| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Pantazopoulou, Vasiliki
(författare)
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Stromal and tumor cell responses to hypoxia and treatment within the glioma microenvironment
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Glioblastoma is the most aggressive primary brain tumor in adults. Despite treatment, tumors invariably recur, and the recurring tumor is resistant to therapies. New approaches are needed for the successful treatment of glioblastoma patients.Tumors are not simply a compilation of molecularly and phenotypically identical neoplastic cells. Instead, the tumor-associated stroma is instrumental in supporting tumor growth. Moreover, the cancer cells themselves are highly plastic, with some of the cells exhibiting stem-like phenotypes. Cancer stemness is linked to more aggressive disease, recurrence, and worse patient outcomes in several cancers. Hypoxic signaling, mediated by the HIF transcription factors, is a cornerstone in the maintenance of cancer stemness in glioblastoma and other cancers.The aim of this thesis was to evaluate how microenvironmental cues affect the interactions between the tumor microenvironment and glioma stem-like cells in glioblastoma. We addressed how treatments and hypoxia affect tumor-associated astrocytes in ways that consequently alter glioma cell properties, and how hypoxia and pseudo-hypoxia are involved in stemness maintenance in glioblastoma. For this work, we used genetically engineered mouse models of glioma, primary stromal and glioma cell lines, classical glioblastoma cell lines, and organotypic slice cultures. We evaluated cell stemness by using multiple functional assays in combination with stem cell marker expression analysis. In papers I and II, we investigated the response of astrocytes to extrinsic factors of the microenvironment, namely radiation and temozolomide treatment, and to intrinsic factors of the microenvironment, namely intermediate and severe hypoxia. Astrocytes became reactive in response to these cues and produced extracellular matrix that altered glioma cell properties, including stemness. In papers III and IV, we investigated the role of hypoxia and pseudo-hypoxia in the maintenance of aggressive glioma phenotypes. We showed that the generation of the cleaved form of the cell surface glycoprotein CD44 leads to the stabilization of the HIFs in the perivascular and the perinecrotic glioma niche, leading to increased hypoxic signaling and glioma cell stemness. Moreover, we showed that p75NTR signaling is involved in the activation of the hypoxic signaling pathway and is also regulating glioma cell stemness and migration in hypoxia.All in all, this thesis elucidated aspects of the glioblastoma microenvironment, namely irradiated and hypoxic astrocytes, and the CD44 and p75NTR signaling, that can lead to the development of new targeted therapeutic strategies.
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| 7. |
- 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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