROUND: Failure of glioblastoma (GBM) therapy is often ascribed to different types of glioblastoma stem-like cells (GSLCs) niche, in particularly, a hypoxic perivascular niche (HPVN) is involved in GBM progression. However, the responsible cells for HPVN remained unclear.METHODS: Immunostaining was performed to determine the cells that are responsible for HPVN. A hypoxic chamber and 3D microfluidic chips were designed to simulate HPVN based on the pathological features of GBM. The phenotype of GSLCs was evaluated by fluorescence scanning in real-time and proliferation and apoptotic assays. The expression of JAG1, DLL4 and Hes1 was determined by immunostaining, ELISA, western-blotting, and q-PCR. Their clinical progonostic significance in GBM HPVN and total tumor tissues were verified by clinical data and TCGA databases.
    RESULTS: Nestin +/CD31 + cells and pericytes constitute the major part of microvessels in HPVN and high ratio of nestin +/CD31 + cells rather than pericytes were responsible for poor prognosis of GBM. A more real HPVN was simulated by hypoxic coculture system in vitro, which was assembled by 3D microfluidic chips and hypoxic chamber. Nestin +/CD31 + cells in HPVN were derived from GSLCs transdifferentiation and could promote GSLCs chemoresistance by providing more JAG1 and DLL4 to induce down-stream Hes1 overexpression. Poor prognosis of GBM was correlated to Hes1 expression of tumor cells in GBM HPVN, and not correlated with total Hes1 expression in GBM tissues.
    CONCLUSION: These results hightlighted the critical role of nestin +/CD31 + cells in HPVN that acts in GBM chemoresistance and revealed the distinctive prognostic value of these molecular markers in HPVN.
    Keywords:  cancer stem cells; chemoresistance; glioblastoma; hypoxia; tumor microenvironment
  4. Neuro Oncol. 2020 Nov 30. pii: noaa256. [Epub ahead of print]
      The treatment of patients with a variety of solid tumors has benefitted from immune checkpoint inhibition targeting the anti-programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) axis. The US Food and Drug Administration (FDA) granted accelerated approval of PD-1 inhibitor pembrolizumab for the treatment of adult and pediatric patients with TMB-high (TMB-H), solid tumors that have progressed following prior treatment and who have no other treatment options, including the extension to tumors of the Central Nervous System (CNS). In general, pan-cancer approvals are viewed positively to empower patients and clinicians. There are subsets (eg, BRAF, NTRK) for which this pathway for approval is appropriate. However, the pan-cancer FDA approval of pembrolizumab raises several concerns regarding the generalizability of the evidence to other tumor types, including managing patients with gliomas and other CNS tumors. The cut off for TMB-H is not well defined. There are intrinsic immunological differences between gliomas and other cancers types, including the immunosuppressive glioma microenvironment, the tumor's effects on systemic immune function, and the transformation of the T cell populations to an exhausted phenotype in glioma. Here we address the caveats with pan-cancer approvals concerning gliomas, complexities of the unique CNS immune environment, and discuss potential predictive biomarkers, including TMB, and explain why the recent approval should be applied with caution in CNS tumors.
    Keywords:  glioblastoma; glioma; high tumor mutational burden (TMB-H); immunobiology; immunotherapy
  5. EBioMedicine. 2020 Nov 27. pii: S2352-3964(20)30510-7. [Epub ahead of print]62 103134
      BACKGROUND: Glioblastoma is the most aggressive primary brain tumour and has a very poor prognosis. Inhibition of c-Src activity in glioblastoma stem cells (GSCs, responsible for glioblastoma lethality) and primary glioblastoma cells by the peptide TAT-Cx43266-283 reduces tumorigenicity, and boosts survival in preclinical models. Because c-Src can modulate cell metabolism and several reports revealed poor clinical efficacy of various antitumoral drugs due to metabolic rewiring in cancer cells, here we explored the inhibition of advantageous GSC metabolic plasticity by the c-Src inhibitor TAT-Cx43266-283.METHODS: Metabolic impairment induced by the c-Src inhibitor TAT-Cx43266-283 in vitro was assessed by fluorometry, western blotting, immunofluorescence, qPCR, enzyme activity assays, electron microscopy, Seahorse analysis, time-lapse imaging, siRNA, and MTT assays. Protein expression in tumours from a xenograft orthotopic glioblastoma mouse model was evaluated by immunofluorescence.
    FINDINGS: TAT-Cx43266-283 decreased glucose uptake in human GSCs and reduced oxidative phosphorylation without a compensatory increase in glycolysis, with no effect on brain cell metabolism, including rat neurons, human and rat astrocytes, and human neural stem cells. TAT-Cx43266-283 impaired metabolic plasticity, reducing GSC growth and survival under different nutrient environments. Finally, GSCs intracranially implanted with TAT-Cx43266-283 showed decreased levels of important metabolic targets for cancer therapy, such as hexokinase-2 and GLUT-3.
    INTERPRETATION: The reduced ability of TAT-Cx43266-283-treated GSCs to survive in metabolically challenging settings, such as those with restricted nutrient availability or the ever-changing in vivo environment, allows us to conclude that the advantageous metabolic plasticity of GSCs can be therapeutically exploited through the specific and cell-selective inhibition of c-Src by TAT-Cx43266-283.
    FUNDING: Spanish Ministerio de Economía y Competitividad (FEDER BFU2015-70040-R and FEDER RTI2018-099873-B-I00), Fundación Ramón Areces. Fellowships from the Junta de Castilla y León, European Social Fund, Ministerio de Ciencia and Asociación Española Contra el Cáncer (AECC).
    Keywords:  Brain tumour; Cancer metabolism; Connexin; GLUT-3; Glioblastoma stem cells; Hexokinase-2
  6. Clin Cancer Res. 2020 Nov 30. pii: clincanres.2400.2020. [Epub ahead of print]
      PURPOSE: Extracellular matrix (ECM) component hyaluronan (HA) facilitates malignant phenotypes of glioblastoma (GBM), however, whether HA impacts response to GBM immunotherapies is not known. Herein, we investigated whether degradation of HA enhances oncolytic virus immunotherapy for GBM.EXPERIMENTAL DESIGN: Presence of HA was examined in patient and murine GBM. Hyaluronidase-expressing oncolytic adenovirus ICOVIR17, and its parental virus ICOVIR15 without transgene, were tested whether they increased animal survival and modulated the immune tumor microenvironment (TME) in orthotopic GBM. HA regulation of NF-kB signaling was examined in virus-infected murine macrophages. We combined ICOVIR17 with PD-1 checkpoint blockade and assessed efficacy and determined mechanistic contributions of tumor-infiltrating myeloid and T cells.
    RESULTS: Treatment of murine orthotopic GBM with ICOVIR17 increased tumor-infiltrating CD8+ T cells and macrophages, and upregulated PD-L1 on GBM cells and macrophages, leading to prolonged animal survival, compared to control virus ICOVIR15. High-molecular weight HA inhibits adenovirus-induced NF-kB signaling in macrophages in vitro, linking HA degradation to macrophage activation. Combining ICOVIR17 with anti-PD-1 antibody further extended the survival of GBM-bearing mice, achieving long-term remission in some animals. Mechanistically, CD4+, CD8+ T cells and macrophages all contributed to the combination therapy that induced tumor-associated pro-inflammatory macrophages and tumor-specific T cell cytotoxicity locally and systemically.
    CONCLUSIONS: Our studies are the first to show that immune-modulatory ICOVIR17 has a dual role of mediating degradation of HA within GBM-ECM and subsequently modifying the immune landscape of the TME, and offers a mechanistic combination immunotherapy with PD-L1/PD-1 blockade that remodels innate and adaptive immune cells.
  7. Redox Biol. 2020 Nov 19. pii: S2213-2317(20)31009-0. [Epub ahead of print]38 101804
      Pharmacological ascorbate (P-AscH-) combined with standard of care (SOC) radiation and temozolomide is being evaluated in a phase 2 clinical trial (NCT02344355) in the treatment of glioblastoma (GBM). Previously published data demonstrated that paramagnetic iron (Fe3+) catalyzes ascorbate's oxidation to form diamagnetic iron (Fe2+). Because paramagnetic Fe3+ may influence relaxation times observed in MR imaging, quantitative MR imaging of P-AscH--induced changes in redox-active Fe was assessed as a biomarker for therapy response. Gel phantoms containing either Fe3+ or Fe2+ were imaged with T2* and quantitative susceptibility mapping (QSM). Fifteen subjects receiving P-AscH- plus SOC underwent T2* and QSM imaging four weeks into treatment. Subjects were scanned: pre-P-AscH- infusion, post-P-AscH- infusion, and post-radiation (3-4 h between scans). Changes in T2* and QSM relaxation times in tumor and normal tissue were calculated and compared to changes in Fe3+ and Fe2+ gel phantoms. A GBM mouse model was used to study the relationship between the imaging findings and the labile iron pool. Phantoms containing Fe3+ demonstrated detectable changes in T2* and QSM relaxation times relative to Fe2+ phantoms. Compared to pre-P-AscH-, GBM T2* and QSM imaging were significantly changed post-P-AscH- infusion consistent with conversion of Fe3+ to Fe2+. No significant changes in T2* or QSM were observed in normal brain tissue. There was moderate concordance between T2* and QSM changes in both progression free survival and overall survival. The GBM mouse model showed similar results with P-AscH- inducing greater changes in tumor labile iron pools compared to the normal tissue. CONCLUSIONS: T2* and QSM MR-imaging responses are consistent with P-AscH- reducing Fe3+ to Fe2+, selectively in GBM tumor volumes and represent a potential biomarker of response. This study is the first application using MR imaging in humans to measure P-AscH--induced changes in redox-active iron.
    Keywords:  GBM; Pharmacological ascorbate; QSM; Quantitative imaging; T2*
  8. Acta Neuropathol Commun. 2020 Dec 01. 8(1): 209
      Glioblastoma is an aggressive form of brain cancer that has seen only marginal improvements in its bleak survival outlook of 12-15 months over the last forty years. There is therefore an urgent need for the development of advanced drug screening platforms and systems that can better recapitulate glioblastoma's infiltrative biology, a process largely responsible for its relentless propensity for recurrence and progression. Recent advances in stem cell biology have allowed the generation of artificial tridimensional brain-like tissue termed cerebral organoids. In addition to their potential to model brain development, these reagents are providing much needed synthetic humanoid scaffolds to model glioblastoma's infiltrative capacity in a faithful and scalable manner. Here, we highlight and review the early breakthroughs in this growing field and discuss its potential future role for glioblastoma research.
    Keywords:  Cancer discovery; Cancer modelling; Cerebral organoids; Glioblastoma
  9. Brain. 2020 Nov 30. pii: awaa343. [Epub ahead of print]
      Immunosuppression of unknown aetiology is a hallmark feature of glioblastoma and is characterized by decreased CD4 T-cell counts and downregulation of major histocompatibility complex class II expression on peripheral blood monocytes in patients. This immunosuppression is a critical barrier to the successful development of immunotherapies for glioblastoma. We recapitulated the immunosuppression observed in glioblastoma patients in the C57BL/6 mouse and investigated the aetiology of low CD4 T-cell counts. We determined that thymic involution was a hallmark feature of immunosuppression in three distinct models of brain cancer, including mice harbouring GL261 glioma, B16 melanoma, and in a spontaneous model of diffuse intrinsic pontine glioma. In addition to thymic involution, we determined that tumour growth in the brain induced significant splenic involution, reductions in peripheral T cells, reduced MHC II expression on blood leucocytes, and a modest increase in bone marrow resident CD4 T cells. Using parabiosis we report that thymic involution, declines in peripheral T-cell counts, and reduced major histocompatibility complex class II expression levels were mediated through circulating blood-derived factors. Conversely, T-cell sequestration in the bone marrow was not governed through circulating factors. Serum isolated from glioma-bearing mice potently inhibited proliferation and functions of T cells both in vitro and in vivo. Interestingly, the factor responsible for immunosuppression in serum is non-steroidal and of high molecular weight. Through further analysis of neurological disease models, we determined that the immunosuppression was not unique to cancer itself, but rather occurs in response to brain injury. Non-cancerous acute neurological insults also induced significant thymic involution and rendered serum immunosuppressive. Both thymic involution and serum-derived immunosuppression were reversible upon clearance of brain insults. These findings demonstrate that brain cancers cause multifaceted immunosuppression and pinpoint circulating factors as a target of intervention to restore immunity.
    Keywords:  T cells; glioblastoma; immunosuppression; neuroimmunology; thymus;  
  10. Cell Death Differ. 2020 Dec 01.
      The human brain organoids derived from pluripotent cells are a new class of three-dimensional tissue systems that recapitulates several neural epithelial aspects. Brain organoids have already helped efficient modeling of crucial elements of brain development and disorders. Brain organoids' suitability in modeling glioma has started to emerge, offering another usefulness of brain organoids in disease modeling. Although the current state-of-the organoids mostly reflect the immature state of the brain, with their vast cell diversity, human brain-like cytoarchitecture, feasibility in culturing, handling, imaging, and tractability can offer enormous potential in reflecting the glioma invasion, integration, and interaction with different neuronal cell types. Here, we summarize the current trend of employing brain organoids in glioma modeling and discuss the immediate challenges. Solving them might lay a foundation for using brain organoids as a pre-clinical 3D substrate to dissect the glioma invasion mechanisms in detail.
  11. Clin Cancer Res. 2020 Dec 03. pii: clincanres.1499.2020. [Epub ahead of print]
      PURPOSE: Diffuse intrinsic pontine glioma (DIPG) is among the deadliest of pediatric brain tumors. Radiation therapy is the standard of care treatment for DIPG, but offers only transient relief of symptoms for DIPG patients without providing significant survival benefit. Oncolytic virotherapy (OV) is an anti-cancer treatment that has been investigated for treating various types of brain tumors.EXPERIMENTAL DESIGN: Here, we have explored the use of mesenchymal stem cells (MSC) for OV delivery and evaluated treatment efficacy using preclinical models of DIPG. The survivin promoter drives the conditional replication of OV used in our studies. The efficiency of OV entry into the cells is mediated by fiber modification with seven lysine residues (CRAd.S.pK7). Patients' samples and cell lines were analyzed for the expression of viral entry proteins and survivin. The ability of MSCs to deliver OV to DIPG was studied in the context of a low dose of irradiation.
    RESULTS: Our results show that DIPG cells and tumors exhibit robust expression of cell surface proteins and survivin that enable efficient OV entry and replication in DIPG cells. MSCs loaded with OV disseminate within a tumor and release OV throughout the DIPG brainstem xenografts in mice. Administration of OV-loaded MSCs with radiotherapy to mice bearing brainstem DIPG xenografts results in more prolonged survival relative to that conferred by either therapy alone (p<0.01).
    CONCLUSIONS: Our study supports oncolytic virus CRAd.S.pK7 encapsulated within MSCs as a therapeutic strategy that merits further investigation and potential translation for DIPG treatment.
  12. Int J Mol Sci. 2020 Nov 30. pii: E9114. [Epub ahead of print]21(23):
      Astrocytomas and, in particular, their most severe form, glioblastoma, are the most aggressive primary brain tumors and those with the poorest vital prognosis. Standard treatment only slightly improves patient survival. Therefore, new therapies are needed. Very few risk factors have been clearly identified but many epidemiological studies have reported a higher incidence in men than women with a sex ratio of 1:4. Based on these observations, it has been proposed that the neurosteroids and especially the estrogens found in higher concentrations in women's brains could, in part, explain this difference. Estrogens can bind to nuclear or membrane receptors and potentially stimulate many different interconnected signaling pathways. The study of these receptors is even more complex since many isoforms are produced from each estrogen receptor encoding gene through alternative promoter usage or splicing, with each of them potentially having a specific role in the cell. The purpose of this review is to discuss recent data supporting the involvement of steroids during gliomagenesis and to focus on the potential neuroprotective role as well as the mechanisms of action of estrogens in gliomas.
    Keywords:  astrocytoma; estrogens; gender; glioblastoma; pregnancy; receptor isoforms; signaling; steroids
  13. Cell. 2020 Nov 20. pii: S0092-8674(20)31529-4. [Epub ahead of print]
      Histone H3.3 glycine 34 to arginine/valine (G34R/V) mutations drive deadly gliomas and show exquisite regional and temporal specificity, suggesting a developmental context permissive to their effects. Here we show that 50% of G34R/V tumors (n = 95) bear activating PDGFRA mutations that display strong selection pressure at recurrence. Although considered gliomas, G34R/V tumors actually arise in GSX2/DLX-expressing interneuron progenitors, where G34R/V mutations impair neuronal differentiation. The lineage of origin may facilitate PDGFRA co-option through a chromatin loop connecting PDGFRA to GSX2 regulatory elements, promoting PDGFRA overexpression and mutation. At the single-cell level, G34R/V tumors harbor dual neuronal/astroglial identity and lack oligodendroglial programs, actively repressed by GSX2/DLX-mediated cell fate specification. G34R/V may become dispensable for tumor maintenance, whereas mutant-PDGFRA is potently oncogenic. Collectively, our results open novel research avenues in deadly tumors. G34R/V gliomas are neuronal malignancies where interneuron progenitors are stalled in differentiation by G34R/V mutations and malignant gliogenesis is promoted by co-option of a potentially targetable pathway, PDGFRA signaling.
    Keywords:  GSX2; H3.3 G34R/V; PDGFRA; cell-of-origin; chromatin conformation; gliomas; interneuron progenitors; oncohistones; pediatric cancer; single-cell transcriptome
  14. Cancers (Basel). 2020 Nov 26. pii: E3531. [Epub ahead of print]12(12):
      Glioblastoma (GBM), a highly invasive and vascular malignancy is shown to rapidly develop resistance and evolve to a more invasive phenotype following bevacizumab (Bev) therapy. Rho Guanine Nucleotide Exchange Factor proteins (RhoGEFs) are mediators of key components in Bev resistance pathways, GBM and Bev-induced invasion. To identify GEFs with enhanced mRNA expression in the leading edge of GBM tumours, a cohort of GEFs was assessed using a clinical dataset. The GEF βPix/COOL-1 was identified, and the functional effect of gene depletion assessed using 3D-boyden chamber, proliferation, and colony formation assays in GBM cells. Anti-angiogenic effects were assessed in endothelial cells using tube formation and wound healing assays. In vivo effects of βPix/COOL-1-siRNA delivered via RGD-Nanoparticle in combination with Bev was studied in an invasive model of GBM. We found that siRNA-mediated knockdown of βPix/COOL-1 in vitro decreased cell invasion, proliferation and increased apoptosis in GBM cell lines. Moreover βPix/COOL-1 mediated endothelial cell migration in vitro. Mice treated with βPix/COOL-1 siRNA-loaded RGD-Nanoparticle and Bev demonstrated a trend towards improved median survival compared with Bev monotherapy. Our hypothesis generating study suggests that the RhoGEF βPix/COOL-1 may represent a target of vulnerability in GBM, in particular to improve Bev efficacy.
    Keywords:  ARHGEF7; Beta-Pix/COOL-1; RhoGEF; anti-invasive therapy; bevacizumab resistance; glioblastoma
  15. Cancers (Basel). 2020 Nov 30. pii: E3585. [Epub ahead of print]12(12):
      (1) We wanted to assess the impact of Ang2 in RCT-induced changes in the environment of glioblastoma. (2) The effect of Ang2 overexpression in tumor cells was studied in the GL261 syngeneic immunocompetent model of GB in response to fractionated RCT. (3) We showed that RCT combined with Ang2 led to tumor clearance for the GL261-Ang2 group by acting on the tumor cells as well as on both vascular and immune compartments. (4) In vitro, Ang2 overexpression in GL261 cells exposed to RCT promoted senescence and induced robust genomic instability, leading to mitotic death. (5) Coculture experiments of GL261-Ang2 cells with RAW 264.7 cells resulted in a significant increase in macrophage migration, which was abrogated by the addition of soluble Tie2 receptor. (6) Together, these preclinical results showed that, combined with RCT, Ang2 acted in an autocrine manner by increasing GB cell senescence and in a paracrine manner by acting on the innate immune system while modulating the vascular tumor compartment. On this preclinical model, we found that an ectopic expression of Ang2 combined with RCT impedes tumor recurrence.
    Keywords:  angiopoietin-2; chemotherapy; glioblastoma; inflammation; microenvironment; radiochemotherapy; radiotherapy; vascularization
  16. Clin Cancer Res. 2020 Dec 02. pii: clincanres.4067.2020. [Epub ahead of print]
      Data indicate that ultra-high dose rate (>106 Gy/s) FLASH-RT delivery of radiation reduces normal tissue damage without compromising tumor response. Orthotopic glioblastoma mouse studies now demonstrate that radiation fraction size, total dose, and number of fractions are critical parameters for FLASH-RT cognitive sparing without compromising tumor response.
  17. Neuro Oncol. 2020 Dec 01. pii: noaa263. [Epub ahead of print]
      BACKGROUND: The conditional reprogramming cell culture method was developed to facilitate growth of senescence-prone normal and neoplastic epithelial cells, and involves co-culture with irradiated fibroblasts and the addition of a small molecule Rho kinase (ROCK) inhibitor. The aim of this study was to determine whether this approach would facilitate the culture of compact low grade gliomas.METHODS: We attempted to culture 4 pilocytic astrocytomas, 2 gangliogliomas, 2 myxopapillary ependymomas, 2 anaplastic gliomas, 2 difficult-to-classify low grade neuroepithelial tumors, a desmoplastic infantile ganglioglioma, and an anaplastic pleomorphic xanthoastrocytoma using a modified conditional reprogramming cell culture approach.
    RESULTS: Conditional reprogramming resulted in robust increases in growth for a majority of these tumors, with fibroblast conditioned media and ROCK inhibition both required. Switching cultures to standard serum containing media, or serum free neurosphere conditions, with or without ROCK inhibition, resulted in decreased proliferation and induction of senescence markers. ROCK inhibition and conditioned media both promoted Akt and Erk1/2 activation. Several cultures, including one derived from a NF1-associated pilocytic astrocytoma (JHH-NF1-PA1) and one from a BRAF p.V600E mutant anaplastic pleomorphic xanthoastrocytoma (JHH-PXA1), exhibited growth sufficient for preclinical testing in vitro. In addition, JHH-NF1-PA1 cells survived and migrated in larval zebrafish orthotopic xenografts, while JHH-PXA1 formed orthotopic xenografts in mice histopathologically similar to the tumor from which it was derived.
    CONCLUSIONS: These studies highlight the potential for the conditional reprogramming cell culture method to promote the growth of glial and glioneuronal tumors in vitro, in some cases enabling the establishment of long-term culture and in vivo models.
    Keywords:  BRAFV600E; Conditional reprogramming; NF1; Senescence; low grade glioma
  18. Nat Commun. 2020 Dec 04. 11(1): 6216
      Histone H3 lysine 27 (H3K27M) mutations represent the canonical oncohistone, occurring frequently in midline gliomas but also identified in haematopoietic malignancies and carcinomas. H3K27M functions, at least in part, through widespread changes in H3K27 trimethylation but its role in tumour initiation remains obscure. To address this, we created a transgenic mouse expressing H3.3K27M in diverse progenitor cell populations. H3.3K27M expression drives tumorigenesis in multiple tissues, which is further enhanced by Trp53 deletion. We find that H3.3K27M epigenetically activates a transcriptome, enriched for PRC2 and SOX10 targets, that overrides developmental and tissue specificity and is conserved between H3.3K27M-mutant mouse and human tumours. A key feature of the H3K27M transcriptome is activation of a RAS/MYC axis, which we find can be targeted therapeutically in isogenic and primary DIPG cell lines with H3.3K27M mutations, providing an explanation for the common co-occurrence of alterations in these pathways in human H3.3K27M-driven cancer. Taken together, these results show how H3.3K27M-driven transcriptome remodelling promotes tumorigenesis and will be critical for targeting cancers with these mutations.