Glial Tumor Cells Research Articles

Correlation of survivin and B-cell lymphoma 2 expression with pathological malignancy and anti-apoptotic properties of glial cell tumors.

Apoptosis, whose mechanism remains unclear, is regulated by multiple factors. B-cell lymphoma 2 (Bcl-2) is a well-known anti-apoptotic mediator. Survivin is also a recently recognized novel family inhibitor of apoptosis protein, which inhibits apoptosis via a pathway distinct from Bcl-2 family members. Survivin and Bcl-2 are expressed in various types of human cancer. In the present study, survivin and Bcl-2 expression were characterized in glial cell tumors, and the correlation with pathological malignancy and anti-apoptotic properties were investigated. Fifty-eight patients who had undergone surgical resection for glial cell tumors were evaluated. The pathological types of glial cell tumors were categorized according to the World Health Organization classification. Survivin and Bcl-2 expression levels were investigated by western blot analysis, and apoptosis was detected by DNA fragmentation analysis. The anti-apoptotic rate of glial cell tumors was calculated in tumor samples according to the expression of survivin and Bcl-2 or co-expression. Survivin was characterized in 60.3%, and Bcl-2 was expressed in 43.1% of glioma samples. Co-expression of survivin and Bcl-2 was observed in 25.9% of the tumor specimens. Survivin expression in astrocytic tumors was identified to be significantly associated with the pathological grade (P<0.05); however, Bcl-2 was not (P>0.05). Anti-apoptotic rate of glial cell tumors were detected in 91.4, 92.0 and 100% of patients exhibiting survivin, Bcl-2 or co-expression, respectively. However, the difference in anti-apoptotic frequency between the three groups was not identified to be statistically significant (P>0.05). The present study suggests that survivin expression is correlated with pathological grades of gliomas. In addition, the expression of survivin or Bcl-2 exerts potent anti-apoptotic properties in gliomas. Thus, survivin or Bcl-2 may serve as potential targets for inducing the apoptosis of gliomas.

Culture cells in a model of microgravity

Abstract The main objective of the work was to clarify the question - how will cell cultures functional state change after microgravity simulation when the shift in full strength direction takes place? Proliferation processes and apoptosis intensity in cell lines of rat glioma and human fibroblasts were compared in changing the position of flasks with cell culture in relation to the horizon. The detection of apoptosis and necrosis processes was carried out using flow cytofluorimetry. It was found that the change in full strength direction provides an inhibitory effect on tumor glial cells and fibroblasts’ proliferative activity enhances along with inhibition of apoptotic processes. Intensification of apoptotic processes in glioma cells and attenuation of cell death processes in normal cells - fibroblasts - are the result of cell cooperation disturbance.

Thymoquinone: An edible redox-active quinone for the pharmacotherapy of neurodegenerative conditions and glial brain tumors. A short review.

There exist few efficient agents in the neurological and neurosurgical armamentarium for treatment of neurotrauma, refractory seizures and high grade glial tumors. Pathophysiological conditions of diverse neural injuries have converging common pathways including oxidative stress and apoptosis. Targeted therapies have been throughly investigated, but limited success has been achieved until now. Phytochemical drugs may provide easily achievable and cheap adjunctive sources. Thymoquinone is an edible quinone obtained from Nigella sativa seed oil and exerts powerful antiinflammatory, antioxidant and antitumor activities in experimental models. Recently emerging studies conducted with animal models suggest that thymoquinone - bearing a very simple molecular structure - significantly crosses the blood brain barrier and exerts neuromodulatory activities. Indeed, in animal studies, the following actions of thymoquinone were demonstrated: 1-Protection against ischemic brain damage. 2-Reduction of epileptic seizures and associated cerebral oxidative injury. 3-Reduction of morphine tolerance and associated oxidative brain damage. 4-Anxiolytic effects and reduction of immobility stress-associated cerebral oxidative injury. 5-Reduction of diabetes-induced cerebral oxidative stress, 6-Reduction of cerebral oxidative injuries induced by noxious exposures including toluene, lead and ionizing radiation. Substantial in vitro data suggest that thymoquinone may be beneficial in treatment of glial tumors. However, there is no clinical study investigating its antitumor effects. In fact, thymoquinone suppresses growth and invasion, and induces apoptosis of glial tumor cells via degrading tubulins and inhibiting 20S proteasome, telomerase, autophagy, FAK and metalloproteinases. A simple and easily available agent may be a promising adjunctive treatment option in neurological and neurosurgical practice.

Oncolytic viruses for therapy of malignant glioma

Effective treatment of malignant brain tumors is still an open problem. Location of tumor in vital areas of the brain significantly limits capasities of surgical treatment. The presence of tumor stem cells resistant to radiation and anticancer drugs in brain tumor complicates use of chemoradiotherapy and causes a high rate of disease recurrence. A technological improvement in bioselection and production of recombinant resulted in creation of viruses with potent oncolytic properties against glial tumors. Recent studies, including clinical trials, showed, that majority of oncolytic viruses are safe. Despite the impressive results of the viral therapy in some patients, the treatment of other patients is not effective; therefore, further improvement of the methods of oncolytic virotherapy is necessary. High genetic heterogeneity of glial tumor cells even within a single tumor determines differences in individual sensitivity of tumor cells to oncolytic viruses. This review analyses the most successful oncolytic virus strains, including those which had reached clinical trials, and discusses the prospects for new approaches to virotherapy of gliomas.

Inhibition of Glioblastoma Cell Growth In Vitro and In Vivo by Brucine, a Component of Chinese Medicine

Glioblastoma multiforme (GBM) is one of the most common glial cell tumors and has drawn more and more attention in the clinic in recent years. Brucine has been reported to significantly suppress gastric cancer, lung cancer, and prostate cancer growth in vivo by inducing cell apoptosis. Here, the effects of brucine on U251 human glioma cell growth were investigated in vitro by cell proliferation assay, FACs, and qPCR in a xenograft tumor model. Treatment with brucine reduced the expression of BCL-2 and cyclooxygenase-2 (COX-2), while upregulated BAX expression in U251 human glioma cells resulted in reduced glioma cell survival rate and inhibited the growth of xenograft tumors. We concluded that brucine has a suppressive effect on U251 human glioma cells in vitro and in vivo, which could help in understanding the role of brucine in glioma cells and guiding drug use in the clinic.

MTR-06A STRATEGY FOR REDUCING HYPOXIA INDUCED CHEMORESISTANCE IN GLIAL CELLS

BACKGROUND: Glioblastoma multiforme is refractory to conventional treatment, highlighting the need for more efficient therapies. Hypoxia, which is a characteristic feature of glioma is markedly responsible for the chemoresistance. A rational combination of drugs has the possibility of improving therapeutic response. Cisplatin (CP) and 2- Deoxy-D-glucose (2-DG) are not very effective as single agents, and hence we have investigated the efficacy and mechanism of action of their combination in glial tumor cell lines, under both normoxia and hypoxia. METHODS: Cell survival analysis after treatment with combination as compared to single agent was done by MTT assay and combination index calculated. MTT results were confirmed through caspase 3/7 assay and propidium iodide staining. Expression of autophagy, apoptosis, endoplasmic reticulum (ER) stress markers were confirmed through Real time PCR and western blotting. ATP assay was done to investigate the effect on cellular metabolism. RESULTS: The combination of CP and 2-DG was synergistic under normoxia and hypoxia with combination index less than 1. Analysis of caspase 3/7 activity and cell cycle (subG1) along with biomarkers of autophagy and apoptosis indicated switch over from autophagic to apoptotic pathways. Since 2-DG induces autophagy through ER stress, reduction in autophagy by the combination was further confirmed by reduction in ER stress marker under both normoxia and hypoxia. CONCLUSION: The in-vitro study showed the potential of the combination for reducing chemoresistance under both normoxia and hypoxia in glioma cells. Abrogation of the chemoresistance by the combination was through attenuation of autophagy by reduction in ER stress.

Exosomal MicroRNAs in Tumoral U87 MG Versus Normal Astrocyte Cells.

Brain glial tumors, and particularly glioblastomas, are tumors with a very poor prognosis. Currently, the parameters that control aggressiveness, migration, or chemoresistance are not well known. In this tumor context, microRNAs are thought to be essential actors of tumorigenesis as they are able to control the expression of numerous genes. microRNAs are not only active in controlling tumor cell pathways, they are also secreted by cells, inside microvesicles called exosomes, and may play specific roles outside the tumor cells in the tumor microenvironment. We analyzed the microRNA content of exosomes produced in vitro by normal glial cells (astrocytes) and tumor glial cells (U87 MG) using Affymetrix microarrays. It appears that the exosome microRNA profiles are qualitatively quite similar. Nevertheless, their quantitative profiles are different and may be potentially taken as an opportunity to carry out assays of diagnostic interest. We submitted the cultured cells to several stresses such as oxygen deprivation or treatments with chemical drugs (GW4869 or 5-Aza-2'- deoxycitidine) to assess the impact of the cellular microRNA profile modifications on the exosome microRNA profiles. We found that modifications of the cellular microRNA content are not strictly mirrored in exosomes. On the basis of these results, we propose that the way microRNAs are released in exosomes is probably the result of a combination of different excretion mechanisms or constraints that concur in a controlled regulation of the exosome microRNA secretion.

Blindness in Tuberous Sclerosis: A Case Report

Tuberous sclerosis (TS) is inherited as an autosomal dominant trait with variable penetrance characterised by glial cell tumor which arises from the cerebral and the retina. Blindness in association with Tuberous sclerosis (TS) is rare. When visual loss occurs it may be associated with hamartomas from retinal or optic nerve involvement or from intracranial (brain) tumours that affect either the part of the brain that processes visual information or from optic nerve damage following raised intracranial pressure. Very few cases of TS with blindness have been reported globally. Deterioration in academic performance might be the first pointer to the visual impairment. We report a case of a 13 year old girl who presented with increasing number of facial rash over an 11 years period, recurrent headache and deteriorating academic performance of 1 year and loss of vision of 6 months with a recent episode of convulsion. Similar skin rashes without other associated symptoms were noticed on the mother and one of the younger siblings. She was a Tanner stage one in development. She had facial angio fibromas, shagreen patches over the left hypochondria, back regions and face. Ophthalmic evaluation showed a visual acuity of being able to count fingers at not more than one meter from the face and only perception of light in the right and left eye respectively, both eyes had brisk pupillary activities, good mydriasis and clear media. The retinal and optic nerve head appeared normal in the right eye whereas in the left eye was a huge tuberous hamartoma of the optic disc and macular as well as generalised vascular occlusion and subretinal fluid. The Computerized tomography (CT) scan showed an Intraventricular tumour, with calcification within the tumours and subependymal. There was associated obstructive hydrocephalus. Patient was managed by a multi disciplinary team of ophthalmologists, neurosurgeons and radiologists, coordinated by a paediatrician. Conclusion: The diagnosis of tuberous sclerosis complex (TSC) was based on the lesions found on clinical examination, imaging, and pathologic studies. The blindness was multi-factorial in cause including intracranial, retinal and optic nerve tumours. Comprehensive medical history, detailed physical examinations and neuroimaging study are essential in making a diagnosis of TSC. Our patient was mis-diagnosed at various health facilities for many years. This delay in making appropriate diagnosis and instituting treatment could have contributed to the eventual outcome. Keywords: Tuberous Sclerosis, Blindness, Deteriorating Academic Performance

Merlin Isoforms 1 and 2 Both Act as Tumour Suppressors and Are Required for Optimal Sperm Maturation.

The tumour suppressor Merlin, encoded by the gene NF2, is frequently mutated in the autosomal dominant disorder neurofibromatosis type II, characterised primarily by the development of schwannoma and other glial cell tumours. However, NF2 is expressed in virtually all analysed human and rodent organs, and its deletion in mice causes early embryonic lethality. Additionally, NF2 encodes for two major isoforms of Merlin of unknown functionality. Specifically, the tumour suppressor potential of isoform 2 remains controversial. In this study, we used Nf2 isoform-specific knockout mouse models to analyse the function of each isoform during development and organ homeostasis. We found that both isoforms carry full tumour suppressor functionality and can completely compensate the loss of the other isoform during development and in most adult organs. Surprisingly, we discovered that spermatogenesis is strictly dependent on the presence of both isoforms. While the testis primarily expresses isoform 1, we noticed an enrichment of isoform 2 in spermatogonial stem cells. Deletion of either isoform was found to cause decreased sperm quality as observed by maturation defects and head/midpiece abnormalities. These defects led to impaired sperm functionality as assessed by decreased sperm capacitation. Thus, we describe spermatogenesis as a new Nf2-dependent process. Additionally, we provide for the first time in vivo evidence for equal tumour suppressor potentials of Merlin isoform 1 and isoform 2.

Textural analysis of pre-therapeutic [18F]-FET-PET and its correlation with tumor grade and patient survival in high-grade gliomas.

Amino acid positron emission tomography (PET) with [18F]-fluoroethyl-L-tyrosine (FET) is well established in the diagnostic work-up of malignant brain tumors. Analysis of FET-PET data using tumor-to-background ratios (TBR) has been shown to be highly valuable for the detection of viable hypermetabolic brain tumor tissue; however, it has not proven equally useful for tumor grading. Recently, textural features in 18-fluorodeoxyglucose-PET have been proposed as a method to quantify the heterogeneity of glucose metabolism in a variety of tumor entities. Herein we evaluate whether textural FET-PET features are of utility for grading and prognostication in patients with high-grade gliomas. One hundred thirteen patients (70men, 43women) with histologically proven high-grade gliomas were included in this retrospective study. All patients received static FET-PET scans prior to first-line therapy. TBR (max and mean), volumetric parameters and textural parameters based on gray-level neighborhood difference matrices were derived from static FET-PET images. Receiver operating characteristic (ROC) and discriminant function analyses were used to assess the value for tumor grading. Kaplan-Meier curves and univariate and multivariate Cox regression were employed for analysis of progression-free and overall survival. All FET-PET textural parameters showed the ability to differentiate between World Health Organization (WHO) grade III and IV tumors (p < 0.001; AUC 0.775). Further improvement in discriminatory power was possible through a combination of texture and metabolic tumor volume, classifying 85% of tumors correctly (AUC 0.830). TBR and volumetric parameters alone were correlated with tumor grade, but showed lower AUC values (0.644 and 0.710, respectively). Furthermore, a correlation of FET-PET texture but not TBR was shown with patient PFS and OS, proving significant in multivariate analysis as well. Volumetric parameters were predictive for OS, but this correlation did not hold in multivariate analysis. Determination of uptake heterogeneity in pre-therapeutic FET-PET using textural features proved valuable for the (sub-)grading of high-grade glioma as well as prediction of tumor progression and patient survival, and showed improved performance compared to standard parameters such as TBR and tumor volume. Our results underscore the importance of intratumoral heterogeneity in the biology of high-grade glial cell tumors and may contribute to individual therapy planning in the future, although they must be confirmed in prospective studies before incorporation into clinical routine.

Biopsy Proven Tumefactive Multiple Sclerosis with Concomitant Glioma: Case Report and Review of the Literature.

We report a case of pathologically confirmed tumefactive multiple sclerosis (MS) followed shortly thereafter by the diagnosis of an oligoastrocytoma. The complexity of diagnosis and management of concomitant presence of tumefactive MS and glial cell tumors is discussed.

Comparing interval and continuous exercise training regimens on neurotrophic factors in rat brain

The research literature suggests that oxidative stress and pro-inflammatory factors influence neurotrophins in vitro. However, there is insufficient information about their effects on exercise training conditions, especially during high intensity trainings. This study aimed to compare the effects of 6weeks of high intensity interval and continuous training regimens on brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), hydrogen peroxide (H2O2), and tumor necrosis factor alpha (TNF-α) in the rat brain. For this purpose, twenty-four Albino Wistar rats were divided into sedentary control (SC), high intensity interval training (HIIT), and continuous training (CT) groups. Both HIIT and CT regimens increased H2O2 level and TNF-α concentration in the brain, and the alterations made were greater following HIIT than CT. In addition, both HIIT and CT regimens increased BDNF and GDNF concentrations significantly, with a higher elevation following HIIT than CT. Furthermore, H2O2 level and TNF-α concentration correlated positively with both BDNF and GDNF concentrations. Generally, high intensity interval training regimen, rather than continuous training regimen, is highly potential to improve BDNF and GDNF through a greater increase in H2O2 and TNF-α as oxidative stress and pro-inflammatory factors.

Effect of cold plasma on glial cell morphology studied by atomic force microscopy.

The atomic force microscope (AFM) is broadly used to study the morphology of cells. The morphological characteristics and differences of the cell membrane between normal human astrocytes and glial tumor cells are not well explored. Following treatment with cold atmospheric plasma, evaluation of the selective effect of plasma on cell viability of tumor cells is poorly understood and requires further evaluation. Using AFM we imaged morphology of glial cells before and after cold atmospheric plasma treatment. To look more closely at the effect of plasma on cell membrane, high resolution imaging was used. We report the differences between normal human astrocytes and human glioblastoma cells by considering the membrane surface details. Our data, obtained for the first time on these cells using atomic force microscopy, argue for an architectural feature on the cell membrane, i.e. brush layers, different in normal human astrocytes as compared to glioblastoma cells. The brush layer disappears from the cell membrane surface of normal E6/E7 cells and is maintained in the glioblastoma U87 cells after plasma treatment.

Diversity of Histologic Patterns and Expression of Cytoskeletal Proteins in Canine Skeletal Osteosarcoma.

Osteosarcoma (OS), the most common bone tumor, includes OS of the head (OSH) and appendicular OS (OSA). In dogs, it is classified into 6 histologic subtypes: osteoblastic, chondroblastic, fibroblastic, telangiectatic, giant cell, and poorly differentiated. This study investigated the significance of the histologic classification relevant to clinical outcome and the histologic and immunohistochemical relationships between pleomorphism and expression of cytoskeletal proteins in 60 cases each of OSH and OSA. Most neoplasms exhibited histologic diversity, and 64% of OS contained multiple subtypes. In addition to the above 6 subtypes, myxoid, round cell, and epithelioid subtypes were observed. Although the epithelioid subtypes were observed in only OSH, no significant difference in the frequency of other subtypes was observed. Also, no significant relevance was observed between the clinical outcome and histologic subtypes. Cytokeratin (CK) was expressed in both epithelioid and sarcomatoid tumor cells in various subtypes, and all CK-positive tumor cells also expressed vimentin. Vimentin and α-smooth muscle actin (SMA) were expressed in all subtypes. A few SMA-positive spindle-shaped tumor cells exhibited desmin expression. Glial fibrillary acidic protein-positive tumor cells were observed in many subtypes, and some of these cells showed neurofilament expression. Although OSH exhibited significantly stronger immunoreactivity for SMA than OSA, no significant difference in other cytoskeletal proteins was observed. Some tumor cells had cytoskeletal protein expression compatible with the corresponding histologic subtypes, such as CK in the epithelioid subtype and SMA in the fibroblastic subtype. Thus, canine skeletal OS is composed of pleomorphic and heterogenous tumor cells as is reflected in the diversity of histologic patterns and expression of cytoskeletal proteins.

Cationic Liposomes Encapsulating Quantum Dots for Enhancing the Intracellular Delivery into Astrocytes “in vitro”

Fluorescent semiconductor nanocrystals called “quantum dots” (QDs) have been synthesized for applications in many areas, such as biomedical sciences as biosensors, disease diagnostics and cell labeling, as well as in electronics and optics. In this work, cadmium telluride (CdTe) QDs functionalized with mercaptosuccinic acid (MSA) was synthesized in aqueous medium by adding a solution of Te2- ions to a solution of cadmium perchlorate and MSA, followed by reflux under argon for 10 h at 95°C. These QDs were characterized by optical spectroscopy, X-ray diffractommetry and transmission electron microscopy (TEM). Cationic liposomes composed of egg phosphatidylcholine (PC) and 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) were prepared by hydrating a lipid film at a lipid ratio of 80:20 respectively. This method consists in drying the lipids and the formation of a film under N2 for 30 min and drying it for 3 h under vacuum to remove residual solvent from the system. The hydration step was performed by adding pure water followed by stirring. The QDs have been synthesized previously encapsulated within these vesicles by the method of freezing and thawing. These vesicles were characterized by Zeta potential, Fluorescence Microscopy and TEM. Primary astrocytes from newborn Wistar rats (Pn 0 - 3, Pn = day of postnatal) were isolated and cultured in Dulbecco's Modified Eagle's Medium supplemented with F −12 (DMEM/F-12) and 10% fetal bovine serum. Upon 80% confluence, the culture medium was removed and fresh serum-free medium was added. Liposomes with and without QDs were tested in these cells with a high unspecific labeling character. The results demonstrate that liposomes present an effective entrapment of these fluorescent probes and are potential candidates for the development of diagnostics of pathologies related to glial tumor cells such as gliomas and glioblastomas.

Glia maturation factor (GMFb) promotes glial and neuronal tumor cell differentiation

Glia maturation factor (GMFb) promotes glial and neuronal tumor cell differentiation

Abstract 3227: JNK2 oligomerization regulates its activation through non-canonical pathways

Abstract C-Jun N-terminal kinases (JNKs) regulate various cellular functions. Their activation is mediated cooperatively by both MKK4 and MKK7. The c-Jun N-terminal kinase 2 (JNK2) isoform is constitutively activated in glial tumor cell lines and human glioblastoma models. We investigated the regulation of JNK2 self-activation in vitro in both cell-free and cell-based experiments. Light scattering analysis suggested that unphosphorylated recombinant JNK2α2 exists in solution as a mixture of monomers, dimers and tetramers. JNK2α2 self-phosphorylates more rapidly in vitro when assayed at low concentration leading to its activation. However, at a slightly higher concentration, the formation of a tetramer is favored, whose ability to self-phosphorylate is suppressed. HEK293T cells that were transfected with varying amounts of pcDNA-JNK2α2 showed that an increased concentration of JNK2α2 (54 kDa) could suppress the appearance of activated JNK2α2 in mammalian cells. A mutant of JNK2 (F170R) thought to stabilize the DFG-out conformation appears to stabilize the formation of a JNK2 tetramer. Taken together our data suggest that oligomerization may regulate non-canonical (self-activation) activation of JNK2. Citation Format: Tamer S. Kaoud, Austin F. Riggs, Kevin N. Dalby. JNK2 oligomerization regulates its activation through non-canonical pathways. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3227. doi:10.1158/1538-7445.AM2014-3227

Primary diffuse leptomeningeal gliomatosis diagnosed on CSF cytology: perseverance pays off

Primary diffuse leptomeningeal gliomatosis is a rare neoplasm defined by the infiltration of the subarachnoid spaces by glial neoplastic cells, without there being a detectable intra-axial glioma. Unlike the meningeal...

EPIGENETICALLY DISTURBED NEURAL STEM/PROGENITOR CELLS IN THE PRE-NEOPLASTIC STAGE OF PDGF-INDUCED MOUSE GLIOMA

BACKGROUND: Platelet-derived growth factors (PDGFs) are produced and secreted by human glioblastoma cells, and the PDGFR-α gene is amplified in a fraction of both low- and high-grade gliomas. Glioma involves interactions between the malignant cells and their microenvironment. We have therefore studied glioma formation in two PDGF-dependent brain tumor models where PDGF is expressed in vivo in astrocytic cells under control of the GFAP-promoter (Hede et al. 2009; Nazarenko et al 2011). PDGF-AL transgenic mice develop a characteristic, lethal phenotype due to highly proliferating oligodendrocyte progenitor cells that spread diffusely throughout the brain. A few of the PDGF-AL mice present with advanced lesions similar to human anaplastic oligoastrocytoma. PDGF-B transgenic mice do not develop brain tumors and are phenotypically normal, but when crossed with p53 null mice, they develop brain tumors at a high rate. The tumors occur between 2-6 months, are similar to human glioblastoma, and consistent with previous findings from human brain tumors Pdgfr-α is localized on glial tumor cells, while Pdgfr-β is on the vasculature. Thus, PDGF-AL and –B differ in their capacity to induce brain tumors. METHODS: Efforts to target the PDGF pathway for treatment of glioma have not been successful. In search for new therapies, we need more knowledge on the early stage of glioma development. Therefore we have used the PDGF-B transgenic mice in crossings with p53null to study the pre-neoplastic stage. Immuno-histochemical stainings and immuno-blot analyses were used to detect changes in histone methylation and the Luminometric Methylation Assay (LUMA) to monitor global DNA methylation in the brain. RESULTS: The hGFAPpPDGFB/Trp53 null (B + p53-/-) mice develop glioblastoma-like brain tumors at a high frequency in adulthood. The present work reveals epigenetic changes in the mouse brain tumors as well as in neural stem/progenitor cells during the histologically normal pre-neoplastic stage of the brain. DNA hypomethylation and elevated Histone3 Lysine9 di-methylation (H3K9Me2) were detected in the tumors. During the pre-neoplastic stage, global DNA hypomethylation was also observed in samples of the adult frontal brain lateral ventricular wall, but could not be observed in whole brain samples. Elevated H3K9Me2 levels were observed in neurosphere cultures from the B + p53-/- pre-neoplastic brain but not in wild type (WT) neurospheres using immuno-blot analysis. The H3K9Me2 level was also higher in brain tumor spheres compared to neurospheres derived from the same mouse. CONCLUSIONS: We propose that epigenetically disturbed neural stem/progenitor cells are the early targets of neoplastic transformation in the brain. SECONDARY CATEGORY: n/a.

The expression of Wnt-inhibitor DKK1 (Dickkopf 1) is determined by intercellular crosstalk and hypoxia in human malignant gliomas.

Wnt signalling pathways regulate proliferation, motility and survival in a variety of human cell types. Dickkopf 1 (DKK1) gene codes for a secreted Wnt inhibitory factor. It functions as tumour suppressor gene in breast cancer and as a pro-apoptotic factor in glioma cells. In this study, we aimed to demonstrate whether the different expression of DKK1 in human glioma-derived cells is dependent on microenvironmental factors like hypoxia and regulated by the intercellular crosstalk with bone-marrow-derived mesenchymal stem cells (bmMSCs). Glioma cell line U87-MG, three cell lines from human glioblastoma grade IV (glioma-derived mesenchymal stem cells) and three bmMSCs were selected for the experiment. The expression of DKK1 in cell lines under normoxic/hypoxic environment or co-culture condition was measured using real-time PCR and enzyme-linked immunoadsorbent assay. The effect of DKK1 on cell migration and proliferation was evaluated by in vitro wound healing assays and sulphorhodamine assays, respectively. Glioma-derived cells U87-MG displayed lower DKK1 expression compared with bmMSCs. Hypoxia led to an overexpression of DKK1 in bmMSCs and U87-MG when compared to normoxic environment, whereas co-culture of U87-MG with bmMSCs induced the expression of DKK1 in both cell lines. Exogenous recombinant DKK1 inhibited cell migration on all cell lines, but did not have a significant effect on cell proliferation of bmMSCs and glioma cell lines. In this study, we showed for the first time that the expression of DKK1 was hypoxia dependent in human malignant glioma cell lines. The induction of DKK1 by intracellular crosstalk or hypoxia stimuli sheds light on the intense adaption of glial tumour cells to environmental alterations.