bims-malgli 2020-09-06 papers

bims-malgli

Biomed News

on Biology of malignant gliomas

Issue of 2020–09–06
fourteen papers selected by
Oltea Sampetrean, Keio University

TERT and DNMT1 expression predict sensitivity to decitabine in gliomas.
mTOR Modulates Intercellular Signals for Enlargement and Infiltration in Glioblastoma Multiforme.
Neoplastic Cells are the Major Source of MT-MMPs in IDH1-Mutant Glioma, Thus Enhancing Tumor-Cell Intrinsic Brain Infiltration.
Glioblastoma Utilizes Fatty Acids and Ketone Bodies for Growth Allowing Progression during Ketogenic Diet Therapy.
Tunneling Nanotubes Mediate Adaptation of Glioblastoma Cells to Temozolomide and Ionizing Radiation Treatment.
RBPJ contributes to the malignancy of glioblastoma and induction of proneural-mesenchymal transition via IL-6-STAT3 pathway.
Targeting isocitrate dehydrogenase mutations in cancer: emerging evidence and diverging strategies.
Genomic profiling of newly diagnosed glioblastoma patients and its potential for clinical utility - a prospective, translational study.
Local intracerebral inhibition of IRE1 by MKC8866 sensitizes glioblastoma to irradiation/chemotherapy in vivo.
Thyroid receptor-interacting protein 13 and EGFR form a feedforward loop promoting glioblastoma growth.
Chloroquine combined with concurrent radiotherapy and temozolomide for newly diagnosed glioblastoma: a phase IB trial.
Days gained response discriminates treatment response in patients with recurrent glioblastoma receiving bevacizumab-based therapies.
The impact of autophagy during the development and survival of glioblastoma.
Intratumoral Distribution of Lactate and the Monocarboxylate Transporters 1 and 4 in Human Glioblastoma Multiforme and Their Relationships to Tumor Progression-Associated Markers.

Neuro Oncol. 2020 Sep 03. pii: noaa207. [Epub ahead of print]

TERT and DNMT1 expression predict sensitivity to decitabine in gliomas.

Jong-Whi Park, Felix Sahm, Bianca Steffl, Isabel Arrillaga-Romany, Daniel Cahill, Michelle Monje, Christel Herold-Mende, Wolfgang Wick, Şevin Turcan.

   BACKGROUND: Decitabine (DAC) is an FDA approved DNA methyltransferase (DNMT) inhibitor that is used in the treatment of patients with myelodysplastic syndromes. Previously, we showed that DAC has marked antitumor activity against gliomas with isocitrate dehydrogenase 1 (IDH1) mutations. Based on promising preclinical results, a clinical trial has been launched to determine the effect of DAC in IDH-mutant gliomas. The next step is to comprehensively assess the efficacy and potential determinants of response to DAC in malignant gliomas.
METHODS: The expression and activity of TERT and DNMT1 were manipulated in patient-derived IDH1-mutant and -wildtype glioma lines, followed by assessment of cell proliferation with DAC treatment alone or in combination with telomerase inhibitors. RNA sequencing, KEGG enrichment and correlation analysis were performed.
RESULTS: IDH1-mutant glioma tumorspheres with hemizygous co-deletion of chromosome arms 1p/19q were particularly sensitive to DAC and showed significant inhibition of DNA replication genes. Our transcriptome analysis revealed that DAC induced CDKN1A/p21 expression, along with down-regulation of TERT. These molecular changes were also observed following doxorubicin treatment, supporting the importance of DAC-induced DNA damage in contributing to this effect. We demonstrated that knockdown of p21 led to TERT up-regulation. Strikingly, TERT overexpression increased DNMT1 levels and DAC sensitivity via a telomerase-independent mechanism. Furthermore, RNAi targeting of DNMT1 abrogated DAC response in TERT-proficient glioma cells.
CONCLUSIONS: DAC down-regulates TERT through p21 induction. Our data points to TERT and DNMT1 levels as potential determinants of response to DAC treatment.

Keywords:  DNMT1; Decitabine; TERT; glioma; p21

DOI:  https://doi.org/10.1093/neuonc/noaa207
Cancers (Basel). 2020 Sep 02. pii: E2486. [Epub ahead of print]12(9):

mTOR Modulates Intercellular Signals for Enlargement and Infiltration in Glioblastoma Multiforme.

Larisa Ryskalin, Francesca Biagioni, Paola Lenzi, Alessandro Frati, Francesco Fornai.

  Recently, exosomal release has been related to the acquisition of a malignant phenotype in glioblastoma cancer stem cells (GSCs). Remarkably, intriguing reports demonstrate that GSC-derived extracellular vesicles (EVs) contribute to glioblastoma multiforme (GBM) tumorigenesis via multiple pathways by regulating tumor growth, infiltration, and immune invasion. In fact, GSCs release tumor-promoting macrovesicles that can disseminate as paracrine factors to induce phenotypic alterations in glioma-associated parenchymal cells. In this way, GBM can actively recruit different stromal cells, which, in turn, may participate in tumor microenvironment (TME) remodeling and, thus, alter tumor progression. Vice versa, parenchymal cells can transfer their protein and genetic contents to GSCs by EVs; thus, promoting GSCs tumorigenicity. Moreover, GBM was shown to hijack EV-mediated cell-to-cell communication for self-maintenance. The present review examines the role of the mammalian Target of Rapamycin (mTOR) pathway in altering EVs/exosome-based cell-to-cell communication, thus modulating GBM infiltration and volume growth. In fact, exosomes have been implicated in GSC niche maintenance trough the modulation of GSCs stem cell-like properties, thus, affecting GBM infiltration and relapse. The present manuscript will focus on how EVs, and mostly exosomes, may act on GSCs and neighbor non tumorigenic stromal cells to modify their expression and translational profile, while making the TME surrounding the GSC niche more favorable for GBM growth and infiltration. Novel insights into the mTOR-dependent mechanisms regulating EV-mediated intercellular communication within GBM TME hold promising directions for future therapeutic applications.

Keywords:  GSC niche; cell-to-cell communication; exosomes; extracellular vesicles; glioma cancer stem cells; tumor microenvironment

DOI:  https://doi.org/10.3390/cancers12092486
Cancers (Basel). 2020 Aug 29. pii: E2456. [Epub ahead of print]12(9):

Neoplastic Cells are the Major Source of MT-MMPs in IDH1-Mutant Glioma, Thus Enhancing Tumor-Cell Intrinsic Brain Infiltration.

Ina Thome, Raphael Lacle, Andreas Voß, Ginette Bortolussi, Georgios Pantazis, Ansgar Schmidt, Catharina Conrad, Ralf Jacob, Nina Timmesfeld, Jörg W Bartsch, Axel Pagenstecher.

  Tumor-cell infiltration is a major obstacle to successful therapy for brain tumors. Membrane-type matrix metalloproteinases (MT-MMPs), a metzincin subfamily of six proteases, are important mediators of infiltration. The cellular source of MT-MMPs and their role in glioma biology, however, remain controversial. Thus, we comprehensively analyzed the expression of MT-MMPs in primary brain tumors. All MT-MMPs were differentially expressed in primary brain tumors. In diffuse gliomas, MT-MMP1, -3, and -4 were predominantly expressed by IDH1mutated tumor cells, while macrophages/microglia contributed significantly less to MT-MMP expression. For functional analyses, individual MT-MMPs were expressed in primary mouse p53-/- astrocytes. Invasion and migration potential of MT-MMP-transduced astrocytes was determined via scratch, matrigel invasion, and novel organotypic porcine spinal slice migration (OPoSSM) and invasion assays. Overall, MT-MMP-transduced astrocytes showed enhanced migration compared to controls. MMP14 was the strongest mediator of migration in scratch assays. However, in the OPoSSM assays, the glycosylphosphatidylinositol (GPI)-anchored MT-MMPs MMP17 and MMP25, not MMP14, mediated the highest infiltration rates of astrocytes. Our data unequivocally demonstrate for the first time that glioma cells, not microglia, are the predominant producers of MT-MMPs in glioma and can act as potent mediators of tumor-cell infiltration into CNS tissue. These proteases are therefore promising targets for therapeutic interventions.

Keywords:  glioma; invasion; isocitrate dehydrogenase; matrix metalloproteases; organotypic cell invasion assay

DOI:  https://doi.org/10.3390/cancers12092456
iScience. 2020 Aug 13. pii: S2589-0042(20)30645-3. [Epub ahead of print]23(9): 101453

Glioblastoma Utilizes Fatty Acids and Ketone Bodies for Growth Allowing Progression during Ketogenic Diet Therapy.

Jantzen Sperry, Michael C Condro, Lea Guo, Daniel Braas, Nathan Vanderveer-Harris, Kristen K O Kim, Whitney B Pope, Ajit S Divakaruni, Albert Lai, Heather Christofk, Maria G Castro, Pedro R Lowenstein, Janel E Le Belle, Harley I Kornblum.

  Glioblastoma (GBM) metabolism has traditionally been characterized by a primary dependence on aerobic glycolysis, prompting the use of the ketogenic diet (KD) as a potential therapy. In this study we evaluated the effectiveness of the KD in GBM and assessed the role of fatty acid oxidation (FAO) in promoting GBM propagation. In vitro assays revealed FA utilization throughout the GBM metabolome and growth inhibition in nearly every cell line in a broad spectrum of patient-derived glioma cells treated with FAO inhibitors. In vivo assessments revealed that knockdown of carnitine palmitoyltransferase 1A (CPT1A), the rate-limiting enzyme for FAO, reduced the rate of tumor growth and increased survival. However, the unrestricted ketogenic diet did not reduce tumor growth and for some models significantly reduced survival. Altogether, these data highlight important roles for FA and ketone body metabolism that could serve to improve targeted therapies in GBM.

Keywords:  Cancer; Diet; Pathophysiology

DOI:  https://doi.org/10.1016/j.isci.2020.101453
iScience. 2020 Aug 13. pii: S2589-0042(20)30642-8. [Epub ahead of print]23(9): 101450

Tunneling Nanotubes Mediate Adaptation of Glioblastoma Cells to Temozolomide and Ionizing Radiation Treatment.

Silvana Valdebenito, Alessandra Audia, Krishna P L Bhat, George Okafo, Eliseo A Eugenin.

  Glioblastoma (GBM) is the most prevalent and aggressive tumor in the central nervous system. Surgical resection followed by concurrent radiotherapy (ionizing radiation [IR]) and temozolomide (TMZ) is the standard of care for GBM. However, a large subset of patients offer resistance or become adapted to TMZ due mainly to the DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT). Thus, alternative mechanisms of MGMT deregulation have been proposed but are heretofore unproven. We show that heterogeneous GBM cells express tunneling nanotubes (TNTs) upon oxidative stress and TMZ/IR treatment. We identified that MGMT protein diffused from resistant to sensitive cells upon exposure to TMZ/IR, resulting in protection against cytotoxic therapy in a TNT-dependent manner. In vivo analysis of resected GBM tumors support our hypothesis that the MGMT protein, but not its mRNA, was associated with TNT biomarkers. We propose that targeting TNT formation could be an innovative strategy to overcome treatment resistance in GBM.

Keywords:  Cancer; Cell Biology

DOI:  https://doi.org/10.1016/j.isci.2020.101450
Cancer Sci. 2020 Sep 03.

RBPJ contributes to the malignancy of glioblastoma and induction of proneural-mesenchymal transition via IL-6-STAT3 pathway.

Guangtao Zhang, Shingo Tanaka, Shabierjiang Jiapaer, Hemragul Sabit, Sho Tamai, Masashi Kinoshita, Mitsutoshi Nakada.

  Notch signaling plays a pivotal role in many cancers, including glioblastoma (GBM). Recombination signal binding protein for immunoglobulin kappa J region (RBPJ) is a key transcription factor of the Notch signaling pathway. Here, we interrogated the function of RBPJ in GBM. Firstly, RBPJ expression of GBM samples was examined. Then, we knocked down RBPJ expression in two GBM cell lines (U251 and T98) and four GBM stem-like cell (GSC) lines derived from surgical samples of GBM (KGS01, KGS07, KGS10 and KGS15) to investigate the effect on cell proliferation, invasion, stemness, and tumor formation ability. Expression of possible downstream targets of RBPJ was also assessed. RBPJ was overexpressed in the GBM samples, downregulation of RBPJ reduced cell proliferation and invasion ability of U251 and T98 cells and cell proliferation ability and stemness of GSC lines. These were accompanied by reduced IL-6 expression, reduced activation of STAT3 and inhibited proneural-mesenchymal transition (PMT). Tumor formation and PMT were also impaired by RBPJ knockdown in vivo. In conclusion, RBPJ promotes cell proliferation, invasion, stemness, and tumor initiation ability in GBM cells through enhanced activation of IL-6-STAT3 pathway and PMT, inhibition of RBPJ may constitute a prospective treatment for GBM.

Keywords:  Glioblastoma; IL-6; RBPJ; STAT3; glioblastoma stem-like cells; proneural-mesenchymal transition

DOI:  https://doi.org/10.1111/cas.14642
Clin Cancer Res. 2020 Sep 03. pii: clincanres.1827.2020. [Epub ahead of print]

Targeting isocitrate dehydrogenase mutations in cancer: emerging evidence and diverging strategies.

Matthew S Waitkus, Hai Yan.

Isocitrate dehydrogenase active-site mutations cause a neomorphic enzyme activity that results in the formation of supraphysiological concentrations of D-2-hydroxyglutarate (D-2HG). D-2HG is thought to be an oncometabolite that drives the formation of cancers in a variety of tissue types by altering the epigenetic state of progenitor cells by inhibiting enzymes involved in histone and DNA demethylation. This model has led to the development of pharmacological inhibitors of mutant IDH activity for anti-cancer therapy, which are now being tested in several clinical trials. Emerging evidence in preclinical glioma models suggests that the epigenetic changes induced by D-2HG may persist even after mutant IDH activity is inhibited and D-2HG has returned to basal levels. Therefore, these results have raised questions as to whether the exploitation of downstream synthetic lethal vulnerabilities, rather than direct inhibition of mutant IDH1, will prove to be a superior therapeutic strategy. In this review, we summarize the preclinical evidence in gliomas and other models on the induction and persistence of D-2HG-induced hypermethylation of DNA and histones, and we examine emerging lines of evidence related to altered DNA repair mechanisms in mutant IDH tumors and their potential for therapeutic exploitation.

DOI: https://doi.org/10.1158/1078-0432.CCR-20-1827
Mol Oncol. 2020 Sep 04.

Genomic profiling of newly diagnosed glioblastoma patients and its potential for clinical utility - a prospective, translational study.

Dorte S Nørøxe, Christina W Yde, Olga Østrup, Signe R Michaelsen, Ane Y Schmidt, Savvas Kinalis, Mathias H Torp, Jane Skjøth-Rasmussen, Jannick Brennum, Petra Hamerlik, Hans S Poulsen, Finn C Nielsen, Ulrik Lassen.

  Glioblastoma (GBM) is an incurable brain tumor for which new treatment strategies are urgently needed. Next-generation sequencing of GBM has most often been performed retrospectively and on archival tissue from both diagnostic and relapse surgeries with limited knowledge of clinical information, including treatment given. We sought to investigate the genomic composition prospectively in treatment-naïve patients, searched for possible targetable aberrations and investigated for prognostic and/or predictive factors. A total of 108 newly diagnosed GBM patients were included. Clinical information, progression-free survival (PFS) and overall survival (OS) were noted. Tissues were analyzed by whole-exome sequencing, SNP- and transcriptome-arrays, and RNA-sequencing; assessed for mutations, fusions, tumor mutational burden (TMB), and chromosomal instability (CI); and classified into GBM subgroups. Each genomic report was discussed at a multidisciplinary tumor board meeting to evaluate for matching trials. From 111 consecutive patients, 97.3% accepted inclusion in this study. Eighty-six (77%) were treated with radiation therapy (RT)/Temozolomide (TMZ) and adjuvant TMZ. One NTRK2 and three FGFR3-TACC3 fusions were identified. Copy number alterations in GRB2 and SMYD4 were significantly correlated with worse median OS together with known clinical variables like age, performance status, steroid dose and O6-methyl-guanine-DNA-methyl-transferase (MGMT)-status. Patients with CI-median or TMB-high had significantly worse median OS compared to CI-low/high or TMB-low/median. In conclusion, performing genomic profiling at diagnosis enables evaluation of genomic-driven therapy at the first progression. Furthermore, TMB-high or CI-median patients had worse median OS, which can support the possibility of offering experimental treatment already at the first line for this group.

Keywords:  Chromosomal instability; Genomic profiling; NTRK fusion; Newly diagnosed glioblastoma; Translational relevance; Tumor mutational burden

DOI:  https://doi.org/10.1002/1878-0261.12790
Cancer Lett. 2020 Aug 31. pii: S0304-3835(20)30442-0. [Epub ahead of print]

Local intracerebral inhibition of IRE1 by MKC8866 sensitizes glioblastoma to irradiation/chemotherapy in vivo.

Pierre Jean Le Reste, Raphael Pineau, Konstantinos Voutetakis, Juhi Samal, Gwénaële Jégou, Stéphanie Lhomond, Adrienne M Gorman, Afshin Samali, John B Patterson, Qingping Zeng, Abhay Pandit, Marc Aubry, Nicolas Soriano, Amandine Etcheverry, Aristotelis Chatziioannou, Jean Mosser, Tony Avril, Eric Chevet.

  Glioblastoma multiforme (GBM) is the most severe primary brain cancer. Despite an aggressive treatment comprising surgical resection and radio/chemotherapy, patient's survival post diagnosis remains short. A limitation for success in finding novel improved therapeutic options for such dismal disease partly lies in the lack of a relevant animal model that accurately recapitulates patient disease and standard of care. In the present study, we have developed an immunocompetent GBM model that includes tumor surgery and a radio/chemotherapy regimen resembling the Stupp protocol and we have used this model to test the impact of the pharmacological inhibition of the endoplasmic reticulum (ER) stress sensor IRE1, on treatment efficacy.

Keywords:  Endoplasmic reticulum; Glioblastoma; IRE1; Unfolded Protein Response

DOI:  https://doi.org/10.1016/j.canlet.2020.08.028
Cancer Lett. 2020 Aug 26. pii: S0304-3835(20)30437-7. [Epub ahead of print]

Thyroid receptor-interacting protein 13 and EGFR form a feedforward loop promoting glioblastoma growth.

Lulu Hu, Dachuan Shen, Dapeng Liang, Ji Shi, Chunyan Song, Ke Jiang, Menglin Ren, Sha Du, Wei Cheng, Jianmei Ma, Shao Li, Xiaolin Bi, Martin P Barr, Zhiyou Fang, Qing Xu, Wenbin Li, Haozhe Piao, Songshu Meng.

  Epidermal growth factor receptor (EGFR) amplification and EGFRvIII mutation drive glioblastoma (GBM) pathogenesis, but their regulation remains elusive. Here we characterized the EGFR/EGFRvIII "interactome" in GBM and identified thyroid receptor-interacting protein 13 (TRIP13), an AAA + ATPase, as an EGFR/EGFRvIII-associated protein independent of its ATPase activity. Functionally, TRIP13 augmented EGFR pathway activation and contributed to EGFR/EGFRvIII-driven GBM growth in GBM spheroids and orthotopic GBM xenograft models. Mechanistically, TRIP13 enhanced EGFR protein abundance in part by preventing Cbl-mediated ubiquitination and proteasomal degradation. Reciprocally, TRIP13 was phosphorylated at tyrosine(Y) 56 by EGFRvIII and EGF-activated EGFR. Abrogating TRIP13 Y56 phosphorylation dramatically attenuated TRIP13 expression-enhanced EGFR signaling and GBM cell growth. Clinically, TRIP13 expression was upregulated in GBM specimens and associated with poor patient outcome. In GBM, TRIP13 localized to cell membrane and cytoplasma and exhibited oncogenic effects in vitro and in vivo, depending on EGFR signaling but not the TRIP13 ATPase activity. Collectively, our findings uncover that TRIP13 and EGFR form a feedforward loop to potentiate EGFR signaling in GBM growth and identify a previously unrecognized ATPase activity-independent mode of action of TRIP13 in GBM biology.

Keywords:  EGFR; EGFRvIII; Glioblastoma (GBM); Osimertinib; TRIP13

DOI:  https://doi.org/10.1016/j.canlet.2020.08.023
Autophagy. 2020 Aug 31.

Chloroquine combined with concurrent radiotherapy and temozolomide for newly diagnosed glioblastoma: a phase IB trial.

Inge Compter, Danielle B P Eekers, Ann Hoeben, Kasper M A Rouschop, Bart Reymen, Linda Ackermans, Jan Beckervordersantforth, Noel J C Bauer, Monique M Anten, Pieter Wesseling, Alida A Postma, Dirk De Ruysscher, Philippe Lambin.

  Treatment of glioblastoma xenografts with chloroquine results in macroautophagy/autophagy inhibition, resulting in a reduction of tumor hypoxia and sensitization to radiation. Preclinical data show that EGFRvIII-expressing glioblastoma may benefit most from chloroquine because of autophagy dependency. This study is the first to explore the safety, pharmacokinetics and maximum tolerated dose of chloroquine in combination with radiotherapy and concurrent daily temozolomide in patients with a newly diagnosed glioblastoma. This study is a single-center, open-label, dose-finding phase I trial. Patients received oral chloroquine daily starting one week before the course of chemoradiation (temozolomide 75 mg/m2/d) until the end of radiotherapy (59.4 Gy/33 fractions). Thirteen patients were included in the study (n = 6: 200 mg, n = 3: 300 mg, n = 4: 400 mg chloroquine). A total of 44 adverse events, possibly related to chloroquine, were registered including electrocardiogram QTc prolongation, irreversible blurred vision and nausea/vomiting resulting in cessation of temozolomide or delay of adjuvant cycles. The maximum tolerated dose was 200 mg chloroquine. Median overall survival was 16 months (range 2 - 32). Median survival was 11.5 months for EGFRvIII- patients and 20 months for EGFRvIII+ patients. A daily dose of 200 mg chloroquine was determined to be the maximum tolerated dose when combined with radiotherapy and concurrent temozolomide for newly diagnosed glioblastoma. Favorable toxicity and promising overall survival support further clinical studies.

Keywords:  autophagy; brain tumor; chloroquine; glioblastoma; radiotherapy; temozolomide

DOI:  https://doi.org/10.1080/15548627.2020.1816343
Neurooncol Adv. 2020 Jan-Dec;2(1):2(1): vdaa085

Days gained response discriminates treatment response in patients with recurrent glioblastoma receiving bevacizumab-based therapies.

Kyle W Singleton, Alyx B Porter, Leland S Hu, Sandra K Johnston, Kamila M Bond, Cassandra R Rickertsen, Gustavo De Leon, Scott A Whitmire, Kamala R Clark-Swanson, Maciej M Mrugala, Kristin R Swanson.

   Background: Accurate assessments of patient response to therapy are a critical component of personalized medicine. In glioblastoma (GBM), the most aggressive form of brain cancer, tumor growth dynamics are heterogenous across patients, complicating assessment of treatment response. This study aimed to analyze days gained (DG), a burgeoning model-based dynamic metric, for response assessment in patients with recurrent GBM who received bevacizumab-based therapies.
Methods: DG response scores were calculated using volumetric tumor segmentations for patients receiving bevacizumab with and without concurrent cytotoxic therapy (N = 62). Kaplan-Meier and Cox proportional hazards analyses were implemented to examine DG prognostic relationship to overall (OS) and progression-free survival (PFS) from the onset of treatment for recurrent GBM.
Results: In patients receiving concurrent bevacizumab and cytotoxic therapy, Kaplan-Meier analysis showed significant differences in OS and PFS at DG cutoffs consistent with previously identified values from newly diagnosed GBM using T1-weighted gadolinium-enhanced magnetic resonance imaging (T1Gd). DG scores for bevacizumab monotherapy patients only approached significance for PFS. Cox regression showed that increases of 25 DG on T1Gd imaging were significantly associated with a 12.5% reduction in OS hazard for concurrent therapy patients and a 4.4% reduction in PFS hazard for bevacizumab monotherapy patients.
Conclusion: DG has significant meaning in recurrent therapy as a metric of treatment response, even in the context of anti-angiogenic therapies. This provides further evidence supporting the use of DG as an adjunct response metric that quantitatively connects treatment response and clinical outcomes.

Keywords:   bevacizumab; combination chemotherapy; glioblastoma; personalized medicine; response evaluation

DOI:  https://doi.org/10.1093/noajnl/vdaa085
Open Biol. 2020 Sep;10(9): 200184

The impact of autophagy during the development and survival of glioblastoma.

Joanne E Simpson, Noor Gammoh.

  Glioblastoma is the most common and aggressive adult brain tumour, with poor median survival and limited treatment options. Following surgical resection and chemotherapy, recurrence of the disease is inevitable. Genomic studies have identified key drivers of glioblastoma development, including amplifications of receptor tyrosine kinases, which drive tumour growth. To improve treatment, it is crucial to understand survival response processes in glioblastoma that fuel cell proliferation and promote resistance to treatment. One such process is autophagy, a catabolic pathway that delivers cellular components sequestered into vesicles for lysosomal degradation. Autophagy plays an important role in maintaining cellular homeostasis and is upregulated during stress conditions, such as limited nutrient and oxygen availability, and in response to anti-cancer therapy. Autophagy can also regulate pro-growth signalling and metabolic rewiring of cancer cells in order to support tumour growth. In this review, we will discuss our current understanding of how autophagy is implicated in glioblastoma development and survival. When appropriate, we will refer to findings derived from the role of autophagy in other cancer models and predict the outcome of manipulating autophagy during glioblastoma treatment.

Keywords:  autophagy; brain tumour; cancer; glioblastoma; receptor tyrosine kinase (RTK); therapy

DOI:  https://doi.org/10.1098/rsob.200184
Int J Mol Sci. 2020 Aug 29. pii: E6254. [Epub ahead of print]21(17):

Intratumoral Distribution of Lactate and the Monocarboxylate Transporters 1 and 4 in Human Glioblastoma Multiforme and Their Relationships to Tumor Progression-Associated Markers.

Carolin Kubelt, Sönke Peters, Hajrullah Ahmeti, Monika Huhndorf, Lukas Huber, Gesa Cohrs, Jan-Bernd Hövener, Olav Jansen, Michael Synowitz, Janka Held-Feindt.

  (1) Background: Metabolic reprogramming has been postulated to be one of the hallmarks of cancer, thus representing a promising therapeutic target also in glioblastoma multiforme (GBM). Hypoxic tumor cells produce lactate, and monocarboxylate transporters (MCTs) play an important role in its distribution; (2) Methods: We examined the distribution of lactate by multi voxel magnetic resonance spectroscopic imaging and ELISA in glioblastoma multiforme (GBM) patients. In addition, we investigated the expression and cellular localization of MCT1, MCT4, and of several markers connected to tumor progression by quantitative PCR and immunofluorescence double-staining in human GBM ex vivo tissues; (3) Results: The highest lactate concentration was found at the center of the vital parts of the tumor. Three main GBM groups could be distinguished according to their regional gene expression differences of the investigated genes. MCT1 and MCT4 were found on cells undergoing epithelial to mesenchymal transition and on tumor stem-like cells. GBM cells revealing an expression of cellular dormancy markers, showed positive staining for MCT4; (4) Conclusion: Our findings indicate the existence of individual differences in the regional distribution of MCT1 and MCT4 and suggest that both transporters have distinct connections to GBM progression processes, which could contribute to the drug resistance of MCT-inhibitors.

Keywords:  EMT; MCT1; MCT4; MRSI; dormancy; glioblastoma; lactate; stemness

DOI:  https://doi.org/10.3390/ijms21176254