Wasserdeprivation und Tyrosinase als Trigger des erythrozytären programmierten Zelltodes

Die Eryptose stellt einen Mechanismus der kernlosen Erythrozyten dar, der analog zur Apoptose der kernhaltigen Körperzellen betrachtet werden kann. Da es den Erythrozyten aufgrund ihrer histologischen und physiologischen Eigenschaften an Zellorganellen wie Mitochondrien und Zellkern mangelt, diese aber für den regulären Prozess der Apoptose in kernhaltigen Zellen benötigt werden, entdeckte man erst vor kurzem die Fähigkeit der Erythrozyten zum programmierten Zelltod, der sogenannten Eryptose. Wie bei den kernhaltigen Zellen stellt die Phosphatidylserin-Exposition an der Zellmembranaußenseite eines der wichtigsten morphologischen Merkmale dar. Außerdem kommt es bei den Erythrozyten zu einem Kalziumeinstrom in die Zelle und nachfolgendem Kaliumausstrom mit Hyperpolarisation und Chloridausstrom aus der Zelle. Osmotisch folgt diesem Gradienten Wasser, welches zu einer Schrumpfung der Zelle führt. Das zytosolische Kalzium und die Ceramid-Bildung stimulieren des Weiteren die Verlagerung von Phosphatidylserin an die Außenseite der Membran. Bisher konnten viele Xenobiotika als auch verschiedene Krankheitsbilder wie Nierenversagen, Malariainfektionen oder Eisenmangelanämie identifiziert werden, die eine erhöhte Eryptoserate in vitro bzw. in vivo aufweisen. In dieser Arbeit wurde zum einen die Sensibilisierung von murinen Erythrozyten nach vorhergehender Dehydratation der Mäuse untersucht. Die Ergebnisse zeigen eine signifikant erhöhte Phosphatidylserin-Exposition an der Zellmembranaußenseite bei den dehydrierten Mäusen im Vergleich zu der Kontrollgruppe. Phosphatidylserin-Exposition ließ sich auch vermehrt nach massivem Kalziumeinstrom durch Ionomycin, Hyperosmolarität, Energiedepletion und oxidativem Stress beobachten. Dehydratation kann also unter bestimmten Umständen mit erhöhtem programmierten Zelltod der Erythrozyten einhergehen. Tyrosinase, ein endogenes Enzym, das unter anderem als Therapie (zusätzlich zu anderen Substanzen) von Malignomen vorgeschlagen wurde, zeigte in unseren Versuchen einen stark eryptotischen Effekt. In verschiedenen Dosierungen triggert Tyrosinase den Kalziumeinstrom in die Erythrozyten, was zu einer nachfolgenden Phosphatidylserin-Exposition an der Zellmembranaußenseite, dem Scrambling, führt. Auch die Ceramid-Menge an der Zellmembranoberfläche konnte bei Tyrosinase-Exposition erhöht gemessen werden. Tyrosinase kann als weitere Substanz mit potenziell eryptotischer Wirkung auf die Blutzellen angesehen werden

Diffuse large B-cell lymphomas in adults with aberrant coexpression of CD10, BCL6, and MUM1 are enriched in IRF4 rearrangements

Diffuse large B-cell lymphoma (DLBCL) with aberrant co-expression of CD10+BCL6+MUM1+ (DLBCL-AE), classified as germinal center B cell (GCB)-type by the Hans algorithm (HA), were genetically characterized. To capture the complexity of these DLBCL-AE, we used an integrated approach including gene expression profiling (GEP), fluorescence in-situ hybridization (FISH), targeted gene sequencing, and copy number (CN) arrays. According to GEP, 32/54 (59%) cases were classified as GCB-DLBCL, 16/54 (30%) as activated B-cell (ABC)-DLBCL and 6/54 (11%) as unclassifiable. The discrepancy between HA and GEP was 41%. Three genetic subgroups were identified. Group 1 included 13/50 (26%) cases without translocations and mainly showing and ABC/MCD molecular profile. Group 2 comprised 11/50 (22%) cases with IRF4 alterations (DLBCL-IRF4), frequent mutations in IRF4 (82%) and NF-?B pathway genes (MYD88, CARD11, and CD79B), and losses of 17p13.2. Five cases each were classified as GCB- or ABC-type. Group 3 included 26/50 (52%) cases with one or several translocations in BCL2/BCL6/MYC/IGH and GCB/EZB molecular profile predominated. Two cases in this latter group showed complex BCL2/BCL6/IRF4 translocations. DLBCL-IRF4 in adults showed a similar CN profile and share recurrent CARD11 and CD79B mutations when compared to LBCL-IRF4 in pediatric population. However, adult cases showed higher genetic complexity, higher mutational load with frequent MYD88 and KMT2D mutations, and more often ABC-GEP. IRF4 mutations were identified only in IRF4-rearranged cases indicating its potential utility in the diagnostic setting. In conclusion, DLBCL-AE are genetically heterogeneous and enriched in cases with IRF4 alterations. DLBCL-IRF4 in adults has many similarities to the pediatric counterpart.Copyright © 2021 American Society of Hematology

A review on tumor heterogeneity and evolution in multiple myeloma: pathological, radiological, molecular genetics, and clinical integration

Recent research has dramatically advanced our understanding of the genetic basis of multiple myeloma (MM). MM displays enormous inter- and intratumoral heterogeneity, and underlies a clonal evolutionary process driven and shaped by diverse factors such as clonal competition, tumor microenvironment, host immunity, and therapy. Two main cytogenetic groups are distinguished: MM with recurrent translocations involving the immunoglobulin heavy chain locus and MM with hyperdiploidy involving the odd chromosomes. The disease virtually always starts with a preneoplastic prodromal phase-monoclonal gammopathy of undetermined significance-that variably progresses to symptomatic MM within a few months or many years. Tumor heterogeneity and its evolution in space and time have important consequences for the clinical management and outcome of MM patients. At diagnosis, spatial intratumoral heterogeneity poses a challenge for classification and risk stratification. During maintenance therapy, clonal evolution may complicate disease monitoring and promote drug resistance. Upon progression or transformation, identifying the dominant disease-driving neoplastic clones and elucidating their properties are key to tailor personalized therapy. In this review, we discuss tumor heterogeneity and clonal evolution in MM, integrating pathological, radiological, molecular genetics, and clinical data. Current and prospective classification schemes and prognostic parameters, incorporating new genetic and proteomic discoveries and advances in imaging, are highlighted. In addition, the roles of the tumor microenvironment, host immunity, and resistance mutations, and their effects on therapy, are discussed. An improved understanding of high-risk disease, tumor heterogeneity, and clonal evolution will guide future therapies and may ultimately lead towards a cure for MM

Stimulation of Erythrocyte Cell Membrane Scrambling by Mushroom Tyrosinase

Background: Mushroom tyrosinase, a copper containing enzyme, modifies growth and survival of tumor cells. Mushroom tyrosinase may foster apoptosis, an effect in part due to interference with mitochondrial function. Erythrocytes lack mitochondria but are able to undergo apoptosis-like suicidal cell death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling leading to phosphatidylserine-exposure at the erythrocyte surface. Signaling involved in the triggering of eryptosis include increase of cytosolic Ca(2+)-activity ([Ca(2+)](i)) and activation of sphingomyelinase with subsequent formation of ceramide. The present study explored, whether tyrosinase stimulates eryptosis. Methods: Cell volume has been estimated from forward scatter, phosphatidylserine-exposure from annexin V binding, [Ca(2+)](i) from Fluo3-fluorescence, and ceramide abundance from binding of fluorescent antibodies in flow cytometry. Results: A 24 h exposure to mushroom tyrosinase (7 U/mL) was followed by a significant increase of [Ca(2+)](i), a significant increase of ceramide abundance, and a significant increase of annexin-V-binding. The annexin-V-binding following tyrosinase treatment was significantly blunted but not abrogated in the nominal absence of extracellular Ca(2+). Tyrosinase did not significantly modify forward scatter. Conclusions: Tyrosinase triggers cell membrane scrambling, an effect, at least partially, due to entry of extracellular Ca(2+) and ceramide formation