Identifizierung und Charakterisierung von Zielgenen des Epstein-Barr Virus nukleären Antigens 2 (EBNA2)

Das Epstein Barr Virus (EBV) ist ein ubiquitär vorkommendes Herpesvirus, mit dem etwa weltweit 90% der erwachsenen Bevölkerung permanent infiziert sind. Die zumeist asymptomatisch verlaufende Infektion betrifft primäre B–Zellen des Rachenraumes, die nach Aufnahme des Virus entweder zur Virus-Produktion (lytischer Zyklus) oder zur Proliferation angeregt werden (Latenzprogramm, Entstehung von B-Lymphoblasten). Letzteres wird durch den viralen Transkriptionsfaktor EBNA2 kontrolliert, der durch seine viralen und zellulären Zielgene ruhende B-Zellen in vitro immortalisieren kann. Die EBV-infizierten B-Lymphoblasten werden in vivo effizient durch T-Zellen erkannt und abgetötet. EBV entkommt der Immunantwort durch Persistenz in Gedächtnis-B-Zellen, die vermutlich durch Differenzierung der infizierten B-Lymphoblasten entstehen. Es gibt Hinweise, dass diese Differenzierung EBV-vermittelt unter der Mitwirkung von T-Helfer-Zellen abläuft, was auf eine komplexe Kommunikation des Virus mit dem Immunsystem schließen lässt. In der vorliegenden Arbeit wurden Mechanismen der EBV-vermittelten B-Zell-Immortalisierung und -Kommunikation untersucht. Ein Vergleich von EBNA2-Zielgenen mit Zielgenen des Protoonkogens c-myc, das bei Überexpression B-Zell-Proliferation induzieren kann, ermöglichte dabei die Unterscheidung von Zielgenen, die mit Proliferation und B-Zell-Kommunikation assoziiert sind. Die methodische Herangehensweise bestand in der Proteom-Analyse (2D-Gelelektrophorese mit massenspektrometrischer Proteinidentifikation), Promotoraktivitäts-Analyse (nukleärer Run-On) und einer umfassenden mRNA-Expressions-Analyse (DNA-Chip-Hybridisierung) konditional oder permanent MYC- oder EBV/EBNA2-abhängig proliferierender Zellen. Die erhaltenen Daten bestätigen, dass die von EBNA2 und MYC gemeinsam induzierten Zielgene in grundlegende Prozesse der Lebenserhaltung wie den Nukleotid-, Protein-, und Polyamin-Stoffwechsel, sowie in die oxidative Stressantwort, DNA-Reparatur und Zellteilung involviert sind. Dagegen waren gegensätzlich regulierte Gene funktionell in den Bereich B-Zell-Signaltransduktion- und B-Zell-Kommunikation einzuordnen. Die EBV-abhängige Proliferation ist sowohl mit der Aktivierung des NFkB-Signalwegs assoziiert, als auch mit der verstärkten Expression zentraler Komponenten der Interferon (IFN)-Antwort (insbesondere STAT1) und mit der Repression von Komponenten des B-Zell-Rezeptors (BCR) und der BCR-Signaltransduktion. Die NFkB-Aktivierung führt zur Induktion von antiapoptotischen Genen und von Chemoattraktoren für T-Helferzellen. Die aus Array- und Protein-Daten hervorgehende EBV/EBNA2-vermittelte Aktivierung des NFkB- und des IFN-Signalweges einerseits und die MYC-vermittelte Repression derselben andererseits könnten das molekulare Bindeglied zwischen EBV-vermittelter T-Zell-Stimulation und MYC-vermittelter Immuntoleranz darstellen. Die chemokinvermittelte T-Zell-Rekrutierung und die vermutlich durch STAT1-Expression begünstigte Antigen-präsentation weisen T-Zellen eine aktive Rolle bei der Reifung von EBV-infizierten Lymphoblasten zu B-Gedächtniszellen zu

Inhibition of IGF1-R overcomes IGFBP7-induced chemotherapy resistance in T-ALL

Background T-cell acute lymphoblastic leukemia (T-ALL) is a genetically heterogeneous disease with the need for treatment optimization. Previously, high expression of Insulin-like growth factor binding protein 7 (IGFBP7), a member of the IGF system, was identified as negative prognostic factor in adult T-ALL patients. Since aberrant IGFBP7 expression was observed in a variety of neoplasia and was relevant for prognosis in T-ALL, we investigated the functional role of IGFBP7 in Jurkat and Molt-4 cells as in vitro models for T-ALL. Methods Jurkat and Molt-4 cells were stably transfected with an IGFBP7 over-expression vector or the empty vector as control. Proliferation of the cells was assessed by WST-1 assays and cell cycle status was measured by flow-cytometry after BrDU/7-AAD staining. The effect of IGFBP7 over-expression on sensitivity to cytostatic drugs was determined in AnnexinV/7-AAD assays. IGF1-R protein expression was measured by Western Blot and flow-cytometric analysis. IGF1-R associated gene expression profiles were generated from microarray gene expression data of 86 T-ALL patients from the Microarrays Innovations in Leukemia (MILE) multicenter study. Results IGFBP7-transfected Jurkat cells proliferated less, leading to a longer survival in a nutrient–limited environment. Both IGFBP7-transfected Jurkat and Molt-4 cells showed an arrest in the G0/G1 cell cycle phase. Furthermore, Jurkat IGFBP7-transfected cells were resistant to vincristine and asparaginase treatment. Surface expression and whole protein measurement of IGF1-R protein expression showed a reduced abundance of the receptor after IGFBP7 transfection in Jurkat cells. Interestingly, combination of the IGF1-R inhibitor NPV-AEW541 restored sensitivity to vincristine in IGFBP7-transfected cells. Additionally, IGF1-R associated GEP revealed an up-regulation of important drivers of T-ALL pathogenesis and regulators of chemo-resistance and apoptosis such as NOTCH1, BCL-2, PRKCI, and TP53. Conclusion This study revealed a proliferation inhibiting effect of IGFBP7 by G0/G1 arrest and a drug resistance-inducing effect of IGFBP7 against vincristine and asparaginase in T-ALL. These results provide a model for the previously observed association between high IGFBP7 expression and chemotherapy failure in T-ALL patients. Since the resistance against vincristine was abolished by IGF1-R inhibition, IGFBP7 could serve as biomarker for patients who may benefit from therapies including IGF1-R inhibitors in combination with chemotherapy

10 Hz amplitude modulated sounds induce short-term tinnitus suppression

Objectives: Acoustic stimulation or sound therapy is proposed as a main treatment option for chronic subjective tinnitus. To further probe the field of acoustic stimulations for tinnitus therapy, this exploratory study compared 10Hz amplitude modulated (AM) sounds (two pure tones, noise, music, and frequency modulated (FM) sounds) and unmodulated sounds (pure tone, noise) regarding their temporary suppression of tinnitus loudness. First, it was hypothesized that modulated sounds elicit larger temporary loudness suppression (residual inhibition) than unmodulated sounds. Second, with manipulation of stimulus loudness and duration of the modulated sounds weaker or stronger effects of loudness suppression were expected, respectively. Methods: We recruited 29 participants with chronic tonal tinnitus from the multidisciplinary Tinnitus Clinic of the University of Regensburg. Participants underwent audiometric, psychometric and tinnitus pitch matching assessments followed by an acoustic stimulation experiment with a tinnitus loudness growth paradigm. In a first block participants were stimulated with all of the sounds for 3 min each and rated their subjective tinnitus loudness to the pre- stimulus loudness every 30 s after stimulus offset. The same procedure was deployed in the second block with the pure tone AM stimuli matched to the tinnitus frequency, manipulated in length (6 min), and loudness (reduced by 30 dB and linear fade out). Repeated measures mixed model analyses of variance (ANOVA) were calculated to assess differences in loudness growth between the stimuli for each block separately. Results: First, we found that all sounds elicit a short-term suppression of tinnitus loudness (seconds to minutes) with strongest suppression right after stimulus offset [F-(6,F- 1331) = 3.74, p < 0.01]. Second, similar to previous findings we found that AM sounds near the tinnitus frequency produce significantly stronger tinnitus loudness suppression than noise [vs. Pink noise: t((27)) = - 4.22, p < 0.0001]. Finally, variants of the AM sound matched to the tinnitus frequency reduced in sound level resulted in less suppression while there was no significant difference observed for a longer stimulation duration. Moreover, feasibility of the overall procedure could be confirmed as scores of both tinnitus loudness and questionnaires were lower after the experiment [ tinnitus loudness: t((27)) = 2.77, p < 0.01; Tinnitus Questionnaire: t((27)) = 2.06, p < 0.05; Tinnitus Handicap Inventory: t((27)) = 1.92, p = 0.065]. Conclusion: Taken together, these results imply that AM sounds, especially in or around the tinnitus frequency, may induce larger suppression than unmodulated sounds. Future studies should thus evaluate this approach in longitudinal studies and real life settings. Furthermore, the putative neural relation of these sound stimuli with a modulation rate in the EEG alpha band to the observed tinnitus suppression should be probed with respective neurophysiological methods

FLT3 mutations in Early T-Cell Precursor ALL characterize a stem cell like leukemia and imply the clinical use of tyrosine kinase inhibitors

Early T-cell precursor acute lymphoblastic leukemia (ETP-ALL) has been identified as high-risk subgroup of acute T-lymphoblastic leukemia (T-ALL) with a high rate of FLT3-mutations in adults. To unravel the underlying pathomechanisms and the clinical course we assessed molecular alterations and clinical characteristics in a large cohort of ETP-ALL (n = 68) in comparison to non-ETP T-ALL adult patients. Interestingly, we found a high rate of FLT3-mutations in ETP-ALL samples (n = 24, 35%). Furthermore, FLT3 mutated ETP-ALL was characterized by a specific immunophenotype (CD2+/CD5-/CD13+/CD33-), a distinct gene expression pattern (aberrant expression of IGFBP7, WT1, GATA3) and mutational status (absence of NOTCH1 mutations and a low frequency, 21%, of clonal TCR rearrangements). The observed low GATA3 expression and high WT1 expression in combination with lack of NOTCH1 mutations and a low rate of TCR rearrangements point to a leukemic transformation at the pluripotent prothymocyte stage in FLT3 mutated ETP-ALL. The clinical outcome in ETP-ALL patients was poor, but encouraging in those patients with allogeneic stem cell transplantation (3-year OS: 74%). To further explore the efficacy of targeted therapies, we demonstrate that T-ALL cell lines transfected with FLT3 expression constructs were particularly sensitive to tyrosine kinase inhibitors. In conclusion, FLT3 mutated ETP-ALL defines a molecular distinct stem cell like leukemic subtype. These data warrant clinical studies with the implementation of FLT3 inhibitors in addition to early allogeneic stem cell transplantation for this high risk subgroup

Macrocyclic tetramers—structural investigation of peptide-peptoid hybrids

Outstanding affinity and specificity are the main characteristics of peptides, rendering them interesting compounds for basic and medicinal research. However, their biological applicability is limited due to fast proteolytic degradation. The use of mimetic peptoids overcomes this disadvantage, though they lack stereochemical information at the α-carbon. Hybrids composed of amino acids and peptoid monomers combine the unique properties of both parent classes. Rigidification of the backbone increases the affinity towards various targets. However, only little is known about the spatial structure of such constrained hybrids. The determination of the three-dimensional structure is a key step for the identification of new targets as well as the rational design of bioactive compounds. Herein, we report the synthesis and the structural elucidation of novel tetrameric macrocycles. Measurements were taken in solid and solution states with the help of X-ray scattering and NMR spectroscopy. The investigations made will help to find diverse applications for this new, promising compound class

Macrocyclic Tetramers—Structural Investigation of Peptide-Peptoid Hybrids

Outstanding affinity and specificity are the main characteristics of peptides, rendering them interesting compounds for basic and medicinal research. However, their biological applicability is limited due to fast proteolytic degradation. The use of mimetic peptoids overcomes this disadvantage, though they lack stereochemical information at the α-carbon. Hybrids composed of amino acids and peptoid monomers combine the unique properties of both parent classes. Rigidification of the backbone increases the affinity towards various targets. However, only little is known about the spatial structure of such constrained hybrids. The determination of the three-dimensional structure is a key step for the identification of new targets as well as the rational design of bioactive compounds. Herein, we report the synthesis and the structural elucidation of novel tetrameric macrocycles. Measurements were taken in solid and solution states with the help of X-ray scattering and NMR spectroscopy. The investigations made will help to find diverse applications for this new, promising compound class

Neurophysiological correlates of residual inhibition in tinnitus: Hints for trait-like EEG power spectra

Objective To investigate oscillatory brain activity changes following acoustic stimulation in tinnitus and whether these changes are associated with behavioral measures of tinnitus loudness. Moreover, differences in ongoing brain activity between individuals with and without residual inhibition (RI) are examined (responders vs. non-responders). Methods Three different types of noise stimuli were administered for acoustic stimulation in 45 tinnitus patients. Subjects resting state brain activity was recorded before and after stimulation via EEG alongside with subjective measurements of tinnitus loudness. Results Delta, theta and gamma band power increased, whereas alpha and beta power decreased from pre to post stimulation. Acoustic stimulation responders exhibited reduced gamma and a trend for enhanced alpha activity with the latter localized in the right inferior temporal gyrus. Post stimulation, individuals experiencing RI showed higher theta, alpha and beta power with a peak power difference in the alpha band localized in the right superior temporal gyrus. Neither correlations with behavioral tinnitus measures nor stimulus-specific changes in EEG activity were present. Conclusions Our observations might be indicative of trait-specific forms of oscillatory signatures in different subsets of the tinnitus population related to acoustic tinnitus suppression. Significance Results and insights are not only useful to understand basic neural mechanisms behind RI but are also valuable for general neural models of tinnitus

Comparing Three Established Methods for Tinnitus Pitch Matching With Respect to Reliability, Matching Duration, and Subjective Satisfaction

The pitch of tinnitus sound is a key characteristic that is of importance to research and sound therapies relying on exact tinnitus pitch matches. The identification of this tinnitus pitch is a challenging task as there is no objective measurement available. During the tinnitus pitch-matching procedure, the participant identifies an external sound that is most similar to the subjective perception of the tinnitus. Several methods have been developed to perform this pitch-matching procedure with tinnitus sufferers. In this study, we aimed to compare the method of adjustment, the two-alternative forced-choice (2AFC) method, and the likeness rating (LR) with respect to reliability, matching duration, and subjective satisfaction. Fifty-nine participants with chronic tinnitus were recruited and performed five consecutive runs of tinnitus matching. The participants were randomized to the three different pitch-matching methods. The intraclass correlation coefficients were .67 for method of adjustment, .63 for 2AFC, and .69 for LR, which can be interpreted as good reliability for all the three methods. However, the 2AFC method revealed significant larger within-subject variability than the other measures. Across the five runs and the three different methods, all participants learned to perform the pitch matching faster and with better self-rated accuracy. Comparing the three pitch-matching methods, LR is more time consuming and the participants were less satisfied with the 2AFC method. Overall, the three pitch-matching methods show good reliability. However, we identified differential aspects for improvement in all methods, which are discussed in this article

Neuroimaging and Neuromodulation: Complementary Approaches for Identifying the Neuronal Correlates of Tinnitus

An inherent limitation of functional imaging studies is their correlational approach. More information about critical contributions of specific brain regions can be gained by focal transient perturbation of neural activity in specific regions with non-invasive focal brain stimulation methods. Functional imaging studies have revealed that tinnitus is related to alterations in neuronal activity of central auditory pathways. Modulation of neuronal activity in auditory cortical areas by repetitive transcranial magnetic stimulation (rTMS) can reduce tinnitus loudness and, if applied repeatedly, exerts therapeutic effects, confirming the relevance of auditory cortex activation for tinnitus generation and persistence. Measurements of oscillatory brain activity before and after rTMS demonstrate that the same stimulation protocol has different effects on brain activity in different patients, presumably related to interindividual differences in baseline activity in the clinically heterogeneous study cohort. In addition to alterations in auditory pathways, imaging techniques also indicate the involvement of non-auditory brain areas, such as the fronto-parietal “awareness” network and the non-tinnitus-specific distress network consisting of the anterior cingulate cortex, anterior insula, and amygdale. Involvement of the hippocampus and the parahippocampal region putatively reflects the relevance of memory mechanisms in the persistence of the phantom percept and the associated distress. Preliminary studies targeting the dorsolateral prefrontal cortex, the dorsal anterior cingulate cortex, and the parietal cortex with rTMS and with transcranial direct current stimulation confirm the relevance of the mentioned non-auditory networks. Available data indicate the important value added by brain stimulation as a complementary approach to neuroimaging for identifying the neuronal correlates of the various clinical aspects of tinnitus