Publications (32)185.24 Total impact
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Article: Hotspot Mutations in H3F3A and IDH1 Define Distinct Epigenetic and Biological Subgroups of Glioblastoma.
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ABSTRACT: Glioblastoma (GBM) is a brain tumor that carries a dismal prognosis and displays considerable heterogeneity. We have recently identified recurrent H3F3A mutations affecting two critical amino acids (K27 and G34) of histone H3.3 in one-third of pediatric GBM. Here, we show that each H3F3A mutation defines an epigenetic subgroup of GBM with a distinct global methylation pattern, and that they are mutually exclusive with IDH1 mutations, which characterize a third mutation-defined subgroup. Three further epigenetic subgroups were enriched for hallmark genetic events of adult GBM and/or established transcriptomic signatures. We also demonstrate that the two H3F3A mutations give rise to GBMs in separate anatomic compartments, with differential regulation of transcription factors OLIG1, OLIG2, and FOXG1, possibly reflecting different cellular origins.Cancer cell 10/2012; 22(4):425-37. · 25.29 Impact Factor -
Article: Unraveling the glioma epigenome: from molecular mechanisms to novel biomarkers and therapeutic targets.
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ABSTRACT: Epigenetic regulation of gene expression by DNA methylation and histone modification is frequently altered in human cancers including gliomas, the most common primary brain tumors. In diffuse astrocytic and oligodendroglial gliomas, epigenetic changes often present as aberrant hypermethylation of 5'-cytosine-guanine (CpG)-rich regulatory sequences in a large variety of genes, a phenomenon referred to as glioma CpG island methylator phenotype (G-CIMP). G-CIMP is particularly common but not restricted to gliomas with isocitrate dehydrogenase 1 (IDH1) or 2 (IDH2) mutation. Recent studies provided a mechanistic link between these genetic mutations and the associated widespread epigenetic modifications. Specifically, 2-hydroxyglutarate, the oncometabolite produced by mutant IDH1 and IDH2 proteins, has been shown to function as a competitive inhibitor of various α-ketoglutarate (α-KG)-dependent dioxygenases, including histone demethylases and members of the ten-eleven-translocation (TET) family of 5-methylcytosine (5mC) hydroxylases. In this review article, we briefly address (i) the basic principles of epigenetic control of gene expression; (ii) the most important methods to analyze focal and global epigenetic alterations in cells and tissues; and (iii) the involvement of epigenetic alterations in the molecular pathogenesis of gliomas. Moreover, we discuss the promising roles of epigenetic alterations as molecular diagnostic markers and novel therapeutic targets, and highlight future perspectives toward unraveling the "glioma epigenome."Brain Pathology 09/2011; 21(6):619-32. · 3.99 Impact Factor -
Article: Molecular signatures classify astrocytic gliomas by IDH1 mutation status.
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ABSTRACT: To identify novel glioma-associated pathomechanisms and molecular markers, we performed an array-based comparative genomic hybridization analysis of 131 diffuse astrocytic gliomas, including 87 primary glioblastomas (pGBIV), 13 secondary glioblastomas (sGBIV), 19 anaplastic astrocytomas (AAIII) and 12 diffuse astrocytomas (AII). All tumors were additionally screened for IDH1 and IDH2 mutations. Expression profiling was performed for 74 tumors (42 pGBIV, 11 sGBIV, 13 AAIII, 8 AII). Unsupervised and supervised bioinformatic analyses revealed distinct genomic and expression profiles separating pGBIV from the other entities. Classifier expression signatures were strongly associated with the IDH1 gene mutation status. Within pGBIV, the rare subtype of IDH1 mutant tumors shared expression profiles with IDH1 mutant sGBIV and was associated with longer overall survival compared with IDH1 wild-type tumors. In patients with IDH1 wild-type pGBIV, PDGFRA gain or amplification as well as 19q gain were associated with patient outcome. Array-CGH analysis additionally revealed homozygous deletions of the FGFR2 gene at 10q26.13 in 2 pGBIV, with reduced FGFR2 mRNA levels being frequent in pGBIV and linked to poor outcome. In conclusion, we report that diffuse astrocytic gliomas can be separated into 2 major molecular groups with distinct genomic and mRNA profiles as well as IDH1 gene mutation status. In addition, our results suggest FGFR2 as a novel glioma-associated candidate tumor suppressor gene on the long arm of chromosome 10.International Journal of Cancer 03/2011; 128(5):1095-103. · 5.44 Impact Factor -
Article: A hypoxic niche regulates glioblastoma stem cells through hypoxia inducible factor 2 alpha.
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ABSTRACT: Glioma growth and progression depend on a specialized subpopulation of tumour cells, termed tumour stem cells. Thus, tumour stem cells represent a critical therapeutic target, but the molecular mechanisms that regulate them are poorly understood. Hypoxia plays a key role in tumour progression and in this study we provide evidence that the hypoxic tumour microenvironment also controls tumour stem cells. We define a detailed molecular signature of tumour stem cell genes, which are overexpressed by tumour cells in vascular and perinecrotic/hypoxic niches. Mechanistically, we show that hypoxia plays a key role in the regulation of the tumour stem cell phenotype through hypoxia-inducible factor 2alpha and subsequent induction of specific tumour stem cell signature genes, including mastermind-like protein 3 (Notch pathway), nuclear factor of activated T cells 2 (calcineurin pathway) and aspartate beta-hydroxylase domain-containing protein 2. Notably, a number of these genes belong to pathways regulating the stem cell phenotype. Consistently, tumour stem cell signature genes are overexpressed in newly formed gliomas and are associated with worse clinical prognosis. We propose that tumour stem cells are maintained within a hypoxic niche, providing a functional link between the well-established role of hypoxia in stem cell and tumour biology. The identification of molecular regulators of tumour stem cells in the hypoxic niche points to specific signalling mechanisms that may be used to target the glioblastoma stem cell population.Brain 04/2010; 133(Pt 4):983-95. · 9.46 Impact Factor -
Article: Rapid and sensitive assessment of the IDH1 and IDH2 mutation status in cerebral gliomas based on DNA pyrosequencing.
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ABSTRACT: Diffusely infiltrating cerebral gliomas frequently carry point mutations in codon 132 of the isocitrate dehydrogenase 1 (IDH1) gene or in codon 172 of the IDH2 gene, which are both clinically important as diagnostic and prognostic markers. Here, we report on a method that allows for the rapid detection of IDH1 and IDH2 mutations based on pyrosequencing. The method is applicable to routinely processed tissue specimens and provides quantitative mutation data within less than one working day. Due to its high sensitivity, the technique may also be used for the diagnostic assessment of IDH1 or IDH2 mutation in tissue samples with low tumor cell content, such as the infiltration zone of diffuse gliomas. Using pyrosequencing and/or conventional cycle sequencing of IDH1 and IDH2 in 262 gliomas, we confirm frequent mutations in diffuse astrocytic and oligodendroglial gliomas, corroborate a prognostic role for IDH1 mutation in primary glioblastomas and show that pleomorphic xanthoastrocytomas generally lack mutations in these genes.Acta Neuropathologica 04/2010; 119(4):501-7. · 9.32 Impact Factor -
Article: Differential proteome analysis of human gliomas stratified for loss of heterozygosity on chromosomal arms 1p and 19q.
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ABSTRACT: Combined deletion of chromosomal arms 1p and 19q is an independent prognostic marker in patients with oligodendroglial brain tumors, including oligodendrogliomas and oligoastrocytomas. However, the relevant genes in these chromosome arms and the molecular mechanisms underlying the prognostic significance of 1p/19q deletion are yet unknown. We used two-dimensional difference gel electrophoresis followed by mass spectrometry to perform a proteome-wide profiling of low-grade oligoastrocytomas stratified for the presence or absence of 1p/19q deletions. Thereby, we identified 22 different proteins showing differential expression in tumors with or without combined deletions of 1p and 19q. Four of the differentially expressed proteins, which are vimentin, villin 2 (ezrin), annexin A1, and glial fibrillary acidic protein, were selected for further analysis. Lower relative expression levels of these proteins in 1p/19q-deleted gliomas were confirmed at the protein level by Western blot analysis and immunohistochemistry. Furthermore, sequencing of sodium bisulfite-treated tumor DNA revealed more frequent methylation of 5'-CpG islands associated with the VIM and VIL2 genes in 1p/19q-deleted gliomas when compared with gliomas without these deletions. In summary, we confirm proteome-wide profiling as a powerful means to identify candidate biomarkers in gliomas. In addition, our data support the hypothesis that 1p/19q-deleted gliomas frequently show epigenetic down-regulation of multiple genes due to aberrant methylation of the 5'-CpG islands.Neuro-Oncology 03/2010; 12(3):243-56. · 5.72 Impact Factor -
Article: Epigenetic downregulation of mitogen-activated protein kinase phosphatase MKP-2 relieves its growth suppressive activity in glioma cells.
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ABSTRACT: Critical tumor suppression pathways in brain tumors have yet to be fully defined. Along with mutational analyses, genome-wide epigenetic investigations may reveal novel suppressor elements. Using differential methylation hybridization, we identified a CpG-rich region of the promoter of the dual-specificity mitogen-activated protein kinase phosphatase-2 gene (DUSP4/MKP-2) that is hypermethylated in gliomas. In 83 astrocytic gliomas and 5 glioma cell lines examined, hypermethylation of the MKP-2 promoter was found to occur relatively more frequently in diffuse or anaplastic astrocytomas and secondary glioblastomas relative to primary glioblastomas. MKP-2 hypermethylation was associated with mutations in TP53 and IDH1, exclusive of EGFR amplification, and with prolonged survival of patients with primary glioblastoma. Expression analysis established that promoter hypermethylation correlated with reduced expression of MKP-2 mRNA and protein. Consistent with a regulatory role, reversing promoter hypermethylation by treating cells with 5-aza-2'-deoxycytidine increased MKP-2 mRNA levels. Furthermore, we found that glioblastoma cell growth was inhibited by overexpression of exogenous MKP-2. Our findings reveal MKP-2 as a common epigenetically silenced gene in glioma, the inactivation of which may play a significant role in glioma development.Cancer Research 02/2010; 70(4):1689-99. · 7.86 Impact Factor -
Article: ECRG4 is a candidate tumor suppressor gene frequently hypermethylated in colorectal carcinoma and glioma.
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ABSTRACT: Cancer cells display widespread changes in DNA methylation that may lead to genetic instability by global hypomethylation and aberrant silencing of tumor suppressor genes by focal hypermethylation. In turn, altered DNA methylation patterns have been used to identify putative tumor suppressor genes. In a methylation screening approach, we identified ECRG4 as a differentially methylated gene. We analyzed different cancer cells for ECRG4 promoter methylation by COBRA and bisulfite sequencing. Gene expression analysis was carried out by semi-quantitative RT-PCR. The ECRG4 coding region was cloned and transfected into colorectal carcinoma cells. Cell growth was assessed by MTT and BrdU assays. ECRG4 localization was analyzed by fluorescence microscopy and Western blotting after transfection of an ECRG4-eGFP fusion gene. We found a high frequency of ECRG4 promoter methylation in various cancer cell lines. Remarkably, aberrant methylation of ECRG4 was also found in primary human tumor tissues, including samples from colorectal carcinoma and from malignant gliomas. ECRG4 hypermethylation associated strongly with transcriptional silencing and its expression could be re-activated in vitro by demethylating treatment with 5-aza-2'-deoxycytidine. Overexpression of ECRG4 in colorectal carcinoma cells led to a significant decrease in cell growth. In transfected cells, ECRG4 protein was detectable within the Golgi secretion machinery as well as in the culture medium. ECRG4 is silenced via promoter hypermethylation in different types of human cancer cells. Its gene product may act as inhibitor of cell proliferation in colorectal carcinoma cells and may play a role as extracellular signaling molecule.BMC Cancer 12/2009; 9:447. · 3.01 Impact Factor -
Article: Hypermethylation and transcriptional downregulation of the TIMP3 gene is associated with allelic loss on 22q12.3 and malignancy in meningiomas.
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ABSTRACT: The gene for the tissue inhibitor of metalloproteinase 3 (TIMP3) on 22q12.3 had been reported to be inactivated by promoter methylation in various types of cancers, with controversial findings in meningiomas. We performed direct sodium bisulfite sequencing in a series of 50 meningiomas, including 27 benign meningiomas [World Health Organization (WHO) grade I], 11 atypical meningiomas (WHO grade II) and 12 anaplastic meningiomas (WHO grade III), and found hypermethylation of TIMP3 in 67% of anaplastic meningiomas, but only 22% of atypical and 17% of benign meningiomas. Moreover, TIMP3 methylation scores were significantly inversely correlated with TIMP3 mRNA expression levels (P = 0.0123), and treatment of the meningioma cell line Ben-Men-1 with demethylating agents induced an increased TIMP3 mRNA expression. TIMP3 is located in the chromosomal band 22q12, the allelic loss of which occurs early in meningioma tumorigenesis and preferentially targets the NF2 tumor suppressor gene. In our tumor panel, all meningiomas with TIMP3 hypermethylation--except for a single case--exhibited allelic losses on 22q12.3. Thus, TIMP3 inactivation by methylation seems fairly exclusive to meningiomas with allelic losses on 22q12 but--in contrast to NF2 mutation--appears to be involved in meningioma progression as it is associated with a more aggressive, high-grade meningioma phenotype.Brain Pathology 10/2009; 20(3):623-31. · 3.99 Impact Factor -
Article: Frequent promoter hypermethylation of Wnt pathway inhibitor genes in malignant astrocytic gliomas.
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ABSTRACT: Aberrant activation of wingless (Wnt) signaling is involved in the pathogenesis of various cancers. Recent studies suggested a role of Wnt signaling in gliomas, the most common primary brain tumors. We investigated 70 gliomas of different malignancy grades for promoter hypermethylation in 8 genes encoding members of the secreted frizzled-related protein (SFRP1, SFRP2, SFRP4, SFRP5), dickkopf (DKK1, DKK3) and naked (NKD1, NKD2) families of Wnt pathway inhibitors. All tumors were additionally analyzed for mutations in exon 3 of the beta-catenin gene (CTNNB1). While none of the tumors carried CTNNB1 mutations, we found frequent promoter hypermethylation of Wnt pathway inhibitor genes, with at least one of these genes being hypermethylated in 6 of 16 diffuse astrocytomas (38%), 4 of 14 anaplastic astrocytomas (29%), 7 of 10 secondary glioblastomas (70%) and 23 of 30 primary glioblastomas (77%). Glioblastomas often demonstrated hypermethylation of 2 or more analyzed genes. Hypermethylation of SFRP1, SFRP2 and NKD2 each occurred in more than 40% of the primary glioblastomas, while DKK1 hypermethylation was found in 50% of secondary glioblastomas. Treatment of SFRP1-, SFRP5-, DKK1-, DKK3-, NKD1- and NKD2-hypermethylated U87-MG glioblastoma cells with 5-aza-2'-deoxycytidine and trichostatin A resulted in increased expression of each gene. Furthermore, SFRP1-hypermethylated gliomas showed significantly lower expression of the respective transcripts when compared with unmethylated tumors. Taken together, our results suggest an important role of epigenetic silencing of Wnt pathway inhibitor genes in astrocytic gliomas, in particular, in glioblastomas, with distinct patterns of hypermethylated genes distinguishing primary from secondary glioblastomas.International Journal of Cancer 10/2009; 126(11):2584-93. · 5.44 Impact Factor -
Chapter: MicroRNA: Biogenesis, Regulation, and Role in Primary Brain Tumors
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ABSTRACT: MicroRNAs (miRNAs) are approximately 22 nucleotides long, endogenous, single-stranded, non-protein-coding RNA molecules that regulate gene expression. To date, more than 600 distinct human miRNAs have been identified. This chapter reviews the current state of the art concerning the genomic organization of miRNA loci, miRNA biogenesis, and the complex mechanisms involved in the miRNA-mediated regulation of gene expression. A particular focus is placed on the techniques that are currently available to assess miRNA expression levels in cells and tissues, as well as the methods used to specifically modulate miRNA expression in vitro and in vivo. In the past few years, it has become increasingly apparent that certain miRNA species are not only involved in the regulation of physiological processes during development, differentiation, aging, and tissue repair, but are also of paramount importance in the pathogenesis of cancer development and progression. Therefore, this chapter also addresses the role of miRNA aberrations in cancer, with a particular focus on recent findings in primary central nervous system tumors, such as gliomas and medulloblastomas, as well as pituitary adenomas. Although the entire field of miRNA-related research is still rather young, further understanding of the role of miRNAs in brain tumor pathogenesis will not only enhance our knowledge on molecular pathomechanisms, but also promises significant advances in brain tumor diagnostics and individually targeted therapy.08/2009: pages 327-354; -
Article: Identification and functional characterization of microRNAs involved in the malignant progression of gliomas.
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ABSTRACT: Diffuse astrocytoma of World Health Organization (WHO) grade II has an inherent tendency to spontaneously progress to anaplastic astrocytoma WHO grade III or secondary glioblastoma WHO grade IV. We explored the role of microRNAs (miRNAs) in glioma progression by investigating the expression profiles of 157 miRNAs in four patients with primary WHO grade II gliomas that spontaneously progressed to WHO grade IV secondary glioblastomas. Thereby, we identified 12 miRNAs (miR-9, miR-15a, miR-16, miR-17, miR-19a, miR-20a, miR-21, miR-25, miR-28, miR-130b, miR-140 and miR-210) showing increased expression, and two miRNAs (miR-184 and miR-328) showing reduced expression upon progression. Validation experiments on independent series of primary low-grade and secondary high-grade astrocytomas confirmed miR-17 and miR-184 as promising candidates, which were selected for functional analyses. These studies revealed miRNA-specific influences on the viability, proliferation, apoptosis and invasive growth properties of A172 and T98G glioma cells in vitro. Using mRNA and protein expression profiling, we identified distinct sets of transcripts and proteins that were differentially expressed after inhibition of miR-17 or overexpression of miR-184 in glioma cells. Taken together, our results support an important role of altered miRNA expression in gliomas, and suggest miR-17 and miR-184 as interesting candidates contributing to glioma progression.Brain Pathology 08/2009; 20(3):539-50. · 3.99 Impact Factor -
Article: Type and frequency of IDH1 and IDH2 mutations are related to astrocytic and oligodendroglial differentiation and age: a study of 1,010 diffuse gliomas.
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ABSTRACT: Somatic mutations in the IDH1 gene encoding cytosolic NADP+-dependent isocitrate dehydrogenase have been shown in the majority of astrocytomas, oligodendrogliomas and oligoastrocytomas of WHO grades II and III. IDH2 encoding mitochondrial NADP+-dependent isocitrate dehydrogenase is also mutated in these tumors, albeit at much lower frequencies. Preliminary data suggest an importance of IDH1 mutation for prognosis showing that patients with anaplastic astrocytomas, oligodendrogliomas and oligoastrocytomas harboring IDH1 mutations seem to fare much better than patients without this mutation in their tumors. To determine mutation types and their frequencies, we examined 1,010 diffuse gliomas. We detected 716 IDH1 mutations and 31 IDH2 mutations. We found 165 IDH1 (72.7%) and 2 IDH2 mutations (0.9%) in 227 diffuse astrocytomas WHO grade II, 146 IDH1 (64.0%) and 2 IDH2 mutations (0.9%) in 228 anaplastic astrocytomas WHO grade III, 105 IDH1 (82.0%) and 6 IDH2 mutations (4.7%) in 128 oligodendrogliomas WHO grade II, 121 IDH1 (69.5%) and 9 IDH2 mutations (5.2%) in 174 anaplastic oligodendrogliomas WHO grade III, 62 IDH1 (81.6%) and 1 IDH2 mutations (1.3%) in 76 oligoastrocytomas WHO grade II and 117 IDH1 (66.1%) and 11 IDH2 mutations (6.2%) in 177 anaplastic oligoastrocytomas WHO grade III. We report on an inverse association of IDH1 and IDH2 mutations in these gliomas and a non-random distribution of the mutation types within the tumor entities. IDH1 mutations of the R132C type are strongly associated with astrocytoma, while IDH2 mutations predominantly occur in oligodendroglial tumors. In addition, patients with anaplastic glioma harboring IDH1 mutations were on average 6 years younger than those without these alterations.Acta Neuropathologica 07/2009; 118(4):469-74. · 9.32 Impact Factor -
Article: Frequent promoter hypermethylation and transcriptional downregulation of the NDRG2 gene at 14q11.2 in primary glioblastoma.
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ABSTRACT: The N-myc downstream-regulated gene 2 (NDRG2) at 14q11.2 has been reported to be downregulated in glioblastoma, and NDRG2 overexpression represses glioblastoma cell proliferation in vitro (Deng et al., Int J Cancer 2003;106;342-7). To further address the role of NDRG2 as a candidate tumor suppressor in human gliomas, we analyzed 67 astrocytic tumors (10 diffuse astrocytomas, 11 anaplastic astrocytomas, 34 primary glioblastomas and 12 secondary glioblastomas) for NDRG2 gene mutation, promoter methylation and expression at the mRNA and protein levels. Using real-time reverse transcription PCR analysis, we found decreased NDRG2 mRNA levels in primary glioblastomas as compared to diffuse and anaplastic astrocytomas. Similarly, immunohistochemistry revealed low or absent NDRG2 protein expression in primary glioblastomas. Mutational analysis of the entire NDRG2 coding sequence did not reveal any tumor-associated DNA sequence alterations. However, sequencing of sodium bisulfite-modified DNA identified hypermethylation of the NDRG2 promoter region in 21 of 34 primary glioblastomas (62%). Moreover, NDRG2 promoter hypermethylation was associated with decreased NDRG2 mRNA expression. In contrast to primary glioblastomas, NDRG2 promoter hypermethylation was detected in only 1 of 11 anaplastic astrocytomas (9%) and was absent in 10 diffuse astrocytomas and 12 secondary glioblastomas. Taken together, our data support NDRG2 as a candidate tumor suppressor gene that is epigenetically silenced in the majority of primary glioblastomas, but not in lower grade astrocytomas and secondary glioblastomas.International Journal of Cancer 12/2008; 123(9):2080-6. · 5.44 Impact Factor -
Article: DNA hypermethylation and aberrant expression of the EMP3 gene at 19q13.3 in Human Gliomas.
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ABSTRACT: Allelic losses on 19q are found in the majority of oligodendroglial tumors and approximately one-third of diffuse astrocytomas. However, the tumor suppressor genes (TSG) on 19q are still elusive. Using cDNA microarray expression profiling, EMP3 at 19q13.3 was among those genes showing the most pronounced expression differences. In line with this, other authors reported EMP3 as being epigenetically silenced in neuroblastomas and astrocytomas. To further investigate EMP3 as a TSG candidate on 19q13.3, we performed molecular analysis of this gene in 162 human gliomas. Mutation analysis did not reveal EMP3 alteration in 132 gliomas. In oligodendroglial tumors, we found that aberrant methylation in the 5'-region of EMP3 was significantly associated with reduced mRNA expression and LOH 19q. In astrocytomas, EMP3 hypermethylation was also paralleled by reduced expression but was independent of the 19q status. EMP3 hypermethylation was detected in more than 80% of diffuse, anaplastic astrocytomas and secondary glioblastomas. Primary glioblastomas, however, mostly lacked EMP3 hypermethylation and frequently overexpressed EMP3. Our data corroborate that oligodendroglial and astrocytic gliomas often show EMP3 hypermethylation and aberrant expression. Furthermore, our findings suggest that primary and secondary glioblastomas are not only characterized by distinct genetic profiles but also differ in their epigenetic aberrations.Brain Pathology 11/2007; 17(4):363-70. · 3.99 Impact Factor -
Article: Identification of novel genes associated with astrocytoma progression using suppression subtractive hybridization and real-time reverse transcription-polymerase chain reaction.
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ABSTRACT: To identify novel genes involved in glioma progression we performed suppression subtractive hybridization combined with cDNA array analysis on 4 patients with primary low-grade gliomas of World Health Organization (WHO) grade II that recurred as secondary glioblastomas (WHO grade IV). Eight genes showing differential expression between primary and recurrent tumors in 3 of the 4 patients were selected for further analysis using real-time reverse transcription-PCR on a series of 10 pairs of primary low-grade and recurrent high-grade gliomas as well as 42 astrocytic gliomas of different WHO grades. These analyses revealed that 5 genes, i.e., AMOG (ATP1B2, 17p13.1), APOD (3q26.2-qter), DMXL1 (5q23.1) DRR1 (TU3A, 3p14.2) and PSD3 (KIAA09428/HCA67/EFA6R, 8p22), were expressed at significantly lower levels in secondary glioblastomas as compared to diffuse astrocytomas of WHO grade II. In addition, AMOG, DRR1 and PSD3 transcript levels were significantly lower in primary glioblastomas than in diffuse astrocytomas. Treatment of glioma cell lines with 5-aza-2'-deoxycytidine and trichostatin A resulted in increased expression of AMOG and APOD transcripts. Sequencing of sodium bisulfite-modified DNA demonstrated AMOG promoter hypermethylation in the glioma cell lines and 1 primary anaplastic astrocytoma with low AMOG expression. Taken together, we identified interesting novel candidate genes that likely contribute to glioma progression and provide first evidence for a role of epigenetic silencing of AMOG in malignant glioma cells.International Journal of Cancer 12/2006; 119(10):2330-8. · 5.44 Impact Factor -
Article: Chordoid Glioma of the Third Ventricle: Immunohistochemical and Molecular Genetic Characterization of a Novel Tumor Entity
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ABSTRACT: Chordoid glioma of the third ventricle was recently reported as a novel tumor entity of the central nervous system with characteristic clinical and histopathological features (Brat et al., J Neuropathol Exp Neurol 57: 283–290, 1998). Here, we report on a histopathological, immunohistochemical and molecular genetic analysis of five cases of this rare neoplasm. All tumors were immunohistochemically investigated for the expression of various differentiation antigens, the proliferation marker Ki-67, and a panel of selected proto-oncogene and tumor suppressor gene products. These studies revealed a strong expression of GFAP, vimentin, and CD34. In addition, most tumors contained small fractions of neoplastic cells immunoreactive for epithelial membrane antigen, S-100 protein, or cytokeratins. The percentage of Ki-67 positive cells was generally low (< 5%). All tumors showed immunoreactivity for the epidermal growth factor receptor and schwan-nomin/merlin. There was no nuclear accumulation of the p53, p21 (Waf-1) and Mdm2 proteins. To examine genomic alterations associated with the development of chordoid gliomas, we screened 4 tumors by comparative genomic hybridization (CGH) analysis. No chromosomal imbalances were detected. More focussed molecular genetic analyses revealed neither aberrations of the TP53 and CDKN2A tumor suppressor genes nor amplification of the EGFR, CDK4, and M DM2 proto-oncogenes. Our data strongly support the hypothesis that chordoid glioma of the third ventricle constitutes a novel tumor entity characterized by distinct morphological and immunohistochemical features, as well as a lack of chromosomal and genetic alterations commonly found in other types of gliomas or in meningiomas.Brain Pathology 04/2006; 9(4):617 - 626. · 3.99 Impact Factor -
Article: Hedgehog signaling in normal urothelial cells and in urothelial carcinoma cell lines.
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ABSTRACT: Constitutive activation of hedgehog signaling, often caused by PTCH1 inactivation and leading to inappropriate activation of GLI target genes, is crucial for the development of several human tumors including basal cell carcinoma of the skin and medulloblastoma. The PTCH1 gene at 9q22 is also considered as a candidate tumor suppressor in transitional cell carcinoma (TCC), of which >50% show LOH in this region. However, only rare mutations have been found in PTCH1. We have therefore investigated GLI-dependent promoter activity and expression of hedgehog pathway components in TCC cell lines and proliferating normal urothelial cells. Normal urothelial cells cultured in serum-free medium, but not TCC lines exhibited low, but significant promoter activity under standard growth conditions. Accordingly, GLI1-3 and PTCH1 mRNAs were expressed at moderate levels, and sonic hedgehog (SHH) mRNA expression was low to undetectable. In co-transfection experiments GLI1 increased promoter activity significantly in one TCC line and further in normal urothelial cells, but less strongly in other TCC lines. Expression patterns of GLI factor mRNAs did not correlate with inducibility. No significant effects of SHH or cyclopamine on proliferation were observed, ruling out autocrine effects. However, SHH induced GLI-dependent promoter activity in normal urothelial cells. Taken together, our data suggest that the hedgehog pathway is weakly active in normal adult urothelial cells and of limited importance in TCC.Journal of Cellular Physiology 05/2005; 203(2):372-7. · 3.87 Impact Factor -
Article: Frequent promoter hypermethylation and low expression of the MGMT gene in oligodendroglial tumors.
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ABSTRACT: Allelic losses on the chromosome arms 1p and 19q have been associated with favorable response to chemotherapy and good prognosis in anaplastic oligodendroglioma patients, but the molecular mechanisms responsible for this relationship are as yet unknown. The DNA repair enzyme O(6)-methylguanine DNA methyltransferase (MGMT) may cause resistance to DNA-alkylating drugs commonly used in the treatment of anaplastic oligodendrogliomas and other malignant gliomas. We report on the analysis of 52 oligodendroglial tumors for MGMT promoter methylation, as well as mRNA and protein expression. Using sequencing of sodium bisulfite-modified DNA, we determined the methylation status of 25 CpG sites within the MGMT promoter. In 46 of 52 tumors (88%), we detected MGMT promoter hypermethylation as defined by methylation of more than 50% of the sequenced CpG sites. Real-time reverse transcription-PCR showed reduced MGMT mRNA levels relative to non-neoplastic brain tissue in the majority of tumors with hypermethylation. Similarly, immunohistochemical analysis showed either no or only small fractions of MGMT positive tumor cells. MGMT promoter hypermethylation was significantly more frequent and the percentage of methylated CpG sites in the investigated MGMT promoter fragment was significantly higher in tumors with loss of heterozygosity on chromosome arms 1p and 19q as compared to tumors without allelic losses on these chromosomes arms. Taken together, our data suggest that MGMT hypermethylation and low or absent expression are frequent in oligodendroglial tumors and likely contribute to the chemosensitivity of these tumors.International Journal of Cancer 02/2005; 113(3):379-85. · 5.44 Impact Factor -
Article: Absence of mutations in the putative tumor suppressor gene KLF6 in glioblastomas and meningiomas.
International Journal of Cancer 10/2004; 111(4):644-5. · 5.44 Impact Factor
Top co-authors
Top Journals
Institutions
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1997–2011
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Heinrich-Heine-Universität Düsseldorf
- • Institut für Neuropathologie
- • Hautklinik
Düsseldorf, North Rhine-Westphalia, Germany
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2009
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Max-Planck-Institut für molekulare Physiologie
Dortmund, North Rhine-Westphalia, Germany
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2001–2006
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Rheinische Friedrich-Wilhelms-Universität Bonn
- Department of Neurobiology
Bonn, North Rhine-Westphalia, Germany
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