Defining activities in neurovascular microsurgery training: entrustable professional activities for vascular neurosurgery.

BACKGROUND: Entrustable professional activities (EPAs) represent an assessment framework with an increased focus on competency-based assessment. Originally developed and adopted for undergraduate medical education, concerns over resident ability to practice effectively after graduation have led to its implementation in residency training but yet not in vascular neurosurgery. Subjective assessment of resident or fellow performance can be problematic, and thus, we aim to define core EPAs for neurosurgical vascular training. METHODS: We used a nominal group technique in a multistep interaction between a team of experienced neurovascular specialists and a medical educator to identify relevant EPAs. Panel members provided feedback on the EPAs until they reached consent. RESULTS: The process produced seven core procedural EPAs for vascular residency and fellowship training, non-complex aneurysm surgery, complex aneurysm surgery, bypass surgery, arteriovenous malformation resection, spinal dural fistula surgery, perioperative management, and clinical decision-making. CONCLUSION: These seven EPAs for vascular neurosurgical training may support and guide the neurosurgical society in the development and implementation of EPAs as an evaluation tool and incorporate entrustment decisions in their training programs.

Primary cilia contribute to the aggressiveness of atypical teratoid/rhabdoid tumors.

Atypical teratoid/rhabdoid tumor (AT/RT) is a highly malignant brain tumor in infants that is characterized by loss of nuclear expression of SMARCB1 or SMARCA4 proteins. Recent studies show that AT/RTs comprise three molecular subgroups, namely AT/RT-TYR, AT/RT-MYC and AT/RT-SHH. The subgroups show distinct expression patterns of genes involved in ciliogenesis, however, little is known about the functional roles of primary cilia in the biology of AT/RT. Here, we show that primary cilia are present across all AT/RT subgroups with specific enrichment in AT/RT-TYR patient samples. Furthermore, we demonstrate that primary ciliogenesis contributes to AT/RT biology in vitro and in vivo. Specifically, we observed a significant decrease in proliferation and clonogenicity following disruption of primary ciliogenesis in AT/RT cell line models. Additionally, apoptosis was significantly increased via the induction of STAT1 and DR5 signaling, as detected by proteogenomic profiling. In a Drosophila model of SMARCB1 deficiency, concomitant knockdown of several cilia-associated genes resulted in a substantial shift of the lethal phenotype with more than 20% of flies reaching adulthood. We also found significantly extended survival in an orthotopic xenograft mouse model of AT/RT upon disruption of primary ciliogenesis. Taken together, our findings indicate that primary ciliogenesis or its downstream signaling contributes to the aggressiveness of AT/RT and, therefore, may constitute a novel therapeutic target.

Virtual auscultation course via video chat in times of COVID-19 improves cardiac auscultation skills compared to literature self-study in third-year medical students: a prospective randomized controlled cross-over study.

Background: Cardiac auscultation is a core clinical skill taught in medical school. Due to contact restrictions during the SARS-CoV-2 pandemic, interaction with patients was very limited. Therefore, a peer-to-peer virtual case-based auscultation course via video conference was established. Methods: A randomized controlled cross-over study was conducted to evaluate whether participation in a virtual auscultation course could improve heart auscultation skills in 3rd-year medical students. A total of sixty medical students were randomly assigned to either the experimental or control group after informed consent was obtained. Due to no-shows, 55 students participated. Depending on allocation, students attended three ninety-minute courses in intervals of one week in a different order: a virtual case-based auscultation course held via video chat, literature self-study, and an on-site course using a high-fidelity auscultation simulator (SAM II). The study's primary endpoint was the performance of the two groups at the simulator after participating in the virtual auscultation course or literature self-study. To evaluate their auscultation skills, students participated in five assessments using the same six pathologies: stenosis and regurgitation of the aortic and mitral valve, ventricular septal defect, and patent ductus arteriosus. Moreover, participants rated their satisfaction with each course and provided a self-assessment of competence. Results: Compared to literature self-study, participation in the virtual auscultation course led to a significantly improved description of heart murmurs at the auscultation simulator with regard to the presence in systole and diastole, low- and high-pitched sounds, and volume dynamics. There was no significant difference between the groups in diagnostic accuracy and identification of the point of maximal intensity. After the virtual course, students showed higher satisfaction rates and a higher increase in self-assessed competence compared to participants who engaged in literature self-study. Conclusions: For the first time, this study demonstrates that a case-based virtual auscultation course can improve aspects of cardiac auscultation skills on a simulator. This may facilitate the further acquisition of an essential clinical skill, even when contact restrictions will be lifted.

Droplet digital PCR-based analyses for robust, rapid, and sensitive molecular diagnostics of gliomas.

Classification of gliomas involves the combination of histological features with molecular biomarkers to establish an integrated histomolecular diagnosis. Here, we report on the application and validation of a set of molecular assays for glioma diagnostics based on digital PCR technology using the QX200™ Droplet Digital™ PCR (ddPCR) system. The investigated ddPCR-based assays enable the detection of diagnostically relevant glioma-associated mutations in the IDH1, IDH2, H3-3A, BRAF, and PRKCA genes, as well as in the TERT promoter. In addition, ddPCR-based assays assessing diagnostically relevant copy number alterations were studied, including 1p/19q codeletion, gain of chromosome 7 and loss of chromosome 10 (+ 7/-10), EGFR amplification, duplication of the BRAF locus, and CDKN2A homozygous deletion. Results obtained by ddPCR were validated by other methods, including immunohistochemistry, Sanger sequencing, pyrosequencing, microsatellite analyses for loss of heterozygosity, as well as real-time PCR- or microarray-based copy number assays. Particular strengths of the ddPCR approach are (1) its high analytical sensitivity allowing for reliable detection of mutations even with low mutant allele frequencies, (2) its quantitative determination of mutant allele frequencies and copy number changes, and (3) its rapid generation of results within a single day. Thus, in line with other recent studies our findings support ddPCR analysis as a valuable approach for molecular glioma diagnostics in a fast, quantitative and highly sensitive manner.

Intratumoral heterogeneity of MYC drives medulloblastoma metastasis and angiogenesis.

BACKGROUND: Intratumoral heterogeneity is crucially involved in metastasis, resistance to therapy, and cancer relapse. Amplifications of the proto-oncogene MYC display notable heterogeneity at the single-cell level and are associated with a particularly dismal prognosis in high-risk medulloblastomas (MBs). The aim of this study was to establish the relevance of interclonal cross-talk between MYC-driven and non-MYC-driven MB cells. METHODS: We used fluorescence in situ hybridization, single-cell transcriptomics, and immunohistochemistry, in vitro isogenic cell models, non-targeted proteomics, mass spectrometry-based metabolite quantification, HUVECs tube formation assay, and orthotopic in vivo experiments to investigate interclonal cross-talk in MB. RESULTS: We found that the release of lactate dehydrogenase A (LDHA) from MYC-driven cells facilitates metastatic seeding and outgrowth, while secretion of dickkopf WNT signaling pathway inhibitor 3 from non-MYC-driven cells promotes tumor angiogenesis. This tumor-supporting interaction between both subclones was abrogated by targeting the secretome through pharmacological and genetic inhibition of LDHA, which significantly suppressed tumor cell migration. CONCLUSION: Our study reveals the functional relevance of clonal diversity and highlights the therapeutic potential of targeting the secretome to interrupt interclonal communication and progression in high-risk MB.

Undergraduate medical education amid COVID-19: a qualitative analysis of enablers and barriers to acquiring competencies in distant learning using focus groups.

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.

Proposed definition of competencies for surgical neuro-oncology training.

OBJECTIVE: The aim of this work is to define competencies and entrustable professional activities (EPAs) to be imparted within the framework of surgical neuro-oncological residency and fellowship training as well as the education of medical students. Improved and specific training in surgical neuro-oncology promotes neuro-oncological expertise, quality of surgical neuro-oncological treatment and may also contribute to further development of neuro-oncological techniques and treatment protocols. Specific curricula for a surgical neuro-oncologic education have not yet been established. METHODS: We used a consensus-building approach to propose skills, competencies and EPAs to be imparted within the framework of surgical neuro-oncological training. We developed competencies and EPAs suitable for training in surgical neuro-oncology. RESULT: In total, 70 competencies and 8 EPAs for training in surgical neuro-oncology were proposed. EPAs were defined for the management of the deteriorating patient, the management of patients with the diagnosis of a brain tumour, tumour-based resections, function-based surgical resections of brain tumours, the postoperative management of patients, the collaboration as a member of an interdisciplinary and/or -professional team and finally for the care of palliative and dying patients and their families. CONCLUSIONS AND RELEVANCE: The present work should subsequently initiate a discussion about the proposed competencies and EPAs and, together with the following discussion, contribute to the creation of new training concepts in surgical neuro-oncology.

Age-stratified clinical performance and survival of patients with IDH-wildtype glioblastoma homogeneously treated by radiotherapy with concomitant and maintenance temozolomide.

OBJECTIVE: Isocitrate dehydrogenase (IDH)-wildtype glioblastomas are the most malignant glial tumours. Median survival is only 14-16 months after diagnosis, with patients aged ≥ 65 years reportedly showing worse outcome. This study aimed to further evaluate the prognostic role of age in a homogenously treated patient cohort. METHODS: The study includes 132 IDH-wildtype glioblastoma patients treated between 2013 and 2017 with open resection followed by radiotherapy with concomitant and maintenance temozolomide. Patients were dichotomized into a non-elderly (< 65 years) and an elderly (≥ 65 years) group. Extent of resection and the O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status were determined for each tumour. Clinical and radiological follow-up data were obtained at 6 weeks after the end of radiation therapy and thereafter in 3-month intervals. Progression-free survival (PFS) and overall survival (OS) were evaluated in univariate and multivariate cox regression analyses. RESULTS: The elderly group consisted of 58 patients (median age: 70.5 years) and the non-elderly group of 74 patients (median age: 55 years). Median pre- and postoperative operative Karnofsky Performance Scale (KPS), Eastern Cooperative Oncology Group (ECOG) score and National Institutes of Stroke Scale (NIHSS) were not significantly different between the groups, but KPS and ECOG scores became significantly worse in the elderly group at 6 weeks after termination of radiation therapy. Neither PFS nor OS differed significantly between the age groups. Patients with MGMT promoter-methylated tumours survived longer. CONCLUSION: Elderly patients in good pre- and postoperative clinical conditions may show similar outcome as younger patients when treated according to standard of care. However, elderly patients may suffer more frequently from clinical deterioration following chemoradiotherapy. In both age groups, MGMT promoter methylation was linked to longer PFS and OS.

Virtual auscultation course for medical students via video chat in times of COVID-19.

Introduction: Auscultation skills are among the basic techniques to be learned in medical school. Such skills are achieved through supervised examination of patients often supported by simulator-based learning. The emergence of COVID-19 has disrupted and continues to hinder hands-on on-site medical training on a global scale. Project description: An effective virtual auscultation course was established in times of contact restrictions due to COVID-19 at the Medical Faculty of the Heinrich Heine University Düsseldorf. The interactive case-based webinar was designed to improve listening techniques, description and interpretation of auscultation findings in an off-site context. Clinical cases with pre-recorded auscultation sounds and additional case-based diagnostics were presented. The course focused on common heart murmurs including aortic and mitral valve stenosis and regurgitation as well as congenital heart defects (ventricular septal defect and patent ductus arteriosus). Results: The course was well received by the students and assessed as being useful and instructive. Assessment of learning effects, such as detection of pathological findings before and after training, is ongoing as part of a subsequent trial. Conclusion: Virtual interactive learning using a sound simulation lesson with clinical case presentations via video chat can well be used as a supplement to practical auscultation training. This learning format could also play a useful role in the curriculum of medical studies once contact restrictions are revoked.

Epidermal Growth Factor Receptor Variant III (EGFRvIII) Positivity in EGFR-Amplified Glioblastomas: Prognostic Role and Comparison between Primary and Recurrent Tumors.

Purpose: Approximately 40% of all glioblastomas have amplified the EGFR gene, and about half of these tumors express the EGFRvIII variant. The prognostic role of EGFRvIII in EGFR-amplified glioblastoma patients and changes in EGFRvIII expression in recurrent versus primary glioblastomas remain controversial, but such data are highly relevant for EGFRvIII-targeted therapies.Experimental Design:EGFR-amplified glioblastomas from 106 patients were assessed for EGFRvIII positivity. Changes in EGFR amplification and EGFRvIII status from primary to recurrent glioblastomas were evaluated in 40 patients with EGFR-amplified tumors and 33 patients with EGFR-nonamplified tumors. EGFR single-nucleotide variants (SNV) were assessed in 27 patients. Data were correlated with outcome and validated in 150 glioblastoma patients from The Cancer Genome Atlas (TCGA) consortium.Results: Sixty of 106 EGFR-amplified glioblastomas were EGFRvIII-positive (56.6%). EGFRvIII positivity was not associated with different progression-free or overall survival. EGFRvIII status was unchanged at recurrence in 35 of 40 patients with EGFR-amplified primary tumors (87.5%). Four patients lost and one patient gained EGFRvIII positivity at recurrence. None of 33 EGFR-nonamplified glioblastomas acquired EGFR amplification or EGFRvIII at recurrence. EGFR SNVs were frequent in EGFR-amplified tumors, but were not linked to survival.Conclusions: EGFRvIII and EGFR SNVs are not prognostic in EGFR-amplified glioblastoma patients. EGFR amplification is retained in recurrent glioblastomas. Most EGFRvIII-positive glioblastomas maintain EGFRvIII positivity at recurrence. However, EGFRvIII expression may change in a subset of patients at recurrence, thus repeated biopsy with reassessment of EGFRvIII status is recommended for patients with recurrent glioblastoma to receive EGFRvIII-targeting agents. Clin Cancer Res; 23(22); 6846-55. ©2017 AACR.

Bericht aus der Praxis/Practice Report: How to successfully establish PAL in medical education. 10 tips to succeed in PAL-based courses in undergraduate medical education (UGME).

This article aims to provide useful suggestions for the implementation of new courses with peer-assisted learning (PAL) in undergraduate medical education (UGME). It presents 10 key tips for needs assessment, clarification of goals and objectives for internal marketing, the choice of teaching formats, fund raising, recruiting of educators, qualification of peer tutors, the fun factor, how to establish a structured and longitudinal curriculum, assessment methods and motivation, collecting feedback and the use of its results. These 10 tips are linked to scientific evidence in the educational literature and elucidated by specific examples, based upon a major PAL project on diagnostic imaging, which can be transferred to other teaching topics as well. In conclusion, the described tips represent a helpful tool to avoid common pitfalls in the planning, implementation, evaluation and quality-assurance of PAL-based educational projects.

Molecular Diagnostics of Gliomas Using Next Generation Sequencing of a Glioma-Tailored Gene Panel.

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.

Practical implications of integrated glioma classification according to the World Health Organization classification of tumors of the central nervous system 2016.

PURPOSE OF REVIEW: Morphological features identifiable by light microscopy have been the basis of brain tumor diagnostics for many decades. The revised WHO classification of tumors of the central nervous system 2016 combines histological and molecular features for an integrated classification. This new approach builds upon advances in brain tumor molecular genetics and has important practical implications. RECENT FINDINGS: Molecular genetic studies revealed distinct glioma entities with specific genetic and epigenetic profiles. Evidence has been accumulated that molecular classification more reliably discriminates glioma entities and better predicts patient outcome than histological classification. Major glioma entities can be distinguished by four molecular biomarkers included in the new WHO classification, namely isocitrate dehydrogenase mutation, codeletion of chromosome arms 1p and 19q, codon 27 lysine-to-methionine mutation in H3 histones, and C11orf95-RELA gene fusions. Each is detectable by common techniques in routinely processed tissue specimens. Their integration into glioma classification greatly improves diagnostic accuracy but also has practical implications concerning establishment and quality control of novel techniques, increased costs and prolonged time to diagnosis. SUMMARY: We summarize the relevant changes in the revised WHO classification of gliomas, outline the integrated approach, and discuss its practical implications and potential challenges.

Role of microRNAs Located on Chromosome Arm 10q in Malignant Gliomas.

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.

[Progressive multifocal leukoencephalopathy following azathioprine and steroid treatment of pulmonary sarcoid disease]. / Progressive multifokale Leukenzephalopathie. Schwerwiegende Komplikation einer Immunsuppression.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system following reactivation of the John-Cunningham-Virus (JVC) in an immunocompromised host. This rare condition is characterized by rapid progressing neurologic symptoms often leading to death. In the following, we report on a rapid evolving deterioration of mental status due to PML in an 53-year-old man during treatment of pulmonary sarcoid disease using azathioprine and steroids. In contrast to reported lethal outcomes, our patient experienced a slow recovery of his cognitive impairment and later on of his palsy following termination of immunosuppression.

Assessing quality and functionality of DNA isolated from FFPE tissues through external quality assessment in tissue banks.

BACKGROUND: Biobanks are becoming increasingly important for assessment of disease risk as well as identification and validation of new diagnostic biomarkers and druggable targets. The validity of data obtained from biobanks is critically limited by the biomaterial quality of the biological samples. External quality assessment (EQA) programs suitable to comprehensively measure the biomaterial quality in archived materials are currently lacking. We report on quantitative assay designs for the analysis of both structural and functional integrity of DNAs that were applied in a first pilot EQA within the priority program on tumor tissue biobanking funded by the German Cancer Aid. METHODS: Participating biobanks isolated DNAs from a standardized set of 10 samples comprising sections of four different formalin-fixed paraffin-embedded tissues using their standard operating procedures. Isolated DNAs and analytical results were returned and analyzed centrally for nucleic acids yield, purity, fragmentation and amplificability at a quantitative level using dedicated assay designs. RESULTS: The amount of extracted DNA varied in isolates ranging between 1.5 µg and 25.8 µg. Quantification of DNA fragmentation and amplificability allowed to highlight considerable discrepancies in DNA quality. Amplicons yielded from the isolates of these identical EQA samples ranged from 105 to 411 bp suggesting differences between residual inhibitors of downstream enzymatic reactions. CONCLUSIONS: The quality of extraction of bioanalytes from biomaterial archives is heterogeneous even for stable biomolecules like DNA isolated with highly standardized methods. EQAs are appropriate tools to uncover strengths and weaknesses in biobanks in a systematic fashion. Biomaterial integrity is insufficiently reflected by standard methods, but needs to be assessed to improve biobank interoperability. Finally, our results also point towards the problem of measuring the quality of more delicate biomolecules like proteins or metabolites.

Unraveling the glioma epigenome: from molecular mechanisms to novel biomarkers and therapeutic targets.

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."

Identification and functional characterization of microRNAs involved in the malignant progression of gliomas.

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 miRNA-specific 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.