The hypermethylation of the O6-methylguanine-DNA methyltransferase gene promoter in gliomas--correlation with array comparative genome hybridization results and IDH1 mutation

The use of molecular markers in the diagnostics of gliomas aids histopathological diagnosis and allows their further classification into clinically significant subgroups. The aim of this study was to characterize the methylation pattern of the O(6) -methylguanine-DNA methyltransferase (MGMT) promoter, gene copy number aberrations, and isocitrate dehydrogenase I (IDH1) mutation in gliomas. We studied 51 gliomas (15 oligodendrogliomas, 18 oligoastrocytomas, 3 astrocytomas, and 15 glioblastomas) by pyrosequencing, array comparative genome hybridization (CGH), and immunohistochemistry. MGMT hypermethylation was observed in 100% of oligoastrocytomas, 93% of oligodendrogliomas, and 47% of glioblastomas. The most frequently altered chromosomal regions were deletions of 1p31.1/21.1-22.2 and 19q13.3qter in oligodendroglial tumors, and losses of 9p21.3, 10q25.3qter, and 10q26.13-26.2 in glioblastomas. Deletions on 9p and 10q, and gain of 7p were associated with the unmethylated MGMT phenotype, whereas deletion of 19q and oligodendroglial morphology was associated with MGMT hypermethylation. IDH1 mutation showed positive correlation with MGMT hypermethylation and loss of 1p/19q. Our results suggest that MGMT promoter methylation, analyzed by pyrosequencing, is a frequent event in oligodendroglial tumors, and it correlates with IDH1 mutation and 19q loss in gliomas. Pyrosequencing proved a good method for assessing the degree of MGMT methylation in formalin-fixed paraffin-embedded glioma samples. However, further studies are needed to confirm a clinically relevant cut-off point for MGMT methylation in gliomas.     

IDH mutations in older patients with diffuse astrocytic gliomas

In 2016, the World Health Organization recommended that isocitrate dehydrogenase (IDH) mutation status be included in the classification of diffuse astrocytic gliomas. IDH mutations are part of the current definition of oligodendrogliomas and are predictive of a better outcome in diffuse astrocytic gliomas. A few studies, examining the role of routine IDH testing in older patients, came to differing conclusions and made differing recommendations regarding a routine IDH testing algorithm with respect to patient age. The purpose of this study was to examine IDH mutations in a series of diffuse astrocytic gliomas [N = 381; 53 diffuse astrocytomas (WHO grade II), 66 anaplastic astrocytomas (WHO grade III) and 262 glioblastomas (WHO grade IV)], paying particular attention to age of patient and any relationship between age and IDH status. IDH status was evaluated by immunohistochemistry with IDH-1 (R132H) antibody and if negative staining was noted, followup polymerase chain reaction (PCR) testing assessing for IDH-1 and IDH-2 mutations was performed. Overall, IDH mutations were discovered in 50.1% of grade II tumors, 54.4% of grade III tumors and 15.1% of grade IV tumors. Of tumors studied, 224 tumors (58.8%) arose in patients 55 years or older. Higher rates of IDH mutations were observed in the patient group less than 55 years of age versus those 55 years or older. By PCR testing in patients 55 years or older, non IDH-1 (R132H) mutations were noted in 0/4 grade II tumors, 3/11 grade III tumors and 26/37 grade IV tumors. The results of this study suggest that although IDH mutations in diffuse astrocytic gliomas are more frequently encountered in patients less than 55 years of age, a significant subset of older patients have mutations that would not be discovered on routine immunohistochemistry and therefore, followup PCR testing is recommended for all patients whose tumors are negative by immunohistochemistry.     

Caveolin-1 expression in diffuse gliomas: correlation with the proliferation index, epidermal growth factor receptor, p53, and 1p/19q status

Caveolin-1 (cav-1) has been proposed as an immunohistochemical marker able to distinguish astroglial from oligodendroglial tumors. In addition, it has been suggested that the reduction of caveolin-1 expression in glioblastoma cells increases their proliferative and invasive potential. Accordingly, the present study investigates caveolin-1 immunoexpression and correlation with the 1p/19q status, histologic grade, proliferation index, epidermal growth factor receptor, and p53 expression in a series of 73 diffuse gliomas. A membranous and cytoplasmic immunolabeling for caveolin-1 was detected in neoplastic cells of 60% of cases. No significant differences in terms of caveolin-1 expression were observed between astrocytomas, oligodendrogliomas, and oligoastrocytomas. In addition, caveolin-1 expression was not correlated with 1p/19q status in oligodendrogliomas and mixed oligoastrocytomas. Caveolin-1 was expressed in most high-grade (World Health Organization III and IV) gliomas. Low caveolin-1 expression correlated with a higher Ki-67 labeling index and the absence of p53 overexpression in glioblastomas, and it was significantly associated with epidermal growth factor receptor overexpression in anaplastic astrocytomas. In conclusion, the present study indicates that caveolin-1 is not useful as diagnostic marker to differentiate grade II astrocytomas from oligodendrogliomas.     

100例中枢神经系统肿瘤的胶质纤维酸性蛋白免疫组化观察

对100例中枢神经系统肿瘤进行GFAP免疫组化观察。结果表明,GFAP主要分布于各种类型的星形细胞瘤,多形性胶质母细胞瘤,混合性胶质瘤及部分室管膜瘤。GFAP染色强度与瘤细胞分化程度有关。本文还探讨了室管膜瘤与少突胶质瘤存在GFAP问题。研究表明GFAP可作为诊断神经胶质瘤的一种有用标记物。     

DNA hypermethylation and aberrant expression of the EMP3 gene at 19q13.3 in Human Gliomas

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.     

Nestin expression in neuroepithelial tumors

Nestin is a marker of early stages of neurocytogenesis. It has been studied in 50 neuroepithelial tumors, mostly gliomas of different malignancy grades, by immunohistochemistry, immunofluorescence, immunoblotting, and confocal microscopy and compared with GFAP and Vimentin. As an early marker of differentiation, Nestin is almost not expressed in diffuse astrocytomas, variably expressed in anaplastic astrocytomas and strongly and irregularly expressed in glioblastomas. Negative in oligodendrogliomas, it stains ependymomas and shows a gradient of expression in pilocytic astrocytomas. In glioblastomas, Nestin distribution does not completely correspond to that of GFAP and Vimentin with which its expression varies in tumor cells in a complementary way, as confirmed by confocal microscopy. Tumor cells can thus either derive from or differentiate toward the neurocytogenetic stages. Hypothetically, they could be put in relation with radial glia where during embriogenesis the three antigens are successively expressed. Completely negative cells of invasive or recurrent glioblastomas may represent malignant selected clones after accumulation of mutations or early stem cells not expressing antigens.     

Galectin-3 as an immunohistochemical tool to distinguish pilocytic astrocytomas from diffuse astrocytomas, and glioblastomas from anaplastic oligodendrogliomas

The distinction of astrocytomas and oligodendrogliomas, mainly pilocytic astrocytomas (PILOs) from infiltrating astrocytomas and oligodendrogliomas (ODs), and high-grade oligodendrogliomas from glioblastomas (GBMs), poses a serious clinical problem. There is no useful immunohistochemical (IHC) marker to differentiate these gliomas, and sometimes the differential diagnosis between them is arbitrary. We identified galectin-3 (Gal-3) as a possible tool to differentiate them based on gene expression profiles of GBMs. We confirmed the differential expression in 45 surgical samples (thirteen GBMs; seven PILOs; 5 grade II ODs; 5 anaplastic oligodendrogliomas [AODs], including 2 Oligo-astrocytomas; 8 diffuse astrocytomas [ASTs], and 7 non-neoplastic samples) by quantification of Gal-3 gene expression by real-time quantitative PCR (rt-PCR). Higher expression of Gal-3 was observed in GBMs and PILOs than in OD, AODs and ASTs. The IHC expression of Gal-3 was evaluated in 90 specimens (fifteen PlLOs, fourteen ASTs, 10 anaplastic astrocytomas, fifteen GBMs, eleven ODs, fifteen AODs, and 10 dysembryoplastic neuroepithelial tumors). The mean labeling score for Gal-3 determined according to the percentage of labeled cells in the tumor bulk was significantly different in GBMs versus AODs and in PILOs versus ASTs. Hence, Gal-3 is differentially expressed in central nervous system tumors, making IHC detection of Gal-3 a useful tool in distinguishing between these gliomas.     

MET Gain in Diffuse Astrocytomas is Associated with Poorer Outcome

Glioblastoma may develop rapidly without evidence for precursor lesions (primary glioblastomas), or progress from diffuse or anaplastic astrocytomas (secondary glioblastomas). Despite having distinct genetic profiles, these glioblastoma subtypes have similar histological features. We hypothesized that the highly malignant phenotype of glioblastoma may be attributable to genetic alterations that are common to both glioblastoma subtypes. In the present study, we first searched for commonly (>35%) amplified genes in glioblastomas with IDH1 mutation (a hallmark of secondary glioblastoma) and those without IDH1 mutation (typical for primary glioblastoma) in data from The Cancer Genome Atlas (TCGA). A total of 25 genes were identified, of which 21 were located at 7q31‐34. We then screened 264 gliomas (70 glioblastomas, 112 diffuse astrocytomas, 82 oligodendrogliomas) for gain of the MET at 7q31.2 with quantitative polymerase chain reaction (PCR). MET gain was detected in primary glioblastomas (47%) and secondary glioblastomas (44%), suggesting that this genetic alteration plays a role in the pathogenesis of both glioblastoma subtypes. MET gain was also common in diffuse astrocytomas (38%), but less frequent in oligodendrogliomas (16%). MET gain in diffuse astrocytomas was associated with shorter survival (median, 43.0 vs. 70.7 months; P = 0.004), suggesting that MET gain is a useful prognostic marker for diffuse astrocytomas.     

IDH1R132H在中枢神经系统胶质瘤中的表达及其鉴别诊断意义

目的 探讨异柠檬酸盐脱氢酶1基因(isocitrate dehydrogenase 1 gene,IDH1)突变的表达产物IDH1R132H在人中枢神经系统胶质瘤中的表达及其在鉴别诊断中的意义.方法 应用免疫组织化学EnVision法检测不同级别胶质瘤75例(包括WHOⅡ级33例,Ⅲ级20例和Ⅳ级22例)与各种原因造成的胶质增生性脑组织中IDH1R132H的表达情况,并与p53的表达情况进行比较分析.结果 IDH1R132H在WHOⅡ级、Ⅲ级和Ⅳ级胶质瘤的表达阳性率分别为57.6%(19/33)、40.0%(8/20)和27.3%(6/22),差异有统计学意义(P=0.024).IDH1R132H的具体表达部位在胶质瘤细胞的胞质、突起以及部分细胞核.除肿瘤主体部分密集增生的肿瘤细胞呈阳性表达以外,包括皮质和白质在内的肿瘤周边区域单个或散在的肿瘤细胞也呈强阳性表达.IDH1R132H阳性病例有额叶受累为主的倾向.胶质增生组织、毛细胞型星形细胞瘤均为阴性表达.另外,p53在WHOⅡ级、Ⅲ级和Ⅳ级胶质瘤的表达阳性率分别为42.4%(14/33)、65.0%(13/20)和77.3%(17/22).IDH1R132H的表达与p53的表达之间没有明确的相关性(P=0.766).结论 IDH1R132H在各级别胶质瘤中均有表达,且随着肿瘤级别的增高呈表达下降趋势.IDH1R132H可以作为鉴别低级别胶质瘤和胶质增生性病变的一个有用的分子标志物.

Abstract：

Objective To investigate the immunohistochemical expression of isocitrate dehydrogenase 1 gene ( IDH1 ) R132H in glioma and its diagnostic utility. Methods Immunohistochemical study of IDH1R132H expression was performed on formalin-fixed paraffin-embedded tissue samples of 75 gliomas, including 33 cases of grade Ⅱ , 20 cases of grade Ⅲ and 22 cases of grade Ⅳ tumors. Six cases of pilocytic astrocytoma and 12 cases of gliosis were used as controls. Results Nineteen in 33 cases of grade Ⅱ (57.6%), 8 in 20 cases of grade Ⅲ (40. 0% ), 6 in 22 cases of grade Ⅳ (27. 3% ) showed positive cytoplasmic staining of IDH1R132H. Scattered invasive glioma cells at the tumor periphery also expressed IDH1R132H. Gliomas involving the frontal lobe showed more strong IDH1R132H staining. In contrast, none of the pilocytic astrocytomas and gliosis showed IDH1R132H staining. Moreover, the rate of p53 immunopositivities were 42. 4% ( 14/33 ) in grade Ⅱ , 65.0% (13/20) in grade Ⅲ and 77.3% (17/22) in grade Ⅳ gliomas. There were no statistic correlations between expression of IDH1R132H and p53.Conclusion IDH1R132H tends to express preferentially in low-grade gliomas, and it thus may serve as a valuable marker in distinguishing low grade gliomas from gliosis.     

Nogo-A: a useful marker for the diagnosis of oligodendroglioma and for identifying 1p19q codeletion

The differential diagnosis between oligodendrogliomas and other gliomas remains a critical issue. The aim of this study is to verify the diagnostic value of Olig-2, Nogo-A, and synaptophysin and their role in identifying 1p19q codeletion. A total of 168 cases of brain tumors were studied: 24 oligodendrogliomas, 23 anaplastic oligodendrogliomas, 2 oligoastrocytomas, 2 anaplastic oligoastrocytomas, 30 glioblastoma multiforme, 2 diffuse astrocytomas, 4 anaplastic astrocytomas, 10 pilocytic astrocytomas, 9 ependymomas, 12 anaplastic ependymomas, 10 central neurocytomas, 10 meningiomas, 10 choroid plexus papillomas, 10 dysembryoplastic neuroepithelial tumors, and 10 metastases. All cases were immunostained with Olig-2, Nogo-A, and synaptophysin. In 79 cases, the status of 1p/19q had already been assessed by fluorescence in situ hybridization. Thus, in selected cases, fluorescence in situ hybridization was repeated in areas with numerous Nogo-A-positive neoplastic cells. Nogo-A was positive in 18 (75%) of 24 oligodendrogliomas, 8 (80%) of 10 dysembryoplastic neuroepithelial tumors, 6 (20%) of 30 glioblastoma multiforme, and 2 (20%) of 10 pilocytic astrocytomas. Olig-2 stained 22 (91.6%) of 24 oligodendrogliomas and all dysembryoplastic neuroepithelial tumors but also 24 (80%) of 30 glioblastoma multiforme and 8 (80%) of 10 pilocytic astrocytomas. Finally, synaptophysin stained 13 (54.1%) of 24 oligodendrogliomas, 3 (10%) of 30 glioblastoma multiforme, 1 (10%) of 10 pilocytic astrocytomas, and all neurocytomas. Among the 79 tested cases, original fluorescence in situ hybridization showed 1p/19q codeletion in 12 (52.2%) of 23 oligodendrogliomas, 8 (38%) of 21 anaplastic oligodendrogliomas, and 1 (4%) of 25 glioblastoma multiforme. However, after carrying out the Nogo-A-driven fluorescence in situ hybridization, 1p/19q codeletion was observed in 8 additional cases. Nogo-A is more useful and specific than Olig-2 in differentiating oligodendrogliomas from other gliomas. Furthermore, using a Nogo-A-driven fluorescence in situ hybridization analysis, it is possible to identify a larger number of 1p19q codeletions in gliomas.     

Chromosome abnormalities in low-grade central nervous system tumors.

Ependymomas, oligodendrogliomas, and low-grade astrocytomas are slow-growing central nervous system (CNS) tumors that occur in both adults and children, whereas craniopharyngiomas and choroid plexus papillomas occur predominantly in children. We examined karyotypes of 32 of these low-grade tumors, including ten oligodendrogliomas, six ependymomas, 11 low-grade astrocytomas, four craniopharyngiomas, and one choroid plexus papilloma. Only normal karyotypes were obtained from 6 oligodendrogliomas. The rest had normal stemlines; three tumors had 45,X,-Y sidelines and one tumor had a sideline of monosomy 22. The most frequent abnormalities in the ependymomas were +7 (three tumors), -21 (two tumors), -22 (two tumors), and del(9)(p22) (two tumors). Gains of chromosome 7 and deletions of 9p were found more often in high-grade gliomas. Seven low-grade astrocytomas had normal stemlines, two had chromosome 7 abnormalities, a pilocystic astrocytoma had +der(15), and one tumor had a -Y sideline. The four craniopharyngiomas and one choroid plexus tumor were all apparently normal. The cytogenetics of low-grade CNS tumors differ from higher grade gliomas in that most low-grade tumors show little deviation from the normal karyotype.     

Ezrin immunoreactivity is associated with increasing malignancy of astrocytic tumors but is absent in oligodendrogliomas

The actin-binding protein ezrin has been associated with motility and invasive behavior of malignant cells. To assess the presence of this protein in human glial cells of the brain and its potential role in benign and malignant glial tumors, we studied ezrin immunoreactivity (IR), proliferation (MIB-1-IR), and apoptosis (terminal dUTP nick-end labeling) in normal human brain tissues from 10 autopsies and tissues from 115 cases of human glial tumors including astro-cytomas, ependymomas, oligodendrogliomas, and glioblastomas. We found weak staining of peripheral processes in normal human brain astrocytes and in World Health Organization grade II benign astrocytomas. Staining was markedly increased in anaplastic astrocytomas (World Health Organization grade III) and clearly strongest in glioblastomas (World Health Organization grade IV). The increase of ezrin-IR correlated significantly with increasing malignancy of astrocytic tumors (P < 0.0001). Statistical analysis revealed a stronger association with increasing malignancy for ezrin-IR than for MIB-1-IR or terminal dUTP nick-end labeling staining. Ezrin-IR was absent in normal oligodendrocytes and in oligodendrogliomas, but pronounced in normal ependymal cells and ependymomas. Ezrin-IR seems to be specific for astrocytes and ependymal glia in the normal brain. Our results indicate that ezrin-IR may provide a useful tool for the distinction of oligodendrogliomas and astrocytomas and for the grading of astrocytic tumors.     

Karyotypes in 90 human gliomas.

Cytogenetic studies were performed on 90 human gliomas including 26 astrocytomas, 12 oligodendrogliomas, three oligo-astrocytomas, seven ependymomas, eight pilocytic astrocytomas, and 33 malignant gliomas (anaplastic astrocytomas and glioblastomas). The most common abnormalities were trisomy 7 in 23 cases, monosomy 22 in 15 cases, losses of the Y chromosome in 19 of 50 male cases, and losses of the X chromosome in 10 of 39 female cases. There are evident differences between the particular subgroups of gliomas. Monosomy 10 and double minutes are typical for malignant gliomas. The 58 determined chromosomal breakpoints were located on 45 different sites. Chromosomes 1, 9, 6, 3, 10, and 17 were predominantly involved.     

Molecular Markers of Gliomas

Gliomas are invasive recurrent brain tumors with high lethality. Gliomas have been morphologically divided into astrocytomas, oligodendrogliomas, and mixed oligoastrocytomas. Gliomas are graded according to the criteria of the World Health Organization criteria as grade I (pilocytic astrocytomas), grade II (low-grade gliomas), grade III (high-grade gliomas), and grade IV (glioblastoma). The mutations of IDH1/2 and TP53 genes and MGMT methylation have been described as prognostic markers of glioma. The aim of the present review is to analyze research and experimental results (Scopus, Web of Science, Pubmed) concerning somatic mutations, aberrant regulation of gene expression of signal pathways, diagnostic and prognostic markers of glioma progression and characterizing various morphological types and grades of glioma. In particular, the specificities of medulloblastomas and ependymomas have been considered in the present review.     

Cytokeratin immunoreactivity in gliomas

Monoclonal antibodies (AE1/3, CAM 5.2 and PKK-1) and polyclonal antisera against the cytokeratin proteins were reacted with a range of astrocytic tumours, oligodendrogliomas and ependymomas. Seven of 12 cases (58%) of glioblastoma multiforme, five of eight (63%) anaplastic astrocytomas and two of five (40%) well-differentiated astrocytomas were immunoreactive with AE1/3 but not with the other anti-cytokeratin antibodies. In oligodendrogliomas, AE1/3 stained isolated astrocyte-like cells as well as scattered neoplastic oligodendrocytes in four of eight cases (50%) cases. Four ependymomas were negative for all cytokeratin markers examined. The immunostaining of astrocytomas and oligodendrogliomas with AE1/3 might represent co-expression of cytokeratin with glial fibrillary acidic protein by gliomas and calls for caution in the use of these antibodies in the differential diagnosis between gliomas and carcinomas.     

IDH1 Mutations in Diffusely Infiltrating Astrocytomas: Grade Specificity, Association With Protein Expression, and Clinical Relevance

IDH1 mutations are frequent genetic alterations in low-grade diffuse gliomas and secondary glioblastoma (GBM). To validate mutation frequency, IDH1 gene at codon 132 was sequenced in 74 diffusely infiltrating astrocytomas: diffuse astrocytoma (DA; World Health Organization [WHO] grade II), anaplastic astrocytoma (AA; WHO grade III), and GBM (WHO grade IV). All cases were immunostained with IDH1-R132H monoclonal antibody. Mutational status was correlated with mutant protein expression, patient age, duration of symptoms, and prognosis of patients with GBM. We detected 31 (41.9%) heterozygous IDH1 mutations resulting in arginine-to-histidine substitution (R132H;CGT-CAT). All 12 DAs (100%), 13 of 14 AAs (92.9%), and 6 of 48 GBMs (12.5%) (5/6 [83.3%] secondary, and 1/42 [2.4%] primary) harbored IDH1 mutations. The correlation between mutational status and protein expression was significant (P < . 001). IDH1 mutation status, though not associated with prognosis of patients with GBM, showed significant association with younger age and longer duration of symptoms in the whole cohort (P < .001). Our study validates IDH1 mutant protein expression across various grades of astrocytoma, and demonstrates a high incidence of IDH1 mutations in DA, AA, and secondary GBM.     

Expression of matrix metalloproteinases and their inhibitors in human brain tumors

Sixty human brain tumors, classified according to the New World Health Organization (WHO) classification including, grade I schwannomas, meningiomas and pilocytic astrocytomas, grade II astrocytomas, grade III anaplastic astrocytomas, grade IV glioblastomas, grade III anaplastic oligodendrogliomas and grade IV glioblastomas and lung and melanoma metastases were analyzed for the expression of three matrix metalloproteinases (MMPs), two tissue inhibitors of MMPs (TIMPs) and for MMP activity. Some correlation was found between MMP expression and the degree of malignancy. Western blotting analysis revealed a more uniform pattern of distribution of MMP-2 (gelatinase A) than of MMP-9 (gelatinase B) and MMP-12 (metalloelastase) among tumors. MMP-9 levels were found to be significantly higher in grade III anaplastic astrocytomas and anaplastic oligodendrogliomas than those in grade I schwannomas and meningiomas. Anaplastic astrocytomas and Grade IV glioblastomas expressed significantly higher levels MMP-12 than grade I meningiomas. All sixty tumors showed a similar pattern of activity in zymography, proMMP-9 being the major species detected. Interestingly, TIMP-1 and TIMP-2 expression levels were especially low in tumors of grade II and grade III but significantly higher in tumors of grade I, particularly in schwannomas. Taken together, these data suggest that: 1) a balance between MMPs and TIMPs has an important role to play in human brain tumors; 2) TIMP expression may be valuable markers for tumor malignancy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Segregation of non‐p.R132H mutations in IDH1 in distinct molecular subtypes of glioma

Mutations in the gene encoding the isocitrate dehydrogenase 1 gene (IDH1) occur at a high frequency (up to 80%) in many different subtypes of glioma. In this study, we have screened for IDH1 mutations in a cohort of 496 gliomas. IDH1 mutations were most frequently observed in low grade gliomas with c.395G>A (p.R132H) representing >90% of all IDH1 mutations. Interestingly, non‐p.R132H mutations segregate in distinct histological and molecular subtypes of glioma. Histologically, they occur sporadically in classic oligodendrogliomas and at significantly higher frequency in other grade II and III gliomas. Genetically, non‐p.R132H mutations occur in tumors with TP53 mutation, are virtually absent in tumors with loss of heterozygosity on 1p and 19q and accumulate in distinct (gene‐expression profiling based) intrinsic molecular subtypes. The IDH1 mutation type does not affect patient survival. Our results were validated on an independent sample cohort, indicating that the IDH1 mutation spectrum may aid glioma subtype classification. Functional differences between p.R132H and non‐p.R132H mutated IDH1 may explain the segregation in distinct glioma subtypes. © 2010 Wiley‐Liss, Inc.     

Expression of Matrix Metalloproteinases and Their Tissue Inhibitors in Human Brain Tumors

In this study, we investigated the expression patterns of 15 matrix metalloproteinases (MMPs) and three tissue inhibitors of metalloproteinase in gliomas, medulloblastomas, and normal brain tissue. By Northern blot analysis we found increased levels of mRNAs encoding for gelatinase A, gelatinase B, two membrane-type MMPs (mt1- and mt2-MMP), and tissue inhibitors of metalloproteinase-1 in glioblastomas and medulloblastomas. We observed a significant increase of mt1-MMP, gelatinase A, gelatinase B, and tissue inhibitors of metalloproteinase-1 in glioblastomas as compared with low-grade astrocytomas, anaplastic astrocytomas, and normal brain. In medulloblastomas, the expression of mt1-MMP, mt2-MMP, and gelatinase A were also increased, but to a lesser extent than that observed in glioblastomas. These data were confirmed at the protein level by immunostaining analysis. Moreover, substrate gel electrophoresis showed that the activated forms of gelatinases A and B were present in glioblastomas and medulloblastomas. These results suggest that increased expression of mt1-MMP/gelatinase A is closely related to the malignant progression observed in gliomas. Furthermore, the present study demonstrates, to our knowledge for the first time, that medulloblastomas express high levels of MMP.