Department of Hematology/Oncology
Hubert Serve has not added Biography.
If you are Hubert Serve and would like to personalize this page please email our Author Liaison for assistance.
Carboplatin/etoposide induces remission of metastasised malignant peripheral nerve tumours (malignant schwannoma) refractory to first-line therapy.
Oncology reports May-Jun, 2002 | Pubmed ID: 11956640
Analysis of FLT3 length mutations in 1003 patients with acute myeloid leukemia: correlation to cytogenetics, FAB subtype, and prognosis in the AMLCG study and usefulness as a marker for the detection of minimal residual disease.
Blood Jul, 2002 | Pubmed ID: 12070009
Analysing c-kit internalization using a functional c-kit-EGFP chimera containing the fluorochrome within the extracellular domain.
Oncogene Jul, 2002 | Pubmed ID: 12085229
The t(8;21) fusion protein, AML1 ETO, specifically represses the transcription of the p14(ARF) tumor suppressor in acute myeloid leukemia.
Nature medicine Jul, 2002 | Pubmed ID: 12091906
Quantification of cyclin A1 and glyceraldehyde-3-phosphate dehydrogenase expression in testicular biopsies of infertile patients by fluorescence real-time RT-PCR.
International journal of andrology Aug, 2002 | Pubmed ID: 12121569
Cyclin A1 and gametogenesis in fertile and infertile patients: a potential new molecular diagnostic marker.
Human reproduction (Oxford, England) Sep, 2002 | Pubmed ID: 12202422
A single amino acid exchange inverts susceptibility of related receptor tyrosine kinases for the ATP site inhibitor STI-571.
The Journal of biological chemistry Feb, 2003 | Pubmed ID: 12435730
Suppression of myeloid transcription factors and induction of STAT response genes by AML-specific Flt3 mutations.
Blood Apr, 2003 | Pubmed ID: 12468433
Cyclin A1 is highly expressed in aggressive testicular germ cell tumors.
Cancer letters Feb, 2003 | Pubmed ID: 12536081
Successive increases in human cyclin A1 promoter activity during spermatogenesis in transgenic mice.
International journal of molecular medicine Mar, 2003 | Pubmed ID: 12579332
Phase I study of liposomal daunorubicin in relapsed and refractory acute myeloid leukemia.
Oncology reports Jul-Aug, 2003 | Pubmed ID: 12792745
Synergistic growth inhibitory effects of interferon-alpha and lovastatin on bcr-abl positive leukemic cells.
International journal of oncology Jul, 2003 | Pubmed ID: 12792788
Specific protein redirection as a transcriptional therapy approach for t(8;21) leukemia.
Proceedings of the National Academy of Sciences of the United States of America Jul, 2003 | Pubmed ID: 12819347
A phase 2 clinical study of SU5416 in patients with refractory acute myeloid leukemia.
Blood Oct, 2003 | Pubmed ID: 12843001
Re: Leptin--a growth factor in normal and malignant breast cells and for normal mammary gland development.
Journal of the National Cancer Institute Aug, 2003 | Pubmed ID: 12902450
MALAT-1, a novel noncoding RNA, and thymosin beta4 predict metastasis and survival in early-stage non-small cell lung cancer.
Oncogene Sep, 2003 | Pubmed ID: 12970751
Redirection of oncoproteins to kill cancer cells.
Cell cycle (Georgetown, Tex.) Nov-Dec, 2003 | Pubmed ID: 14504468
E- and A-type cyclins as markers for cancer diagnosis and prognosis.
Expert review of molecular diagnostics Sep, 2003 | Pubmed ID: 14510182
Evidence for allelic evolution of C/EBPalpha mutations in acute myeloid leukaemia.
British journal of haematology Nov, 2003 | Pubmed ID: 14616999
An innovative phase I clinical study demonstrates inhibition of FLT3 phosphorylation by SU11248 in acute myeloid leukemia patients.
Clinical cancer research : an official journal of the American Association for Cancer Research Nov, 2003 | Pubmed ID: 14654525
6-Thioguanine, cytarabine, and daunorubicin (TAD) and high-dose cytarabine and mitoxantrone (HAM) for induction, TAD for consolidation, and either prolonged maintenance by reduced monthly TAD or TAD-HAM-TAD and one course of intensive consolidation by sequential HAM in adult patients at all ages with de novo acute myeloid leukemia (AML): a randomized trial of the German AML Cooperative Group.
Journal of clinical oncology : official journal of the American Society of Clinical Oncology Dec, 2003 | Pubmed ID: 14673036
Multicolor karyotyping in acute myeloid leukemia.
Leukemia & lymphoma Nov, 2003 | Pubmed ID: 14738135
High-throughput analysis of genome-wide receptor tyrosine kinase expression in human cancers identifies potential novel drug targets.
Clinical cancer research : an official journal of the American Association for Cancer Research Feb, 2004 | Pubmed ID: 14977821
Translocation products in acute myeloid leukemia activate the Wnt signaling pathway in hematopoietic cells.
Molecular and cellular biology Apr, 2004 | Pubmed ID: 15024077
Epigenetic regulation of tumor suppressors in t(8:21)-containing AML.
Annals of hematology Jun, 2004 | Pubmed ID: 15052372
Identification of interaction partners and substrates of the cyclin A1-CDK2 complex.
The Journal of biological chemistry Aug, 2004 | Pubmed ID: 15159402
Flt3 receptor tyrosine kinase as a drug target in leukemia.
Current pharmaceutical design , 2004 | Pubmed ID: 15180525
Evolution of FLT3-ITD and D835 activating point mutations in relapsing acute myeloid leukemia and response to salvage therapy.
Leukemia research Oct, 2004 | Pubmed ID: 15289019
S100 family members and trypsinogens are predictors of distant metastasis and survival in early-stage non-small cell lung cancer.
Cancer research Aug, 2004 | Pubmed ID: 15313892
Identification of a novel activating mutation (Y842C) within the activation loop of FLT3 in patients with acute myeloid leukemia (AML).
Blood Jan, 2005 | Pubmed ID: 15345593
Expression of SOCS-1, suppressor of cytokine signalling-1, in human melanoma.
The Journal of investigative dermatology Oct, 2004 | Pubmed ID: 15373779
Influence of keratinocyte growth factor on clonal growth of epithelial tumor cells, lymphoma and leukemia cells and on sensitivity of tumor cells towards 5-fluorouracil in vitro.
International journal of oncology Oct, 2004 | Pubmed ID: 15375550
The cyclin A1-CDK2 complex regulates DNA double-strand break repair.
Molecular and cellular biology Oct, 2004 | Pubmed ID: 15456866
A phase 1 study of SU11248 in the treatment of patients with refractory or resistant acute myeloid leukemia (AML) or not amenable to conventional therapy for the disease.
Blood Feb, 2005 | Pubmed ID: 15459012
The serine-threonine kinase MNK1 is post-translationally stabilized by PML-RARalpha and regulates differentiation of hematopoietic cells.
Oncogene Dec, 2004 | Pubmed ID: 15516979
RGS2 is an important target gene of Flt3-ITD mutations in AML and functions in myeloid differentiation and leukemic transformation.
Blood Mar, 2005 | Pubmed ID: 15536149
Genome-wide screening for prognosis-predicting genes in early-stage non-small-cell lung cancer.
Lung cancer (Amsterdam, Netherlands) Aug, 2004 | Pubmed ID: 15552795
In vivo analyses of UV-irradiation-induced p53 promoter binding using a novel quantitative real-time PCR assay.
International journal of oncology Feb, 2005 | Pubmed ID: 15645135
Flt3 tandem duplication mutations cooperate with Wnt signaling in leukemic signal transduction.
Blood May, 2005 | Pubmed ID: 15650056
Identification of metastasis-associated receptor tyrosine kinases in non-small cell lung cancer.
Cancer research Mar, 2005 | Pubmed ID: 15753374
Alterations of lymphoid enhancer factor-1 isoform expression in solid tumors and acute leukemias.
Acta biochimica et biophysica Sinica Mar, 2005 | Pubmed ID: 15756419
AML-associated Flt3 kinase domain mutations show signal transduction differences compared with Flt3 ITD mutations.
Blood Jul, 2005 | Pubmed ID: 15769897
Expression patterns of mitotic and meiotic cell cycle regulators in testicular cancer and development.
International journal of cancer. Journal international du cancer Aug, 2005 | Pubmed ID: 15800920
Cyclin A1, the alternative A-type cyclin, contributes to G1/S cell cycle progression in somatic cells.
Oncogene Apr, 2005 | Pubmed ID: 15829981
Tyrosine phosphorylation regulates maturation of receptor tyrosine kinases.
Molecular and cellular biology May, 2005 | Pubmed ID: 15831474
Roles of tyrosine residues 845, 892 and 922 in constitutive activation of murine FLT3 kinase domain mutant.
Oncogene Dec, 2005 | Pubmed ID: 16091740
Receptor for platelet-activating factor (PAF) is not detectable by flow cytometry on the surface of myeloid leukemic cells.
Annals of hematology Nov, 2005 | Pubmed ID: 16094532
Signal transduction of oncogenic Flt3.
International journal of hematology Aug, 2005 | Pubmed ID: 16146838
Clinical resistance to the kinase inhibitor PKC412 in acute myeloid leukemia by mutation of Asn-676 in the FLT3 tyrosine kinase domain.
Blood Jan, 2006 | Pubmed ID: 16150941
The molecular pathogenesis of acute myeloid leukemia.
Critical reviews in oncology/hematology Nov, 2005 | Pubmed ID: 16236521
Acute myeloid leukemia presenting with a uterus tumor.
Annals of hematology Jan, 2006 | Pubmed ID: 16237527
Treatment of older patients with AML.
Critical reviews in oncology/hematology Nov, 2005 | Pubmed ID: 16246568
Constitutive activation of Akt by Flt3 internal tandem duplications is necessary for increased survival, proliferation, and myeloid transformation.
Cancer research Nov, 2005 | Pubmed ID: 16266983
First-line systemic treatment with gefitinib in stage IV non-small cell lung cancer.
Oncology reports Dec, 2005 | Pubmed ID: 16273252
Treatment of AML in biological subgroups.
Hematology (Amsterdam, Netherlands) , 2005 | Pubmed ID: 16276628
Targeting receptor kinases by a novel indolinone derivative in multiple myeloma: abrogation of stroma-derived interleukin-6 secretion and induction of apoptosis in cytogenetically defined subgroups.
Blood Mar, 2006 | Pubmed ID: 16278310
Emerging Flt3 kinase inhibitors in the treatment of leukaemia.
Expert opinion on emerging drugs Mar, 2006 | Pubmed ID: 16503833
Wnt signaling regulates transendothelial migration of monocytes.
Journal of leukocyte biology Jun, 2006 | Pubmed ID: 16565323
Double induction containing either two courses or one course of high-dose cytarabine plus mitoxantrone and postremission therapy by either autologous stem-cell transplantation or by prolonged maintenance for acute myeloid leukemia.
Journal of clinical oncology : official journal of the American Society of Clinical Oncology Jun, 2006 | Pubmed ID: 16735702
Growth inhibition and induction of apoptosis in acute myeloid leukemia cells by new indolinone derivatives targeting fibroblast growth factor, platelet-derived growth factor, and vascular endothelial growth factor receptors.
Molecular cancer therapeutics Dec, 2006 | Pubmed ID: 17172413
Decitabine and vitamin D3 differentially affect hematopoietic transcription factors to induce monocytic differentiation.
International journal of oncology Feb, 2007 | Pubmed ID: 17203216
The C/EBPdelta tumor suppressor is silenced by hypermethylation in acute myeloid leukemia.
Blood May, 2007 | Pubmed ID: 17234736
DNA methylation of tumor suppressor genes in clinical remission predicts the relapse risk in acute myeloid leukemia.
Cancer research Feb, 2007 | Pubmed ID: 17283175
Oncogenic signaling in acute myeloid leukemia.
Current drug targets Feb, 2007 | Pubmed ID: 17305501
Activation mechanisms of STAT5 by oncogenic Flt3-ITD.
Blood Jul, 2007 | Pubmed ID: 17356133
Flt3-dependent transformation by inactivating c-Cbl mutations in AML.
Blood Aug, 2007 | Pubmed ID: 17446348
DNA damage response involves modulation of Ku70 and Rb functions by cyclin A1 in leukemia cells.
International journal of cancer. Journal international du cancer Aug, 2007 | Pubmed ID: 17455244
New molecular therapy targets in acute myeloid leukemia.
Recent results in cancer research. Fortschritte der Krebsforschung. Progrès dans les recherches sur le cancer , 2007 | Pubmed ID: 17607931
CDDO induces granulocytic differentiation of myeloid leukemic blasts through translational up-regulation of p42 CCAAT enhancer binding protein alpha.
Blood Nov, 2007 | Pubmed ID: 17671235
Analysis of the genetic interactions between Cyclin A1, Atm and p53 during spermatogenesis.
Asian journal of andrology Nov, 2007 | Pubmed ID: 17968459
Chromatin modifications induced by PML-RARalpha repress critical targets in leukemogenesis as analyzed by ChIP-Chip.
Blood Mar, 2008 | Pubmed ID: 18024792
Identification of acute myeloid leukaemia associated microRNA expression patterns.
British journal of haematology Jan, 2008 | Pubmed ID: 18173753
Adjuvant therapy with small hairpin RNA interference prevents non-small cell lung cancer metastasis development in mice.
Cancer research Mar, 2008 | Pubmed ID: 18339871
Adaptor protein Lnk associates with Tyr(568) in c-Kit.
The Biochemical journal Oct, 2008 | Pubmed ID: 18588518
Activation of Wnt signaling in cKit-ITD mediated transformation and imatinib sensitivity in acute myeloid leukemia.
International journal of hematology Sep, 2008 | Pubmed ID: 18668305
Activation of Wnt signalling in acute myeloid leukemia by induction of Frizzled-4.
International journal of oncology Dec, 2008 | Pubmed ID: 19020754
S100A2 induces metastasis in non-small cell lung cancer.
Clinical cancer research : an official journal of the American Association for Cancer Research Jan, 2009 | Pubmed ID: 19118029
Dose-dense induction with sequential high-dose cytarabine and mitoxantone (S-HAM) and pegfilgrastim results in a high efficacy and a short duration of critical neutropenia in de novo acute myeloid leukemia: a pilot study of the AMLCG.
Blood Apr, 2009 | Pubmed ID: 19131552
Frequent CBL mutations associated with 11q acquired uniparental disomy in myeloproliferative neoplasms.
Blood Jun, 2009 | Pubmed ID: 19387008
Increased human telomerase reverse transcriptase (hTERT) mRNA expression but not telomerase activity is related to survival in curatively resected non-small cell lung cancer.
Anticancer research Apr, 2009 | Pubmed ID: 19414359
Construction and application of an inducible system for homogenous expression levels in bulk cell lines.
PloS one , 2009 | Pubmed ID: 19649290
An open-label, Phase I study of cediranib (RECENTIN) in patients with acute myeloid leukemia.
Leukemia research Feb, 2010 | Pubmed ID: 19674789
E3 ligase-defective Cbl mutants lead to a generalized mastocytosis and myeloproliferative disease.
Blood Nov, 2009 | Pubmed ID: 19734451
Mislocalized activation of oncogenic RTKs switches downstream signaling outcomes.
Molecular cell Oct, 2009 | Pubmed ID: 19854140
BCR-ABL enhances differentiation of long-term repopulating hematopoietic stem cells.
Blood Apr, 2010 | Pubmed ID: 20053753
Pim2 cooperates with PML-RARalpha to induce acute myeloid leukemia in a bone marrow transplantation model.
Blood Jun, 2010 | Pubmed ID: 20215640
The EPHB6 receptor tyrosine kinase is a metastasis suppressor that is frequently silenced by promoter DNA hypermethylation in non-small cell lung cancer.
Clinical cancer research : an official journal of the American Association for Cancer Research Apr, 2010 | Pubmed ID: 20371680
Profiling of histone H3 lysine 9 trimethylation levels predicts transcription factor activity and survival in acute myeloid leukemia.
Blood Nov, 2010 | Pubmed ID: 20498303
Low SMC1A protein expression predicts poor survival in acute myeloid leukemia.
Oncology reports Jul, 2010 | Pubmed ID: 20514443
Adaptor protein Lnk inhibits c-Fms-mediated macrophage function.
Journal of leukocyte biology Oct, 2010 | Pubmed ID: 20571037
Increased levels of 2-hydroxyglutarate in AML patients with IDH1-R132H and IDH2-R140Q mutations.
European journal of haematology Nov, 2010 | Pubmed ID: 20659156
The deacetylase inhibitor LAQ824 induces notch signalling in haematopoietic progenitor cells.
Leukemia research Jan, 2011 | Pubmed ID: 20674020
Liposomal cytarabine is effective and tolerable in the treatment of central nervous system relapse of acute lymphoblastic leukemia and very aggressive lymphoma.
Haematologica Feb, 2011 | Pubmed ID: 20952517
The European LeukemiaNet: achievements and perspectives.
Haematologica Jan, 2011 | Pubmed ID: 21048032
Complete remission and early death after intensive chemotherapy in patients aged 60 years or older with acute myeloid leukaemia: a web-based application for prediction of outcomes.
Lancet Dec, 2010 | Pubmed ID: 21131036
Increased HDAC1 deposition at hematopoietic promoters in AML and its association with patient survival.
Leukemia research May, 2011 | Pubmed ID: 21176959
Novel imatinib-sensitive PDGFRA-activating point mutations in hypereosinophilic syndrome induce growth factor independence and leukemia-like disease.
Blood Mar, 2011 | Pubmed ID: 21224473
AML1/ETO induces self-renewal in hematopoietic progenitor cells via the Groucho-related amino-terminal AES protein.
Blood Apr, 2011 | Pubmed ID: 21245488
Adaptor protein Lnk binds to PDGF receptor and inhibits PDGF-dependent signaling.
Experimental hematology May, 2011 | Pubmed ID: 21310211
Enhanced immune response after a second dose of an AS03-adjuvanted H1N1 influenza A vaccine in patients after hematopoietic stem cell transplantation.
Biology of blood and marrow transplantation : journal of the American Society for Blood and Marrow Transplantation Oct, 2011 | Pubmed ID: 21324375
Allogeneic transplantation as post-remission therapy for cytogenetically high-risk acute myeloid leukemia: landmark analysis from a single prospective multicenter trial.
Haematologica Jul, 2011 | Pubmed ID: 21459795
Inhibitor of cyclin-dependent kinase (CDK) interacting with cyclin A1 (INCA1) regulates proliferation and is repressed by oncogenic signaling.
The Journal of biological chemistry Aug, 2011 | Pubmed ID: 21540187
High single-drug activity of nelarabine in relapsed T-lymphoblastic leukemia/lymphoma offers curative option with subsequent stem cell transplantation.
Blood Sep, 2011 | Pubmed ID: 21715318
Antifungal management and resource use in patients with acute myeloid leukaemia after chemotherapy--retrospective analysis of changes over 3 yr in a German hospital.
European journal of haematology Jan, 2012 | Pubmed ID: 21883484
Adjuvant therapy for resectable high-risk soft tissue sarcoma: feasibility and efficacy of a sandwich chemoradiotherapy strategy.
Cancer chemotherapy and pharmacology Mar, 2012 | Pubmed ID: 21947168
Whole-exome sequencing identifies somatic mutations of BCOR in acute myeloid leukemia with normal karyotype.
Blood Dec, 2011 | Pubmed ID: 22012066
Survey and analysis of the efficacy and prescription pattern of sorafenib in patients with acute myeloid leukemia.
Leukemia & lymphoma Jun, 2012 | Pubmed ID: 22054287
Genome-wide analysis of histone H3 acetylation patterns in AML identifies PRDX2 as an epigenetically silenced tumor suppressor gene.
Blood Mar, 2012 | Pubmed ID: 22207736
Adult patients with acute lymphoblastic leukemia and molecular failure display a poor prognosis and are candidates for stem cell transplantation and targeted therapies.
Blood Aug, 2012 | Pubmed ID: 22442346
Outcome of relapsed adult lymphoblastic leukemia depends on response to salvage chemotherapy, prognostic factors, and performance of stem cell transplantation.
Blood Sep, 2012 | Pubmed ID: 22493293
SOCS1 cooperates with FLT3-ITD in the development of myeloproliferative disease by promoting the escape from external cytokine control.
Blood Aug, 2012 | Pubmed ID: 22517899
IT behind a platform for Translational Cancer Research - concept and objectives.
Studies in health technology and informatics , 2012 | Pubmed ID: 22874378
A special query tool in the hospital information system to recognize patients and to increase patient numbers for clinical trials.
Studies in health technology and informatics , 2012 | Pubmed ID: 22874393
Deacetylase inhibitors modulate proliferation and self-renewal properties of leukemic stem and progenitor cells.
Cell cycle (Georgetown, Tex.) Sep, 2012 | Pubmed ID: 22895185
A novel hierarchical prognostic model of AML solely based on molecular mutations.
Blood Oct, 2012 | Pubmed ID: 22915647
Outcome of elderly patients with acute promyelocytic leukemia: results of the German Acute Myeloid Leukemia Cooperative Group.
Annals of hematology Jan, 2013 | Pubmed ID: 23090499
Evaluation of the proposed reporting system of the European LeukemiaNet and recommendations for prognosis of acute myeloid leukemia.
Leukemia research Feb, 2013 | Pubmed ID: 23237559
Feasibility of azacitidine added to standard chemotherapy in older patients with acute myeloid leukemia--a randomised SAL pilot study.
PloS one , 2012 | Pubmed ID: 23300745
β2 integrin-derived signals induce cell survival and proliferation of AML blasts by activating a Syk/STAT signaling axis.
Blood May, 2013 | Pubmed ID: 23509157
High-dose cytarabine consolidation with or without additional amsacrine and mitoxantrone in acute myeloid leukemia: results of the prospective randomized AML2003 trial.
Journal of clinical oncology : official journal of the American Society of Clinical Oncology Jun, 2013 | Pubmed ID: 23630210
Sorafenib in combination with intensive chemotherapy in elderly patients with acute myeloid leukemia: results from a randomized, placebo-controlled trial.
Journal of clinical oncology : official journal of the American Society of Clinical Oncology Sep, 2013 | Pubmed ID: 23897964
Cutting edge: feed-forward activation of phospholipase Cγ2 via C2 domain-mediated binding to SLP65.
Journal of immunology (Baltimore, Md. : 1950) Dec, 2013 | Pubmed ID: 24166973
Smac mimetic primes apoptosis-resistant acute myeloid leukaemia cells for cytarabine-induced cell death by triggering necroptosis.
Cancer letters Mar, 2014 | Pubmed ID: 24184825
[Patient blood management--How does it work in practice?--the interdisciplinary cooperation].
Anästhesiologie, Intensivmedizin, Notfallmedizin, Schmerztherapie : AINS Apr, 2014 | Pubmed ID: 24792600
A transgenic mouse model demonstrating the oncogenic role of mutations in the polycomb-group gene EZH2 in lymphomagenesis.
Blood Jun, 2014 | Pubmed ID: 24802772
PADI4 acts as a coactivator of Tal1 by counteracting repressive histone arginine methylation.
Nature communications , 2014 | Pubmed ID: 24874575
CD133-targeted gene transfer into long-term repopulating hematopoietic stem cells.
Molecular therapy : the journal of the American Society of Gene Therapy Jan, 2015 | Pubmed ID: 25189742
Improved outcome of adult Burkitt lymphoma/leukemia with rituximab and chemotherapy: report of a large prospective multicenter trial.
Blood Dec, 2014 | Pubmed ID: 25359988
Allogeneic Stem-Cell Transplantation in Patients With NPM1-Mutated Acute Myeloid Leukemia: Results From a Prospective Donor Versus No-Donor Analysis of Patients After Upfront HLA Typing Within the SAL-AML 2003 Trial.
Journal of clinical oncology : official journal of the American Society of Clinical Oncology Feb, 2015 | Pubmed ID: 25547501
FLT3-ITD and TLR9 employ Bruton's tyrosine kinase to activate distinct transcriptional programs mediating AML cell survival and proliferation.
Blood Jan, 2015 | Pubmed ID: 25605370
Hanibal Bohnenberger1,
Philipp Ströbel1,
Sebastian Mohr2,
Jasmin Corso3,
Tobias Berg2,
Henning Urlaub3,4,
Christof Lenz3,4,
Hubert Serve2,5,6,
Thomas Oellerich2,5,6
1Institute of Pathology, University Medical Center, Göttingen,
2Department of Hematology/Oncology, Goethe University of Frankfurt,
3Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry,
4Bioanalytics, Institute of Clinical Chemistry, University Medical Center, Göttingen,
5, German Cancer Consortium,
6, German Cancer Research Center
Copyright © 2024 MyJoVE Corporation. Alle Rechte vorbehalten