Anke Ehlers

Deep Sequencing of MYC DNA-Binding Sites in Burkitt Lymphoma

Background MYC is a key transcription factor involved in central cellular processes such as regulation of the cell cycle, histone acetylation and ribosomal biogenesis. It is overexpressed in the majority of human tumors including aggressive B-cell lymphoma. Especially Burkitt lymphoma (BL) is a highlight example for MYC overexpression due to a chromosomal translocation involving the c-MYC gene. However, no genome-wide analysis of MYC-binding sites by chromatin immunoprecipitation (ChIP) followed by next generation sequencing (ChIP-Seq) has been conducted in BL so far. Methodology/Principal Findings ChIP-Seq was performed on 5 BL cell lines with a MYC-specific antibody giving rise to 7,054 MYC-binding sites after bioinformatics analysis of a total of approx. 19 million sequence reads. In line with previous findings, binding sites accumulate in gene sets known to be involved in the cell cycle, ribosomal biogenesis, histone acetyltransferase and methyltransferase complexes demonstrating a regulatory role of MYC in these processes. Unexpectedly, MYC-binding sites also accumulate in many B-cell relevant genes. To assess the functional consequences of MYC binding, the ChIP-Seq data were supplemented with siRNA- mediated knock-downs of MYC in BL cell lines followed by gene expression profiling. Interestingly, amongst others, genes involved in the B-cell function were up-regulated in response to MYC silencing. Conclusion/Significance The 7,054 MYC-binding sites identified by our ChIP-Seq approach greatly extend the knowledge regarding MYC binding in BL and shed further light on the enormous complexity of the MYC regulatory network. Especially our observations that (i) many B-cell relevant genes are targeted by MYC and (ii) that MYC down-regulation leads to an up-regulation of B-cell genes highlight an interesting aspect of BL biology.

Classical Hodgkin’s lymphoma shows epigenetic features of abortive plasma cell differentiation

Background Epigenetic changes are involved in the extinction of the B-cell gene expression program of classical Hodgkin’s lymphoma. However, little is known regarding epigenetic similarities between cells of classical Hodgkin’s lymphoma and plasma cell myeloma, both of which share extinction of the gene expression program of mature B cells. Design and Methods Global histone H3 acetylation patterns were determined in cell lines derived from classical Hodgkin’s lymphoma, plasma cell myeloma and B-cell lymphoma by chromatin immunoprecipitation and subsequent hybridization onto promoter tiling arrays. H3K27 trimethylation was analyzed by chromatin immunoprecipitation and real-time DNA polymerase chain reaction for selected genes. Epigenetic modifications were compared to gene expression data. Results Characteristic B-cell genes were hypoacetylated in classical Hodgkin’s lymphoma and plasma cell myeloma cell lines as demonstrated by comparison of their histone H3 acetylation patterns to those of B-cell lines. However, the number of genes jointly hyperacetylated and expressed in classical Hodgkin’ lymphoma and plasma cell myeloma cell lines, such as IRF4/MUM1 and RYBP, is limited. Moreover, H3K27 trimethylation for selected characteristic B-cell genes revealed that this additional epigenetic silencing is much more prevalent in classical Hodgkin’s lymphoma than in plasma cell myeloma. Conclusions Our epigenetic data support the view that classical Hodgkin’s lymphoma is characterized by abortive plasma cell differentiation with a down-regulation of characteristic B-cell genes but without activation of most genes typical of plasma cells.

Höchstmengen für Vitamine und Mineralstoffe in Nahrungsergänzungsmitteln

ZusammenfassungIn Deutschland greift etwa ein Drittel der Erwachsenen regelmäßig zu Nahrungsergänzungsmitteln (NEM). Neben Vitaminen und Mineralstoffen enthalten die Produkte teilweise auch sonstige Stoffe mit physiologischer Wirkung wie Aminosäuren, Fettsäuren, Pflanzenextrakte oder Mikroorganismen. Die Werbung verspricht positive Effekte für Gesundheit, Wohlbefinden und verbesserte Leistungsfähigkeit. Fragen zur Produktsicherheit werden selten thematisiert. Schon im Jahr 2002 wurde in der Europäischen Union (EU) eine Richtlinie (2002/46/EG) zur Angleichung der Rechtsvorschriften der Mitgliedstaaten über NEM erlassen, die auch die Festlegung von Höchstmengen vorsieht. In Deutschland und anderen europäischen Ländern wurden seither verschiedene Modelle für die Höchstmengenableitung für Vitamine und Mineralstoffe entwickelt und diskutiert. Bis heute wurden jedoch auf EU-Ebene keine verbindlichen Höchstmengen festgelegt. Länder wie Dänemark und Frankreich haben daher mittlerweile nationale Regelungen getroffen. Vor diesem Hintergrund hat das Bundesinstitut für Risikobewertung (BfR) auf Basis des derzeitigen wissenschaftlichen Kenntnisstandes Vorschläge für Vitamin- und Mineralstoffhöchstmengen in NEM erarbeitet. Produkte, die diese Empfehlungen einhalten und entsprechend den Herstelleranweisungen eingenommen werden, sind für Personen ab 15 Jahren sicher.AbstractAbout one third of the adults in Germany are using food supplements regularly. Besides vitamins and minerals, these products also contain other substances such as amino acids, fatty acids, plant extracts or microorganisms. Advertising promises positive effects for health, well-being and improved performance. Product safety issues are rarely discussed. Already in the year 2002, a directive (2002/46/EC) on the approximation of the laws of the EU Member States concerning food supplements was adopted, which also provides settings of maximum levels. Since then, different models for the quantitative derivation of maximum levels for vitamins and minerals have been developed and discussed in Germany and other European countries. However, to date no binding maximum levels for vitamins and minerals in food supplements have been set at EU level. Meanwhile, EU member states such as Denmark and France have adopted national regulations. Against this background, the Federal Institute for Risk Assessment (BfR) has developed proposals for maximum levels for vitamins and minerals in food supplements. Vitamin and mineral supplements which comply with these recommendations and are taken according to the manufacturer’s instructions are safe for persons from 15 years of age.

Erratum zu: Höchstmengen für Vitamine und Mineralstoffe in Nahrungsergänzungsmitteln

In Tabelle 1, erste Zeile, letzte Spalte (Bemerkungen zu Vitamin D) wurde angegeben, dass laut Gemeinsamer Expertenkommission von BVL/BfArM Vitamin D-haltige Präparate bis zu einer Tagesdosis von 20 µg noch als Nahrungsergänzungsmittel (NEM) eingestuft werden können, während Präparate mit höheren Dosierungen als Arzneimittel anzusehen sind (BVL/BfArM 2016).

Ein Vitamin mit zwei Gesichtern

ZusammenfassungIn den 1930er-Jahren wurde beobachtet, dass bestimmte Formen der megaloblastischen Anämie in der Schwangerschaft mit Leber- und Hefeextrakten behandelt werden können. Der dafür verantwortliche Faktor wurde in den 1940er-Jahren aus Spinatblättern isoliert und in Anlehnung an das lateinische Wort für Blatt (folium) als Folat bezeichnet. Folat ist für den Menschen ein essenzieller Nährstoff. Die synthetische Form des Vitamins – Folsäure – wird in Nahrungsergänzungsmitteln, Arzneimitteln und angereicherten Lebensmitteln verwendet. Der gezielte Einsatz von Folsäure begann in den 1980er-Jahren, nachdem in einer Reihe von Studien beobachtet worden war, dass durch Folsäureeinnahmen vor und in der Schwangerschaft das Risiko für Neuralrohrdefekte (NRD) verringert werden kann. In der Folge wurden weltweit Empfehlungen zur perikonzeptionellen Folsäuresupplementierung gegeben und in vielen Ländern Anreicherungsprogramme gestartet. Die so erzielten Steigerungen der Folsäureaufnahme waren mit signifikanten Rückgängen der NRD-Raten verbunden. Jedoch wurde parallel dazu in den USA und Kanada ein – vorübergehender – Anstieg von Kolorektalkrebserkrankungen beobachtet. Aus tierexperimentellen und Humanstudiendaten lässt sich mittlerweile ein komplexer Zusammenhang zwischen Folat/Folsäure und Krebs ableiten: So sind Folataufnahmen in Höhe der Zufuhrempfehlungen bei gesunden Menschen im Allgemeinen mit einem geringeren Risiko für Krebserkrankungen verbunden, während unter bestimmten Bedingungen hohe Aufnahmen von Folsäure das Risiko für die Entstehung oder Progression von Krebs erhöhen können. Da Nahrungsfolat nicht mit unerwünschten Effekten assoziiert ist, steht Folsäure im Mittelpunkt des Forschungsinteresses zur Aufklärung der Ursachen für den beobachteten Zusammenhang.AbstractIn the late 1930s, it was discovered that liver and yeast extracts can be used to correct certain cases of megaloblastic anemia in pregnancy. The factor responsible for this was isolated from spinach leaves in the 1940s, and referred to as folate, axa0term derived from the Latin word folium for leaf. Folate is considered an essential nutrient for human beings. Folic acid, the synthetic form of the vitamin, is used in dietary supplements, medicines and fortified foods. Since the 1980s, it has been recommended that women who plan to become pregnant and pregnant women during the first trimester of pregnancy take folic acid supplements. This recommendation was based on studies that revealed that periconceptional folic acid supplementation can reduce the risk for neural tube defects (NTDs). Many countries later implemented folic acid fortification programs. The resulting population-wide increase of folic acid intakes led to significant reductions in NTD rates. However, axa0temporarily increased colorectal cancer incidence has been reported to coincide with the fortification programs in the USA and Canada. On the basis of currently available data from experimental and human studies it can be concluded that the association between folate/folic acid and cancer is rather complex: Folate intake in the range of the dietary reference intake (DRI) is associated with axa0reduced risk for cancer in healthy populations, whereas high intakes of folic acid might result in an increased risk for cancer incidence or progression in persons with precancerous lesions and under certain conditions. Since no adverse effects have been observed in association with the intake of dietary folate, research activities that aim at investigating cause and effect relationships focus on folic acid.In the late 1930s, it was discovered that liver and yeast extracts can be used to correct certain cases of megaloblastic anemia in pregnancy. The factor responsible for this was isolated from spinach leaves in the 1940s, and referred to as folate, axa0term derived from the Latin word folium for leaf. Folate is considered an essential nutrient for human beings. Folic acid, the synthetic form of the vitamin, is used in dietary supplements, medicines and fortified foods. Since the 1980s, it has been recommended that women who plan to become pregnant and pregnant women during the first trimester of pregnancy take folic acid supplements. This recommendation was based on studies that revealed that periconceptional folic acid supplementation can reduce the risk for neural tube defects (NTDs). Many countries later implemented folic acid fortification programs. The resulting population-wide increase of folic acid intakes led to significant reductions in NTD rates. However, axa0temporarily increased colorectal cancer incidence has been reported to coincide with the fortification programs in the USA and Canada. On the basis of currently available data from experimental and human studies it can be concluded that the association between folate/folic acid and cancer is rather complex: Folate intake in the range of the dietary reference intake (DRI) is associated with axa0reduced risk for cancer in healthy populations, whereas high intakes of folic acid might result in an increased risk for cancer incidence or progression in persons with precancerous lesions and under certain conditions. Since no adverse effects have been observed in association with the intake of dietary folate, research activities that aim at investigating cause and effect relationships focus on folic acid.