Peter Brossart

University of Bonn - Medical Center, Bonn, North Rhine-Westphalia, Germany

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Publications (155)919.79 Total impact

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    ABSTRACT: Specialized blood cells are generated through the entire life of an organism by differentiation of a small number of hematopoietic stem cells (HSC). There are strictly regulated mechanisms assuring a constant and controlled production of mature blood cells. Although such mechanisms are not completely understood, some factors regulating cell cycle and differentiation have been identified. We have previously shown that Caspase-3 is an important regulator of HSC homeostasis and cytokine responsiveness. p21cip1/waf1 is a known cell cycle regulator, however its role in stem cell homeostasis seems to be limited. Several reports indicate interactions between p21cip1/waf1 and Caspase-3 in a cell type dependent manner. Here we studied the impact of simultaneous depletion of both factors on HSC homeostasis. Depletion of both Caspase-3 and p21cip1/waf1 resulted in an even more pronounced increase in the frequency of hematopoietic stem and progenitor cells. In addition, simultaneous deletion of both genes revealed a further increase of cell proliferation compared to single knock-outs and WT control mice, while apoptosis or self-renewal ability were not affected in any of the genotypes. Upon transplantation, p21cip1/waf1-/- bone marrow did not reveal significant alterations in engraftment of lethally irradiated mice, while Caspase-3 deficient HSPC displayed a significant reduction of blood cell production. However, when both p21cip1/waf1 and Caspase-3 were eliminated this differentiation defect caused by Caspase-3 deficiency was abrogated.
    PLoS ONE 10/2014; 9(10):e109266. · 3.53 Impact Factor
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    ABSTRACT: The objective was to evaluate the prognostic and predictive impact of allelic ratio and insertion site (IS) of internal tandem duplications (ITD), as well as concurrent gene mutations with regard to postremission therapy in 323 patients with FLT3-ITD positive acute myeloid leukemia (AML). Increasing FLT3-ITD allelic ratio (p=0.004) and IS in the tyrosine kinase domain 1 (TKD1, p=0.06) were associated with low complete remission (CR) rates. After postremission therapy including intensive chemotherapy (CTX, n=121) or autologous hematopoietic stem cell transplantation (HSCT, n=17), an allelic ratio ≥0.51 was associated with an unfavorable relapse-free (RFS, p=0.0008) and overall survival (OS, p=0.004); after allogeneic HSCT (n=93), outcome was significantly improved in patients with a high allelic ratio (RFS, p=0.02; OS, p=0.03), whereas no benefit was seen in patients with low allelic ratio (RFS, p=0.38; OS, p=0.64). Multivariable analyses revealed a high allelic ratio as a predictive factor for the beneficial effect of allogeneic HSCT; ITD IS in TKD1 remained an unfavorable factor, whereas no prognostic impact of concurrent gene mutations was observed. The clinical trials described herein were previously published or are registered as follows: AML HD93, reference 29; AML HD98A, reference 30; AMLSG 07-04, ClinicalTrials.gov identifier: NCT00151242.
    Blood 09/2014; · 9.78 Impact Factor
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    ABSTRACT: Outcome of AML patients older than 60 years has remained poor due to unfavorable disease characteristics and patient-related factors. The randomized AMLSG 06-04 protocol was designed based on in vitro synergistic effects of valproic acid (VPA) and all-trans retinoic acid (ATRA) with chemotherapy. Between 2004 and 2006, 186 patients were randomized to receive 2 induction cycles with idarubicin, cytarabine and ATRA with VPA (VPA) or without (STANDARD). In all patients consolidation therapy was intended. Complete remission rates after induction tended to be lower in VPA compared to STANDARD (40% vs. 52%; p=0.14) due to a higher early death rate (26% vs. 14%; p=0.06). The main toxicities attributed to VPA were delayed hematologic recovery and grade 3/4 infections observed predominantly during the second induction cycle. After restricting VPA to the first induction cycle and reducing the dose of idarubicin, these toxicities dropped to rates observed in STANDARD. After a median follow-up time of 84 months, event-free and overall survival were not different between the two arms (p=0.95 and p=0.57, respectively). However, relapse-free-survival was significantly superior in VPA compared to STANDARD (24.4% vs. 6.4% at 5 years, p=0.02). Explorative subset analyses revealed that AML with mutated NPM1 may particularly benefit from VPA. This study was registered at clinicaltrials.gov, identifier: NCT00151255.
    Blood 05/2014; · 9.78 Impact Factor
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    ABSTRACT: Lenalidomide activates the immune system, but the exact immunomodulatory mechanisms of lenalidomide in vivo are poorly defined. In an observational study we assessed the impact of lenalidomide on different populations of immune cells in multiple myeloma patients. Lenalidomide therapy was associated with increased amounts of a CD8+ T cell subset, phenotypically staged between classical central memory T cells (TCM) and effector memory T cells (TEM), consequently termed TCM/TEM. The moderate expression of perforin/granzyme and phenotypic profile of these cells identifies them as not yet terminally differentiated, which makes them promising candidates for the anti-tumor response. In addition, lenalidomide-treated patients showed higher abundance of CD14+ myeloid cells co-expressing CD15. This population was able to inhibit both CD4+ and CD8+ T cell proliferation in vitro and could thus be defined as a yet undescribed novel myeloid-derived suppressor cell (MDSC) subtype. We observed a striking correlation between levels of TCM/TEM, mature Tregs and CD14+CD15+ MDSCs. In summary, lenalidomide induces both activating and inhibitory components of the immune system, indicating the existence of potential counter-regulatory mechanisms. These findings provide new insights into the immunomodulatory action of lenalidomide.
    Clinical & Experimental Immunology 04/2014; · 3.41 Impact Factor
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    ABSTRACT: Recent work has identified dysfunctional Hippo signaling to be involved in maintenance and progression of various human cancers, although data on clear cell renal cell carcinoma (ccRCC) have been limited. Here, we provide evidence implicating aberrant Hippo signaling in ccRCC proliferation, invasiveness, and metastatic potential. Nuclear overexpression of the Hippo target Yes-associated protein (YAP) was found in a subset of patients with ccRCC. Immunostaining was particularly prominent at the tumor margins and highlighted neoplastic cells invading the tumor-adjacent stroma. Short hairpin RNA-mediated knockdown of YAP significantly inhibited proliferation, migration, and anchorage-independent growth of ccRCC cells in soft agar and led to significantly reduced murine xenograft growth. Microarray analysis of YAP knockdown versus mock-transduced ccRCC cells revealed down-regulation of endothelin 1, endothelin 2, cysteine-rich, angiogenic inducer, 61 (CYR61), and c-Myc in ccRCC cells as well as up-regulation of the cell adhesion molecule cadherin 6. Signaling pathway impact analysis revealed activation of the p53 signaling and cell cycle pathways as well as inhibition of mitogen-activated protein kinase signaling on YAP down-regulation. Our data suggest CYR61 and c-Myc as well as signaling through the endothelin axis as bona fide downstream effectors of YAP and establish aberrant Hippo signaling as a potential therapeutic target in ccRCC.
    Translational oncology. 04/2014; 7(2):309-21.
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    Dominik Wolf, Annkristin Heine, Peter Brossart
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    ABSTRACT: Harnessing the host immune system to eradicate cancer has a high therapeutic potential. One paradigm of anticancer immunotherapy is represented by allogeneic stem cell transplantation. In this setting, the host must be conditioned prior to transplantation, allowing for engraftment and subsequent graft-vs.-tumor reactivity. Conditioning may also be a prerequisite for the efficacy of other immunotherapeutic regimens. In particular, tumor debulking followed by conditioning (aimed at blocking endogenous inhibitory stimuli, for instance upon the depletion of regulatory T cells or the inhibition of immune checkpoints) and subsequent immunization (for instance by means of patient-tailored vaccines) based on innovative adjuvants (such as RIG-I ligands) may allow for the elicitation of superior antitumor immune responses. Repetitive boosting might then maintain immunosurveillance. An intense wave of investigation on the optimal timing of immunostimulatory interventions with respect to the administration of immunogenic chemotherapeutics and on the use of small drugs that promote efficient antitumor immune responses will end up in the generation of highly effective immunotherapeutic anticancer regimens.
    Oncoimmunology. 01/2014; 3(1):e27588.
  • Annkristin Heine, Peter Brossart, Dominik Wolf
    Blood 11/2013; 122(23):3843-4. · 9.78 Impact Factor
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    ABSTRACT: Tigecycline (TGC) is a first-in-class glycylcycline with an expanded spectrum of activity. Although TGC has not been prospectively studied in febrile neutropenia (FN), we observed that occasionally critically ill neutropenic patients unresponsive to other antibiotics were treated with TGC in our departments. The aim of our study was to analyse effectiveness and toxicity of TGC in FN. Data of infectious episodes treated with TGC were retrospectively collected. Baseline data of patients, haematological malignancy, infection and adverse events were documented. Success was defined as defervescence (≥7 days) in the absence of any sign of persistent infection. Data of 35 patients with haematological malignancies and FN were evaluated. Median duration of neutropenia was 25 days (range 6-69 days). The type of infection was pneumonia in 24 patients, four microbiologically documented infections, three clinically documented infections and four with fever of unknown origin. The TGC was administered after a median of two (range 1-5) prior antibiotic regimens. Treatment was successful in 15 (43 %) patients. In patients with prolonged neutropenia (≥28 days), response was significantly lower (13 vs. 79 %; p = 0.001). Eight (23 %) patients died during the fever episode. Grade 3-4 toxicity occurred in five (14 %) patients. Our results showed promising response rates to TGC and very low toxicity rates compared to the generally low response rate of third-line antibiotic therapies, indicating that TGC may be a successful alternative for salvage treatment of febrile neutropenia, but further study is needed.
    Infection 08/2013; · 2.44 Impact Factor
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    ABSTRACT: Tyrosine kinase inhibitors induce sustained disease remissions in chronic myeloid leukemia by exploiting the addiction of this type of leukemia to the activity of the fusion oncogene BCR-ABL. However, these agents fail to eradicate CML stem cells which are ultimately responsible for disease relapses upon treatment discontinuation. Evidence that the immune system can effectively reject CML stem cells potentially leading to patient cure is provided by the experience with patients receiving allogeneic bone marrow transplantations. Compelling evidence indicates that more modern, antigen-specific immunotherapeutic approaches are also feasible and hold strong potential to be clinically effective. Amongst these, particularly promising is the use of autologous dendritic cells pulsed with antigens or direct application of in vitro transcribed RNA encoding for leukemia-associated antigens, since this approach allows to circumvent HLA-restriction of the leukemia-associated T cell epitopes that have been eventually identified. Combining these strategies with monoclonal antibodies, such as anti-CTLA-4 or anti-PD-1, may help to obtain even stronger immune responses and better clinical results. This narrative review addresses this topic by focusing in particular on the cell-based immunotherapeutic strategies for CML and on the issue of the leukemia-associated antigens to be selected for targeting.
    Current cancer drug targets 07/2013; · 5.13 Impact Factor
  • Bone marrow transplantation 07/2013; · 3.00 Impact Factor
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    ABSTRACT: The JAK-inhibitor Ruxolitinib decreases constitutional symptoms and spleen size of myelofibrosis (MF) patients by mechanisms distinct from its anti-clonal activity. Here we investigated whether Ruxolitinib affects dendritic cell (DC) biology. The in vitro development of monocyte-derived DCs was almost completely blocked when the compound was added throughout the differentiation period. Furthermore, when applied solely during the final LPS-induced maturation step, Ruxolitinib reduced DC activation as demonstrated by decreased IL-12 production and attenuated expression of activation markers. Ruxolitinib also impaired both in vitro and in vivo DC migration. Dysfunction of Ruxolitinib-exposed DCs was further underlined by their impaired induction of allogeneic and antigen-specific T cell responses. Ruxolitinib-treated mice immunized with OVA/CpG induced markedly reduced in vivo activation and proliferation of OVA-specific CD8(+) T cells compared to vehicle-treated controls. Finally, using an adenoviral infection model, we show that Ruxolitinib-exposed mice exhibit delayed adenoviral clearance. Our results demonstrate that Ruxolitinib significantly affects DC differentiation and function leading to impaired T cell activation. DC dysfunction may result in increased infection rates in Ruxolitinib-treated patients. However, our findings may also explain the outstanding anti-inflammatory and immunomodulating activity of JAK-inhibitors currently used in the treatment of MF and autoimmune diseases.
    Blood 06/2013; · 9.78 Impact Factor
  • Savita Bisht, Georg Feldmann, Peter Brossart
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    ABSTRACT: Introduction: Despite being the second most common malignancy of the pancreas, pancreatic neuroendocrine tumors (PNET) have long been understudied due to their low incidence and heterogeneous clinical presentation. Emerging data from a Phase III trial demonstrates improved progression-free survival of patients with advanced PNET on treatment with sunitinib . Areas covered: This article reviews the role of sunitinib, a multitargeted tyrosine kinase inhibitor with potent antiangiogenic and antitumor effects, in the clinical management of PNET. Furthermore, the authors also discuss the pharmacokinetics and pharmacodynamics as well as other clinically relevant aspects regarding sunitinib. Expert opinion: A recent Phase III clinical trial of sunitinib demonstrated significant improvement of progression-free survival in patients with advanced or metastatic well-differentiated PNET that led to its approval in several countries, including Europe and United States. This marks a significant step forward in the clinical management of this disease and spurs hopes to further improve overall survival in this once difficult-to-treat set of patients in the coming years. Fields of future interest will include evaluation of combinatorial regimens, including conventional cytotoxic agents as well as additional targeted drugs in order to overcome resistance to sunitinib.
    Expert Opinion on Drug Metabolism &amp Toxicology 04/2013; · 2.94 Impact Factor
  • Annals of Hematology 04/2013; · 2.87 Impact Factor
  • Journal of Clinical Oncology 03/2013; · 18.04 Impact Factor
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    ABSTRACT: Periodontitis is one of the most prevalent human inflammatory diseases. The major clinical phenotypes of this polymicrobial, biofilm-mediated disease are chronic and aggressive periodontitis, the latter being characterized by a rapid course of destruction that is generally attributed to an altered immune-inflammatory response against periodontal pathogens. Still, the biological basis for the pathophysiological distinction of the two disease categories has not been well documented yet. Type I NKT cells are a lymphocyte subset with important roles in regulating immune responses to either tolerance or immunity, including immune responses against bacterial pathogens. In this study, we delineate the mechanisms of NKT cell activation in periodontal infections. We show an infiltration of type I NKT cells in aggressive, but not chronic, periodontitis lesions in vivo. Murine dendritic cells infected with aggressive periodontitis-associated Aggregatibacter actinomycetemcomitans triggered a type I IFN response followed by type I NKT cell activation. In contrast, infection with Porphyromonas gingivalis, a principal pathogen in chronic periodontitis, did not induce NKT cell activation. This difference could be explained by the absence of a type I IFN response to P. gingivalis infection. We found these IFNs to be critical for NKT cell activation. Our study provides a conceivable biological distinction between the two periodontitis subforms and identifies factors required for the activation of the immune system in response to periodontal bacteria.
    The Journal of Immunology 01/2013; · 5.52 Impact Factor
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    ABSTRACT: Management of patients suffering from metastatic malignant melanoma and brain metastasis remains challenging in routine clinical practice. The inhibitory anti-CTLA-4 antibody ipilimumab has recently been approved as second-line therapeutic option for melanoma patients. Increasing evidence suggests distinct therapeutic activity on central nervous system metastases, although this continues to be actively debated. Here, we present the case of a patient suffering from metastatic melanoma, including symptomatic brain metastasis, who showed a partial response to ipilimumab in extracranial tumor manifestations, while the disease was progressing intracranially. Subsequently, intracranial disease progression could be managed by local irradiation. An overview of currently available literature on the efficacy of ipilimumab in melanoma patients with central nervous system metastases is provided.
    Case Reports in Oncology 01/2013; 6(1):229-235.
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    ABSTRACT: Imatinib (IM) has been described to modulate the function of dendritic cells and T lymphocytes and to affect the expression of antigen in CML cells. In our study, we investigated the effect of the tyrosine kinase inhibitors IM and nilotinib (NI) on antigen presentation and processing by analyzing the proteasomal activity in CML cell lines and patient samples. We used a biotinylated active site-directed probe, which covalently binds to the proteasomally active beta-subunits in an activity-dependent fashion. Additionally, we analyzed the cleavage and processing of HLA-A3/11- and HLA-B8-binding peptides derived from BCR-ABL by IM- or NI-treated isolated 20S immunoproteasomes using mass spectrometry. We found that IM treatment leads to a reduction in MHC-class I expression which is in line with the inhibition of proteasomal activity. This process is independent of BCR-ABL or apoptosis induction. In vitro digestion experiments using purified proteasomes showed that generation of epitope-precursor peptides was significantly altered in the presence of NI and IM. Treatment of the immunoproteasome with these compounds resulted in an almost complete reduction in the generation of long precursor peptides for the HLA-A3/A11 and -B8 epitopes while processing of the short peptide sequences increased. Treatment of isolated 20S proteasomes with serine-/threonine- and tyrosine-specific phosphatases induced a significant downregulation of the proteasomal activity further indicating that phosphorylation of the proteasome regulates its function and antigen processing. Our results demonstrate that IM and NI can affect the immunogenicity of malignant cells by modulating proteasomal degradation and the repertoire of processed T cell epitopes.
    Cancer Immunology and Immunotherapy 11/2012; · 3.64 Impact Factor
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    ABSTRACT: Introduction: Pancreatic neuroendocrine tumors (PNET) represent the second most common primary malignancy of the pancreas. Until recently, therapeutic options for advanced PNET have been limited. Areas covered: A recently published Phase III clinical trial demonstrated striking therapeutic activity of the mTOR inhibitor everolimus in advanced PNET and led to its approval for this indication by the FDA. This review discusses this landmark discovery in the context of currently available therapeutic options, pathophysiology and molecular genetics of PNET. Expert opinion: The approval of everolimus for the treatment of PNET marks a major step forward in the clinical management of this disease and represents a notable example of the successful translation of a targeted therapy that was initially developed based on findings at the lab bench, into everyday clinical practice. These results encourage hopes that the overall therapeutic efficacy of such approaches can be further enhanced by the introduction of combinatorial regimens, simultaneously targeting more than one oncogenic signaling pathway, as well as by stratification of patients based on the individual genetic setup of their tumors.
    Expert Opinion on Pharmacotherapy 08/2012; 13(14):2073-84. · 2.86 Impact Factor
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    ABSTRACT: Metastatic renal cell carcinoma (RCC) seems to be resistant to conventional chemo- and radiotherapy and the general treatment regimen of cytokine therapy produces only modest responses while inducing severe side effects. Nowadays standard of care is the treatment with VEGF-inhibiting agents or mTOR inhibition; nevertheless, immunotherapy can induce complete remissions and long-term survival in selected patients. Among different adoptive lymphocyte therapies, cytokine-induced killer (CIK) cells have a particularly advantageous profile as these cells are easily available, have a high proliferative rate, and exhibit a high antitumor activity. Here, we reviewed clinical studies applying CIK cells, either alone or with standard therapies, for the treatment of RCC. The adverse events in all studies were mild, transient, and easily controllable. In vitro studies revealed an increased antitumor activity of peripheral lymphocytes of participants after CIK cell treatment and CIK cell therapy was able to induce complete clinical responses in RCC patients. The combination of CIK cell therapy and standard therapy was superior to standard therapy alone. These studies suggest that CIK cell immunotherapy is a safe and competent treatment strategy for RCC patients and further studies should investigate different treatment combinations and schedules for optimal application of CIK cells.
    Clinical and Developmental Immunology 01/2012; 2012:473245. · 3.06 Impact Factor
  • S.P. Haen, P. Brossart, H.-G. Rammensee
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    ABSTRACT: Die aktive Immunisierung gegen maligne Erkrankungen hat in den letzten Jahren bahnbrechende Erfolge verzeichnet. Immer mehr definierte Zielantigene finden Einzug in klinische Studien, und mit Ipilimumab und Sipuleucel-T wurden die ersten beiden aktiven Immuntherapeutika zugelassen. Beide bedienen sich individueller Gegebenheiten des Patientenimmunsystems. Auch Vakzinierungsstudien untersuchen individualisierte Ansätze, die darauf abzielen, jeden Tumor möglichst gezielt therapeutisch angreifen zu können und dabei möglichst geringe autoinflammatorische Nebenwirkungen zu induzieren. Dieser Artikel gibt einen Überblick über aktuelle therapeutische Ansätze wie die Vakzinierung mit autologen dendritischen Zellen, autologen oder allogenen Ganzzellvakzinen und die Möglichkeiten einer Vakzinierung mit definierten Tumorantigenen.
    Der Onkologe 01/2012; 18(9). · 0.13 Impact Factor

Publication Stats

5k Citations
919.79 Total Impact Points

Institutions

  • 2009–2014
    • University of Bonn - Medical Center
      Bonn, North Rhine-Westphalia, Germany
  • 2008–2014
    • University of Bonn
      Bonn, North Rhine-Westphalia, Germany
  • 2003–2009
    • Università degli Studi di Genova
      • Dipartimento di Medicina sperimentale (DIMES)
      Genova, Liguria, Italy
  • 1998–2009
    • University of Tuebingen
      • • Division of Oncology, haematology, clinical immunology, rheumatology and pneumology
      • • Department of Internal Medicine
      Tübingen, Baden-Württemberg, Germany
  • 2007
    • Johannes Gutenberg-Universität Mainz
      Mayence, Rheinland-Pfalz, Germany
  • 2005–2006
    • Universitätsklinikum Tübingen
      • Department of Medicine
      Tübingen, Baden-Württemberg, Germany
  • 2004–2005
    • Massachusetts Institute of Technology
      • Department of Biology
      Cambridge, Massachusetts, United States
  • 1997
    • University of Washington Seattle
      • Department of Immunology
      Seattle, WA, United States
  • 1996–1997
    • Howard Hughes Medical Institute
      Ashburn, Virginia, United States