Key Points• EZH2 mutations occur in more than 25% of follicular lymphoma patients.• Mutations predominantly represent an early/clonal event in the pathogenesis of the disease.Gain of function mutations in the H3K27 methyltransferase EZH2 represent a promising therapeutic target in germinal center lymphomas. In this study, we assessed the frequency and distribution of EZH2 mutations in a large cohort of patients with follicular lymphoma (FL) (n 5 366) and performed a longitudinal analysis of mutation during the disease progression from FL to transformed FL (tFL) (n 5 33). Mutations were detected at 3 recurrent mutation hot spots (Y646, A682, and A692) in 27% of FL cases with variant allele frequencies (VAF) ranging from 2% to 61%. By comparing VAF of EZH2 with other mutation targets (CREBBP, MLL2, TNFRSF14, and MEF2B), we were able to distinguish patients harboring clonal EZH2 mutation from rarer cases with subclonal mutations. Overall, the high incidence of EZH2 mutations in FL and their stability during disease progression makes FL an appropriate disease to evaluate EZH2 targeted therapy. (Blood. 2013; 122(18):3165-3168) Introduction Next-generation sequencing (NGS) studies have shown frequent mutations in epigenetic regulators in almost all cases of follicular lymphoma (FL).1,2 These include EZH2, the catalytic subunit of PRC2, which catalyzes trimethylation of lysine 27 on histone H3 (H3K27me3), a repressive chromatin mark.3 Somatic gain-of-function mutations of EZH2 at codon Y646 (previously Y641) were identified in 7% to 22% of FLs and germinal center B-cell type diffuse large B-cell lymphomas leading to elevated H3K27 trimethylation [4][5][6][7][8] with mutations at codons A682 and A692 described in isolated cases of diffuse large B-cell lymphomas. 2,9-11 As highly selective EZH2 inhibitors have now been developed, [12][13][14] we set out to assess EZH2 mutation status, the effect of mutations on global gene expression, and the clonal representation of EZH2 mutations as the disease progresses. Study design Patient samplesGenomic DNA from 181 diagnostic FL patients with accompanying clinical and gene expression data 15 were obtained through the Lymphoma/Leukemia Molecular Profiling Project consortium. DNA from 185 additional FL patients (56 obtained at diagnosis and 129 at relapse) and 33 paired FL and transformed FL (tFL) samples were sourced from the tissue archive at the Barts Cancer The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked "advertisement" in accordance with 18 USC section 1734.The publisher or recipient acknowledges right of the US government to retain a nonexclusive, royalty-free license in and to any copyright covering the article.BLOOD, 31 OCTOBER 2013 x VOLUME 122, NUMBER 18 3165For personal use only. on May 9, 2018. by guest www.bloodjournal.org From Institute. The study was approved by the London Research Ethical Committee (05/Q0605/140) and was conducted in accordance with the...

The spectrum of the clinical manifestation and the course of folliculotropic mycosis fungoides are broad and differ from classic mycosis fungoides. Folliculotropic neoplastic T-cell proliferation is associated with activation of inflammatory reactive T- and B-lymphoid cells, mesenchymal cells and changes in the hair follicle.

Primary central nervous system lymphomas (PCNSL) are aggressive non-Hodgkin lymphomas affecting the central nervous system (CNS). Although immunophenotyping studies suggested an uniform activated B-cell (ABC) origin, more recently a spectrum of ABC and germinal center B-cell (GC) cases has been proposed, with the molecular subtypes of PCNSL still being a matter of debate. With the emergence of novel therapies demonstrating different efficacy between the ABC and GC patient groups, precise assignment of molecular subtype is becoming indispensable. To determine the molecular subtype of 77 PCNSL and 17 secondary CNS lymphoma patients, we used the NanoString Lymphoma Subtyping Test (LST), a gene expression-based assay representing a more accurate technique of subtyping compared with standard immunohistochemical (IHC) algorithms. Mutational landscapes of 14 target genes were determined using ultra-deep next-generation sequencing. Using the LST-assay, a significantly lower proportion (80% vs 95%) of PCNSL cases displayed ABC phenotype compared with the IHC-based characterization. The most frequently mutated genes included MYD88, PIM1, and KMT2D. In summary, we successfully applied the LST-assay for molecular classification of PCNSL, reporting higher proportion of cases with GC phenotype compared with IHC analyses, leading to a more precise patient stratification potentially applicable in the diagnostic algorithm of PCNSL.

BackgroundBioenergetic characterisation of malignant tissues revealed that different tumour cells can catabolise multiple substrates as salvage pathways, in response to metabolic stress. Altered metabolism in gliomas has received a lot of attention, especially in relation to IDH mutations, and the associated oncometabolite D-2-hydroxyglutarate (2-HG) that impact on metabolism, epigenetics and redox status. Astrocytomas and oligodendrogliomas, collectively called diffuse gliomas, are derived from astrocytes and oligodendrocytes that are in metabolic symbiosis with neurons; astrocytes can catabolise neuron-derived glutamate and gamma-aminobutyric acid (GABA) for supporting and regulating neuronal functions.MethodsMetabolic characteristics of human glioma cell models – including mitochondrial function, glycolytic pathway and energy substrate oxidation – in relation to IDH mutation status and after 2-HG incubation were studied to understand the Janus-faced role of IDH1 mutations in the progression of gliomas/astrocytomas. The metabolic and bioenergetic features were identified in glioma cells using wild-type and genetically engineered IDH1-mutant glioblastoma cell lines by metabolic analyses with Seahorse, protein expression studies and liquid chromatography-mass spectrometry.ResultsU251 glioma cells were characterised by high levels of glutamine, glutamate and GABA oxidation. Succinic semialdehyde dehydrogenase (SSADH) expression was correlated to GABA oxidation. GABA addition to glioma cells increased proliferation rates. Expression of mutated IDH1 and treatment with 2-HG reduced glutamine and GABA oxidation, diminished the pro-proliferative effect of GABA in SSADH expressing cells. SSADH protein overexpression was found in almost all studied human cases with no significant association between SSADH expression and clinicopathological parameters (e.g. IDH mutation).ConclusionsOur findings demonstrate that SSADH expression may participate in the oxidation and/or consumption of GABA in gliomas, furthermore, GABA oxidation capacity may contribute to proliferation and worse prognosis of gliomas. Moreover, IDH mutation and 2-HG production inhibit GABA oxidation in glioma cells. Based on these data, GABA oxidation and SSADH activity could be additional therapeutic targets in gliomas/glioblastomas.Electronic supplementary materialThe online version of this article (10.1186/s13046-018-0946-5) contains supplementary material, which is available to authorized users.

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