bims-malgli Biomed News
on Biology of malignant gliomas
Issue of 2020‒11‒08
twenty papers selected by
Oltea Sampetrean
Keio University


  1. Pharmacol Ther. 2020 Oct 31. pii: S0163-7258(20)30252-7. [Epub ahead of print] 107721
    Kunadis E, Lakiotaki E, Korkolopoulou P, Piperi C.
      Glioblastoma (GBM) is the most common primary brain tumor in adults, and the most lethal form of glioma, characterized by variable histopathology, aggressiveness and poor clinical outcome and prognosis. GBMs constitute a challenge for oncologists because of their molecular heterogeneity, extensive invasion, and tendency to relapse. Glioma cells demonstrate a variety of deregulated genomic pathways and extensive interplay with epigenetic alterations. Epigenetic modifications have emerged as essential players in GBM research, with biomarker potential for tumor classification and prognosis and for drug targeting. Histone posttranslational modifications (PTMs) are crucial regulators of chromatin architecture and gene expression, playing a pivotal role in malignant transformation, tumor development and progression. Alteration in the expression of genes coding for lysine and arginine methyltransferases (G9a, SUV39H1 and SETDB1) and acetyltransferases and deacetylases (KAT6A, SIRT2, SIRT7, HDAC4, 6, 9) contribute to GBM pathogenesis. In addition, proteins of the sumoylation pathway are upregulated in GBM cell lines, including E1 (SAE1), E2 (Ubc9) components, and a SUMO-specific protease (SENP1). Preclinical and clinical studies are currently in progress targeting epigenetic enzymes in gliomas, including a new generation of histone deacetylase (HDAC), protein arginine methyltransferase (PRMT) and bromodomain (BRD) inhibitors. Herein, we provide an update on recent advances in glioma epigenetic research, focusing on the role of histone modifications and the use of epigenetic therapy as a valid treatment option for glioblastoma.
    Keywords:  Epigenetic therapy; Glioblastoma; Glioblastoma therapy; Histone modifications; Histone target therapy
    DOI:  https://doi.org/10.1016/j.pharmthera.2020.107721
  2. Front Oncol. 2020 ;10 576701
    Grigorieva EV.
      Radiotherapy is an important therapeutic approach to treating malignant tumors of different localization, including brain cancer. Glioblastoma multiforme (GBM) represents the most aggressive brain tumor, which develops relapsed disease during the 1st year after the surgical removal of the primary node, in spite of active adjuvant radiochemotherapy. More and more evidence suggests that the treatment's success might be determined by the balance of expected antitumor effects of the treatment and its non-targeted side effects on the surrounding brain tissue. Radiation-induced damage of the GBM microenvironment might create tumor-susceptible niche facilitating proliferation and invasion of the residual glioma cells and the disease relapse. Understanding of molecular mechanisms of radiation-induced changes in brain ECM might help to reconsider and improve conventional anti-glioblastoma radiotherapy, taking into account the balance between its antitumor and ECM-destructing activities. Although little is currently known about the radiation-induced changes in brain ECM, this review summarizes current knowledge about irradiation effects onto the main components of brain ECM such as proteoglycans, glycosaminoglycans, glycoproteins, and the enzymes responsible for their modification and degradation.
    Keywords:  brain irradiation; chondroitin sulfate; extracellular matrix; glioblastoma radiotherapy; heparan sulfate; heparanase; metalloproteinase; proteoglycan expression
    DOI:  https://doi.org/10.3389/fonc.2020.576701
  3. Cancers (Basel). 2020 Oct 29. pii: E3175. [Epub ahead of print]12(11):
    Wenger KJ, Richter C, Burger MC, Urban H, Kaulfuss S, Harter PN, Sreeramulu S, Schwalbe H, Steinbach JP, Hattingen E, Bähr O, Pilatus U.
      BACKGROUND: BAY1436032 is a fluorine-containing inhibitor of the R132X-mutant isocitrate dehydrogenase (mIDH1). It inhibits the mIDH1-mediated production of 2-hydroxyglutarate (2-HG) in glioma cells. We investigated brain penetration of BAY1436032 and its effects using 1H/19F-Magnetic Resonance Spectroscopy (MRS).METHODS: 19F-Nuclear Magnetic Resonance (NMR) Spectroscopy was conducted on serum samples from patients treated with BAY1436032 (NCT02746081 trial) in order to analyze 19F spectroscopic signal patterns and concentration-time dynamics of protein-bound inhibitor to facilitate their identification in vivo MRS experiments. Hereafter, 30 mice were implanted with three glioma cell lines (LNT-229, LNT-229 IDH1-R132H, GL261). Mice bearing the IDH-mutated glioma cells received 5 days of treatment with BAY1436032 between baseline and follow-up 1H/19F-MRS scan. All other animals underwent a single scan after BAY1436032 administration. Mouse brains were analyzed by liquid chromatography-mass spectrometry (LC-MS/MS).
    RESULTS: Evaluation of 1H-MRS data showed a decrease in 2-HG/total creatinine (tCr) ratios from the baseline to post-treatment scans in the mIDH1 murine model. Whole brain concentration of BAY1436032, as determined by 19F-MRS, was similar to total brain tissue concentration determined by Liquid Chromatography with tandem mass spectrometry (LC-MS/MS), with a signal loss due to protein binding. Intratumoral drug concentration, as determined by LC-MS/MS, was not statistically different in models with or without R132X-mutant IDH1 expression.
    CONCLUSIONS: Non-invasive monitoring of mIDH1 inhibition by BAY1436032 in mIDH1 gliomas is feasible.
    Keywords:  19F MR spectroscopy; 1H MR spectroscopy; 2-hydroxyglutarate; IDH mutation; IDH1 inhibitor; glioma; murine model; small molecule inhibitor; targeted therapy
    DOI:  https://doi.org/10.3390/cancers12113175
  4. Cancers (Basel). 2020 Nov 04. pii: E3260. [Epub ahead of print]12(11):
    Lee JA, Ayat N, Sun Z, Tofilon PJ, Lu ZR, Camphausen K.
      Radiation therapy is a mainstay in the standard of care for glioblastoma (GBM), thus inhibiting the DNA damage response (DDR) is a major strategy to improve radiation response and therapeutic outcomes. Small interfering RNA (siRNA) therapy holds immeasurable potential for the treatment of GBM, however delivery of the siRNA payload remains the largest obstacle for clinical implementation. Here we demonstrate the effectiveness of the novel nanomaterial, ECO (1-aminoethylimino[bis(N-oleoylcysteinylaminoethyl) propionamide]), to deliver siRNA targeting DDR proteins ataxia telangiectasia mutated and DNA-dependent protein kinase (DNApk-cs) for the radiosensitzation of GBM in vitro and in vivo. ECO nanoparticles (NPs) were shown to efficiently deliver siRNA and silence target protein expression in glioma (U251) and glioma stem cell lines (NSC11, GBMJ1). Importantly, ECO NPs displayed no cytotoxicity and minimal silencing of genes in normal astrocytes. Treatment with ECO/siRNA NPs and radiation resulted in the prolonged presence of γH2AX foci, indicators of DNA damage, and increased radiosensitivity in all tumor cell lines. In vivo, intratumoral injection of ECO/siDNApk-cs NPs with radiation resulted in a significant increase in survival compared with injection of NPs alone. These data suggest the ECO nanomaterial can effectively deliver siRNA to more selectively target and radiosensitize tumor cells to improve therapeutic outcomes in GBM.
    Keywords:  DNA damage repair; gene silencing; glioblastoma; nanoparticles; radiation; siRNA
    DOI:  https://doi.org/10.3390/cancers12113260
  5. Cell Mol Life Sci. 2020 Nov 05.
    Blandin AF, Cruz Da Silva E, Mercier MC, Glushonkov O, Didier P, Dedieu S, Schneider C, Devy J, Etienne-Selloum N, Dontenwill M, Choulier L, Lehmann M.
      Overexpression of EGFR drives glioblastomas (GBM) cell invasion but these tumours remain resistant to EGFR-targeted therapies such as tyrosine kinase inhibitors (TKIs). Endocytosis, an important modulator of EGFR function, is often dysregulated in glioma cells and is associated with therapy resistance. However, the impact of TKIs on EGFR endocytosis has never been examined in GBM cells. In the present study, we showed that gefitinib and other tyrosine kinase inhibitors induced EGFR accumulation in early-endosomes as a result of an increased endocytosis. Moreover, TKIs trigger early-endosome re-localization of another membrane receptor, the fibronectin receptor alpha5beta1 integrin, a promising therapeutic target in GBM that regulates physiological EGFR endocytosis and recycling in cancer cells. Super-resolution dSTORM imaging showed a close-proximity between beta1 integrin and EGFR in intracellular membrane compartments of gefitinib-treated cells, suggesting their potential interaction. Interestingly, integrin depletion delayed gefitinib-mediated EGFR endocytosis. Co-endocytosis of EGFR and alpha5beta1 integrin may alter glioma cell response to gefitinib. Using an in vitro model of glioma cell dissemination from spheroid, we showed that alpha5 integrin-depleted cells were more sensitive to TKIs than alpha5-expressing cells. This work provides evidence for the first time that EGFR TKIs can trigger massive EGFR and alpha5beta1 integrin co-endocytosis, which may modulate glioma cell invasiveness under therapeutic treatment.
    Keywords:  Adhesion receptors; Brain cancer; Cell migration; Growth factors receptors; Membrane trafficking
    DOI:  https://doi.org/10.1007/s00018-020-03686-6
  6. Neuro Oncol. 2020 Nov 03. pii: noaa255. [Epub ahead of print]
    Yi K, Zhan Q, Wang Q, Tan Y, Fang C, Wang Y, Zhou J, Yang C, Li Y, Kang C.
      BACKGROUND: Metabolism remodeling is a hallmark of glioblastoma (GBM) that regulates tumor proliferation and the immune microenvironment. Previous studies have reported that increased polymerase 1 and transcript release factor (PTRF) levels are associated with a worse prognosis in glioma patients. However, the biological role and the molecular mechanism of PTRF in GBM metabolism remain unclear.METHODS: The relationship between PTRF and lipid metabolism in GBM was detected by non-targeted metabolomics profiling and subsequent lipidomics analysis. Western blotting, qRT-PCR, and immunoprecipitation were conducted to explore the molecular mechanism of PTRF in lipid metabolism. A sequence of in vitro and in vivo experiments (both xenograft tumor and intracranial tumor mouse models) were used to detect the tumor-specific impacts of PTRF.
    RESULTS: Here, we show that PTRF triggers a cytoplasmic phospholipase A2 (cPLA2)-mediated phospholipid remodeling pathway that promotes GBM tumor proliferation and suppresses tumor immune responses. Research in primary cell lines from GBM patients revealed that cells overexpressing PTRF show increased cPLA2 activity -resulting from increased protein stability -and exhibit remodeled phospholipid composition. Subsequent experiments revealed that PTRF overexpression alters the endocytosis capacity and energy metabolism of GBM cells. Finally, in GBM xenograft and intracranial tumor mouse models, we showed that inhibiting cPLA2 activity blocks tumor proliferation and prevents PTRF-induced reduction in CD8 + tumor-infiltrating lymphocytes.
    CONCLUSIONS: The PTRF-cPLA2 lipid remodeling pathway promotes tumor proliferation and suppresses immune responses in GBM. In addition, our findings highlight multiple new therapeutic targets for GBM.
    Keywords:  Energy metabolism; Glioblastoma; PTRF; Phospholipid remodeling; cPLA2
    DOI:  https://doi.org/10.1093/neuonc/noaa255
  7. Neuro Oncol. 2020 Nov 01. pii: noaa247. [Epub ahead of print]
    Dejaegher J, Solie L, Hunin Z, Sciot R, Capper D, Siewert C, Van Cauter S, Wilms G, van Loon J, Ectors N, Fieuws S, Pfister SM, Van Gool SW, De Vleeschouwer S.
      BACKGROUND: Histologically classified Glioblastomas (GBM) can have different clinical behavior and response to therapy, for which molecular subclassifications have been proposed. We evaluated the relationship of epigenetic GBM subgroups with immune cell infiltrations, systemic immune changes during radiochemotherapy and clinical outcome.METHODS: 450K genome-wide DNA methylation was assessed on tumor tissue from 93 patients with newly diagnosed GBM, treated with standard radiochemotherapy and experimental immunotherapy. Tumor infiltration of T cells, myeloid cells and PD-1 expression were evaluated. Circulating immune cell populations and selected cytokines were assessed on blood samples taken before and after radiochemotherapy.
    RESULTS: Forty-two tumors had a mesenchymal, 27 a RTK II, 17 a RTK I and 7 an IDH DNA methylation pattern Mesenchymal tumors had the highest amount of tumor-infiltrating CD3+ and CD8+ T cells and IDH tumors the lowest. There were no significant differences for CD68+ cells, FoxP3+ cells and PD-1 expression between groups. Systemically, there was a relative increase of CD8+ T cells and CD8+ PD-1 expression and a relative decrease of CD4+ T cells after radiochemotherapy in all subgroups except IDH tumors. Overall survival was the longest in the IDH group (median 36 months), intermediate in RTK II tumors (27 months) and significantly lower in mesenchymal and RTK I groups (15.5 and 16 months respectively).
    CONCLUSIONS: Methylation based stratification of GBM is related to T cell infiltration and survival, with IDH and mesenchymal tumors representing both ends of a spectrum. DNA methylation profiles could be useful in stratifying patients for immunotherapy trials.
    Keywords:  DNA methylation; glioblastoma; immune infiltration; tumor microenvironment
    DOI:  https://doi.org/10.1093/neuonc/noaa247
  8. Front Immunol. 2020 ;11 585616
    Daubon T, Hemadou A, Romero Garmendia I, Saleh M.
      Glioblastoma (GBM) are the most common tumors of the central nervous system and among the deadliest cancers in adults. GBM overall survival has not improved over the last decade despite optimization of therapeutic standard-of-care. While immune checkpoint inhibitors (ICI) have revolutionized cancer care, they unfortunately have little therapeutic success in GBM. Here, we elaborate on normal brain and GBM-associated immune landscapes. We describe the role of microglia and tumor-associated macrophages (TAMs) in immune suppression and highlight the impact of energy metabolism in immune evasion. We also describe the challenges and opportunities of immunotherapies in GBM and discuss new avenues based on harnessing the anti-tumor activity of myeloid cells, vaccines, chimeric antigen receptors (CAR)-T and -NK cells, oncolytic viruses, nanocarriers, and combination therapies.
    Keywords:  CART-T cell; glioblastoma; immune response; immunotherapy; macrophage
    DOI:  https://doi.org/10.3389/fimmu.2020.585616
  9. Neuro Oncol. 2020 Nov 01. pii: noaa249. [Epub ahead of print]
    Vitanza NA, Biery MC, Myers C, Ferguson E, Zheng Y, Girard EJ, Przystal JM, Park G, Noll A, Pakiam F, Winter CA, Morris SM, Sarthy J, Cole BL, Leary SES, Crane C, Lieberman NAP, Mueller S, Nazarian J, Gottardo R, Brusniak MY, Mhyre AJ, Olson JM.
      BACKGROUND: Diffuse midline gliomas (DMGs), including diffuse intrinsic pontine gliomas (DIPGs), have a dismal prognosis with less than 2% surviving 5-years post-diagnosis. The majority of DIPGs and all DMGs harbor mutations altering the epigenetic regulatory histone tail (H3 K27M). Investigations addressing DMG epigenetics have identified few promising drugs, including the HDAC inhibitor (HDACi) panobinostat. Here, we use clinically-relevant DMG models to identify and validate other effective HDACi and their biomarkers of response.METHODS: HDACi were tested across biopsy-derived treatment-naïve in vitro and in vivo DMG models with biologically-relevant radiation-resistance. RNA sequencing was performed to define and compare drug efficacy, and to map predictive biomarkers of response.
    RESULTS: Quisinostat and romidepsin showed efficacy with a low nanomolar IC50 values (~50 and ~5 nM, respectively). Comparative transcriptome analyses across quisinostat, romidepsin, and panobinostat showed a greater degree of shared biological effects between quisinostat and panobinostat, and less overlap with romidepsin. However, some transcriptional changes were consistent across all three drugs at similar biologically effective doses, such as overexpression of TNNT1 and downregulation of COL20A1, identifying these as potential vulnerabilities or on-target biomarkers in DMG. Quisinostat and romidepsin significantly (p <0.0001) inhibited in vivo tumor growth.
    CONCLUSIONS: Our data highlights the utility of treatment-naïve biopsy-derived models; establishes quisinostat and romidepsin as effective in vivo; illuminates potential mechanisms and/or biomarkers of DMG cell lethality due to HDAC inhibition; and emphasizes the need for brain-tumor-penetrant versions of potentially efficacious agents.
    Keywords:  H3 K27M-mutant (DMG); diffuse intrinsic pontine glioma (DIPG); diffuse midline glioma; histone deacetylase inhibitor (HDACi); quisinostat, romidepsin
    DOI:  https://doi.org/10.1093/neuonc/noaa249
  10. Neuro Oncol. 2020 Nov 01. pii: noaa251. [Epub ahead of print]
    Sievers P, Sill M, Schrimpf D, Stichel D, Reuss DE, Sturm D, Hench J, Frank S, Krskova L, Vicha A, Zapotocky M, Bison B, Castel D, Grill J, Debily MA, Harter PN, Snuderl M, Kramm CM, Reifenberger G, Korshunov A, Jabado N, Wesseling P, Wick W, Solomon DA, Perry A, Jacques TS, Jones C, Witt O, Pfister SM, von Deimling A, Jones DTW, Sahm F.
      BACKGROUND: Malignant astrocytic gliomas in children show a remarkable biological and clinical diversity. Small in-frame insertions or missense mutations in the EGFR gene have recently been identified in a distinct subset of pediatric-type bithalamic gliomas with a unique DNA methylation pattern.METHODS: Here, we investigated an epigenetically homogeneous cohort of malignant gliomas (n=58) distinct from other subtypes and enriched for pediatric cases and thalamic location, in comparison with this recently identified subtype of pediatric bithalamic gliomas.
    RESULTS: EGFR gene amplification was detected in 16/58 (27%) tumors, and missense mutations or small in-frame insertions in EGFR were found in 20/30 tumors with available sequencing data (67%; five of them co-occurring with EGFR amplification). Additionally, eight of the 30 tumors (27%) harbored an H3.1 or H3.3 K27M mutation (six of them with a concomitant EGFR alteration). All tumors tested showed loss of H3K27me3 staining, with evidence of EZHIP overexpression in the H3 wildtype cases. Although some tumors indeed showed a bithalamic growth pattern, a significant proportion of tumors occurred in the unilateral thalamus or in other (predominantly midline) locations.
    CONCLUSIONS: Our findings present a distinct molecular class of pediatric-type malignant gliomas largely overlapping with the recently reported bithalamic gliomas characterized by EGFR alteration, but additionally showing a broader spectrum of EGFR alterations and tumor localization. Global H3K27me3 loss in this group appears to be mediated by either H3 K27 mutation or EZHIP overexpression. EGFR inhibition may represent a potential therapeutic strategy in these highly aggressive gliomas.
    Keywords:   EGFR mutation; (bi-)thalamic; H3 K27M mutation; K27me3; Pediatric-type high-grade glioma
    DOI:  https://doi.org/10.1093/neuonc/noaa251
  11. Brain. 2020 Nov 03. pii: awaa273. [Epub ahead of print]
    Fuentes-Fayos AC, Vázquez-Borrego MC, Jiménez-Vacas JM, Bejarano L, Pedraza-Arévalo S, L-López F, Blanco-Acevedo C, Sánchez-Sánchez R, Reyes O, Ventura S, Solivera J, Breunig JJ, Blasco MA, Gahete MD, Castaño JP, Luque RM.
      Glioblastomas remain the deadliest brain tumour, with a dismal ∼12-16-month survival from diagnosis. Therefore, identification of new diagnostic, prognostic and therapeutic tools to tackle glioblastomas is urgently needed. Emerging evidence indicates that the cellular machinery controlling the splicing process (spliceosome) is altered in tumours, leading to oncogenic splicing events associated with tumour progression and aggressiveness. Here, we identify for the first time a profound dysregulation in the expression of relevant spliceosome components and splicing factors (at mRNA and protein levels) in well characterized cohorts of human high-grade astrocytomas, mostly glioblastomas, compared to healthy brain control samples, being SRSF3, RBM22, PTBP1 and RBM3 able to perfectly discriminate between tumours and control samples, and between proneural-like or mesenchymal-like tumours versus control samples from different mouse models with gliomas. Results were confirmed in four additional and independent human cohorts. Silencing of SRSF3, RBM22, PTBP1 and RBM3 decreased aggressiveness parameters in vitro (e.g. proliferation, migration, tumorsphere-formation, etc.) and induced apoptosis, especially SRSF3. Remarkably, SRSF3 was correlated with patient survival and relevant tumour markers, and its silencing in vivo drastically decreased tumour development and progression, likely through a molecular/cellular mechanism involving PDGFRB and associated oncogenic signalling pathways (PI3K-AKT/ERK), which may also involve the distinct alteration of alternative splicing events of specific transcription factors controlling PDGFRB (i.e. TP73). Altogether, our results demonstrate a drastic splicing machinery-associated molecular dysregulation in glioblastomas, which could potentially be considered as a source of novel diagnostic and prognostic biomarkers as well as therapeutic targets for glioblastomas. Remarkably, SRSF3 is directly associated with glioblastoma development, progression, aggressiveness and patient survival and represents a novel potential therapeutic target to tackle this devastating pathology.
    Keywords:  PDGFRB pathway; SRSF3; antitumour therapy; glioblastoma; splicing machinery
    DOI:  https://doi.org/10.1093/brain/awaa273
  12. Cancers (Basel). 2020 Oct 29. pii: E3178. [Epub ahead of print]12(11):
    Sinha A, Saleh A, Endersby R, Yuan SH, Chokshi CR, Brown KR, Kuzio B, Kauppinen T, Singh SK, Baker SJ, McKinnon PJ, Katyal S.
      PTEN mutation occurs in a variety of aggressive cancers and is associated with poor patient outcomes. Recent studies have linked mutational loss of PTEN to reduced RAD51 expression and function, a key factor involved in the homologous recombination (HR) pathway. However, these studies remain controversial, as they fail to establish a definitive causal link to RAD51 expression that is PTEN-dependent, while other studies have not been able to recapitulate the relationship between the PTEN expression and the RAD51/HR function. Resolution of this apparent conundrum is essential due to the clinically-significant implication that PTEN-deficient tumors may be sensitive to poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) commonly used in the clinical management of BRCA-mutated and other HR-deficient (HRD) tumors.METHODS: Primary Pten-deficient (and corresponding wild-type) mouse embryonic fibroblasts (MEFs) and astrocytes and PTEN-null human tumor cell lines and primary cells were assessed for RAD51 expression (via the Western blot analysis) and DNA damage repair analyses (via alkali comet and γH2AX foci assays). RAD51 foci analysis was used to measure HR-dependent DNA repair. Xrcc2-deficient MEFs served as an HR-deficient control, while the stable knockdown of RAD51 (shRAD51) served to control for the relative RAD51/HR-mediated repair and the phospho-53BP1 foci analysis served to confirm and measure non-homologous end joining (NHEJ) activity in PTEN-deficient and shRAD51-expressing (HRD) lines. Cell proliferation studies were used to measure any potential added sensitivity of PTEN-null cells to the clinically-relevant PARPi, olaparib. RAD51 levels and DNA damage response signaling were assessed in PTEN-mutant brain tumor initiating cells (BTICs) derived from primary and recurrent glioblastoma multiforme (GBM) patients, while expression of RAD51 and its paralogs were examined as a function of the PTEN status in the RNA expression datasets isolated from primary GBM tumor specimens and BTICs.
    RESULTS: Pten knockout primary murine cells display unaltered RAD51 expression, endogenous and DNA strand break-induced RAD51 foci and robust DNA repair activity. Defective HR was only observed in the cells lacking Xrcc2. Likewise, human glioblastoma multiforme (GBM) cell lines with known PTEN deficiency (U87, PTEN-mutated; U251 and U373, PTEN-null) show apparent expression of RAD51 and display efficient DNA repair activity. Only GBM cells stably expressing shRNAs against RAD51 (shRAD51) display dysfunctional DNA repair activity and reduced proliferative capacity, which is exacerbated by PARPi treatment. Furthermore, GBM patient-derived BTICs displayed robust RAD51 expression and intact DNA damage response signaling in spite of PTEN-inactivating mutations. RNA expression analysis of primary GBM tissue specimens and BTICs demonstrate stable levels of RAD51 and its paralogs (RAD51B, RAD51C, RAD51D, XRCC2, XRCC3, and DMC1), regardless of the PTEN mutational status.
    CONCLUSIONS: Our findings demonstrate definitively that PTEN loss does not alter the RAD51 expression, its paralogs, or the HR activity. Furthermore, deficiency in PTEN alone is not sufficient to impart enhanced sensitivity to PARPi associated with HRD. This study is the first to unequivocally demonstrate that PTEN deficiency is not linked to the RAD51 expression or the HR activity amongst primary neural and non-neural Pten-null cells, PTEN-deficient tumor cell lines, and primary PTEN-mutant GBM patient-derived tissue specimens and BTICs.
    Keywords:  DNA damage; HRD; PARP inhibitor; PTEN; RAD51; RAD51 foci; RNA expression; alkaline comet assay; base excision repair; brain tumor initiating cells; combination therapy; glioblastoma multiforme; homologous recombination; olaparib; synthetic lethality; γH2AX foci
    DOI:  https://doi.org/10.3390/cancers12113178
  13. Cancer Res. 2020 Nov 06. pii: canres.2270.2020. [Epub ahead of print]
    Li J, Liao T, Liu H, Yuan H, Ouyang T, Wang J, Chai S, Li J, Chen J, Li X, Zhao H, Xiong N.
      Glioma stem cells (GSC) are a subpopulation of tumor cells with special abilities to proliferate and differentiate in gliomas. They are one of the main causes of tumor recurrence, especially under hypoxic conditions. Although long noncoding RNAs (lncRNA) are known to be involved in numerous biological processes and are implied in the occurrence of certain diseases, their role in tumor development and progression remains poorly understood. Here we explored the mechanisms by which lncRNA derived from hypoxic glioma stem cells (H-GSC) cause glioma progression. Isolation and identification of the Linc01060 gene, the exosomes containing them, and the proteins from tumor cells regulating the gene allowed for studying the effects of Linc01060 on proliferation and glycometabolism. H-GSC exerted their effects by transferring exosomes to glioma cells, resulting in a significant increase in Linc01060 levels. Mechanistically, Linc01060 directly interacted with the transcription factor myeloid zinc finger 1 (MZF1) and enhanced its stability. Linc01060 facilitated nuclear translocation of MZF1 and promoted MZF1-mediated c-Myc transcriptional activities. In addition, c-Myc enhanced the accumulation of the hypoxia-inducible factor-1 alpha (HIF-1α) at the post-transcriptional level. HIF-1α bound the hormone response elements (HRE) of the Linc01060 promoter, upregulating the transcription of Linc01060 gene. Clinically, Linc01060 was upregulated in glioma and was significantly correlated with tumor grade and poor clinical prognosis. Overall, these data show that secretion of Linc01060-containing exosomes from hypoxic glioma stem cells activates pro-oncogenic signaling pathways in glioma cells to promote disease progression.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-20-2270
  14. Biomaterials. 2020 Oct 23. pii: S0142-9612(20)30709-2. [Epub ahead of print]267 120463
    Quader S, Liu X, Toh K, Su YL, Maity AR, Tao A, Paraiso WKD, Mochida Y, Kinoh H, Cabral H, Kataoka K.
      The crucial balance of stability in blood-circulation and tumor-specific delivery has been suggested as one of the challenges for effective bench-to-bedside translation of nanomedicines (NMs). Herein, we developed a supramolecularly enabled tumor-extracellular (Tex) pH-triggered NM that can maintain the micellar structure with the entrapped-drug during systemic circulation and progressively release drug in the tumor by rightly sensing heterogeneous tumor-pH. Desacetylvinblastine hydrazide (DAVBNH), a derivative of potent anticancer drug vinblastine, was conjugated to an aliphatic ketone-functionalized poly(ethylene glycol)-b-poly(amino acid) copolymer and the hydrolytic stability of the derived hydrazone bond was efficiently tailored by exploiting the compartmentalized structure of polymer micelle. We confirmed an effective and safe therapeutic application of Tex pH-sensitive DAVBNH-loaded micelle (Tex-micelle) in orthotopic glioblastoma (GBM) models, extending median survival to 1.4 times in GBM xenograft and 2.6 times in GBM syngeneic model, compared to that of the free DAVBNH. The work presented here offers novel chemical insights into the molecular design of smart NMs correctly sensing Tex-pH via programmed functionalities. The practical engineering strategy based on a clinically relevant NM platform, and the encouraging therapeutic application of Tex-micelle in GBM, one of the most lethal human cancers, thus suggests the potential clinical translation of this system against other types of common cancers, including GBM.
    Keywords:  Glioblastoma; Nanomedicine; Progressive drug release; Supramolecular assembly; Tumor extracellular pH; pH-triggered
    DOI:  https://doi.org/10.1016/j.biomaterials.2020.120463
  15. Cancers (Basel). 2020 Oct 31. pii: E3210. [Epub ahead of print]12(11):
    Lee K, Koo H, Kim Y, Kim D, Son E, Yang H, Lim Y, Hur M, Lee HW, Choi SW, Nam DH.
      We aimed to evaluate the preclinical efficacy of GC1118, a novel anti-epidermal growth factor receptor (EGFR) monoclonal antibody (mAb), against glioblastoma (GBM) tumors using patient-derived xenograft (PDX) models. A total of 15 distinct GBM PDX models were used to evaluate the therapeutic efficacy of GC1118. Genomic data derived from PDX models were analyzed to identify potential biomarkers associated with the anti-tumor efficacy of GC1118. A patient-derived cell-based high-throughput drug screening assay was performed to further validate the efficacy of GC1118. Compared to cetuximab, GC1118 exerted comparable growth inhibitory effects on the GBM tumors in the PDX models. We confirmed that GC1118 accumulated within the tumor by crossing the blood-brain barrier in in vivo specimens and observed the survival benefit in GC1118-treated intracranial models. Genomic analysis revealed high EGFR amplification as a potent biomarker for predicting the therapeutic efficacy of GC1118 in GBM tumors. In summary, GC1118 exerted a potent anti-tumor effect on GBM tumors in PDX models, and its therapeutic efficacy was especially pronounced in the tumors with high EGFR amplification. Our study supports the importance of patient stratification based on EGFR copy number variation in clinical trials for GBM. The superiority of GC1118 over other EGFR mAbs in GBM tumors should be assessed in future studies.
    Keywords:  amplification; epidermal growth factor receptor; glioblastoma; monoclonal; xenograft
    DOI:  https://doi.org/10.3390/cancers12113210
  16. Neoplasia. 2020 Oct 22. pii: S1476-5586(20)30160-3. [Epub ahead of print]22(12): 689-701
    Grassi ES, Jeannot P, Pantazopoulou V, Berg TJ, Pietras A.
      Tumor cell behaviors associated with aggressive tumor growth such as proliferation, therapeutic resistance, and stem cell characteristics are regulated in part by soluble factors derived from the tumor microenvironment. Tumor-associated astrocytes represent a major component of the glioma tumor microenvironment, and astrocytes have an active role in maintenance of normal neural stem cells in the stem cell niche, in part via secretion of soluble delta-like noncanonical Notch ligand 1 (DLK1). We found that astrocytes, when exposed to stresses of the tumor microenvironment such as hypoxia or ionizing radiation, increased secretion of soluble DLK1. Tumor-associated astrocytes in a glioma mouse model expressed DLK1 in perinecrotic and perivascular tumor areas. Glioma cells exposed to recombinant DLK1 displayed increased proliferation, enhanced self-renewal and colony formation abilities, and increased levels of stem cell marker genes. Mechanistically, DLK1-mediated effects on glioma cells involved increased and prolonged stabilization of hypoxia-inducible factor 2alpha, and inhibition of hypoxia-inducible factor 2alpha activity abolished effects of DLK1 in hypoxia. Forced expression of soluble DLK1 resulted in more aggressive tumor growth and shortened survival in a genetically engineered mouse model of glioma. Together, our data support DLK1 as a soluble mediator of glioma aggressiveness derived from the tumor microenvironment.
    Keywords:  DLK1; Glioma; HIF-2a; Hypoxia; Stem cell niche; Tumor-associated astrocytes
    DOI:  https://doi.org/10.1016/j.neo.2020.10.005
  17. Clin Transl Med. 2020 Oct;10(6): e181
    Tao Z, Li X, Wang H, Chen G, Feng Z, Wu Y, Yin H, Zhao G, Deng Z, Zhao C, Li Y, Sun T, Zhou Y.
      Bromodomain and extraterminal domain (BET) family proteins are considered to be epigenetic readers that regulate gene expression by recognizing acetyl lysine residues on histones and nonhistone chromatin factors and have been classified as curative targets for a variety of cancers. Glioma-initiating cells (GICs), which commit self-renewal, perpetual proliferation, multidirectional differentiation, and vigorous tumorigenicity, sustain the peculiar genetic and epigenetic diversification in the GBM patients, thus, GICs result in tumor recurrence. Abundant evidence demonstrates that BET proteins regulate differentiation of stem cells. However, it endures ambiguous how individual BET proteins take part in GIC advancement, and how do small molecule inhibitors like I-BET151 target functional autonomous BET proteins. Here, we validated that BRD4, not BRD2 or BRD3, has value in targeted glioma therapy. We announce a signaling pathway concerning BRD4 and Notch1 that sustains the self-renewal of GICs. Moreover, in-depth mechanistic research showed that BRD4 was concentrated at the promoter region of Notch1 and may be involved in the process of tumor metabolism. Furthermore, in intracranial models, I-BET151 eliminated U87 GICs' tumorigenicity. The outcomes of this research could be conducive to design clinical trials for treatment of glioma based on BRD4.
    Keywords:  BET protein; BRD4; glioma-initiating cells; notch1; self-renewal; tumorigenicity
    DOI:  https://doi.org/10.1002/ctm2.181
  18. Cancer Discov. 2020 Nov;10(11): 1629-1631
    Pirozzi CJ, Yan H.
      Tumors mutated in IDH1 tend to have lower levels of the essential substrate NAD+. In this issue of Cancer Discovery, Nagashima and colleagues exploit this metabolic sensitivity by devising a combinatorial therapy that both further reduces the pools as well as sequesters the remaining substrate in PAR chains, sensitizing the cells to temozolomide and PARG inhibition.See related article by Nagashima et al., p. 1672.
    DOI:  https://doi.org/10.1158/2159-8290.CD-20-1215
  19. Drug Discov Today. 2020 Nov 03. pii: S1359-6446(20)30465-7. [Epub ahead of print]
    Lal S, Snape TJ.
      Central nervous system (CNS) cancers are among the most aggressive and devastating. Furthermore, because of the lack of neuro-oncologists and neurosurgeons in many parts of the world, the specialized treatment options of CNS cancers are not fully available worldwide. Among various strategies of inducing death in cancer cells, inhibition of poly(ADP-ribose) polymerase (PARP) has emerged as a beneficial therapy when combined with other anticancer agents. In this review, we provide a detailed therapeutic update of PARP inhibitors (PARPis) that have shown clinical activity against glioma.
    DOI:  https://doi.org/10.1016/j.drudis.2020.10.029
  20. Acta Neuropathol Commun. 2020 Nov 04. 8(1): 179
    Fontanilles M, Marguet F, Beaussire L, Magne N, Pépin LF, Alexandru C, Tennevet I, Hanzen C, Langlois O, Jardin F, Laquerrière A, Sarafan-Vasseur N, Di Fiore F, Clatot F.
      The clinical implications of plasmatic cell-free and tumor DNA (cfDNA and ctDNA) are challenging in glioblastoma. This prospective study included 52 consecutive newly diagnosed glioblastoma (n = 49) or gliosarcoma (n = 3) patients treated with concomitant temozolomide and radiotherapy (RT-TMZ), followed by a TMZ maintenance phase. Plasma samples were collected at baseline, before RT-TMZ (pre-RT-TMZ) and at the end of adjuvant TMZ, or at the time of progression in cases of progressive disease (PD). The cfDNA concentration was measured with a fluorometric method, and ctDNA was detected using targeted droplet digital PCR. The main objectives were to analyze the associations between cfDNA and ctDNA measurements during the course of treatment with PD and survival. There was a significant decrease in median cfDNA concentration from baseline to pre-RT-TMZ-19.4 versus 9.7 ng/mL (p < 0.0001)-in the entire cohort. In patients with PD, a significant increase in cfDNA concentration from pre-RT-TMZ to time of PD was observed, from 9.7 versus 13.1 ng/mL (p = 0.037), respectively, while no difference was observed for nonprogressive patients. Neither the cfDNA concentration at baseline nor its kinetics correlated with survival. ctDNA was detected in 2 patients (3.8%) and only in gliosarcoma subtypes.Trial registration ClinicalTrial, NCT02617745. Registered 1 December 2015, https://clinicaltrials.gov/ct2/show/NCT02617745?term=glioplak&draw=2&rank=1 .
    Keywords:  Cell-free DNA; Circulating tumor DNA; Glioblastoma; Liquid biopsy; TERT promoter mutation
    DOI:  https://doi.org/10.1186/s40478-020-01057-7