Clonal expansion and epigenetic reprogramming following deletion or amplification of mutant .

mutation is the earliest genetic alteration in low-grade gliomas (LGGs), but its role in tumor recurrence is unclear. Mutant IDH1 drives overproduction of the oncometabolite d-2-hydroxyglutarate (2HG) and a CpG island (CGI) hypermethylation phenotype (G-CIMP). To investigate the role of mutant IDH1 at recurrence, we performed a longitudinal analysis of 50 mutant LGGs.

Mutant IDH1 Expression Drives TERT Promoter Reactivation as Part of the Cellular Transformation Process.

Mutations in the isocitrate dehydrogenase gene IDH1 are common in low-grade glioma, where they result in the production of 2-hydroxyglutarate (2HG), disrupted patterns of histone methylation, and gliomagenesis. IDH1 mutations also cosegregate with mutations in the ATRX gene and the TERT promoter, suggesting that IDH mutation may drive the creation or selection of telomere-stabilizing events as part of immortalization/transformation process. To determine whether and how this may occur, we investigated the phenotype of pRb-/p53-deficient human astrocytes engineered with IDH1 wild-type (WT) or R132H-mutant (IDH1) genes as they progressed through their lifespan.

Glioma Groups Based on 1p/19q, IDH, and TERT Promoter Mutations in Tumors.

Background: The prediction of clinical behavior, response to therapy, and outcome of infiltrative glioma is challenging. On the basis of previous studies of tumor biology, we defined five glioma molecular groups with the use of three alterations: mutations in the TERT promoter, mutations in IDH, and codeletion of chromosome arms 1p and 19q (1p/19q codeletion). We tested the hypothesis that within groups based on these features, tumors would have similar clinical variables, acquired somatic alterations, and germline variants.

CDKN2A loss is associated with shortened overall survival in lower-grade (World Health Organization Grades II-III) astrocytomas.

Lower-grade (World Health Organization Grades II and III) gliomas vary widely in clinical behavior and are classified as astrocytic, oligodendroglial, or mixed. Anaplasia depends greatly on mitotic activity, with CDKN2A loss considered as the most common mechanism for cell cycle dysregulation. We investigated whether loss of the CDKN2A gene is associated with overall survival across pathologically and genetically defined glioma subtypes.

The differential diagnosis of pilocytic astrocytoma with atypical features and malignant glioma: an analysis of 16 cases with emphasis on distinguishing molecular features.

Rare pilocytic astrocytomas (PA) have atypical histologic and clinicoradiologic features that raise the differential diagnosis of glioblastoma. Whether ancillary studies can supplement histopathologic examination in placing these cases accurately on the spectrum of WHO Grade I PA to higher-grade glioma is not always clear, partly because these cases are not common. Here, ten PAs with atypical clinicoradiologic and histologic features and six pediatric glioblastoma multiforme (pGBMs) were analyzed for BRAF V600E, IDH1, IDH2, and TP53 mutations.

The alternative lengthening of telomere phenotype is significantly associated with loss of ATRX expression in high-grade pediatric and adult astrocytomas: a multi-institutional study of 214 astrocytomas.

Loss-of-function of alpha thalassemia/mental retardation syndrome X-linked (ATRX) protein leads to a phenotype called alternative lengthening of telomeres (ALT) in some tumors. High-grade astrocytomas comprise a heterogeneous group of central nervous system tumors. We examined a large cohort of adult (91) and pediatric (n=88) high-grade astrocytomas as well as lower grade forms (n=35) for immunohistochemical loss of ATRX protein expression and the presence of ALT using telomere-specific fluorescence in situ hybridization, with further correlation to other known genetic alterations.

PDGFRA amplification is common in pediatric and adult high-grade astrocytomas and identifies a poor prognostic group in IDH1 mutant glioblastoma.

High-grade astrocytomas (HGAs), corresponding to World Health Organization grades III (anaplastic astrocytoma) and IV (glioblastoma; GBM), are biologically aggressive, and their molecular classification is increasingly relevant to clinical management. PDGFRA amplification is common in HGAs, although its prognostic significance remains unclear. Using fluorescence in situ hybridization (FISH), the most sensitive technique for detecting PDGFRA copy number gains, we determined PDGFRA amplification status in 123 pediatric and 263 adult HGAs.

Gene expression profile identifies tyrosine kinase c-Met as a targetable mediator of antiangiogenic therapy resistance.

Purpose: To identify mediators of glioblastoma antiangiogenic therapy resistance and target these mediators in xenografts.

Experimental Design: We conducted microarray analysis comparing bevacizumab-resistant glioblastomas (BRG) with pretreatment tumors from the same patients. We established novel xenograft models of antiangiogenic therapy resistance to target candidate resistance mediator(s).