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Glioma Cells in the Tumor Periphery Have a Stem Cell Phenotype.

ABSTRACT: Gliomas are highly infiltrative tumors incurable with surgery. Although surgery removes the bulk tumor, tumor cells in the periphery are left behind resulting in tumor relapses. The aim of the present study was to characterize the phenotype of tumor cells in the periphery focusing on tumor stemness, proliferation and chemo-resistance. This was investigated in situ in patient glioma tissue as well as in orthotopic glioblastoma xenografts. We identified 26 gliomas having the R132 mutation in Isocitrate DeHydrogenase 1 (mIDH1). A double immunofluorescence approach identifying mIDH1 positive tumor cells and a panel of markers was used. The panel comprised of six stem cell-related markers (CD133, Musashi-1, Bmi-1, Sox-2, Nestin and Glut-3), a proliferation marker (Ki-67) as well as a chemo-resistance marker (MGMT). Computer-based automated classifiers were designed to measure the mIDH1 positive nucleus area-fraction of the chosen markers. Moreover, orthotopic glioblastoma xenografts from five different patient-derived spheroid cultures were obtained and the tumor cells identified by human specific immunohistochemical markers. The results showed that tumor cells in the periphery of patient gliomas expressed stem cell markers, however for most markers at a significantly lower level than in the tumor core. The Ki-67 level was slightly reduced in the periphery, whereas the MGMT level was similar. In orthotopic glioblastoma xenografts all markers showed similar levels in the core and periphery. In conclusion tumor cells in the periphery of patient gliomas have a stem cell phenotype, although it is less pronounced than in the tumor core. Novel therapies aiming at preventing recurrence should therefore take tumor stemness into account. Migrating cells in orthotopic glioblastoma xenografts preserve expression and stem cell markers. The orthotopic model therefore has a promising translational potential.

SUBMITTER: Munthe S

PROVIDER: S-EPMC4865242 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Glioma Cells in the Tumor Periphery Have a Stem Cell Phenotype.

Munthe Sune S Petterson Stine Asferg SA Dahlrot Rikke Hedegaard RH Poulsen Frantz Rom FR Hansen Steinbjørn S Kristensen Bjarne Winther BW

PloS one 20160512 5

Gliomas are highly infiltrative tumors incurable with surgery. Although surgery removes the bulk tumor, tumor cells in the periphery are left behind resulting in tumor relapses. The aim of the present study was to characterize the phenotype of tumor cells in the periphery focusing on tumor stemness, proliferation and chemo-resistance. This was investigated in situ in patient glioma tissue as well as in orthotopic glioblastoma xenografts. We identified 26 gliomas having the R132 mutation in Isoci ...[more]

PMID: 27171431

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Project description:BackgroundExosomes are nanoscale membrane vesicles secreted by both normal and cancer cells, and cancer cell-derived exosomes play an important role in the cross-talk between cancer cells and other cellular components in the tumor microenvironment. Mesenchymal stem cells (MSCs) have tropism for tumors and have been used as tumor-tropic vectors for tumor therapy; however, the safety of such therapeutic use of MSCs is unknown. In this study, we investigated the role of glioma cell-derived exosomes in the tumor-like phenotype transformation of human bone marrow mesenchymal stem cells (hBMSCs) and explored the underlying molecular mechanisms.MethodsThe effect of exosomes from U251 glioma cells on the growth of hBMSCs was evaluated with the CCK-8 assay, KI67 staining, and a cell cycle distribution assessment. The migration and invasion of hBMSCs were evaluated with a Transwell assay. A proteomics and bioinformatics approach, together with Western blotting and reverse transcriptase-polymerase chain reaction, was used to investigate the effect of U251 cell-derived exosomes on the proteome of hBMSCs.ResultsU251 cell-derived exosomes induced a tumor-like phenotype in hBMSCs by enhancing their proliferation, migration, and invasion and altering the production of proteins involved in the regulation of the cell cycle. Moreover, U251 cell-derived exosomes promoted the production of the metastasis-related proteins MMP-2 and MMP-9, glioma marker GFAP, and CSC markers (CD133 and Nestin). The ten differentially expressed proteins identified participated in several biological processes and exhibited various molecular functions, mainly related to the inactivation of glycolysis. Western blotting showed that U251 cell-derived exosomes upregulated the levels of Glut-1, HK-2, and PKM-2, leading to the induction of glucose consumption and generation of lactate and ATP. Treatment with 2-deoxy-D-glucose significantly reversed these effects of U251 cell-derived exosomes on hBMSCs.ConclusionsOur data demonstrate that glioma cell-derived exosomes activate glycolysis in hBMSCs, resulting in their tumor-like phenotype transformation. This suggests that interfering with the interaction between exosomes and hBMSCs in the tumor microenvironment has potential as a therapeutic approach for glioma. ᅟ.

Project description:IntroductionGlioblastoma (GBM) is the most common primary malignant brain tumor in humans and, even with aggressive treatment that includes surgical resection, radiation (IR), and chemotherapy administration, prognosis is poor due to tumor recurrence. There is evidence that within GBMs a small number of glioma stem-like cells (GSLCs) exist, which are thought to be therapy resistant and are thus capable of repopulating a tumor after treatment. Like most cancers, GBMs largely employ aerobic glycolysis to create ATP, a phenomenon known as the Warburg Effect. There is no consensus on the metabolic characteristics of cancer stem cells. GSLCs have been shown to rely more heavily on oxidative phosphorylation, but there is also evidence that cancer stem cells can adapt their metabolism by fluctuating between energy pathways or acquiring intermediate metabolic phenotypes. We hypothesized that the metabolism of GSLCs differs from that of differentiated GBM tumor cell lines, and that the steady state metabolism would be differentially altered following radiation treatment.Materials and methodsWe evaluated the oxygen consumption rate, extracellular acidification rate, and metabolic enzyme levels of GBM cell lines and GSLCs before and after irradiation using extracellular flux assays. We also measured absolute metabolite levels in these cells via mass spectroscopy with and without radiation treatment.ResultsGSLCs were found to be significantly more quiescent in comparison to adherent GBM cell lines, highlighted by lower glycolytic and maximal respiratory capacities as well as lower oxygen consumption and extracellular acidification rates. Analysis of individual metabolite concentrations revealed lower total metabolite concentrations overall but also elevated levels of metabolites in different energy pathways for GSLCs compared to GBM cell lines. Additionally, the metabolism of both GSLCs and GBM cell lines were found to be altered by IR.ConclusionsWhile there is not one metabolic alteration that distinguishes irradiated GSLC metabolism from that of GBM cell lines, therapies targeting more metabolically quiescent tumor cells and thus the resistant GSLC population may increase a cancer's sensitivity to radiotherapy.

Project description:BackgroundGlioma stem cells (GSCs) are considered the initial cells of gliomas, contributing to therapeutic resistance. Patient-derived GSCs well recapitulate the heterogeneity of their parent glioma tissues, which can be classified into different subtypes. Likewise, previous works identified GSCs as two distinct subtypes, mesenchymal (MES) and proneural (PN) subtypes, and with general recognition, the MES subtype is considered a more malignant phenotype characterized by high invasion and radioresistance. Therefore, understanding the mechanisms involved in the MES phenotype is necessary for glioblastoma treatment.MethodsData for bioinformatic analysis were obtained from The Cancer Genome Atlas (TCGA) and The Gene Expression Omnibus (GEO) database. An antibody was used to block cell surface glucose-regulated protein 78 (csGRP78). Apoptosis and cell cycle analyses were performed to evaluate radiation damage. Immunofluorescence staining was applied to assess protein expression and distribution. Mass spectrometry combined with bioinformatic analysis was used to screen downstream molecules. Intracranial GSC-derived xenografts were established for in vivo experiments.ResultsTotal GRP78 expression was associated with MES GSC stemness, and csGRP78 was highly expressed in MES GSCs. Targeting csGRP78 suppressed the self-renewal and radioresistance of MES GSCs in vitro and in vivo, accompanied by downregulation of the STAT3, NF-κB and C/EBPβ pathways. Mass spectrometry revealed the potential downstream β-site APP-cleaving enzyme 2 (BACE2), which was regulated by csGRP78 via lysosomal degradation. Knockdown of BACE2 inactivated NF-κB and C/EBPβ and significantly suppressed the tumorigenesis and radioresistance of MES GSCs in vitro and in vivo.ConclusionsCell surface GRP78 was preferentially expressed in MES GSCs and played a pivotal role in MES phenotype maintenance. Thus, blocking csGRP78 in MES GSCs with a high-specificity antibody might be a promising novel therapeutic strategy.

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Glioma Cells in the Tumor Periphery Have a Stem Cell Phenotype.

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Glioma Cells in the Tumor Periphery Have a Stem Cell Phenotype.

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