Subtype-specific differences in the cellular glioblastoma microenvironment

Einleitung Das Glioblastom ist der häufigste und aggressivste maligne hirneigene Tumor. Um das Verständnis der Pathophysiologie der Erkrankung zu verbessern sowie die Entwicklung personalisierter Therapiestrategien voranzutreiben, hat sich die Forschung intensiv um die Identifizierung klinisch relevanter Subgruppen bemüht. Eine der häufigsten Klassifizierungen basiert auf unterschiedlichen Genexpressionsprofilen und unterteilt Glioblastome in die Subtypen Proneural, Mesenchymal und Klassisch. Auch die zellulären Bestandteile des Tumormikromilieus und ihr Einfluss auf das Tumorwachstum sind zunehmend in den Fokus der wissenschaftlichen Arbeit gerückt. Insbesondere Tumor-assoziierte Makrophagen (TAM), eine gemischte Zellpopulation, welche sich aus aktivierten Mikroglia und eingewanderten Monozyten zusammensetzt, sowie T-Zellen spielen dabei eine übergeordnete Rolle. Das Ziel dieser Studie war es, die Immunzellinfiltration in den jeweiligen Subtypen des Glioblastoms zu charakterisieren. Methodik Genexpressionsdaten des The Cancer Genome Atlas (TCGA) wurden hinsichtlich der unterschiedlichen Immunprofile der Subtypen sowie ihrer Auswirkungen auf das Patientenüberleben analysiert. Zudem wurden Formalin-fixierte, Paraffin-eingebettete Gewebeproben mittels NanoString nCounter Technologie auf molekularer Ebene charakterisiert und den jeweiligen Subgruppen zugeordnet. Daraufhin wurde eine automatisierte immunhistochemische Färbung mit Antikörpern gegen IBA1, einem spezifischen Marker Tumor-assoziierter Makrophagen, sowie gegen die T-Zellproteine CD3, CD8 und FOXP3 durchgeführt. Die Quantifizierung der Immunzellinfiltration erfolgte mithilfe einer standardisierten Bildanalyse. Anhand der genannten Marker- Kombination wurde zudem ein mathematisches Modell entwickelt, mit welchem der Subtyp eines Glioblastoms vorhergesagt werde sollte. Ergebnisse Die Analysen sowohl auf Ebene der Genexpression als auch der Immunhistochemie offenbarten große Unterschiede in der Zusammensetzung der Immunzellen im Mikromilieu der Glioblastom-Subtypen. Mesenchymale Tumoren zeichneten sich durch eine signifikant erhöhte Infiltration von TAM sowie zytotoxischer, Helfer- und regulatorischer T-Zellen aus. Zudem wurde eine positive Korrelation zwischen TAM und den jeweiligen T-Zellpopulationen festgestellt. In der Überlebenszeitanalyse, basierend auf Daten des TCGA, zeichnete sich ein gegenteiliger Effekt hoher AIF1-Werte, eines Gens, welches für IBA1 kodiert, in Proneuralen und Mesenchymalen Tumoren ab: in Ersteren waren hohe Expressionsniveaus mit einer schlechteren Prognose vergesellschaftet, während sie bei Letzteren mit einem Überlebensvorteil einhergingen. Das statistische Prädiktionsmodell konnte Mesenchymale Glioblastome mit einer hohen Wahrscheinlichkeit identifizieren. Schlussfolgerungen Um die Prognose von Glioblastom-Patienten zu verbessern sind gezielte Therapiestrategien notwendig, welche die Heterogenität der Entität berücksichtigen. Die Ergebnisse dieser Studie untermauern die Hypothese, dass es unterschiedliche Subtypen des Glioblastoms gibt, und dass diese sich nicht nur hinsichtlich ihres molekularen Profils, sondern auch in der Zusammensetzung ihres zellulären Immun- Mikromilieus unterscheiden. Diese Ergebnisse werden hoffentlich zur Entwicklung effektiverer Immuntherapien beitragen. Zukünftige Studien sind erforderlich, um die Subtyp-spezifischen Funktionen der Immunzellen in der Pathogenese des Glioblastoms zu beleuchten.Background Glioblastoma (GBM) is the most common and aggressive malignant primary brain tumor in adults. In order to improve our understanding of its complex pathophysiology and facilitate the advancement of personalized treatment options, recent research efforts have been undertaken to identify clinically relevant subgroups. As a result, three molecular subtypes have been consistently proposed: Proneural, Mesenchymal, and Classical GBM. Concurrently, constituents of the tumor microenvironment and their tumor-promoting properties have received growing attention. Special emphasis has been placed on tumor-associated macrophages (TAMs), a mixed cell population of activated brain-resident microglia and infiltrating monocyte-derived macrophages, as well as on different T cell populations. The aim of this study was to investigate how the cellular immune profile differs among the GBM subtypes. Methods Gene expression data obtained from The Cancer Genome Atlas (TCGA) were utilized to analyze subtype-specific differences in the immune profiles as well as the effects of marker levels on patient survival. Subsequently, human formalin-fixed, paraffinembedded tumor samples were molecularly characterized using NanoString nCounter Technology and assigned to the three GBM subtypes. Automated immunohistochemical staining was performed for IBA1, a specific marker of TAMs, as well as CD3, CD8 and FOXP3, which represent different T cell-populations. Image analysis was then carried out to quantify immune cell infiltration. Furthermore, the marker combination was employed to develop a statistical model to predict the GBM subtype of a tumor based on its immune profile. Results TCGA and immunohistochemical analyses demonstrated stark differences in the composition of the immune cell compartment among the GBM subtypes. Mesenchymal GBM was characterized by significantly higher levels of TAMs as well as cytotoxic, helper and regulatory T cells. Moreover, a positive correlation between TAM and T cell infiltration was observed. Survival analysis based on TCGA data revealed a converse effect of AIF1, a gene encoding the TAM-marker IBA1, in Proneural and Mesenchymal GBM: in the former, high expression was associated with a worse prognosis, while conferring a survival benefit in the latter. The subtype prediction-model was able to identify Mesenchymal tumors with a high sensitivity. Conclusion In order to improve patient outcomes, therapies that take into account tumor diversity are required. In this study, we demonstrated that GBMs are characterized not only by differences in their molecular profile, but also by a considerable heterogeneity of their immune microenvironment. This will hopefully contribute to the development of more effective immunotherapeutic approaches. Further research is required to illuminate the subtype-specific functional role that immune cells play in GBM pathogenesis

an analysis of current capacity, needs and barriers

Background In times of increasing global challenges to health, it is crucial to create a workforce capable of tackling these complex issues. Even though a lack of GHE in Germany is perceived by multiple stakeholders, no systematic analysis of the current landscape exists. The aim of this study is to provide an analysis of the global health education (GHE) capacity in Germany as well as to identify gaps, barriers and future strategies. Methods An online search in combination with information provided by student representatives, course coordinators and lecturers was used to create an overview of the current GHE landscape in Germany. Additionally, a semi-structured questionnaire was sent to GHE educators and students engaged in global health (GH) to assess the capacity of German GHE, its barriers and suggested strategies for the future. Results A total of 33 GHE activities were identified at 18 German universities. Even though medical schools are the main provider of GHE (42%), out of 38 medical schools, only 13 (34%) offer any kind of GHE. Modules offered for students of other health-related professions constitute 27% of all activities. Most survey respondents (92%, n = 48) consider current GHE activities in Germany insufficient. Suggested formats were GHE as part of medical curricula (82%, n = 45) and dual degree MD/MPH or PhD programs. Most important barriers mentioned were low priority of GH at faculties and academic management levels (n = 41, 75%) as well as lack of necessary institutional structures (n = 33, 60%). Conclusions Despite some innovative academic approaches, there is clearly a need for more systematic GHE in Germany. GHE educators and students can take an important role advocating for more awareness at university management level and suggesting ways to institutionalize GHE to overcome barriers. This study provides key evidence, relevant perceptions and suggestions to strengthen GHE in Germany

Global health education in Germany: an analysis of current capacity, needs and barriers

Abstract Background In times of increasing global challenges to health, it is crucial to create a workforce capable of tackling these complex issues. Even though a lack of GHE in Germany is perceived by multiple stakeholders, no systematic analysis of the current landscape exists. The aim of this study is to provide an analysis of the global health education (GHE) capacity in Germany as well as to identify gaps, barriers and future strategies. Methods An online search in combination with information provided by student representatives, course coordinators and lecturers was used to create an overview of the current GHE landscape in Germany. Additionally, a semi-structured questionnaire was sent to GHE educators and students engaged in global health (GH) to assess the capacity of German GHE, its barriers and suggested strategies for the future. Results A total of 33 GHE activities were identified at 18 German universities. Even though medical schools are the main provider of GHE (42%), out of 38 medical schools, only 13 (34%) offer any kind of GHE. Modules offered for students of other health-related professions constitute 27% of all activities. Most survey respondents (92%, n = 48) consider current GHE activities in Germany insufficient. Suggested formats were GHE as part of medical curricula (82%, n = 45) and dual degree MD/MPH or PhD programs. Most important barriers mentioned were low priority of GH at faculties and academic management levels (n = 41, 75%) as well as lack of necessary institutional structures (n = 33, 60%). Conclusions Despite some innovative academic approaches, there is clearly a need for more systematic GHE in Germany. GHE educators and students can take an important role advocating for more awareness at university management level and suggesting ways to institutionalize GHE to overcome barriers. This study provides key evidence, relevant perceptions and suggestions to strengthen GHE in Germany

Human Mesenchymal glioblastomas are characterized by an increased immune cell presence compared to Proneural and Classical tumors

Glioblastoma (GBM) is the most aggressive malignant primary brain tumor in adults, with a median survival of 14.6 months. Recent efforts have focused on identifying clinically relevant subgroups to improve our understanding of pathogenetic mechanisms and patient stratification. Concurrently, the role of immune cells in the tumor microenvironment has received increasing attention, especially T cells and tumor-associated macrophages (TAM). The latter are a mixed population of activated brain-resident microglia and infiltrating monocytes/monocyte-derived macrophages, both of which express ionized calcium-binding adapter molecule 1 (IBA1). This study investigated differences in immune cell subpopulations among distinct transcriptional subtypes of GBM. Human GBM samples were molecularly characterized and assigned to Proneural, Mesenchymal or Classical subtypes as defined by NanoString nCounter Technology. Subsequently, we performed and analyzed automated immunohistochemical stainings for TAM as well as specific T cell populations. The Mesenchymal subtype of GBM showed the highest presence of TAM, CD8(+), CD3(+) and FOXP3(+) T cells, as compared to Proneural and Classical subtypes. High expression levels of the TAM-related gene AIF1, which encodes the TAM-specific protein IBA1, correlated with a worse prognosis in Proneural GBM, but conferred a survival benefit in Mesenchymal tumors. We used our data to construct a mathematical model that could reliably identify Mesenchymal GBM with high sensitivity using a combination of the aforementioned cell-specific IHC markers. In conclusion, we demonstrated that molecularly distinct GBM subtypes are characterized by profound differences in the composition of their immune microenvironment, which could potentially help to identify tumors amenable to immunotherapy

A comparative study of 10-Fr vs. 7-Fr straight plastic stents in the treatment of postcholecystectomy bile leak

Background: Biliary decompression is a key factor in the treatment of postcholecystectomy bile leak. However, the optimal size of the stent introduced by therapeutic endoscopic retrograde cholangiopancreatography (ERCP) is yet to be determined. The aim of the study was to compare the effectiveness of two straight plastic stents with different sizes (10-Fr and 7-Fr) in the treatment of postcholecystectomy bile leak. Methods: Between January 2003 and August 2006, 63 patients underwent therapeutic ERCP for postcholecystectomy bile leak. After visualization of the bile duct injury, endoscopic sphincterotomy was performed and the patients were randomized to receive either a 7-Fr (31 subjects, group A) or a 10-Fr (32 subjects, group B) straight plastic stent for four weeks. The success of the endoscopic treatment was determined by the elimination of the symptoms and the removal of the drain without any adverse outcomes. Results: The endoscopic intervention was successful in 29 patients of group A (93.54%) and in 31 patients of group B (96.87%). In the remaining two patients of group A, the 7-Fr stent was substituted by a 10-Fr stent after 7 days because the leak remained unaffected, resulting in healing of the leaks. Surgery was required in the remaining one patient of group B. Eight patients developed post-ERCP pancreatitis (5 mild, 2 moderate, 1 severe), which was treated conservatively. Conclusions: This trial suggests that the stent size does not affect the outcome of the endoscopic intervention in postcholecystectomy bile leaks due to minor biliary tract injury; however, larger cohorts are required to confirm the optimal stent size in bile leaks due to major bile duct injury