Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 8 de 8
Filter
Add more filters










Database
Language
Publication year range
1.
Viruses ; 13(8)2021 08 03.
Article in English | MEDLINE | ID: mdl-34452401

ABSTRACT

Human papillomavirus (HPV) positive and negative head and neck squamous cell carcinoma (HNSCC) are known to have differential phenotypes, including the incidence and location of metastases. HPV positive (HPV+) HNSCC are more likely to metastasize to distant sites, such as the lung, brain, and skin. Among these locations, metastasis to the brain is a rare event, and little is known about specific risk factors for this phenotype. In this report, we describe two patients who developed brain metastases from HNSCC. Both patient tumors had p16INK4a overexpression, suggesting these tumors were HPV+. This was confirmed after PCR, in situ hybridization, and mass spectrometry detected the presence of HPV type 16 (HPV16) DNA, RNA and protein. To further characterize the presence of HPV16, we used a target enrichment strategy on tumor DNA and RNA to isolate the viral sequences from the brain metastases. Analysis by targeted next generation sequencing revealed that both tumors had the HPV genome integrated into the host genome at known hotspots, 8q24.21 and 14q24.1. Applying a similar target enrichment strategy to a larger cohort of HPV+ HNSCC brain metastases could help to identify biomarkers that can predict metastasis and/or identify novel therapeutic options.


Subject(s)
Brain Neoplasms/virology , DNA, Viral/genetics , Human papillomavirus 16/genetics , Oropharyngeal Neoplasms/virology , Papillomavirus Infections/complications , Squamous Cell Carcinoma of Head and Neck/virology , Virus Integration/genetics , Aged , Cohort Studies , Human papillomavirus 16/pathogenicity , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Oropharyngeal Neoplasms/diagnostic imaging , Papillomavirus Infections/virology
2.
Cell Rep ; 29(10): 3173-3186.e7, 2019 12 03.
Article in English | MEDLINE | ID: mdl-31801081

ABSTRACT

Sox17, a SoxF family member transiently upregulated during postnatal oligodendrocyte (OL) development, promotes OL cell differentiation, but its function in white matter development and pathology in vivo is unknown. Our analysis of oligodendroglial- and OL-progenitor-cell-targeted ablation in vivo using a floxed Sox17 mouse establishes a dependence of postnatal oligodendrogenesis on Sox17 and reveals Notch signaling as a mediator of Sox17 function. Following Sox17 ablation, reduced numbers of Olig2-expressing cells and mature OLs led to developmental hypomyelination and motor dysfunction. After demyelination, Sox17 deficiency inhibited OL regeneration. OL decline was unexpectedly preceded by transiently increased differentiation and a reduction of OL progenitor cells. Evidence of a dual role for Sox17 in progenitor cell expansion by Notch and differentiation involving TCF7L2 expression were found. A program of progenitor expansion and differentiation promoted by Sox17 through Notch thus contributes to OL production and determines the outcome of white matter repair.


Subject(s)
Cell Differentiation/genetics , Cell Proliferation/genetics , HMGB Proteins/genetics , Oligodendrocyte Precursor Cells/physiology , SOXF Transcription Factors/genetics , Animals , Cell Cycle/genetics , Cells, Cultured , Demyelinating Diseases/metabolism , Female , Gene Expression Regulation, Developmental/genetics , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Oligodendrocyte Transcription Factor 2/genetics , Rats , Rats, Sprague-Dawley , Signal Transduction/genetics
3.
Cell Rep ; 13(10): 2090-7, 2015 Dec 15.
Article in English | MEDLINE | ID: mdl-26628380

ABSTRACT

Reactive astrogliosis is an essential and ubiquitous response to CNS injury, but in some cases, aberrant activation of astrocytes and their release of inhibitory signaling molecules can impair endogenous neural repair processes. Our lab previously identified a secreted intercellular signaling molecule, called endothelin-1 (ET-1), which is expressed at high levels by reactive astrocytes in multiple sclerosis (MS) lesions and limits repair by delaying oligodendrocyte progenitor cell (OPC) maturation. However, as ET receptors are widely expressed on neural cells, the cell- and receptor-specific mechanisms of OPC inhibition by ET-1 action remain undefined. Using pharmacological approaches and cell-specific endothelin receptor (EDNR) ablation, we show that ET-1 acts selectively through EDNRB on astrocytes--and not OPCs--to indirectly inhibit remyelination. These results demonstrate that targeting specific pathways in reactive astrocytes represents a promising therapeutic target in diseases with extensive reactive astrogliosis, including MS.


Subject(s)
Astrocytes/metabolism , Demyelinating Diseases/metabolism , Neural Stem Cells/metabolism , Receptor, Endothelin B/metabolism , Animals , Cell Differentiation/physiology , Disease Models, Animal , Endothelin-1/metabolism , Immunohistochemistry , Mice , Mice, Inbred C57BL , Mice, Mutant Strains , Microscopy, Electron, Transmission , Neural Stem Cells/cytology , Oligodendroglia/cytology , Oligodendroglia/metabolism , Regeneration/physiology
4.
Nat Neurosci ; 18(5): 674-82, 2015 May.
Article in English | MEDLINE | ID: mdl-25821912

ABSTRACT

Diffuse white matter injury (DWMI), a leading cause of neurodevelopmental disabilities in preterm infants, is characterized by reduced oligodendrocyte formation. NG2-expressing oligodendrocyte precursor cells (NG2 cells) are exposed to various extrinsic regulatory signals, including the neurotransmitter GABA. We investigated GABAergic signaling to cerebellar white matter NG2 cells in a mouse model of DWMI (chronic neonatal hypoxia). We found that hypoxia caused a loss of GABAA receptor-mediated synaptic input to NG2 cells, extensive proliferation of these cells and delayed oligodendrocyte maturation, leading to dysmyelination. Treatment of control mice with a GABAA receptor antagonist or deletion of the chloride-accumulating transporter NKCC1 mimicked the effects of hypoxia. Conversely, blockade of GABA catabolism or GABA uptake reduced NG2 cell numbers and increased the formation of mature oligodendrocytes both in control and hypoxic mice. Our results indicate that GABAergic signaling regulates NG2 cell differentiation and proliferation in vivo, and suggest that its perturbation is a key factor in DWMI.


Subject(s)
Cerebellum/pathology , Demyelinating Diseases/etiology , Hypoxia, Brain/physiopathology , Neural Stem Cells/cytology , Neurogenesis/physiology , Oligodendroglia/cytology , Receptors, GABA-A/physiology , White Matter/injuries , gamma-Aminobutyric Acid/physiology , Action Potentials/drug effects , Animals , Animals, Newborn , Asphyxia Neonatorum/pathology , Carbachol/pharmacology , Cell Count , Cells, Cultured , Cerebellum/growth & development , Demyelinating Diseases/chemically induced , Disease Models, Animal , Female , GABA-A Receptor Antagonists/toxicity , Hypoxia, Brain/pathology , Interneurons/pathology , Male , Mice , Mice, Knockout , Mice, Transgenic , Neurogenesis/drug effects , Nipecotic Acids/pharmacology , Nipecotic Acids/therapeutic use , Purkinje Cells/pathology , Solute Carrier Family 12, Member 2/deficiency , Solute Carrier Family 12, Member 2/physiology , Tiagabine , Vigabatrin/pharmacology , Vigabatrin/therapeutic use
5.
Carcinogenesis ; 31(10): 1889-96, 2010 Oct.
Article in English | MEDLINE | ID: mdl-20663777

ABSTRACT

DNA double-strand breaks (DSBs) are the most deleterious lesion inflicted by ionizing radiation. Although DSBs are potentially carcinogenic, it is not clear whether complex DSBs that are refractory to repair are more potently tumorigenic compared with simple breaks that can be rapidly repaired, correctly or incorrectly, by mammalian cells. We previously demonstrated that complex DSBs induced by high-linear energy transfer (LET) Fe ions are repaired slowly and incompletely, whereas those induced by low-LET gamma rays are repaired efficiently by mammalian cells. To determine whether Fe-induced DSBs are more potently tumorigenic than gamma ray-induced breaks, we irradiated 'sensitized' murine astrocytes that were deficient in Ink4a and Arf tumor suppressors and injected the surviving cells subcutaneously into nude mice. Using this model system, we find that Fe ions are potently tumorigenic, generating tumors with significantly higher frequency and shorter latency compared with tumors generated by gamma rays. Tumor formation by Fe-irradiated cells is accompanied by rampant genomic instability and multiple genomic changes, the most interesting of which is loss of the p15/Ink4b tumor suppressor due to deletion of a chromosomal region harboring the CDKN2A and CDKN2B loci. The additional loss of p15/Ink4b in tumors derived from cells that are already deficient in p16/Ink4a bolsters the hypothesis that p15 plays an important role in tumor suppression, especially in the absence of p16. Indeed, we find that reexpression of p15 in tumor-derived cells significantly attenuates the tumorigenic potential of these cells, indicating that p15 loss may be a critical event in tumorigenesis triggered by complex DSBs.


Subject(s)
Cyclin-Dependent Kinase Inhibitor p15/physiology , DNA Breaks, Double-Stranded , Neoplasms/etiology , Animals , Cells, Cultured , Chromosome Aberrations , Chromosome Deletion , Cyclin-Dependent Kinase Inhibitor p15/genetics , Cyclin-Dependent Kinase Inhibitor p16/genetics , Cyclin-Dependent Kinase Inhibitor p16/physiology , DNA Repair , Genomic Instability , Humans , Mice
6.
Cancer Res ; 70(13): 5457-64, 2010 Jul 01.
Article in English | MEDLINE | ID: mdl-20530668

ABSTRACT

Glioblastomas (GBM) are lethal brain tumors that are highly resistant to therapy. The only meaningful improvement in therapeutic response came from use of the S(N)1-type alkylating agent temozolomide in combination with ionizing radiation. However, no genetic markers that might predict a better response to DNA alkylating agents have been identified in GBMs, except for loss of O(6-)methylguanine-DNA methyltransferase via promoter methylation. In this study, using genetically defined primary murine astrocytes as well as human glioma lines, we show that loss of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) confers sensitivity to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a functional analogue of temozolomide. We find that MNNG induces replication-associated DNA double-strand breaks (DSB), which are inefficiently repaired in PTEN-deficient astrocytes and trigger apoptosis. Mechanistically, this is because PTEN-null astrocytes are compromised in homologous recombination (HR), which is important for the repair of replication-associated DSBs. Our results suggest that reduced levels of Rad51 paralogs in PTEN-null astrocytes might underlie the HR deficiency of these cells. Importantly, the HR deficiency of PTEN-null cells renders them sensitive to the poly(ADP-ribose) polymerase (PARP) inhibitor ABT-888 due to synthetic lethality. In sum, our results tentatively suggest that patients with PTEN-null GBMs (about 36%) may especially benefit from treatment with DNA alkylating agents such as temozolomide. Significantly, our results also provide a rational basis for treating the subgroup of patients who are PTEN deficient with PARP inhibitors in addition to the current treatment regimen of radiation and temozolomide.


Subject(s)
Brain Neoplasms/drug therapy , DNA Repair , Dacarbazine/analogs & derivatives , Glioblastoma/drug therapy , Methylnitronitrosoguanidine/pharmacology , PTEN Phosphohydrolase/deficiency , Poly(ADP-ribose) Polymerase Inhibitors , Animals , Antineoplastic Agents, Alkylating/pharmacology , Astrocytes/drug effects , Astrocytes/enzymology , Astrocytes/physiology , Benzimidazoles/pharmacology , Brain Neoplasms/enzymology , Brain Neoplasms/genetics , Cyclin-Dependent Kinase Inhibitor p16/deficiency , Cyclin-Dependent Kinase Inhibitor p16/genetics , Cyclin-Dependent Kinase Inhibitor p16/metabolism , DNA Damage , Dacarbazine/pharmacology , Glioblastoma/enzymology , Glioblastoma/genetics , Mice , Mice, Transgenic , PTEN Phosphohydrolase/genetics , PTEN Phosphohydrolase/metabolism , Recombination, Genetic , Temozolomide
7.
Clin Cancer Res ; 16(1): 154-63, 2010 Jan 01.
Article in English | MEDLINE | ID: mdl-20048334

ABSTRACT

PURPOSE: Telomerase activity is one of the hallmarks of cancer and is a highly relevant therapeutic target. The effects of a novel human telomerase antagonist, imetelstat, on primary human glioblastoma (GBM) tumor-initiating cells were investigated in vitro and in vivo. EXPERIMENTAL DESIGN: Tumor-initiating cells were isolated from primary GBM tumors and expanded as neurospheres in vitro. The GBM tumor-initiating cells were treated with imetelstat and examined for the effects on telomerase activity levels, telomere length, proliferation, clonogenicity, and differentiation. Subsequently, mouse orthotopic and subcutaneous xenografts were used to assess the in vivo efficacy of imetelstat. RESULTS: Imetelstat treatment produced a dose-dependent inhibition of telomerase (IC(50) 0.45 micromol/L). Long-term imetelstat treatment led to progressive telomere shortening, reduced rates of proliferation, and eventually cell death in GBM tumor-initiating cells. Imetelstat in combination with radiation and temozolomide had a dramatic effect on cell survival and activated the DNA damage response pathway. Imetelstat is able to cross the blood-brain barrier in orthotopic GBM xenograft tumors. Fluorescently labeled GBM tumor cells isolated from orthotopic tumors, following systemic administration of imetelstat (30 mg/kg every day for three days), showed approximately 70% inhibition of telomerase activity. Chronic systemic treatment produced a marked decrease in the rate of xenograft subcutaneous tumor growth. CONCLUSION: This preclinical study supports the feasibility of testing imetelstat in the treatment of GBM patients, alone or in combination with standard therapies.


Subject(s)
Antineoplastic Agents/therapeutic use , Brain Neoplasms/drug therapy , Enzyme Inhibitors/therapeutic use , Glioblastoma/drug therapy , Neoplastic Stem Cells/drug effects , Telomerase/antagonists & inhibitors , Animals , Blood-Brain Barrier/drug effects , Cell Line, Tumor , Cell Proliferation , Dose-Response Relationship, Drug , Drug Delivery Systems , Humans , Mice , Mice, SCID , Neoplastic Stem Cells/radiation effects , Oligonucleotides/pharmacology , Xenograft Model Antitumor Assays
8.
Cancer Res ; 69(10): 4252-9, 2009 May 15.
Article in English | MEDLINE | ID: mdl-19435898

ABSTRACT

Glioblastoma multiforme (GBM) is the most lethal of brain tumors and is highly resistant to ionizing radiation (IR) and chemotherapy. Here, we report on a molecular mechanism by which a key glioma-specific mutation, epidermal growth factor receptor variant III (EGFRvIII), confers radiation resistance. Using Ink4a/Arf-deficient primary mouse astrocytes, primary astrocytes immortalized by p53/Rb suppression, as well as human U87 glioma cells, we show that EGFRvIII expression enhances clonogenic survival following IR. This enhanced radioresistance is due to accelerated repair of DNA double-strand breaks (DSB), the most lethal lesion inflicted by IR. The EGFR inhibitor gefitinib (Iressa) and the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 attenuate the rate of DSB repair. Importantly, expression of constitutively active, myristylated Akt-1 accelerates repair, implicating the PI3K/Akt-1 pathway in radioresistance. Most notably, EGFRvIII-expressing U87 glioma cells show elevated activation of a key DSB repair enzyme, DNA-dependent protein kinase catalytic subunit (DNA-PKcs). Enhanced radioresistance is abrogated by the DNA-PKcs-specific inhibitor NU7026, and EGFRvIII fails to confer radioresistance in DNA-PKcs-deficient cells. In vivo, orthotopic U87-EGFRvIII-derived tumors display faster rates of DSB repair following whole-brain radiotherapy compared with U87-derived tumors. Consequently, EGFRvIII-expressing tumors are radioresistant and continue to grow following whole-brain radiotherapy with little effect on overall survival. These in vitro and in vivo data support our hypothesis that EGFRvIII expression promotes DNA-PKcs activation and DSB repair, perhaps as a consequence of hyperactivated PI3K/Akt-1 signaling. Taken together, our results raise the possibility that EGFR and/or DNA-PKcs inhibition concurrent with radiation may be an effective therapeutic strategy for radiosensitizing high-grade gliomas.


Subject(s)
DNA Damage , DNA Repair , DNA, Neoplasm/genetics , ErbB Receptors/genetics , Glioblastoma/genetics , Animals , Astrocytes/drug effects , Astrocytes/physiology , Astrocytes/radiation effects , Brain Neoplasms/drug therapy , Brain Neoplasms/genetics , Brain Neoplasms/mortality , Brain Neoplasms/pathology , Brain Neoplasms/radiotherapy , Cell Line, Tumor , Combined Modality Therapy , DNA Damage/radiation effects , DNA Repair/radiation effects , DNA, Neoplasm/radiation effects , Dacarbazine/analogs & derivatives , Dacarbazine/therapeutic use , Drug Resistance, Neoplasm , Fibroblasts/drug effects , Fibroblasts/physiology , Fibroblasts/radiation effects , Glioblastoma/drug therapy , Glioblastoma/mortality , Glioblastoma/pathology , Glioblastoma/radiotherapy , Humans , Mice , Radiation, Ionizing , Survival Analysis , Survivors , Temozolomide
SELECTION OF CITATIONS
SEARCH DETAIL
...