| 1. |
- Alexander, Jes, et al.
(författare)
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Multimodal single-cell analysis reveals distinct radioresistant stem-like and progenitor cell populations in murine glioma
- 2020
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Ingår i: GLIA. - : Wiley. - 0894-1491 .- 1098-1136. ; 68:12, s. 2486-2502
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Tidskriftsartikel (refereegranskat)abstract
- Radiation therapy is part of the standard of care for gliomas and kills a subset of tumor cells, while also altering the tumor microenvironment. Tumor cells with stem-like properties preferentially survive radiation and give rise to glioma recurrence. Various techniques for enriching and quantifying cells with stem-like properties have been used, including the fluorescence activated cell sorting (FACS)-based side population (SP) assay, which is a functional assay that enriches for stem-like tumor cells. In these analyses, mouse models of glioma have been used to understand the biology of this disease and therapeutic responses, including the radiation response. We present combined SP analysis and single-cell RNA sequencing of genetically-engineered mouse models of glioma to show a time course of cellular response to radiation. We identify and characterize two distinct tumor cell populations that are inherently radioresistant and also distinct effects of radiation on immune cell populations within the tumor microenvironment.
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| 2. |
- Berg, Tracy J., et al.
(författare)
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The Irradiated Brain Microenvironment Supports Glioma Stemness and Survival via Astrocyte-Derived Transglutaminase 2
- 2021
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Ingår i: Cancer Research. - : American Association For Cancer Research (AACR). - 0008-5472 .- 1538-7445. ; 81:8, s. 2101-2115
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Tidskriftsartikel (refereegranskat)abstract
- The tumor microenvironment plays an essential role in supporting glioma stemness and radioresistance. Following radiotherapy, recurrent gliomas form in an irradiated microenvironment. Here we report that astrocytes, when pre-irradiated, increase stemness and survival of cocultured glioma cells. Tumor-naive brains increased reactive astrocytes in response to radiation, and mice subjected to radiation prior to implantation of glioma cells developed more aggressive tumors. Extracellular matrix derived from irradiated astrocytes were found to be a major driver of this phenotype and astrocyte-derived transglutaminase 2 (TGM2) was identified as a promoter of glioma stemness and radioresistance. TGM2 levels increased after radiation in vivo and in recurrent human glioma, and TGM2 inhibitors abrogated glioma stemness and survival. These data suggest that irradiation of the brain results in the formation of a tumor-supportive microenvironment. Therapeutic targeting of radiation-induced, astrocyte-derived extracellular matrix proteins may enhance the efficacy of standard-of-care radiotherapy by reducing stemness in glioma. Significance: These findings presented here indicate that radiotherapy can result in a tumor-supportive microenvironment, the targeting of which may be necessary to overcome tumor cell therapeutic resistance and recurrence.
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| 3. |
- Johansson, Elinn, et al.
(författare)
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CD44 interacts with HIF-2α to modulate the hypoxic phenotype of perinecrotic and perivascular glioma cells
- 2017
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 20:7, s. 1641-1653
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Tidskriftsartikel (refereegranskat)abstract
- Hypoxia-inducible factors enhance glioma stemness, and glioma stem cells have an amplified hypoxic response despite residing within a perivascular niche. Still, little is known about differential HIF regulation in stem versus bulk glioma cells. We show that the intracellular domain of stem cell marker CD44 (CD44ICD) is released at hypoxia, binds HIF-2α (but not HIF-1α), enhances HIF target gene activation, and is required for hypoxia-induced stemness in glioma. In a glioma mouse model, CD44 was restricted to hypoxic and perivascular tumor regions, and in human glioma, a hypoxia signature correlated with CD44. The CD44ICD was sufficient to induce hypoxic signaling at perivascular oxygen tensions, and blocking CD44 cleavage decreased HIF-2α stabilization in CD44-expressing cells. Our data indicate that the stem cell marker CD44 modulates the hypoxic response of glioma cells and that the pseudo-hypoxic phenotype of stem-like glioma cells is achieved by stabilization of HIF-2α through interaction with CD44, independently of oxygen.
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| 4. |
- Berg, Tracy J, et al.
(författare)
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Radiotherapy-induced remodeling of the tumor microenvironment by stromal cells
- 2022
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Ingår i: Seminars in Cancer Biology. - : Elsevier BV. - 1096-3650 .- 1044-579X. ; 86:Part 3, s. 846-856
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Forskningsöversikt (refereegranskat)abstract
- Cancer cells reside amongst a complex milieu of stromal cells and structural features known as the tumor microenvironment. Often cancer cells divert and co-opt functions of stromal cells of the microenvironment to support tumor progression and treatment resistance. During therapy targeting cancer cells, the stromal cells of the microenvironment receive therapy to the same extent as cancer cells. Stromal cells therefore activate a variety of responses to the damage induced by these therapies, and some of those responses may support tumor progression and resistance. We review here the response of stromal cells to cancer therapy with a focus on radiotherapy in glioblastoma. We highlight the response of endothelial cells and the vasculature, macrophages and microglia, and astrocytes, as well as describing resulting changes in the extracellular matrix. We emphasize the complex interplay of these cellular factors in their dynamic responses. Finally, we discuss their resulting support of cancer cells in tumor progression and therapy resistance. Understanding the stromal cell response to therapy provides insight into complementary therapeutic targets to enhance tumor response to existing treatment options.
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| 5. |
- Cifani, Paolo, et al.
(författare)
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Hunting for Protein Markers of Hypoxia by Combining Plasma Membrane Enrichment with a New Approach to Membrane Protein Analysis
- 2011
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Ingår i: Journal of Proteome Research. - : American Chemical Society (ACS). - 1535-3893 .- 1535-3907. ; 10:4, s. 1645-1656
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Tidskriftsartikel (refereegranskat)abstract
- Nontransient hypoxia is strongly associated with malignant lesions, resulting in aggressive behavior and resistance to treatment. We present an analysis of mRNA and protein expression changes in neuroblastoma cell lines occurring upon the transition from normoxia to hypoxia. The correlation between mRNA and protein level changes was poor, although some known hypoxia-driven genes and proteins correlated well. We present previously undescribed membrane proteins expressed under hypoxic conditions that are candidates for evaluation as biomarkers.
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| 6. |
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| 7. |
- Gélabert, Caroline
(författare)
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Micro-environmental control of tumor differentiation and invasiveness
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The transforming growth factor β (TGFβ) family participates in embryonic development and adult tissue homeostasis. In early stages of tumorigenesis, TGFβ promotes cell cycle arrest and apoptosis; however, in advanced malignancies, TGFβ promotes tumor cell migration and metastasis via the induction of epithelial-tomesenchymal transition (EMT). A new aspect of the regulation of TGFβ signalling is the participation of non-coding RNAs, molecules that are not translated into proteins but are nevertheless important regulators of gene expression. The expression of the long non-coding RNA LINC00707 was identified being down-regulated by TGFβ by engaging the transcription factor KLF6. LINC00707 resides in the cytoplasm where it interacts with and sequesters the Smad proteins, which mediate TGFβ signals. Thus, when TGFβ signaling downregulates LINC00707, the Smad complex is free to enter the nucleus and regulate its target genes implicated in the EMT process. It is also important to consider the biology of cells in their microenvironment. The growth of solid tumors leads to regional deprivation of nutrients within a tumor. Glutamine deprivation in mesenchymal and epithelial hepatocellular carcinoma cell lines showed a large change in gene expression related to TGFβ signaling in cells adapted to glutamine deprivation, suggesting a dependence of TGFβ signaling on glutamine metabolism. In mesenchymal cells, we observed a mesenchymal-to-epithelial transition associated with reduced metabolic activity and a reduced generation of reactive oxygen species. Mitochondrial reactive oxygen species are known for their capacity to regulate various signalling pathways associated with diverse cellular responses. This work also identified the polarity protein Par3 as a negative regulator of mitochondrial activity in glioblastoma cells. Moreover, Par3 leads to suppressed invasiveness and sustained clonogenicity of glioblastoma cells.In summary, this work describes novel regulatory mechanisms that affect different aspects of cancer biology in both epithelial (carcinoma) and nonepithelial (glial) tumor cells. A central component that unifies these new mechanisms of cancer cell regulation is the TGFβ signaling pathway. In addition to its novel findings, this work opens several questions whose investigation can provide deeper mechanistic understanding of the action of the key RNAs or proteins analysed in this thesis.
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| 8. |
- Grassi, Elisa Stellaria, et al.
(författare)
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Emerging Roles of DLK1 in the Stem Cell Niche and Cancer Stemness
- 2022
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Ingår i: Journal of Histochemistry and Cytochemistry. - : SAGE Publications. - 0022-1554 .- 1551-5044. ; 70:1, s. 17-28
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Forskningsöversikt (refereegranskat)abstract
- DLK1 is a maternally imprinted, paternally expressed gene coding for the transmembrane protein Delta-like homologue 1 (DLK1), a non-canonical NOTCH ligand with well-described roles during development, and tumor-supportive functions in several aggressive cancer forms. Here, we review the many functions of DLK1 as a regulator of stem cell pools and tissue differentiation in tissues such as brain, muscle, and liver. Furthermore, we review recent evidence supporting roles for DLK1 in the maintenance of aggressive stem cell characteristics of tumor cells, specifically focusing on central nervous system tumors, neuroblastoma, and hepatocellular carcinoma. We discuss NOTCH -dependent as well as NOTCH-independent functions of DLK1, and focus particularly on the complex pattern of DLK1 expression and cleavage that is finely regulated from a spatial and temporal perspective. Progress in recent years suggest differential functions of extracellular, soluble DLK1 as a paracrine stem cell niche-secreted factor, and has revealed a role for the intracellular domain of DLK1 in cell signaling and tumor stemness. A better understanding of DLK1 regulation and signaling may enable therapeutic targeting of cancer stemness by interfering with DLK1 release and/or intracellular signaling.
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| 9. |
- Grassi, Elisa Stellaria, et al.
(författare)
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Hypoxia-induced release, nuclear translocation, and signaling activity of a DLK1 intracellular fragment in glioma
- 2020
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Ingår i: Oncogene. - : Springer Science and Business Media LLC. - 0950-9232 .- 1476-5594.
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Tidskriftsartikel (refereegranskat)abstract
- Glioblastoma multiforme is characterized in part by severe hypoxia associated with tumor necrosis. The cellular response to hypoxia can influence several properties of tumor cells associated with aggressive tumor growth, including metabolic adaptations and tumor cell migration and invasion. Here, we found that Delta Like Non-Canonical Notch Ligand 1 (DLK1) expression was elevated as compared with normal brain in a genetically engineered mouse model of glioma, and that DLK1 expression increased with tumor grade in human glioma samples. DLK1 expression was highest in hypoxic and perivascular tumor areas, and we found that hypoxia induced the release and nuclear translocation of an intracellular fragment of DLK1 in murine glioma as well as in human glioma cultures. Release of the intracellular fragment was dependent on ADAM17 and Hypoxia-inducible Factor 1alpha and 2alpha (HIF-1alpha/HIF-2alpha), as ADAM17 inhibitors and HIF1A/HIF2A siRNA blocked DLK1 cleavage. Expression of a cleavable form of DLK1 amplified several hypoxia-induced traits of glioma cells such as colony formation, stem cell marker gene expression, a PI3K-pathway-mediated metabolic shift, and enhanced invasiveness. Effects of DLK1 were dependent on DLK1-cleavage by ADAM17, as expression of non-cleavable DLK1 could not replicate the DLK1-induced hypoxic phenotype. Finally, forced expression of DLK1 resulted in more invasive tumor growth in a PDGFB-induced glioma mouse model without affecting overall survival. Together, our findings suggest a previously undescribed role for DLK1 as an intracellular signaling molecule.
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| 10. |
- Grassi, Elisa S., et al.
(författare)
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Niche-derived soluble DLK1 promotes glioma growth
- 2020
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Ingår i: Neoplasia (United States). - : Elsevier BV. - 1522-8002 .- 1476-5586. ; 22:12, s. 689-701
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 11. |
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| 12. |
- Karlsson, Jenny, et al.
(författare)
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Arsenic trioxide-induced neuroblastoma cell death is accompanied by proteolytic activation of nuclear Bax.
- 2007
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Ingår i: Oncogene. - : Springer Science and Business Media LLC. - 1476-5594 .- 0950-9232. ; 26:42, s. 6150-6159
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Tidskriftsartikel (refereegranskat)abstract
- Arsenic trioxide (As2O3) is toxic to multidrug-resistant neuroblastoma cells in vivo and in vitro. In neuroblastoma, As2O3 does not exert its cell death-promoting effects via a classical apoptotic pathway. A death mechanism involving proteolytic cleavage of Bax to a p18 form seems to be of importance, because inhibition of Bax cleavage coincides with diminished cell death. As existing models of cell death implicate Bax in the intrinsic apoptotic pathway, triggering death after Bax translocation to the mitochondria, we investigated the cellular localization of p18 Bax by subcellular fractionation. After As2O3 treatment, p18 Bax was only present in nuclei-enriched, mitochondria-depleted fractions. Cytoplasmic p21 Bax levels decreased, whereas total (p21 and p18) nuclear Bax increased. Overexpressed p21 Bax localized to the cytoplasm and nuclei, whereas overexpressed p18 Bax localized to extra-nuclear structures only. The inability of overexpressed p18 Bax to locate to the nucleus, and the As2O3-induced reduction of p21 Bax in the cytosol, suggest an As2O3-induced mechanism where p18 Bax gets cleaved and 'trapped' in the nucleus. This model is strengthened by the observation that calpain, the protease responsible for p18 Bax generation, is present in the nuclei, and that nuclear calpain is induced by increasing As2O3 and Ca2+ levels.
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| 13. |
- Löfstedt, Tobias, et al.
(författare)
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Hypoxia inducible factor-2alpha in cancer.
- 2007
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Ingår i: Cell Cycle. - 1551-4005. ; 6:8, s. 919-926
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Tidskriftsartikel (refereegranskat)abstract
- Poorly oxygenated ( hypoxic) tumors are frequently more aggressive compared to corresponding tumors that are better oxygenated. Adaptation to hypoxia is primarily mediated by two closely related hypoxia inducible transcription factor complexes, HIF-1 and HIF-2, which become stabilized and activated at low oxygen levels. Whether HIF-1 and HIF-2 have different roles in tumorigenesis is an open question and an issue we discuss. With focus on HIF-2, we summarize reported phenotypical changes of HIF genetic models and HIF expression patterns during normal development, in adult non - malignant tissues and in tumors. We further address the much - discussed subject of target gene preferences between HIF-1 and HIF-2, given that both transcription factors bind to the same DNA motif. Finally, we also discuss the observations that the oxygen - sensitive HIF-2 alpha subunit is accumulated and active under non - hypoxic conditions as exemplified by HIF-2 alpha expressing tumor macrophages and neuroblastoma cells located in seemingly well - vascularized tumor regions and how this phenomenon is related to tumor aggressiveness.
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| 14. |
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| 15. |
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| 16. |
- Noguera, Rosa, et al.
(författare)
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HIF-1{alpha} and HIF-2{alpha} Are Differentially Regulated In vivo in Neuroblastoma: High HIF-1{alpha} Correlates Negatively to Advanced Clinical Stage and Tumor Vascularization.
- 2009
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Ingår i: Clinical Cancer Research. - 1078-0432. ; 15:23, s. 7130-7136
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Hypoxia is considered to be a major driving force behind tumor angiogenesis. The stabilization and activation at hypoxia of the hypoxia-inducible factors HIF-1alpha and HIF-2alpha and the concomitant induction of expression of vascular endothelial growth factor (VEGF) and other proangiogenic factors provide a molecular frame for hypoxia-driven tumor angiogenesis. This study has investigated how HIF and VEGF protein levels relate to each other with regard to vascularization, tumor stage, and overall survival in neuroblastoma. EXPERIMENTAL DESIGN: Tissue cores taken from tumor specimens representing 93 children with neuroblastoma were arranged on a microarray and stained for HIF-1alpha, HIF-2alpha, VEGF, and CD31 proteins. Both fraction of positive cells and staining intensity were evaluated and protein levels were correlated with each other and with clinical variables. RESULTS: Although high levels of both HIF-1alpha (P < 0.001) and HIF-2alpha (P < 0.001) correlated positively to VEGF expression, they did not fully correlate with each other. Moreover, HIF-1alpha (P = 0.002) and VEGF (P < 0.001), but not HIF-2alpha, correlated negatively to vascularization as determined by CD31 staining abundance. VEGF expression or degree of vascularization did not correlate with tumor stage or overall survival. High HIF-1alpha levels correlated with low tumor stage (P < 0.001) and were associated with a favorable patient prognosis (P = 0.08). CONCLUSIONS: The discordant results on expression of HIF-1alpha and HIF-2alpha suggest that these two proteins are differentially regulated in vivo, thus reflecting distinctive protein expression/stabilization mechanisms. The association between HIF-1alpha and favorable outcome stresses the importance of discriminating HIF-2alpha from HIF-1alpha expression and has implications for using HIFs as treatment targets. (Clin Cancer Res 2009;15(23):OF1-7).
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| 17. |
- Pantazopoulou, Vasiliki, et al.
(författare)
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Hypoxia-Induced Reactivity of Tumor-Associated Astrocytes Affects Glioma Cell Properties
- 2021
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Ingår i: Cells. - : MDPI AG. - 2073-4409. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Glioblastoma is characterized by extensive necrotic areas with surrounding hypoxia. The cancer cell response to hypoxia in these areas is well-described; it involves a metabolic shift and an increase in stem cell-like characteristics. Less is known about the hypoxic response of tumor-associated astrocytes, a major component of the glioma tumor microenvironment. Here, we used primary human astrocytes and a genetically engineered glioma mouse model to investigate the response of this stromal cell type to hypoxia. We found that astrocytes became reactive in response to intermediate and severe hypoxia, similarly to irradiated and temozolomide-treated astrocytes. Hypoxic astrocytes displayed a potent hypoxia response that appeared to be driven primarily by hypoxia-inducible factor 2-alpha (HIF-2α). This response involved the activation of classical HIF target genes and the increased production of hypoxia-associated cytokines such as TGF-β1, IL-3, angiogenin, VEGF-A, and IL-1 alpha. In vivo, astrocytes were present in proximity to perinecrotic areas surrounding HIF-2α expressing cells, suggesting that hypoxic astrocytes contribute to the glioma microenvironment. Extracellular matrix derived from hypoxic astrocytes increased the proliferation and drug efflux capability of glioma cells. Together, our findings suggest that hypoxic astrocytes are implicated in tumor growth and potentially stemness maintenance by remodeling the tumor microenvironment.
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| 18. |
- Papadakos, Konstantinos S, et al.
(författare)
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Sushi domain-containing protein 4 binds to epithelial growth factor receptor and initiates autophagy in an EGFR phosphorylation independent manner
- 2022
-
Ingår i: Journal of Experimental and Clinical Cancer Research. - : Springer Science and Business Media LLC. - 1756-9966. ; 41:1, s. 363-363
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Sushi domain-containing protein 4 (SUSD4) is a recently discovered protein with unknown cellular functions. We previously revealed that SUSD4 can act as complement inhibitor and as a potential tumor suppressor.METHODS: In a syngeneic mouse model of breast cancer, tumors expressing SUSD4 had a smaller volume compared with the corresponding mock control tumors. Additionally, data from three different expression databases and online analysis tools confirm that for breast cancer patients, high mRNA expression of SUSD4 in the tumor tissue correlates with a better prognosis. In vitro experiments utilized triple-negative breast cancer cell lines (BT-20 and MDA-MB-468) stably expressing SUSD4. Moreover, we established a cell line based on BT-20 in which the gene for EGFR was knocked out with the CRISPR-Cas9 method.RESULTS: We discovered that the Epithelial Growth Factor Receptor (EGFR) interacts with SUSD4. Furthermore, triple-negative breast cancer cell lines stably expressing SUSD4 had higher autophagic flux. The initiation of autophagy required the expression of EGFR but not phosphorylation of the receptor. Expression of SUSD4 in the breast cancer cells led to activation of the tumor suppressor LKB1 and consequently to the activation of AMPKα1. Finally, autophagy was initiated after stimulation of the ULK1, Atg14 and Beclin-1 axis in SUSD4 expressing cells.CONCLUSIONS: In this study we provide novel insight into the molecular mechanism of action whereby SUSD4 acts as an EGFR inhibitor without affecting the phosphorylation of the receptor and may potentially influence the recycling of EGFR to the plasma membrane.
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| 19. |
- Pettersson, Helen, et al.
(författare)
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Arsenic trioxide and neuroblastoma cytotoxicity.
- 2007
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Ingår i: Journal of Bioenergetics and Biomembranes. - : Springer Science and Business Media LLC. - 1573-6881 .- 0145-479X. ; 39:1, s. 35-41
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Forskningsöversikt (refereegranskat)abstract
- The majority of aggressive forms of the childhood tumor neuroblastoma can with current treatment protocols not be cured and possess a major challenge in pediatric oncology. After initial rounds of chemotherapy, surgery and irradiation, which in most cases result in tumor regression, these aggressive neuroblastomas relapse and frequently develop drug resistance. As approximately 50% of the children with neuroblastoma have an aggressive form, there is a compelling demand for new treatment strategies. Arsenic trioxide has the capacity to kill multidrug-resistant neuro-blastoma cells in vitro and in vivo and the drug is currently being evaluated in clinical trials. In this report we discuss the background to the use of arsenic trioxide in cancer therapy and the currently known mechanisms by which arsenic trioxide kills human neuroblastoma cells.
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| 20. |
- Pettersson, Helen, et al.
(författare)
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Arsenic trioxide is highly cytotoxic to small cell lung carcinoma cells.
- 2009
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Ingår i: Molecular Cancer Therapeutics. - 1538-8514 .- 1535-7163. ; 8:1, s. 160-170
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Tidskriftsartikel (refereegranskat)abstract
- Small cell lung carcinoma (SCLC) is an extremely aggressive form of cancer and current treatment protocols are insufficient. SCLC have neuroendocrine characteristics and show phenotypical similarities to the childhood tumor neuroblastoma. As multidrug-resistant neuroblastoma cells are highly sensitive to arsenic trioxide (As2O3) in vitro and in vivo, we here studied the cytotoxic effects of As2O3 on SCLC cells. As2O3 induced pronounced cell death in SCLC cells at clinically relevant concentrations, and also at hypoxia. SCLC cells were more sensitive than non-SCLC cells to As2O3. Cell death was mainly due to necrosis, although apoptotic responses were also seen. A significant in vivo effect of As2O3 on SCLC growth was shown in a nude mice-xenograft model, although a fraction of the treated tumor-bearing animals did not respond. The nonresponding SCLC tumors differed in morphology and cell organization compared with treatment-responsive tumors, which in turn, showed decreased vascularization and higher expression of neuroendocrine markers compared with control tumors. Our results suggest a potential clinical application of As2O3 in SCLC therapy. In addition to cell death induction, antiangiogenic induction of differentiation may also be part of the in vivo effect of As2O3 on SCLC growth, as suggested by an increase in neuroendocrine markers in cultured cells.
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| 21. |
- Pietras, Alexander
(författare)
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Cancer stem cells in tumor heterogeneity.
- 2011
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Ingår i: Advances in Cancer Research. - 0065-230X. ; 112, s. 255-281
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Tidskriftsartikel (refereegranskat)abstract
- Cancer cells within a given tumor were long regarded as a largely homogeneous group of cells originating from a common progenitor cell. However, it is increasingly appreciated that there is a considerable heterogeneity within tumors also on the tumor cell level. This heterogeneity extends to virtually all measurable properties of cancer cells, ranging from differentiation state, proliferation rate, migratory and invasive capacity to size, and therapeutic response. Such heterogeneity likely represents a major therapeutic hurdle, but the mechanisms underlying its emergence remain poorly understood and a controversial topic. The cancer stem cell model of tumor progression has gained increasing support during the past several years. In this review, I will discuss some major implications of the cancer stem cell hypothesis on the origins of tumor heterogeneity, focusing both on heterogeneity within the tumor cells proper and on potential transdifferentiation of cancer stem cells into stromal and endothelial lineages, as well as on heterogeneity of the therapeutic response. Evidence for and against a direct and causal role of cancer stem cells in the emergence of tumor heterogeneity will be weighed and alternative explanations for apparently contradictory observations discussed. Finally, I will discuss the potential origins of cancer stem cells and the various implications of origin to the contribution to tumor heterogeneity, and outline some future directions.
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| 22. |
- Pietras, Alexander, et al.
(författare)
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HIF-2 alpha maintains an undifferentiated state in neural crest-like human neuroblastoma tumor-initiating cells
- 2009
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 106:39, s. 16805-16810
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Tidskriftsartikel (refereegranskat)abstract
- High hypoxia-inducible factor-2 alpha (HIF-2 alpha) protein levels predict poor outcome in neuroblastoma, and hypoxia dedifferentiates cultured neuroblastoma cells toward a neural crest-like phenotype. Here, we identify HIF-2 alpha as a marker of normoxic neural crest-like neuroblastoma tumor-initiating/stem cells (TICs) isolated from patient bone marrows. Knockdown of HIF-2 alpha reduced VEGF expression and induced partial sympathetic neuronal differentiation when these TICs were grown in vitro under stem cell-promoting conditions. Xenograft tumors of HIF-2 alpha-silenced cells were widely necrotic, poorly vascularized, and resembled the bulk of tumor cells in clinical neuroblastomas by expressing additional sympathetic neuronal markers, whereas control tumors were immature, well-vascularized, and stroma-rich. Thus, HIF-2 alpha maintains an undifferentiated state of neuroblastoma TICs. Because low differentiation is associated with poor outcome and angiogenesis is crucial for tumor growth, HIF-2 alpha is an attractive target for neuroblastoma therapy.
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| 23. |
- Pietras, Alexander, et al.
(författare)
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High levels of HIF-2alpha highlight an immature neural crest-like neuroblastoma cell cohort located in a perivascular niche.
- 2008
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Ingår i: Journal of Pathology. - : Wiley. - 0022-3417. ; 214:4, s. 482-488
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Tidskriftsartikel (refereegranskat)abstract
- High HIF-2alpha protein levels in the sympathetic nervous system-derived childhood tumour neuroblastoma as well as immature phenotype correlate to unfavourable outcome. Here we show that a small subset of perivascularly located, strongly HIF-2alpha-positive tumour cells (MYCN amplified) lacks expression of differentiation markers, but expresses neural crest and early sympathetic progenitor marker genes such as Notch-1, HES-1, c-Kit, dHAND, and vimentin. HIF-2alpha- and CD68-positive tumour-associated macrophages were frequently found close to the immature and HIF-2alpha-positive neuroblastoma cells and as VEGF levels are high in the perivascular niche, we hypothesize that neuroblastoma neural crest-like cells and macrophages cooperate to facilitate angiogenesis and thereby contribute to the aggressive neuroblastoma phenotype. Copyright (c) 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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| 24. |
- Pietras, Alexander
(författare)
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Hypoxia-Inducible Factors in Tumor Cell Differentiation and Tumor Vascularization
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mammalian cells, including tumor cells, adapt to hypoxia via stabilization of two transcription factors - Hypoxia-inducible factor (HIF)-1alpha and HIF-2alpha. Among other consequences, hypoxia is a main driving force behind angiogenesis. The differentiation stage of tumor cells is recognized as an important clinical factor in several malignancies including neuroblastoma. Tumors with an immature phenotype are more aggressive than differentiated tumors. Moreover, recent hypotheses on tumor progression stipulate that maintenance of tumor growth is dependent on immature cells called tumor-initiating cells (TICs). Here, we identify HIF-2alpha as a marker of immature neuroblastoma cells and TICs isolated from patient bone marrows irrespective of oxygen levels. We further demonstrate that HIF-2alpha is required to maintain the undifferentiated state, as knockdown of HIF-2alpha induced differentiation. Knockdown of HIF-2alpha revealed a role for HIF-2alpha in recruitment of new blood vessels to experimental neuroblastomas, as the resulting xenograft tumors were highly necrotic. In addition and in agreement with in vitro data, we show that HIF-1alpha and HIF-2alpha proteins are differentially regulated in clinical neuroblastomas. While both proteins correlated with expression of VEGF, only HIF-2alpha was associated with aggressive disease and only HIF-1alpha correlated with tumor hypoxia. Finally, we demonstrate a novel mechanism of HIF regulation of endothelial tube formation via Notch regulation. HIF-dependent JAG2 induction in hypoxic tumor cells alters Notch activity in tumor cells and adjacent endothelial cells and thus represents a novel layer of complexity of hypoxia/Notch interplay. Together, our findings reveal novel roles of HIFs in regulation of tumor cell differentiation and tumor vascularization.
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| 25. |
- Pietras, Alexander, et al.
(författare)
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JAG2 induction in hypoxic tumor cells alters Notch signaling and enhances endothelial cell tube formation.
- 2011
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Ingår i: Molecular Cancer Research. - 1557-3125. ; 9, s. 626-636
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Tidskriftsartikel (refereegranskat)abstract
- Several studies have revealed links between hypoxia and activation of Notch in solid tumors. While most reports have focused on icN1 stabilization by direct interaction with HIF proteins, little attention has been given to Notch ligand regulation during hypoxia. Here we show that the Notch ligand JAG2 is transcriptionally activated by hypoxia in a HIF-1α dependent manner. Hypoxic JAG2 induction resulted in elevated Notch activity in tumor cells, as was measured by increased icN1 levels and induction of the Notch target gene HEY1. In primary tumor material, JAG2 expression correlated with vascular development and angiogenesis gene signatures. In line with this, co-culture experiments of endothelial cells with hypoxic breast cancer cells displayed a reduction in number of capillary-like tubes formed upon JAG2 siRNA treatment of the breast cancer cells. Together these results suggest that a hypoxic induction of JAG2 in tumor cells mediates a hypoxia-regulated cross-talk between tumor and endothelial cells.
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| 26. |
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| 27. |
- Pietras, Alexander, et al.
(författare)
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The HIF-2alpha-Driven Pseudo-Hypoxic Phenotype in Tumor Aggressiveness, Differentiation, and Vascularization.
- 2010
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Ingår i: Diverse Effects of Hypoxia on Tumor Progression. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0070-217X. - 9783642133299 - 9783642133282 ; 345, s. 1-20
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Bokkapitel (refereegranskat)abstract
- Cellular adaptation to diminished tissue oxygen tensions, hypoxia, is largely governed by the hypoxia inducible transcription factors, HIF-1 and HIF-2. Tumor hypoxia and high HIF protein levels are frequently associated with aggressive disease. In recent years, high tumor cell levels of HIF-2 and the oxygen sensitive subunit HIF-2alpha have been associated with unfavorable disease and shown to be highly expressed in tumor stem/initiating cells originating from neuroblastoma and glioma, respectively. In these cells, HIF-2 is active under nonhypoxic conditions as well, creating a pseudo-hypoxic phenotype with clear influence on tumor behavior. Neuroblastoma tumor initiating cells are immature with a neural crest-like phenotype and downregulation of HIF-2alpha in these cells results in neuronal sympathetic differentiation and the cells become phenotypically similar to the bulk of neuroblastoma cells found in clinical specimens. Knockdown of HIF-2alpha in neuroblastoma and glioma tumor stem/initiating cells leads to reduced levels of VEGF and poorly vascularized, highly necrotic tumors. As high HIF-2alpha expression further correlates with disseminated disease as demonstrated in neuroblastoma, glioma, and breast carcinoma, we propose that targeting HIF-2alpha and/or the pseudo-hypoxic phenotype induced by HIF-2 under normoxic conditions has great clinical potential.
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| 28. |
- Pietras, Alexander
(författare)
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What (H)IF isoform matters? : A deubiquitinase can tune the hypoxic response
- 2022
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Ingår i: EMBO Journal. - : EMBO. - 1460-2075 .- 0261-4189. ; 41:7
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Tidskriftsartikel (refereegranskat)abstract
- Context-specific control mechanisms of hypoxia-inducible transcription factors HIF-1alpha and HIF-2alpha in tumors exposed to oxygen shortage remain incompletely understood. In this issue, Zhang et al (2022) identify a deubiquitinase that differentially stabilizes HIF-2alpha in stem-like glioblastoma cells, suggesting potential implications for regulation of the hypoxic response in a wide array of tissues and cancers.
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| 29. |
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| 30. |
- Tong, Bei, et al.
(författare)
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The p75 neurotrophin receptor enhances HIF-dependent signaling in glioma
- 2018
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Ingår i: Experimental Cell Research. - : Elsevier BV. - 0014-4827. ; 371:1, s. 122-129
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Tidskriftsartikel (refereegranskat)abstract
- Tumor hypoxia is associated with several features of aggressive glioma growth, including migration, invasion, and stemness. Most of the cellular adaptation to hypoxia is mediated by the hypoxia-inducible factors HIF-1α and HIF-2α, but regulation of these factors by both oxygen-dependent and –independent mechanisms in brain tumors is only partially understood. Here, we show that the p75 neurotrophin receptor (p75NTR) is stabilized at hypoxia in murine glioma in vivo, as well as in primary human glioma cultures in vitro. Expression of p75NTR resulted in increased stabilization of HIF-1α and HIF-2α, and RNAi or pharmacologic targeting of p75NTR diminished HIF stabilization and HIF-dependent signaling at hypoxia. Consequentially, p75NTR inhibition resulted in decreased migration, invasion, and stemness in response to hypoxia, suggesting that p75NTR is a central regulator of hypoxia-induced glioma aggressiveness. Together, our findings support the literature that identifies p75NTR as a potential therapeutic target in brain tumors.
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| 31. |
- Tuysuz, Emre Can, et al.
(författare)
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Tumor suppressor role of the complement inhibitor CSMD1 and its role in TNF-induced neuroinflammation in gliomas
- 2024
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Ingår i: Journal of Experimental and Clinical Cancer Research. - 1756-9966. ; 43, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The complement inhibitor CSMD1 acts as a tumor suppressor in various types of solid cancers. Despite its high level of expression in the brain, its function in gliomas, malignant brain tumors originating from glial cells, has not been investigated.METHODS: Three cohorts of glioma patients comprising 1500 patients were analyzed in our study along with their clinical data. H4, U-118 and U-87 cell lines were used to investigate the tumor suppressor function of CSMD1 in gliomas. PDGFB-induced brain tumor model was utilized for the validation of in vitro data.RESULTS: The downregulation of CSMD1 expression correlated with reduced overall and disease-free survival, elevated tumor grade, wild-type IDH genotype, and intact 1p/19q status. Moreover, enhanced activity was noted in the neuroinflammation pathway. Importantly, ectopic expression of CSMD1 in glioma cell lines led to decreased aggressiveness in vitro. Mechanically, CSMD1 obstructed the TNF-induced NF-kB and STAT3 signaling pathways, effectively suppressing the secretion of IL-6 and IL-8. There was also reduced survival in PDGFB-induced brain tumors in mice when Csmd1 was downregulated.CONCLUSIONS: Our study has identified CSMD1 as a tumor suppressor in gliomas and elucidated its role in TNF-induced neuroinflammation, contributing to a deeper understanding of glioma pathogenesis.
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| 32. |
- Vincent, Theresa, et al.
(författare)
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A SNAIL1–SMAD3/4 transcriptional repressor complex promotes TGF‑β mediated epithelial–mesenchymal transition
- 2009
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Ingår i: Nature Cell Biology. - : Springer Science and Business Media LLC. - 1465-7392 .- 1476-4679. ; 11:8, s. 943-950
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Tidskriftsartikel (refereegranskat)abstract
- Epithelial-mesenchymal transition (EMT) is essential for organogenesis and is triggered during carcinoma progression to an invasive state. Transforming growth factor-β (TGF-β) cooperates with signalling pathways, such as Ras and Wnt, to induce EMT, but the molecular mechanisms are not clear. Here, we report that SMAD3 and SMAD4 interact and form a complex with SNAIL1, a transcriptional repressor and promoter of EMT. The SNAIL1-SMAD3/4 complex was targeted to the gene promoters of CAR, a tight-junction protein, and E-cadherin during TGF-β-driven EMT in breast epithelial cells. SNAIL1 and SMAD3/4 acted as co-repressors of CAR, occludin, claudin-3 and E-cadherin promoters in transfected cells. Conversely, co-silencing of SNAIL1 and SMAD4 by siRNA inhibited repression of CAR and occludin during EMT. Moreover, loss of CAR and E-cadherin correlated with nuclear co-expression of SNAIL1 and SMAD3/4 in a mouse model of breast carcinoma and at the invasive fronts of human breast cancer. We propose that activation of a SNAIL1-SMAD3/4 transcriptional complex represents a mechanism of gene repression during EMT.
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| 33. |
- Wee, Boyoung, et al.
(författare)
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ABCG2 regulates self-renewal and stem cell marker expression but not tumorigenicity or radiation resistance of glioma cells
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Glioma cells with stem cell traits are thought to be responsible for tumor maintenance and therapeutic failure. Such cells can be enriched based on their inherent drug efflux capability mediated by the ABC transporter ABCG2 using the side population assay, and their characteristics include increased self-renewal, high stem cell marker expression and high tumorigenic capacity in vivo. Here, we show that ABCG2 can actively drive expression of stem cell markers and self-renewal in glioma cells. Stem cell markers and self-renewal was enriched in cells with high ABCG2 activity, and could be specifically inhibited by pharmacological and genetic ABCG2 inhibition. Importantly, despite regulating these key characteristics of stem-like tumor cells, ABCG2 activity did not affect radiation resistance or tumorigenicity in vivo. ABCG2 effects were Notch-independent and mediated by diverse mechanisms including the transcription factor Mef. Our data demonstrate that characteristics of tumor stem cells are separable, and highlight ABCG2 as a potential driver of glioma stemness.
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