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  1. Article ; Online: Tumor-initiating and -propagating cells: cells that we would like to identify and control.

    Tysnes, Berit Bølge

    Neoplasia (New York, N.Y.)

    2009  Volume 12, Issue 7, Page(s) 506–515

    Abstract: Identification of the cell types capable of initiating and sustaining growth of the neoplastic clone in vivo is a fundamental problem in cancer research. It is likely that tumor growth can be sustained both by rare cancer stem-like cells and selected ... ...

    Abstract Identification of the cell types capable of initiating and sustaining growth of the neoplastic clone in vivo is a fundamental problem in cancer research. It is likely that tumor growth can be sustained both by rare cancer stem-like cells and selected aggressive clones and that the nature of the mutations, the cell of origin, and its environment will contribute to tumor propagation. Genomic instability, suggested as a driving force in tumorigenesis, may be induced by genetic and epigenetic changes. The feature of self-renewal in stem cells is shared with tumor cells, and deviant function of the stem cell regulatory networks may, in complex ways, contribute to malignant transformation and the establishment of a cancer stem cell-like phenotype. Understanding the nature of the more quiescent cancer stem-like cells and their niches has the potential to develop novel cancer therapeutic protocols including pharmacological targeting of self-renewal pathways. Drugs that target cancer-related inflammation may have the potential to reeducate a tumor-promoting microenvironment. Because most epigenetic modifications may be reversible, DNA methylation and histone deacetylase inhibitors can be used to induce reexpression of genes that have been silenced epigenetically. Design of therapies that eliminate cancer stem-like cells without eliminating normal stem cells will be important. Further insight into the mechanisms by which pluripotency transcription factors (e.g., OCT4, SOX2, and Nanog), polycomb repressive complexes and microRNA balance selfrenewal and differentiation will be essential for our understanding of both embryonic differentiation and human carcinogenesis and for the development of new treatment strategies.
    MeSH term(s) Cell Differentiation/physiology ; Cell Proliferation ; Cell Separation/methods ; Cell Transformation, Neoplastic/pathology ; Humans ; Infections/complications ; Infections/pathology ; Inflammation/complications ; Inflammation/pathology ; Models, Biological ; Neoplasm Invasiveness/pathology ; Neoplasms/pathology ; Neoplastic Stem Cells/pathology ; Regeneration/physiology
    Language English
    Publishing date 2009-04-29
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ZDB-ID 1483840-0
    ISSN 1476-5586 ; 1522-8002
    ISSN (online) 1476-5586
    ISSN 1522-8002
    DOI 10.1593/neo.10290
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Tumor-Initiating and -Propagating Cells

    Berit Bølge Tysnes

    Neoplasia : An International Journal for Oncology Research, Vol 12, Iss 7, Pp 506-

    Cells That We Would to Identify and Control

    2010  Volume 515

    Abstract: Identification of the cell types capable of initiating and sustaining growth of the neoplastic clone in vivo is a fundamental problem in cancer research. It is likely that tumor growth can be sustained both by rare cancer stem-like cells and selected ... ...

    Abstract Identification of the cell types capable of initiating and sustaining growth of the neoplastic clone in vivo is a fundamental problem in cancer research. It is likely that tumor growth can be sustained both by rare cancer stem-like cells and selected aggressive clones and that the nature of the mutations, the cell of origin, and its environment will contribute to tumor propagation. Genomic instability, suggested as a driving force in tumorigenesis, may be induced by genetic and epigenetic changes. The feature of self-renewal in stem cells is shared with tumor cells, and deviant function of the stem cell regulatory networks may, in complex ways, contribute to malignant transformation and the establishment of a cancer stem cell-like phenotype. Understanding the nature of the more quiescent cancer stem-like cells and their niches has the potential to develop novel cancer therapeutic protocols including pharmacological targeting of self-renewal pathways. Drugs that target cancer-related inflammation may have the potential to reeducate a tumor-promoting microenvironment. Because most epigenetic modifications may be reversible, DNA methylation and histone deacetylase inhibitors can be used to induce reexpression of genes that have been silenced epigenetically. Design of therapies that eliminate cancer stem-like cells without eliminating normal stem cells will be important. Further insight into the mechanisms by which pluripotency transcription factors (e.g., OCT4, SOX2, and Nanog), polycomb repressive complexes and microRNA balance selfrenewal and differentiation will be essential for our understanding of both embryonic differentiation and human carcinogenesis and for the development of new treatment strategies.
    Keywords Medicine ; R ; Internal medicine ; RC31-1245 ; Neoplasms. Tumors. Oncology. Including cancer and carcinogens ; RC254-282
    Subject code 610
    Publishing date 2010-07-01T00:00:00Z
    Publisher Elsevier
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article: DNA repair and cancer stem-like cells--potential partners in glioma drug resistance?

    Johannessen, Tor-Christian Aase / Bjerkvig, Rolf / Tysnes, Berit Bølge

    Cancer treatment reviews

    2008  Volume 34, Issue 6, Page(s) 558–567

    Abstract: Glioblastoma is the most malignant and frequent primary brain tumour in adults. Current treatment remains insufficient as these tumours display a diffuse infiltrative growth pattern and tend to recur despite extensive debulking surgery followed by radio- ...

    Abstract Glioblastoma is the most malignant and frequent primary brain tumour in adults. Current treatment remains insufficient as these tumours display a diffuse infiltrative growth pattern and tend to recur despite extensive debulking surgery followed by radio- and chemotherapy. The alkylating agents carmustine (1,3-bis-(2-chloroethyl)-1-nitrosourea, or BCNU) and temozolomide (TMZ) are the drugs of choice for adjuvant glioma chemotherapy. However, several independent DNA repair mechanisms can restore the integrity of alkylated DNA bases, and thus contribute to drug resistance and subsequent therapy failure. Recent work suggests that glioblastomas develop as cellular and functional hierarchies through small subpopulations of stem cell-like cancer cells that are responsible for tumour initiation and maintenance. Such cells also appear to possess enhanced DNA repair capacity compared to other cells within the tumours. Challenges in glioblastoma therapy are to determine (1) whether the cancer stem-like cell subpopulations represent a clinically novel target for therapy, and (2) which additional treatment strategies should be applied to improve quality of life and prolong survival of glioblastoma patients. This review addresses clinically relevant mechanisms which contribute to glioma resistance towards current alkylating agent-based chemotherapy, and discusses related mechanisms and treatment strategies in the light of the cancer stem cell hypothesis.
    MeSH term(s) Antineoplastic Agents/therapeutic use ; Brain Neoplasms/drug therapy ; Brain Neoplasms/genetics ; DNA Repair ; DNA, Neoplasm/genetics ; Drug Resistance, Neoplasm ; Glioma/drug therapy ; Glioma/genetics ; Humans ; Neoplastic Stem Cells/drug effects
    Chemical Substances Antineoplastic Agents ; DNA, Neoplasm
    Language English
    Publishing date 2008-10
    Publishing country Netherlands
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ZDB-ID 125102-8
    ISSN 1532-1967 ; 0305-7372
    ISSN (online) 1532-1967
    ISSN 0305-7372
    DOI 10.1016/j.ctrv.2008.03.125
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: The DNA repair protein ALKBH2 mediates temozolomide resistance in human glioblastoma cells.

    Johannessen, Tor-Christian Aase / Prestegarden, Lars / Grudic, Amra / Hegi, Monika E / Tysnes, Berit Bølge / Bjerkvig, Rolf

    Neuro-oncology

    2012  Volume 15, Issue 3, Page(s) 269–278

    Abstract: Introduction: Glioblastoma multiforme (GBM; World Health Organization astrocytoma grade IV) is the most frequent and most malignant primary brain tumor in adults. Despite multimodal therapy, all such tumors practically recur during the course of therapy, ...

    Abstract Introduction: Glioblastoma multiforme (GBM; World Health Organization astrocytoma grade IV) is the most frequent and most malignant primary brain tumor in adults. Despite multimodal therapy, all such tumors practically recur during the course of therapy, causing a median survival of only 14.6 months in patients with newly diagnosed GBM. The present study was aimed at examining the expression of the DNA repair protein AlkB homolog 2 (ALKBH2) in human GBM and determining whether it could promote resistance to temozolomide chemotherapy.
    Methods: ALKBH2 expression in GBM cell lines and in human GBM was determined by quantitative real-time PCR (qRT-PCR) and gene expression analysis, respectively. Drug sensitivity was assessed in GBM cells overexpressing ALKBH2 and in cells in which ALKBH2 expression was silenced by small-interfering (si)RNA. ALKBH2 expression following activation of the p53 pathway was examined by western blotting and qRT-PCR.
    Results: ALKBH2 was abundantly expressed in established GBM cell lines and human GBM, and temozolomide exposure increased cellular ALKBH2 expression levels. Overexpression of ALKBH2 in the U87 and U251 GBM cell lines enhanced resistance to the methylating agents temozolomide and methyl methanesulfonate but not to the nonmethylating agent doxorubicin. Conversely, siRNA-mediated knockdown of ALKBH2 increased sensitivity of GBM cells to temozolomide and methyl methanesulfonate but not to doxorubicin or cisplatin. Nongenotoxic activation of the p53 pathway by the selective murine double minute 2 antagonist nutlin-3 caused a significant decrease in cellular ALKBH2 transcription levels.
    Conclusion: Our findings identify ALKBH2 as a novel mediator of temozolomide resistance in human GBM cells. Furthermore, we place ALKBH2 into a new cellular context by showing its regulation by the p53 pathway.
    MeSH term(s) AlkB Homolog 2, Alpha-Ketoglutarate-Dependent Dioxygenase ; Antineoplastic Agents, Alkylating/pharmacology ; Blotting, Western ; Brain Neoplasms/drug therapy ; Brain Neoplasms/genetics ; Brain Neoplasms/pathology ; Cell Adhesion/drug effects ; Cell Movement/drug effects ; Cell Proliferation/drug effects ; DNA Repair Enzymes/antagonists & inhibitors ; DNA Repair Enzymes/genetics ; DNA Repair Enzymes/metabolism ; Dacarbazine/analogs & derivatives ; Dacarbazine/pharmacology ; Dioxygenases/antagonists & inhibitors ; Dioxygenases/genetics ; Dioxygenases/metabolism ; Drug Resistance, Neoplasm ; Flow Cytometry ; Gene Expression Regulation, Neoplastic ; Glioblastoma/drug therapy ; Glioblastoma/genetics ; Glioblastoma/pathology ; Humans ; RNA, Messenger/genetics ; RNA, Small Interfering/genetics ; Real-Time Polymerase Chain Reaction ; Reverse Transcriptase Polymerase Chain Reaction ; Temozolomide ; Tumor Cells, Cultured ; Tumor Stem Cell Assay
    Chemical Substances Antineoplastic Agents, Alkylating ; RNA, Messenger ; RNA, Small Interfering ; Dacarbazine (7GR28W0FJI) ; Dioxygenases (EC 1.13.11.-) ; ALKBH2 protein, human (EC 1.14.11.33) ; AlkB Homolog 2, Alpha-Ketoglutarate-Dependent Dioxygenase (EC 1.14.11.33) ; DNA Repair Enzymes (EC 6.5.1.-) ; Temozolomide (YF1K15M17Y)
    Language English
    Publishing date 2012-12-20
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2028601-6
    ISSN 1523-5866 ; 1522-8517
    ISSN (online) 1523-5866
    ISSN 1522-8517
    DOI 10.1093/neuonc/nos301
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Alginate-Encapsulated Producer Cells

    Frits Thorsen Ph.D., M. Sc. / Tracy-Ann Read / Morten Lund-Johansen / Berit Bølge Tysnes / Rolf Bjerkvig

    Cell Transplantation, Vol

    A Potential New Approach for the Treatment of Malignant Brain Tumors

    2000  Volume 9

    Abstract: In recent years gene therapy has evolved as a new treatment for brain tumors, where genetically engineered cells can be used to deliver specific substances to target cells. However, clinical success has been limited due to insufficient gene transfer, ... ...

    Abstract In recent years gene therapy has evolved as a new treatment for brain tumors, where genetically engineered cells can be used to deliver specific substances to target cells. However, clinical success has been limited due to insufficient gene transfer, lack of prolonged gene expression, and immunorejection of producer cells. These obstacles may be overcome by encapsulating producer cells into immunoisolating substances such as alginate. This may provide a stable in situ delivery system of specific proteins, which can interfere with tumor growth and differentiation. This article represents a fundamental study describing the in vitro and the in vivo behavior of alginate-encapsulated producer cells. The viability and cell cycle distribution of encapsulated NIH 3T3 cells was studied by confocal laser scanning microscopy (CLSM) and by flow cytometry. The CLSM study showed a high viability of the encapsulated NIH 3T3 cells during 9 weeks in culture. The flow cytometric analysis revealed a change in cellular ploidy after 1 week in culture, with normalization in ploidy after 3 and 9 weeks. The production of the bacterial E. coli β-galactosidase in alginate-encapsulated BT4CnVlacZ cells was studied by x-gal staining, and the cells expressed prolonged β-galactosidase activity. H528 hybridoma cells producing monoclonal antibodies (mAbs) against the human epidermal growth factor receptor (EGFR) were encapsulated in alginate, and the mAb release was determined. The release of mAbs stabilized around 400 ng/ml/h after 12 days in vitro. To actually demonstrate that alginate-encapsulated H528 cells potentially inhibit a heterogeneous glioma cell population, cell migration from human GaMg glioma spheroids was studied during stimulation with EGF in the presence of encapsulated H528 cells. The migration in vitro was totally inhibited in the presence of H528 encapsulated cells. Alginate beads with H528 cells were also implanted into rat brains, and after 9 weeks the distribution of mAbs within the brain was studied by ...
    Keywords Medicine ; R
    Subject code 610
    Language English
    Publishing date 2000-11-01T00:00:00Z
    Publisher SAGE Publishing
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article: Angiogenesis-independent tumor growth mediated by stem-like cancer cells.

    Sakariassen, Per Ø / Prestegarden, Lars / Wang, Jian / Skaftnesmo, Kai-Ove / Mahesparan, Rupavathana / Molthoff, Carla / Sminia, Peter / Sundlisaeter, Eirik / Misra, Anjan / Tysnes, Berit Bølge / Chekenya, Martha / Peters, Hans / Lende, Gabriel / Kalland, Karl Henning / Øyan, Anne M / Petersen, Kjell / Jonassen, Inge / van der Kogel, Albert / Feuerstein, Burt G /
    Terzis, A Jorge A / Bjerkvig, Rolf / Enger, Per Øyvind

    Proceedings of the National Academy of Sciences of the United States of America

    2006  Volume 103, Issue 44, Page(s) 16466–16471

    Abstract: In this work, highly infiltrative brain tumors with a stem-like phenotype were established by xenotransplantation of human brain tumors in immunodeficient nude rats. These tumors coopted the host vasculature and presented as an aggressive disease without ...

    Abstract In this work, highly infiltrative brain tumors with a stem-like phenotype were established by xenotransplantation of human brain tumors in immunodeficient nude rats. These tumors coopted the host vasculature and presented as an aggressive disease without signs of angiogenesis. The malignant cells expressed neural stem cell markers, showed a migratory behavior similar to normal human neural stem cells, and gave rise to tumors in vivo after regrafting. Serial passages in animals gradually transformed the tumors into an angiogenesis-dependent phenotype. This process was characterized by a reduction in stem cells markers. Gene expression profiling combined with high throughput immunoblotting analyses of the angiogenic and nonangiogenic tumors identified distinct signaling networks in the two phenotypes. Furthermore, proinvasive genes were up-regulated and angiogenesis signaling genes were down-regulated in the stem-like tumors. In contrast, proinvasive genes were down-regulated in the angiogenesis-dependent tumors derived from the stem-like tumors. The described angiogenesis-independent tumor growth and the uncoupling of invasion and angiogenesis, represented by the stem-like cancer cells and the cells derived from them, respectively, point at two completely independent mechanisms that drive tumor progression. This article underlines the need for developing therapies that specifically target the stem-like cell pools in tumors.
    MeSH term(s) Animals ; Biopsy ; Chromosomes, Human/genetics ; Disease Progression ; Gene Expression Regulation ; Humans ; Immunohistochemistry ; Neoplasm Invasiveness ; Neoplasm Transplantation ; Neoplasms/blood supply ; Neoplasms/genetics ; Neoplasms/pathology ; Phenotype ; Rats ; Rats, Nude ; Signal Transduction ; Stem Cells ; Survival Rate ; Tumor Cells, Cultured
    Language English
    Publishing date 2006-10-31
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 209104-5
    ISSN 1091-6490 ; 0027-8424
    ISSN (online) 1091-6490
    ISSN 0027-8424
    DOI 10.1073/pnas.0607668103
    Database MEDical Literature Analysis and Retrieval System OnLINE

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