Justus Duyster

Universitätsklinikum Freiburg, Freiburg an der Elbe, Lower Saxony, Germany

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Publications (145)1094.63 Total impact

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    ABSTRACT: Acute graft-versus-host disease (GvHD) limits the success of allogeneic hematopoietic cell transplantation (allo-HCT), therefore a better understanding of its biology may improve therapeutic options. We observed miR-146a upregulation in T cells of mice developing acute GvHD compared to untreated mice. Transplanting miR-146a(-/-) T cells caused increased GvHD severity, elevated TNF serum levels and reduced survival. TNF receptor-associated factor 6(TRAF6), a verified target of miR-146a, was upregulated in miR-146a(-/-) T cells following alloantigen stimulation. Higher TRAF6 levels translated into increased NF-κB activity and TNF production in miR-146a(-/-) T cells. Conversely, the detrimental effect of miR-146a deficiency in T cells was antagonized by TNF blockade, while phytochemical induction of miR-146a or its overexpression using a miR-146a mimic reduced GvHD severity. In humans, the minor genotype of the SNP rs2910164 in HCT donors, which reduces expression of miR-146a, was associated with severe acute GvHD (grade III/IV). We show that miR-146a functions as a negative regulator of donor T cells in GvHD by targeting TRAF6, leading to reduced TNF transcription. Since miR-146a expression can be exogenously enhanced, our results provide a novel, targeted molecular approach to mitigate GvHD.
    Blood 09/2014; · 9.78 Impact Factor
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    ABSTRACT: Acute graft-versus-host disease (GVHD) considerably limits wider usage of allogeneic hematopoietic cell transplantation (allo-HCT). Antigen-presenting cells and T cells are populations customarily associated with GVHD pathogenesis. Of note, neutrophils are the largest human white blood cell population. The cells cleave chemokines and produce reactive oxygen species, thereby promoting T cell activation. Therefore, during an allogeneic immune response, neutrophils could amplify tissue damage caused by conditioning regimens. We analyzed neutrophil infiltration of the mouse ileum after allo-HCT by in vivo myeloperoxidase imaging and found that infiltration levels were dependent on the local microbial flora and were not detectable under germ-free conditions. Physical or genetic depletion of neutrophils reduced GVHD-related mortality. The contribution of neutrophils to GVHD severity required reactive oxygen species (ROS) because selective Cybb (encoding cytochrome b-245, beta polypeptide, also known as NOX2) deficiency in neutrophils impairing ROS production led to lower levels of tissue damage, GVHD-related mortality and effector phenotype T cells. Enhanced survival of Bcl-xL transgenic neutrophils increased GVHD severity. In contrast, when we transferred neutrophils lacking Toll-like receptor-2 (TLR2), TLR3, TLR4, TLR7 and TLR9, which are normally less strongly activated by translocating bacteria, into wild-type C57BL/6 mice, GVHD severity was reduced. In humans, severity of intestinal GVHD strongly correlated with levels of neutrophils present in GVHD lesions. This study describes a new potential role for neutrophils in the pathogenesis of GVHD in both mice and humans.
    Nature medicine. 05/2014;
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    ABSTRACT: Graft-versus-host-disease (GvHD) is a severe complication of allogeneic hematopoietic cell transplantation (allo-HCT) characterized by the production of high levels of pro-inflammatory cytokines. Activated Janus kinases (JAKs) are required for T effector cell responses in different inflammatory diseases and their blockade could potently reduce acute GvHD. We observed that inhibition of JAK1/2 signaling resulted in reduced proliferation of effector T cells and suppression of pro-inflammatory cytokine production in response to alloantigen in mice. In vivo JAK 1/2 inhibition improved survival of mice developing acute GvHD and reduced histopathologic GvHD grading, serum levels of pro-inflammatory cytokines and expansion of alloreactive luc-transgenic T cells. Mechanistically, we could show that ruxolitinib impaired differentiation of CD4(+) T cells into IFN-γ and IL17A-producing cells, both T cell phenotypes are linked to GvHD. Conversely, ruxolitinib treatment in allo-HCT recipients increased FoxP3(+) regulatory T cells, which are linked to immunological tolerance. Based on these results, we treated 6 patients suffering from steroid-refractory GvHD with ruxolitinib. All patients responded with respect to clinical GvHD symptoms and serum levels of pro-inflammatory cytokines. In summary, ruxolitinib represents a novel targeted approach in GvHD by suppression of pro-inflammatory signaling that mediates tissue damage and by promotion of tolerogenic Treg cells.
    Blood 04/2014; · 9.78 Impact Factor
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    ABSTRACT: BACKGROUND Little is known about the factors that predict for gastrointestinal stromal tumor (GIST) recurrence in patients treated with adjuvant imatinib.METHODS Risk factors for GIST recurrence were identified, and 2 risk stratification scores were developed using the database of the Scandinavian Sarcoma Group (SSG) XVIII trial, where 358 patients with high-risk GIST with no overt metastases were randomly assigned to adjuvant imatinib 400 mg/day either for 12 or 36 months after surgery. The findings were validated in the imatinib arm of the American College of Surgeons Oncology Group Z9001 trial, where 359 patients with GIST were randomized to receive imatinib and 354 were to receive placebo for 12 months.RESULTSFive factors (high tumor mitotic count, nongastric location, large size, rupture, and adjuvant imatinib for 12 months) were independently associated with unfavorable recurrence-free survival (RFS) in a multivariable analysis in the SSGXVIII cohort. A risk score based on these 5 factors had a concordance index with GIST recurrence of 78.9%. When a simpler score consisting of the 2 strongest predictive factors (mitotic count and tumor site) was devised, the groups with the lowest, intermediate high, and the highest risk had 5-year RFS of 76.7%, 47.5%, and 8.4%, respectively. Both scores were strongly associated with RFS in the validation cohort (P < .001 for each comparison).CONCLUSIONS The scores generated were effective in stratifying the risk of GIST recurrence in patient populations treated with adjuvant imatinib. Patients with nongastric GIST with a high mitotic count are at a particularly high risk for recurrence. Cancer 2014 © 2014 The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society.
    Cancer 04/2014; · 5.20 Impact Factor
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    ABSTRACT: Lung cancer is the leading cause of cancer-related deaths worldwide. Recently, we have shown that Notch1 inhibition resulted in substantial cell death of non-small cell lung cancer (NSCLC) cells in vitro. New compounds targeting Notch signal transduction have been developed and are now being tested in clinical trials. However, the tumorigenic role of individual Notch receptors in vivo remains largely unclear. Using a Kras(G12D)-driven endogenous NSCLC mouse model, we analyzed the effect of conditional Notch1 and Notch2 receptor deletion on NSCLC tumorigenesis. Notch1 deficiency led to a reduced early tumor formation and lower activity of MAPK compared with the controls. Unexpectedly, Notch2 deletion resulted in a dramatically increased carcinogenesis and increased MAPK activity. These mice died significantly earlier due to rapidly growing tumor burden. We found that Notch1 regulates Ras/MAPK pathway via HES1-induced repression of the DUSP1 promoter encoding a phosphatase specifically suppressing pERK1/2. Interestingly, Notch1 but not Notch2 ablation leads to decreased HES1 and DUSP1 expression. However, Notch2-depleted tumors showed an appreciable increase in β-catenin expression, a known activator of HES1 and important lung cancer oncogene. Characteristically for β-catenin upregulation, we found that the majority of Notch2-deficient tumors revealed an undifferentiated phenotype as determined by their morphology, E-Cadherin and TTF1 expression levels. In addition, these carcinomas showed aggressive growth patterns with bronchus invasion and obstruction. Together, we show that Notch2 mediates differentiation and has tumor suppressor functions during lung carcinogenesis, whereas Notch1 promotes tumor initiation and progression. These data are further supported by immunohistochemical analysis of human NSCLC samples showing loss or downregulation of Notch2 compared with normal lung tissue. In conclusion, this is the first study characterizing the in vivo functions of Notch1 and Notch2 in Kras(G12D)-driven NSCLC tumorigenesis. These data highlight the clinical importance of a thorough understanding of Notch signaling especially with regard to Notch-targeted therapies.Oncogene advance online publication, 10 February 2014; doi:10.1038/onc.2013.592.
    Oncogene 02/2014; · 8.56 Impact Factor
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    ABSTRACT: FLT3 is the most frequently mutated kinase in acute myeloid leukemia (AML). Internal tandem duplications (ITDs) in the juxta-membrane region constitute the majority of activating FLT3 mutations. Several FLT3 kinase inhibitors were developed and tested in the clinic with significant success. However, recent studies have reported the development of secondary drug resistance in patients treated with FLT3 inhibitors. Since FLT3-ITD is an HSP90 client kinase, we here explored if targeting the stability of drug-resistant FLT3 mutant protein could be a potential therapeutic option. We observed that HSP90 inhibitor treatment resulted in the degradation of inhibitor-resistant FLT3-ITD mutants and selectively induced toxicity in cells expressing FLT3-ITD mutants. Thus, HSP90 inhibitors provide a potential therapeutic choice to overcome secondary drug resistance following TKI treatment in FLT3-ITD positive AML.
    PLoS ONE 01/2014; 9(5):e97116. · 3.73 Impact Factor
  • Annals of Hematology 12/2013; · 2.87 Impact Factor
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    ABSTRACT: The success of allogeneic hematopoietic cell transplantation is limited by acute graft-versus-host disease (GvHD), a severe complication accompanied by high mortality rates. Yet, the molecular mechanisms initiating this disease remain poorly defined. In this study, we show that, after conditioning therapy, intestinal commensal bacteria and the damage-associated molecular pattern uric acid contribute to Nlrp3 inflammasome-mediated IL-1β production and that gastrointestinal decontamination and uric acid depletion reduced GvHD severity. Early blockade of IL-1β or genetic deficiency of the IL-1 receptor in dendritic cells (DCs) and T cells improved survival. The Nlrp3 inflammasome components Nlrp3 and Asc, which are required for pro-IL-1β cleavage, were critical for the full manifestation of GvHD. In transplanted mice, IL-1β originated from multiple intestinal cell compartments and exerted its effects on DCs and T cells, the latter being preferentially skewed toward Th17. Compatible with these mouse data, increased levels of active caspase-1 and IL-1β were found in circulating leukocytes and intestinal GvHD lesions of patients. Thus, the identification of a crucial role for the Nlrp3 inflammasome sheds new light on the pathogenesis of GvHD and opens a potential new avenue for the targeted therapy of this severe complication.
    Journal of Experimental Medicine 08/2013; · 13.21 Impact Factor
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    ABSTRACT: PURPOSEThe prognosis of elderly patients with acute myeloid leukemia (AML) is still dismal even with intensive chemotherapy. In this trial, we compared the antileukemic activity of standard induction and consolidation therapy with or without the addition of the kinase inhibitor sorafenib in elderly patients with AML. PATIENTS AND METHODS All patients received standard cytarabine and daunorubicin induction (7+3 regimen) and up to two cycles of intermediate-dose cytarabine consolidation. Two hundred one patients were equally randomly assigned to receive either sorafenib or placebo between the chemotherapy cycles and subsequently for up to 1 year after the beginning of therapy. The primary objective was to test for an improvement in event-free survival (EFS). Overall survival (OS), complete remission (CR) rate, tolerability, and several predefined subgroup analyses were among the secondary objectives.ResultsAge, sex, CR and early death (ED) probability, and prognostic factors were balanced between both study arms. Treatment in the sorafenib arm did not result in significant improvement in EFS or OS. This was also true for subgroup analyses, including the subgroup positive for FLT3 internal tandem duplications. Results of induction therapy were worse in the sorafenib arm, with higher treatment-related mortality and lower CR rates. More adverse effects occurred during induction therapy in the sorafenib arm, and patients in this arm received less consolidation chemotherapy as a result of higher induction toxicity.DiscussionIn conclusion, combination of standard induction and consolidation therapy with sorafenib in the schedule investigated in our trial is not beneficial for elderly patients with AML.
    Journal of Clinical Oncology 07/2013; · 18.04 Impact Factor
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    ABSTRACT: In gastrointestinal stromal tumor (GIST), there is no biomarker available that indicates success or failure of therapy. We hypothesized that tumor specific CKIT or PDGFRA mutant DNA fragments can be detected and quantified in plasma samples of GIST patients. We prospectively collected 291 plasma samples from 38 subjects with GIST harbouring activating mutations of CKIT or PDGFRA detected in tumor tissue, irrespective of current disease status or treatment. We used allele-specific Ligation PCR to detect mutant free circulating (fc)DNA. We were able to detect fcDNA harbouring the tumor mutation in 15 out of 38 patients. Patients with active disease displayed significantly higher amounts of mutant fcDNA compared to patients in CR. The amount of mutant fcDNA correlated with disease course. We observed repeated positive test results or an increase of mutant fcDNA in five patients with progressive disease or relapse. A decline of tumor fcDNA or conversion from positive to negative was seen in five patients responding to treatment. A negative to positive conversion was seen in two patients with relapse and one patient with progression. In two cases, we aimed to identify additional mutations, and found four additional exchanges, including mutations not known from sequentially performed tumor biopsies. Our results indicate that free circulating DNA harbouring tumor specific mutations in the plasma of patients with GIST can be used as tumor-specific biomarker. The detection of resistance mutations in plasma samples might allow earlier treatment changes and obviates the need for repeated tumor biopsies.
    Clinical Cancer Research 07/2013; · 7.84 Impact Factor
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    ABSTRACT: BACKGROUND: Formation of asymmetric kinase dimers is required for wt-EGFR activation upon ligand stimulation. The role of receptor dimerization in oncogenic EGFRvIII mutant activation is not completely understood and the molecular details of EGFRvIII interactions within homo-dimers and hetero-dimers are not elucidated yet. FINDINGS: By employing mutations that disrupt the asymmetric kinase dimer interface in EGFRvIII, we demonstrate that the mechanism of oncogenic EGFRvIII mutant activation is similar to that of the full-length wild-type EGFR. Surprisingly, the monomeric EGFRvIII lacks autophosphorylation and the formation of asymmetric kinase dimers is indispensable for oncogenic kinase activation. In addition, we show that ERBB3 can act as an activator of EGFRvIII by forming asymmetric kinase dimer in a ligand-independent manner. Interestingly, we found that the formation of asymmetric kinase dimer is dispensable for ERBB3 phosphorylation by the activated EGFR kinase as well as the ERBB2 kinase thus revealing a novel model for receptor function. CONCLUSIONS: Lateral signaling is a novel mechanism of signal propagation via ERBB3 upon activation by EGFR/ERBB2 kinase even in the absence of their ability to form asymmetric kinase dimers.
    Cell Communication and Signaling 06/2013; 11(1):39. · 5.09 Impact Factor
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    ABSTRACT: A phase I dose-escalation study of MSC1992371A, an oral aurora kinase inhibitor, was carried out in patients with hematologic malignancies. Patients received escalating doses either on days 1-3 and 8-10 (n=36) or on days 1-6 (n=39) of a 21-day cycle. The maximum tolerated doses were 37 and 28mg/m(2)/day, respectively. Dose-limiting toxicities included severe neutropenia with infection and sepsis, mucositis/stomatitis, and diarrhea. Complete responses occurred in 3 patients. Four disease-specific expansion cohorts then received the dose and schedule dictated by the escalation phase but the study was prematurely discontinued due to hematologic and gastrointestinal toxicity at clinically effective doses.
    Leukemia research 06/2013; · 2.36 Impact Factor
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    ABSTRACT: PURPOSE: Dasatinib and nilotinib are active in imatinib resistant CML and many patients undergo sequential treatment. We aimed at modelling sequential TKI resistance in vitro to compare the sequences imatinib-nilotinib-dasatinib and imatinib-dasatinib-nilotinib. EXPERIMENTAL DESIGN: We designed an in vitro-model for sequential TKI resistance in CML. Replicates of imatinib resistant cell lines were treated with dasatinib or nilotinib. Second line resistant replicates were exposed to 3rd line treatment. RESULTS: Growth of all replicates in all three lines of treatment was associated with T315I. However, T315I occurred with low abundance and did not increase during sequential treatment. Nilotinib 2nd line more often gave rise to sequential resistance compared to dasatinib due to pre-existing P-loop mutations, especially at suboptimal drug concentration. In contrast, mutations predisposing to dasatinib resistance such as F317C/V and V299L did not occur before dasatinib exposure. Nilotinib 3rd line did not overcome imatinib-dasatinib resistance due to pre-existing T315I or P-loop/V299L or P-loop/F317 exchanges. Dasatinib 3rd line suppressed imatinib-nilotinib resistant replicates with residual sensitivity. CONCLUSIONS: Sequential acquisition of BCR-ABL drug resistance mutations in CML might be underestimated. Resistance to sequential TKI monotherapy in vitro more often was associated with stepwise acquisition of drug-specific compound mutations compared to T315I. Pre-existing mutations strongly limited the activity of both 3rd line treatments, and the activity of nilotinib 2nd line in vitro critically depended on drug concentration.
    Clinical Cancer Research 04/2013; · 7.84 Impact Factor
  • Journal of Clinical Oncology 01/2013; · 18.04 Impact Factor
  • Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 01/2013; · 10.16 Impact Factor
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    ABSTRACT: The role of HSP90 in stabilization of oncogenic tyrosine kinases made it an attractive therapeutic target for treating cancer but the molecular basis underlying the interaction between the HSP90 chaperone and client kinases is not elucidated yet. Using kinase inhibitors we show that the inactive conformation of ERBB2 does not interact with HSP90 chaperone and is thus not amenable to degradation upon HSP90 inhibitor treatment, while active ERBB2 kinase conformation promotes interaction with the HSP90 machinery and thus is degraded upon HSP90 inhibitor treatment. Interestingly, the kinase-chaperone interaction is disrupted in case of BCR-ABL and FLT3-ITD when bound to inhibitors irrespective of whether they block the kinase in an active or inactive conformation and thus our results indicate that the stability of the active kinase conformation varies between different kinases.
    PLoS ONE 01/2013; 8(7):e68394. · 3.73 Impact Factor
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    Blood Cancer Journal 01/2013; 3:e104. · 1.40 Impact Factor
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    ABSTRACT: NIPA is an F-Box like protein that contributes to the timing of mitotic entry. It targets nuclear Cyclin B1 for ubiquitination in interphase while in G2/M-phase NIPA is inactivated by phosphorylation to allow for Cyclin B1 accumulation, a critical event for proper G2/M-transition. We recently specified three serine residues of NIPA and could demonstrate a sequential phosphorylation at G2/M, where initial S354 and S359 phosphorylation is most crucial for SCFNIPA inactivation. In this study, we identify ERK2 to be the responsible kinase for this critical initial phosphorylation step. Using in vitro kinase assays we found both ERK1 and ERK2 to phosphorylate NIPA with high efficiency. Mutation of either S354 or S359 abolished ERK-dependent NIPA phosphorylation. Pharmacologic inhibition of ERK1/2 in cell lines resulted in decreased NIPA phosphorylation at G2/M. By combining cell cycle synchronization with stable expression of shRNAs targeting either ERK1 or ERK2 we show that ERK2 but not ERK1 mediates NIPA inactivation at G2/M. ERK2 knockdown led to a delay at the G2/M-transition, a phenotype also observed in cells expressing a phosphodeficient mutant of NIPA. Thus, our data add to the recently described divergent functions of ERK1 and ERK2 in cell cycle regulation, which in part might be due to the differential ability of these kinases to phosphorylate and inactivate NIPA at G2/M.
    Journal of Biological Chemistry 09/2012; · 4.65 Impact Factor
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    ABSTRACT: NIPA (nuclear interaction partner of ALK) is an F-box-like protein that monitors the timing of mitotic entry. Constitutively active NIPA delays mitotic entry by preventing accumulation of nuclear cyclin B1. Here, we have investigated the consequences of Nipa inactivation by using a conditional knockout strategy. Nipa-deficient animals are viable but show a lower birth rate and reduced body weight. Furthermore, Nipa-deficient males are sterile owing to a block of spermatogenesis during meiotic prophase. Whereas Nipa-/- mouse embryonic fibroblasts show no severe phenotype, Nipa-/- spermatocytes arrest during stage IV of the epithelial cycle with subsequent TUNEL-positive apoptosis resulting from improper synapsis, defects in the repair of DNA double-stranded breaks and synaptonemal complex formation. Moreover, we show nuclear accumulation of cyclin B1 with a subsequent premature increase in G2/M kinase activity in Nipa-/- spermatocytes. Together, these results reveal a novel role for NIPA in meiosis.
    Development 06/2012; 139(14):2523-34. · 6.60 Impact Factor
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    ABSTRACT: Adjuvant imatinib administered for 12 months after surgery has improved recurrence-free survival (RFS) of patients with operable gastrointestinal stromal tumor (GIST) compared with placebo. To investigate the role of imatinib administration duration as adjuvant treatment of patients who have a high estimated risk for GIST recurrence after surgery. Patients with KIT-positive GIST removed at surgery were entered between February 2004 and September 2008 to this randomized, open-label phase 3 study conducted in 24 hospitals in Finland, Germany, Norway, and Sweden. The risk of GIST recurrence was estimated using the modified National Institutes of Health Consensus Criteria. Imatinib, 400 mg per day, orally for either 12 months or 36 months, started within 12 weeks of surgery. The primary end point was RFS; the secondary end points included overall survival and treatment safety. Two hundred patients were allocated to each group. The median follow-up time after randomization was 54 months in December 2010. Diagnosis of GIST was confirmed in 382 of 397 patients (96%) in the intention-to-treat population at a central pathology review. KIT or PDGFRA mutation was detected in 333 of 366 tumors (91%) available for testing. Patients assigned for 36 months of imatinib had longer RFS compared with those assigned for 12 months (hazard ratio [HR], 0.46; 95% CI, 0.32-0.65; P < .001; 5-year RFS, 65.6% vs 47.9%, respectively) and longer overall survival (HR, 0.45; 95% CI, 0.22-0.89; P = .02; 5-year survival, 92.0% vs 81.7%). Imatinib was generally well tolerated, but 12.6% and 25.8% of patients assigned to the 12- and 36-month groups, respectively, discontinued imatinib for a reason other than GIST recurrence. Compared with 12 months of adjuvant imatinib, 36 months of imatinib improved RFS and overall survival of GIST patients with a high risk of GIST recurrence. clinicaltrials.gov Identifier: NCT00116935.
    JAMA The Journal of the American Medical Association 03/2012; 307(12):1265-72. · 29.98 Impact Factor

Publication Stats

4k Citations
1,094.63 Total Impact Points

Institutions

  • 2013–2014
    • Universitätsklinikum Freiburg
      • Department of Internal Medicine I
      Freiburg an der Elbe, Lower Saxony, Germany
    • University of Zurich
      Zürich, Zurich, Switzerland
  • 1998–2013
    • Technische Universität München
      • Medizinische Klinik und Poliklinik III - Hämatologie/Onkologie
      München, Bavaria, Germany
  • 2009
    • Otto-von-Guericke-Universität Magdeburg
      • Clinic for Haematology and Oncology
      Magdeburg, Saxony-Anhalt, Germany
  • 2004–2008
    • Johannes Gutenberg-Universität Mainz
      • III. Department of Medicine
      Mayence, Rheinland-Pfalz, Germany
  • 2000–2001
    • Institut für klinische Pharmakologie
      Stuttgart, Baden-Württemberg, Germany
    • University of Wuerzburg
      • Institute for Medical Radiation and Cell Research
      Würzburg, Bavaria, Germany
    • Robert-Bosch Krankenhaus
      Stuttgart, Baden-Württemberg, Germany
  • 1996–1998
    • Universität Ulm
      • Department of Internal Medicine
      Ulm, Baden-Württemberg, Germany
  • 1991
    • Evangelische Hochschule Freiburg, Germany
      Freiburg, Baden-Württemberg, Germany