Type and frequency of IDH1 and IDH2 mutations are related to astrocytic and oligodendroglial differentiation and age: a study of 1,010 diffuse gliomas

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.     

An analysis of 170 glioma patients and systematic review to investigate the association between IDH-1 mutations and preoperative glioma-related epilepsy

Seizure is a common presenting symptom of glioma, and many biomarkers have been suggested to be associated with preoperative seizure; however, the relationships between IDH (isocitrate dehydrogenase) mutations and glioma-related epilepsy only recently been studied. The authors aimed to examine the correlations between IDH mutations in glioma patients with preoperative seizures and tumor location. A series of 170 glioma samples were analyzed for IDH1 R132H mutations (amino acid change from arginine to histidine at codon 132) with immunohistochemistry (IHC) staining and for IDH mutations with direct DNA sequencing when the IHC results were negative. If either the IHC or direct DNA sequencing result was positive, the IDH status was defined as mutated. The results of the IDH mutation examinations were used to analyze the relationship between mutations and glioma-related epilepsy. The study population consisted of 64 (37.6%) World Health Organization (WHO) grade II gliomas, 58 (34.1%) grade III, and 48 (28.3%) grade IV gliomas. A total of 84 samples with IDH1 mutations were observed in our study, and 54 of these presented with seizures as the initial symptoms, whereas 28 of the patients with wild-type IDH status presented with seizures (p = 0.043 for the WHO grade II gliomas, p = 0.002 for the grade III gliomas and p = 0.942 for the grade IV gliomas, chi-squared tests). Among the WHO grade II and III gliomas, IDH1 mutations were significantly associated with preoperative seizures, but no significant relationship between IDH mutations and preoperative seizures was found with glioblastoma multiforme.     

Metabolism of glioma and IDH1/IDH2 mutations

Many known oncogenic signaling pathways involved in gliomagenesis have strong consequences on tumor cell metabolism, and promote the switch from oxidative phosphorylation to aerobic glycolysis, for ATP generation. However, the interest on metabolism has been recently renewed by the discovery of recurrent mutation of IDH1 genes by systematic sequencing of a glioblastoma series. IDH1 encodes the cytoplasmic NADP dependent isocitrate dehydrogenase 1 that catalyzes the oxidative decarboxylation of isocitrate into α-ketoglutarate. IDH1, more rarely IDH2, is mutated in 40% of gliomas (roughly 70% of low-grade gliomas, 50% of grade III, and 5 to 10% of primary glioblastomas). IDH1/IDH2 mutations are associated with genomic profile, being present in nearly all the 1p19q codeleted gliomas, and virtually absent in gliomas with EGFR amplification. It is a strong and independent predictor of survival, whatever grade considered. IDH1/IDH2 mutation results in a new enzymatic activity transforming α-ketoglutarate into 2-hydroxyglutarate (2-HG). The oncometabolite 2-HG accumulates in the cell and acts as a competitive inhibitor of many α-ketoglutarate dependent cellular reactions. The cellular consequences of this mutation offer potential targets for the development of novel therapeutics.     

Anaplastic oligodendroglioma metastasizing to the bone marrow: a unique case report and literature review

Oligodendrogliomas are a rare type of primary brain tumor. They are genetically defined as diffuse gliomas carrying mutation in isocitrate dehydrogenase type 1 (IDH1) or type 2 (IDH2) and codeletion of chromosomes 1p and 19q. The WHO grading system distinguishes two histopathologic grades of ODs: grade II (low-grade) and grade III (anaplastic oligodendroglioma or AO). These tumors rarely metastasize outside of central nervous system with only few cases reported in the literature. Here we present a case of an AO, which metastasized to the bone marrow and other sites within a year of diagnosis despite aggressive treatment measures. Our patient eventually succumbed to his disease, raising many questions about this rare condition, its natural course and optimal management strategy.     

Diffuse glioma – Rare homozygous IDH point mutation,is it an oncogenetic mechanism?

Isocitrate dehydrogenase (IDH1/IDH2) mutations in gliomas of WHO grade II/III and secondary glioblastoma are almost always heterozygous missense mutations. Here, we report an extremely rare case of homozygous IDH1R132H mutation in a recurrent WHO grade III anaplastic astrocytoma. The authors here also review the relevant literature for the possible metabolic impact of homozygous IDH1/2 mutations in the gliomagenesis.     

脑胶质瘤病人血清β2微球蛋白含量的变化

目的 探讨脑胶质瘤病人血清β2微球蛋白（β2-MG）含量的变化。方法 收集2015~2017年手术切除及病理确诊的胶质瘤标本124例，其中WHO Ⅰ级9例，Ⅱ级28例，Ⅲ级34例，Ⅳ级53例。术前2~3 d采取静脉血，通过胶乳免疫比浊法检测血清β2-MG含量；并使用石蜡包埋的胶质瘤组织分别通过毛细管电泳法检测基因异柠檬酸脱氢酶1（IDH1）突变和PCR荧光探针法检测06-甲基鸟嘌呤DNA甲基转移酶（MGMT）基因甲基化状态。结果 WHO Ⅳ级胶质瘤病人血清β2-MG含量显著高于其他级别（WHO Ⅰ~Ⅲ级）胶质瘤（P<0.05）。IDH1突变型胶质瘤病人血清β2-MG含量显著低于野生型病人（P<0.05）。MGMT甲基化胶质瘤病人血清β2-MG含量与非甲基化病人之间无明显差异（P>0.05）。结论 血清β2-MG含量对于WHO Ⅳ级胶质瘤与其他级别件胶质瘤的鉴别以及IDH1突变与野生型的鉴别中可能具有重要的参考意义。     

BRAF alterations are frequent in cerebellar low-grade astrocytomas with diffuse growth pattern

Cerebellar low-grade astrocytomas with a diffuse pattern of growth are uncommon, comprising World Health Organization (WHO) grade II diffuse astrocytomas (DA) and a minority of WHO grade I pilocytic astrocytomas (PA), so-called PA, "diffuse variant." Among 106 cerebellar low-grade astrocytomas (WHO grade I and II) operated on at the Mayo Clinic (1984-2010), we identified 19 such cases: 8 PA, "diffuse variant," 5 DA, and 6 that we were unable to classify further (low-grade astrocytomas, subtype indeterminate). We characterized these tumors using immunohistochemistry and currently available molecular markers (IDH1/2 mutations and BRAF mutation/fusion gene status) and investigated whether the markers could be used to aid the diagnostic process in combination with the clinical and pathologic features. KIAA1549-BRAF fusion was detected in 4 PA, "diffuse variant," 2 DA, and 2 low-grade astrocytomas, subtype indeterminate, indicating that these tumors were molecularly consistent with PA, the most common subtype of the series. A BRAF V600E mutation was detected in 1 PA, "diffuse variant" case; an IDH1 R132G mutation was found in 1 DA case. These results suggest that KIAA1549-BRAF fusion status and IDH1/2 and BRAF V600E mutational analyses may assist in the histologic classification of this diagnostically challenging group of tumors and result in a more accurate and objective combined molecular and histologic classification.     

Expression of mutated isocitrate dehydrogenase-1 in gliomas is associated with p53 and EGFR expression

Gliomas are the most common primary brain tumours. Several independent studies have shown that isocitrate dehydrogenase 1 (IDH1) mutation in diffuse gliomas is associated with a more favourable patient outcome. The aim of this study was to evaluate the prognostic relevance of an antibody specifically detecting the R132H point mutation of IDH1 in tissue sections in a large series of human gliomas. Surgical specimens of 220 consecutive patients with infiltrative low and high-grade gliomas were included in this retrospective study. In multivariate analysis, IDH expression did not reach significance (p = 0.122) in regard to prognosis, in contrast to WHO grade and age at time of surgery (p < 0.001, Cox regression). A significant correlation of p53 expression to mutated IDH1 and histological grading and an inverse correlation to truncated EGFR expression were observed (p < 0.001, Mann-Whitney test). In sum, our results indicate that IDHR132H mutation correlates significantly with p53 and inversely with EGFR mutations. Further studies should investigate whether these correlations reflect involvement of these three molecules in a common signalling pathway.     

Cerebellar high‐grade astrocytoma with IDH mutations in the elderly: A report of two cases

Cerebellar high‐grade gliomas are rare, and likely to affect younger patients compared with those of cerebral origin. Recent genetic analyses have revealed that isocitrate dehydrogenase (IDH) 1/2 mutations are rare in infratentorial gliomas. In this paper, we report two elderly cases of IDH‐mutated cerebellar high‐grade glioma with unusual histological features and uncommon patient ages. One case was an 83‐year‐old man, whose tumor was predominantly composed of densely packed round‐to‐polygonal epithelioid cells. The other was a 75‐year‐old woman's high‐grade astrocytoma characterized by cord‐like structures and the perivascular papillary arrangements with varying amounts of myxoid matrix. The former harbored IDH1 R132H mutation, whereas the latter had IDH2 R172K mutation. According to our literature review, eight cases of IDH‐mutated infratentorial gliomas including the present cases have been reported, and four had mutations other than IDH1 R132H. Moreover, we herein report the first elderly case of IDH2‐mutation. Although the number is limited, IDH‐mutant infratentorial diffuse gliomas may have clinical, histological and genetic features different from supratentorial cases.     

Frequent ATRX mutations and loss of expression in adult diffuse astrocytic tumors carrying IDH1/IDH2 and TP53 mutations

Gliomas are the most common primary brain tumors in children and adults. We recently identified frequent alterations in chromatin remodelling pathways including recurrent mutations in H3F3A and mutations in ATRX (α-thalassemia/mental-retardation-syndrome-X-linked) in pediatric and young adult glioblastoma (GBM, WHO grade IV astrocytoma). H3F3A mutations were specific to pediatric high-grade gliomas and identified in only 3.4?% of adult GBM. Using sequencing and/or immunohistochemical analyses, we investigated ATRX alterations (mutation/loss of expression) and their association with TP53 and IDH1 or IDH2 mutations in 140 adult WHO grade II, III and IV gliomas, 17 pediatric WHO grade II and III astrocytomas and 34 pilocytic astrocytomas. In adults, ATRX aberrations were detected in 33?% of grade II and 46?% of grade III gliomas, as well as in 80?% of secondary and 7?% of primary GBMs. They were absent in the 17 grade II and III astrocytomas in children, and the 34 pilocytic astrocytomas. ATRX alterations closely overlapped with mutations in IDH1/2 (p?<?0.0001) and TP53 (p?<?0.0001) in samples across all WHO grades. They were prevalent in astrocytomas and oligoastrocytomas, but were absent in oligodendrogliomas (p?<?0.0001). No significant association of ATRX mutation/loss of expression and alternative lengthening of telomeres was identified in our cohort. In summary, our data show that ATRX alterations are frequent in adult diffuse gliomas and are specific to astrocytic tumors carrying IDH1/2 and TP53 mutations. Combined alteration of these genes may contribute to drive the neoplastic growth in a major subset of diffuse astrocytomas in adults.     

Combined molecular analysis of BRAF and IDH1 distinguishes pilocytic astrocytoma from diffuse astrocytoma

Separation of pilocytic astrocytoma from diffuse astrocytomas frequently poses problems mostly related to small sample size. Precise classification and grading are essential due to different therapeutic strategies prompted by diagnoses of pilocytic astrocytoma WHO grade I, diffuse astrocytomas WHO grade II or anaplastic astrocytoma WHO grade III. Recently, genomic aberrations with a high specificity for distinct glioma entities have been described. Pilocytic astrocytomas carry a duplication at chromosome band 7q34 containing a BRAF–KIAA1549 gene fusion in the majority of cases. IDH1 mutations are observed very frequently in adult astrocytomas and IDH2 mutations have been reported in some astrocytomas. We examined a series of 120 astrocytomas including 70 pilocytic astrocytomas WHO grade I and 50 diffuse astrocytomas WHO grade II for both, BRAF–KIAA1549 fusion with a newly developed FISH assay and mutations in IDH1 and IDH2 by direct sequencing. Pilocytic astrocytomas contained the BRAF fusion in 49 cases (70%) but neither IDH1 nor IDH2 mutations. Astrocytomas WHO grade II exhibited IDH1 mutations in 38 cases (76%) but neither IDH2 mutations nor BRAF fusions. Thus, combined molecular analysis of BRAF and IDH1 is a sensitive and highly specific approach to separate pilocytic astrocytoma from diffuse astrocytoma.     

Analysis of the IDH1 codon 132 mutation in brain tumors

A recent study reported on mutations in the active site of the isocitrate dehydrogenase (IDH1) gene in 12% of glioblastomas. All mutations detected resulted in an amino acid exchange in position 132. We analyzed the genomic region spanning wild type R132 of IDH1 by direct sequencing in 685 brain tumors including 41 pilocytic astrocytomas, 12 subependymal giant cell astrocytomas, 7 pleomorphic xanthoastrocytomas, 93 diffuse astrocytomas, 120 adult glioblastomas, 14 pediatric glioblastomas, 105 oligodendrogliomas, 83 oligoastrocytomas, 31 ependymomas, 58 medulloblastomas, 9 supratentorial primitive neuroectodermal tumors, 17 schwannomas, 72 meningiomas and 23 pituitary adenomas. A total of 221 somatic IDH1 mutations were detected and the highest frequencies occurred in diffuse astrocytomas (68%), oligodendrogliomas (69%), oligoastrocytomas (78%) and secondary glioblastomas (88%). Primary glioblastomas and other entities were characterized by a low frequency or absence of mutations in amino acid position 132 of IDH1. The very high frequency of IDH1 mutations in WHO grade II astrocytic and oligodendroglial gliomas suggests a role in early tumor development.     

Rapid and sensitive assessment of the IDH1 and IDH2 mutation status in cerebral gliomas based on DNA pyrosequencing

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.     

Isocitrate dehydrogenase mutations: a challenge to traditional views on the genesis and malignant progression of gliomas

Isocitrate dehydrogenases (IDHs) convert isocitrate to α-ketoglutarate by oxidative decarboxylation and are thereby involved in multiple metabolic processes. Mutations in the genes encoding IDH1 and IDH2 were first reported in human gliomas in 2008 and later on also identified in a minority of patients with acute myeloid leukemia. The mutations universally affect codons 132 in IDH1 and 172 in IDH2 and result in decreased enzymatic activity. The oncogenic pathway triggered by IDH mutations may involve the activation of hypoxia-inducible factor pathway as well as the acquisition of a novel (gain of enzymatic) function consuming NADPH and generating α-hydroxyglutarate. Most intriguingly, IDH mutations are observed in ～70-80% of grade II/III gliomas and the majority of secondary glioblastomas, but only 10% of primary glioblastomas, suggesting a different cellular origin of the gliomas, which had previously been viewed as a multistep process of malignant progression. Understanding the oncogenic pathway mediated by mutant IDH might result in the development of novel, tailored pharmacological therapies for human glioma patients.     

IDH2 mutation in gliomas including novel mutation

Glioblastomas (GBMs) are the most aggressive type of primary brain tumors and provide a dismal prognosis. Thus far, several key genes have been identified in GBMs as prognostic and therapeutic targets. Mutations in two isocitrate dehydrogenase (IDH) genes, IDH1 and IDH2, commonly occur in low‐grade gliomas and secondary high‐grade gliomas, but are rare in primary GBMs. These mutations alter the catalytic activity of IDH proteins, promoting gliomagenesis. Gliomas with IDH1 or IDH2 mutation have better outcomes than do gliomas with wild‐type IDH. The hot spots of IDH1 mutations (R132) and IDH2 mutations (R140 and R172) are well known and are considered as a possible biochemical explanation for the differing clinical characteristics of primary and secondary GBMs. We sought to find the incidence of IDH2 mutation and the characteristics of the gliomas with IDH2 mutation. Among 134 gliomas, which were operated in our hospital consecutively, we studied IDH1 and IDH2 mutations by Sanger sequencing and IDH2 mutation was identified in seven cases (5.2%, four oligodendrogliomas and three GBMs). IDH2 mutation was found in 3.3% of GBMs (3/90 cases) and 9.0% (4/44) of grades II to III gliomas. Here, we report the clinicopathological characteristics of the gliomas with IDH2 mutations including two cases of primary GBM carrying a novel missense IDH2 mutation (c. 484C>T, p. P162S).     

Patients with IDH1 wild type anaplastic astrocytomas exhibit worse prognosis than IDH1-mutated glioblastomas, and IDH1 mutation status accounts for the unfavorable prognostic effect of higher age: implications for classification of gliomas

WHO grading of human brain tumors extends beyond a strictly histological grading system by providing a basis predictive for the clinical behavior of the respective neoplasm. For example, patients with glioblastoma WHO grade IV usually show a less favorable clinical course and receive more aggressive first-line treatment than patients with anaplastic astrocytoma WHO grade III. Here we provide evidence that the IDH1 status is more prognostic for overall survival than standard histological criteria that differentiate high-grade astrocytomas. We sequenced the isocitrate dehydrogenase 1 gene (IDH1) at codon 132 in 382 patients with anaplastic astrocytoma and glioblastoma from the NOA-04 trial and from a prospective translational cohort study of the German Glioma Network. Patients with anaplastic astrocytomas carried IDH1 mutations in 60%, and patients with glioblastomas in 7.2%. IDH1 was the most prominent single prognostic factor (RR 2.7; 95% CI 1.6-4.5) followed by age, diagnosis and MGMT. The sequence from more favorable to poorer outcome was (1) anaplastic astrocytoma with IDH1 mutation, (2) glioblastoma with IDH1 mutation, (3) anaplastic astrocytoma without IDH1 mutation and (4) glioblastoma without IDH1 mutation (p < 0.0001). In this combined set of anaplastic astrocytomas and glioblastomas both, IDH1 mutation and IDH1 expression status were of greater prognostic relevance than histological diagnosis according to the current WHO classification system. Our data indicate that much of the prognostic significance of patient age is due to the predominant occurrence of IDH1 mutations in younger patients. Immunohistochemistry using a mutation-specific antibody recognizing the R132H mutation yielded similar results. We propose to complement the current WHO classification and grading of high-grade astrocytic gliomas by the IDH1 mutation status and to use this combined histological and molecular classification in future clinical trials.     

Genetic alterations and biomarkers for glioma

Over the last decade, significant progress has been made in understanding glioma on a molecular level. However, optimal incorporation of molecular markers into clinical care is still controversial. Here, the potential utility of genetic alterations found in gliomas in refining histological diagnosis, prognosis, and predictive values for treatment selection is reviewed. Among all, O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation, 1p/19q codeletion, and isocitrate dehydrogenase 1 (IDH1) mutations have been identified as favorable prognostic markers. MGMT promoter methylation is the only potential predictive marker for response to temozolomide and alkylating agents in glioblastoma (GBM), but it is not of assistance in diagnostics. IDH1 mutations and 1p/19q codeletion are also useful for classifying and grading gliomas, since 1p/19q codeletion is tightly linked to oligodendroglial lineage, and IDH1 mutations are restricted to grade II/III gliomas, while not to primary GBM. BRAF fusion is a good marker for pilocytic astrocytoma. High-throughput profiling techniques for gene expression and epigenetic modification have provided new subtype classifications for GBM as well as lower grade gliomas, which may be of prognostic and predictive values. Efforts to identify molecular markers that predict the benefits of novel molecularly targeted treatments will enable better patient stratification and individualization of treatment.     

Early atypical malignant transformation of diffuse low-grade astrocytoma: The importance of genotyping

Diffuse astrocytoma (WHO grade II) has classically been considered a slow growing tumour, typically affecting young adults, with tendency for late malignant conversion. We describe a case of early atypical malignant transformation of diffuse astrocytoma seventeen months after complete surgical removal, as an intraventricular high-grade glioma (HGG). Retrospective laboratory findings for the presence of IDH 1/2 (isocitrate dehydrogenase) mutations were negative. There is growing evidence that IDH-wildtype (wt) astrocytomas behave more aggressively, therefore identifying IDH-mutation status should be mandatory in order to determine disease prognosis and guide treatment course.     

DMBT1 homozygous deletion in diffuse astrocytomas is associated with unfavorable clinical outcome

Primary glioblastomas develop with a short clinical history, without evidence for less malignant precursor lesions, while secondary glioblastomas slowly develop via progression from diffuse astrocytoma (WHO grade II) or anaplastic astrocytoma (WHO grade III). The time until progression and the clinical outcome of diffuse astrocytomas vary significantly. We have shown that IDH1 mutations reliably distinguish between primary glioblastomas (without IDH1 mutations) and secondary glioblastomas (with IDH1 mutations). The most frequent genetic alteration shared by primary and secondary glioblastomas is loss of heterozygosity at 10q (up to 60% of cases). Here, we first assessed The Cancer Genome Atlas data to identify gene loss at 10q in glioblastomas with or without IDH1 mutations. Using log-ratio thresholds of -1.0, 10 genes were identified; with the log-ratio thresholds of -2.0, only the DMBT1 (deleted in malignant brain tumor 1) gene at 10q26.13 remained as a deleted gene in glioblastomas with or without IDH1 mutations (12.5% vs 8.0%). We then analyzed a total of 404 gliomas by differential polymerase chain reaction and found a DMBT1 homozygous deletion at a similar frequency in primary and secondary glioblastomas (19.6% vs 20.8%). A fraction (11.3%) of diffuse astrocytomas showed a DMBT1 homozygous deletion that was significantly associated with a shorter overall survival (52.8 vs 84.0 months; p = 0.003). These results indicate that a DMBT1 homozygous deletion is present in a fraction of diffuse astrocytomas and that it is associated with an unfavorable clinical outcome.     

lncRNA MIR4435-2HG的表达水平及甲基化状态与脑胶质瘤病理分级的关系

目的 探讨长链非编码RNA MIR4435-2HG的表达水平及甲基化状态与脑胶质瘤病理分级的关系.方法 选取2019年1～12月手术切除的脑胶质瘤组织110例和颅脑损伤内减压术中切除正常脑组织20例(对照组).采用实时荧光定量PCR和甲基化特异性PCR检测组织和血清MIR4435-2HG水平及甲基化状态.结果 110例...