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 miRNAspecific 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.

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Current classification of gliomas is based on histological criteria according to the World Health Organization (WHO) classification of tumors of the central nervous system. Over the past years, characteristic genetic profiles have been identified in various glioma types. These can refine tumor diagnostics and provide important prognostic and predictive information. We report on the establishment and validation of gene panel next generation sequencing (NGS) for the molecular diagnostics of gliomas. We designed a glioma-tailored gene panel covering 660 amplicons derived from 20 genes frequently aberrant in different glioma types. Sensitivity and specificity of glioma gene panel NGS for detection of DNA sequence variants and copy number changes were validated by single gene analyses. NGS-based mutation detection was optimized for application on formalin-fixed paraffin-embedded tissue specimens including small stereotactic biopsy samples. NGS data obtained in a retrospective analysis of 121 gliomas allowed for their molecular classification into distinct biological groups, including (i) isocitrate dehydrogenase gene (IDH) 1 or 2 mutant astrocytic gliomas with frequent α-thalassemia/mental retardation syndrome X-linked (ATRX) and tumor protein p53 (TP53) gene mutations, (ii) IDH mutant oligodendroglial tumors with 1p/19q codeletion, telomerase reverse transcriptase (TERT) promoter mutation and frequent Drosophila homolog of capicua (CIC) gene mutation, as well as (iii) IDH wildtype glioblastomas with frequent TERT promoter mutation, phosphatase and tensin homolog (PTEN) mutation and/or epidermal growth factor receptor (EGFR) amplification. Oligoastrocytic gliomas were genetically assigned to either of these groups. Our findings implicate gene panel NGS as a promising diagnostic technique that may facilitate integrated histological and molecular glioma classification.

We summarize the relevant changes in the revised WHO classification of gliomas, outline the integrated approach, and discuss its practical implications and potential challenges.

Due to comprehensive social distancing measures related to the COVID-19 pandemic, medical faculties worldwide have made a virtue of necessity in resorting to online teaching. Medical faculties grapple with how to convey clinical competencies to students in this context. There is a need for research not only to map but also to explain the effect of these secondary measures on students' learning and mental wellbeing. During a period of ongoing comprehensive social distancing measures in Germany, we translated a competency-based curriculum including obstetrics, paediatrics, and human genetics to an e-learning course based on online patient and teacher encounters. In our qualitative study on students' and teachers' views, we identify potential enablers and drivers as well as barriers and challenges to undergraduate medical education under lockdown. In summer 2020, we conducted six focus group interviews to investigate medical students' and teachers' perspectives, experiences and attitudes. All focus groups were videotaped, transcribed verbatim and coded. To guide our deductive and inductive analysis, we applied the theoretical framework of Regmi and Jones. Content analysis was performed in a multi-perspective group. We identified five major themes contributing to a successful use of clinical competency-based e-learning under lockdown: Communication (with teachers, students, and patients), Mental wellbeing, Structure and self-organization, Technical issues, and Learning and commitment. We discuss enablers and potential barriers within all themes and their overlap and link them in an explanatory model. In our setting, students and teachers find e-learning holds strong potential and especially in times of COVID-19 it is greatly appreciated. We broaden the understanding of the impact of distant learning on acquiring competencies, on attitudes, and on mental wellbeing. Our model may serve for a thoughtful, necessary transition to future e-learning and hybrid programs for a competency-based medical education with ongoing social distancing measures.

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."

Aims Aberrant expression of microRNAs (miRNAs) is frequent in various cancers including gliomas. We aimed to characterize the role of miR‐16‐5p as a candidate tumour suppressor miRNA in gliomas. Methods Real‐time PCR‐based approaches were used for miRNA and mRNA expression profiling of glioma and non‐neoplastic brain tissues as well as glioma cell lines. Protein levels were determined by Western blotting. In vitro analyses were performed following overexpression of miR‐16‐5p, trichostatin A (TSA) treatment, and siRNA‐mediated knock‐down of HDAC3 in glioma cells. Effects of miR‐16‐5p on glioma cell viability, apoptosis and response to irradiation and temozolomide (TMZ) were assessed. Results Expression of miR‐16‐5p was reduced relative to control brain tissue in isocitrate dehydrogenase (IDH)‐mutant astrocytomas of World Health Organization (WHO) grades II, III and IV, and a subset of IDH‐wildtype glioblastomas WHO grade IV. MiR‐16‐5p expression was lower in IDH‐mutant than in IDH‐wildtype gliomas, and down‐regulated in IDH‐wildtype glioma lines. MiR‐16‐5p overexpression reduced expression of important cell cycle and apoptosis regulators in glioma cells, including CDK6, CDC25A, CCND3, CCNE1, WEE1, CHEK1, BCL2 and MCL1. In line, CDK6, WEE1, CHEK1, BCL2 and MCL1 transcript levels were increased in WHO grade III or IV gliomas. TSA treatment and HDAC3 knockdown in glioma cells induced miR‐16‐5p up‐regulation and reduced expression of its targets. Moreover, miR‐16‐5p overexpression inhibited proliferation and induced apoptosis in various glioma cell lines and increased sensitivity of A172 glioma cells to irradiation and TMZ. Conclusion Reduced expression of miR‐16‐5p contributes to glioma cell proliferation, survival and resistance to cytotoxic therapy.

Deletions of chromosome arm 10q are found in most glioblastomas and subsets of lower grade gliomas. Mutations in the PTEN gene at 10q23.3 are restricted to less than half of the 10q-deleted gliomas, suggesting additional glioma-associated tumor suppressors on 10q. We investigated 64 astrocytic gliomas of different malignancy grades for aberrant expression of 16 microRNAs (miRNAs) on 10q. Thereby, we identified four miRNAs (miR-107, miR-146b-5p, miR-346, miR-1287-5p) whose expression was frequently down-regulated in anaplastic astrocytomas and/or glioblastomas. DNA methylation analyses revealed 5'-CpG site hypermethylation of miR-346 in more than two-thirds of primary glioblastomas, while aberrant 5'-CpG site methylation of miR-146b-5p was frequent in IDH1-mutant astrocytomas and secondary glioblastomas. Overexpression of either of the four miRNAs in glioma cell lines reduced cell proliferation and/or increased caspase-3/7 activity. Expression analyses of miRNA overexpressing glioma cells and 3'-untranslated region luciferase reporter gene assays revealed evidence that these miRNAs post-transcriptionally regulate expression of glioma-relevant genes, including CDK6 (miR-107), EGFR (miR-146b-5p, miR-1287-5p), TERT and SEMA6A (miR-346), all of which are overexpressed in malignant gliomas in situ. In summary, we show that the 10q-located miRNAs miR-107, miR-146b-5p, miR-346 and miR-1287-5p are frequently down-regulated in malignant gliomas and thereby may support overexpression of important glioma growth-promoting genes.