Michael A Morgan

Publications of Michael A Morgan

• Mutations affecting mRNA splicing define distinct clinical phenotypes and correlate with patient outcome in myelodysplastic syndromes.

  Authors: Frederik Damm, Olivier Kosmider, Véronique Gelsi-Boyer, Aline Renneville, Nadine Carbuccia, Claire Hidalgo-Curtis, Véronique Della-Valle, Lucile Couronné, Laurianne Scourzic, Virginie Chesnais [......] François Dreyfus, Thomas Prébet, Stéphane de Botton, Norbert Vey, Michael A Morgan, Nicholas C P Cross, Claude Preudhomme, Daniel Birnbaum, Olivier A Bernard, Michaela Fontenay

  Blood. 02/2012;

  A cohort of MDS patients was examined for mutations affecting four splice genes (SF3B1, SRSF2, ZRSR2 and U2AF35) and evaluated in the context of clinical and molecular markers. Splice gene mutationsA cohort of MDS patients was examined for mutations affecting four splice genes (SF3B1, SRSF2, ZRSR2 and U2AF35) and evaluated in the context of clinical and molecular markers. Splice gene mutations were detected in 95 of 221 patients. These mutations were mutually exclusive and less likely to occur in patients with complex cytogenetics or TP53 mutations. SF3B1(mut) patients presented with lower hemoglobin levels, increased WBC and platelet counts and were more likely to have DNMT3A mutations. SRSF2(mut) patients clustered in RAEB-1 and RAEB-2 subtypes and exhibited pronounced thrombocytopenias. ZRSR2(mut) patients clustered in IPSS int-1 and int-2 risk-groups, had higher percentages of bone marrow blasts and more often displayed isolated neutropenias. SRSF2 and ZRSR2 mutations were more common in TET2(mut) patients. U2AF35(mut) patients had an increased prevalence of chromosome 20 deletions and ASXL1 mutations. Multivariate analysis revealed an inferior overall-survival (OS) and a higher AML transformation rate for the genotype ZRSR2(mut)/TET2(wt) (OS: HR 3.3; 95%CI 1.4 - 7.7; P=.006; AML transformation: HR 3.6; 95%CI 2 - 4.2; P=.026). Our results demonstrate that splice gene mutations are among the most frequent molecular aberrations in MDS, define distinct clinical phenotypes and show preferential associations with mutations targeting transcriptional regulation.

• Modulation of anthracycline-induced cytotoxicity by targeting the prenylated proteome in myeloid leukemia cells.

  Authors: Michael A Morgan, Fredrick O Onono, H Peter Spielmann, Thangaiah Subramanian, Michaela Scherr, Letizia Venturini, Iris Dallmann, Arnold Ganser, Christoph W M Reuter

  Journal of molecular medicine (Berlin, Germany). 09/2011; 90(2):149-61.

  Deregulation of Ras/ERK signaling in myeloid leukemias makes this pathway an interesting target for drug development. Myeloid leukemia cell lines were screened for idarubicin-induced apoptosis,Deregulation of Ras/ERK signaling in myeloid leukemias makes this pathway an interesting target for drug development. Myeloid leukemia cell lines were screened for idarubicin-induced apoptosis, cell-cycle progression, cell-cycle-dependent MAP kinase kinase (MEK-1/2) activation, and Top2 expression. Cell-cycle-dependent activation of MEK/ERK signaling was blocked using farnesyltransferase inhibitor (FTI) BMS-214,662 and dual prenyltransferase inhibitor (DPI) L-778,123 to disrupt Ras signaling. Idarubicin caused a G2/M cell-cycle arrest characterized by elevated diphosphorylated MEK-1/2 and Top2α expression levels. The FTI/DPIs elicited distinct effects on Ras signaling, protein prenylation, cell cycling and apoptosis. Combining these FTI/DPIs with idarubicin synergistically inhibited proliferation of leukemia cell lines, but the L-778,123+idarubicin combination exhibited synergistic growth inhibition over a greater range of drug concentrations. Interestingly, combined FTI/DPI treatment synergistically inhibited cell proliferation, induced apoptosis and nearly completely blocked protein prenylation. Inhibition of K-Ras expression by RNA interference or blockade of its post-translational prenylation led to increased BMS-214,662-induced apoptosis. Our results suggest that nearly complete inhibition of protein prenylation using an FTI + DPI combination is the most effective method to induce apoptosis and to block anthracycline-induced activation of ERK signaling.

• A tagging-via-substrate approach to detect the farnesylated proteome using two-dimensional electrophoresis coupled with Western blotting.

  Authors: Fredrick O Onono, Michael A Morgan, H Peter Spielmann, Douglas A Andres, Thangaiah Subramanian, Arnold Ganser, Christoph W M Reuter

  Molecular & cellular proteomics : MCP. 04/2010; 9(4):742-51.

  Prenylation is a post-translational modification critical for the proper function of multiple physiologically important proteins, including small G-proteins, such as Ras. Methods allowing rapid andPrenylation is a post-translational modification critical for the proper function of multiple physiologically important proteins, including small G-proteins, such as Ras. Methods allowing rapid and selective detection of protein farnesylation and geranylgeranylation are fundamental for the understanding of prenylated protein function and for monitoring efficacy of drugs such as farnesyltransferase inhibitors (FTIs). Although the natural substrates for prenyltransferases are farnesyl pyrophosphate and geranylgeranyl pyrophosphate, farnesyltransferase has been shown to incorporate isoprenoid analogues into protein substrates. In this study, protein prenyltransferase targets were labeled using anilinogeraniol, the alcohol precursor to the unnatural farnesyl pyrophosphate analogue 8-anilinogeranyl diphosphate in a tagging-via-substrate approach. Antibodies specific for the anilinogeranyl moiety were used to detect the anilinogeranyl-modified proteins. Coupling this highly effective labeling/detection method with two-dimensional electrophoresis and subsequent Western blotting allowed simple, rapid analysis of the complex farnesylated proteome. For example, this method elucidated the differential effects induced by two chemically distinct FTIs, BMS-214,662 and L-778,123. Although both FTIs strongly inhibited farnesylation of many proteins such as Lamins, NAP1L1, N-Ras, and H-Ras, only the dual prenylation inhibitor L-778,123 blocked prenylation of Pex19, RhoB, K-Ras, Cdc42, and Rap1. This snapshot approach has significant advantages over traditional techniques, including radiolabeling, anti-farnesyl antibodies, or mass spectroscopy, and enables dynamic analysis of the farnesylated proteome.

• Carboplatin plus weekly docetaxel as salvage chemotherapy in docetaxel-resistant and castration-resistant prostate cancer.

  Authors: Christoph W M Reuter, Michael A Morgan, Philipp Ivanyi, Martin Fenner, Arnold Ganser, Viktor Grünwald

  World journal of urology. 03/2010; 28(3):391-8.

  There is no proven, effective, standard second-line chemotherapy for castration- and docetaxel-resistant prostate cancer (DRPC). Recent data suggest that carboplatin may be effective in combinationThere is no proven, effective, standard second-line chemotherapy for castration- and docetaxel-resistant prostate cancer (DRPC). Recent data suggest that carboplatin may be effective in combination with docetaxel in this setting; however, the optimal docetaxel/carboplatin-based regimen is still unclear. We identified 43 consecutive patients with DRPC treated with carboplatin (AUC5 d1) and docetaxel (35 mg/m(2) d1, 8, 15 q4w i.v.) as a second-line or subsequent salvage chemotherapy until discontinuation of therapy due to disease progression or unacceptable toxicity. Decreased prostate-specific antigen (> or =50% PSA) was observed in 22/43 (51.2%, 95% CI, 35.5, 66.7%) patients, with > or =90% reduction in 12/43 patients (27.9%). At the time of analysis, the median follow-up time for all patients was 10.4 months. Median progression-free survival (PFS) for all patients was 6.5 months (95% CI 4.1, 8.9), and median overall survival (OS) was 15.8 months (95% CI 12.1, 18.5). In PSA responders, PFS was 9.5 (95% CI 8.2, 19.0) months versus 3.3 (95% CI 2.6, 4.0) months in PSA non-responders (P < 0.0001; hazard ratio (HR) 0.108) and OS was 24.4 months (95% CI 19.5, 29.4) versus 7.8 (95% CI 5.2, 10.3) months (P = 0.001; HR 0.232). Established prognostic factors were associated with survival. This regimen was reasonably well tolerated, with leukopenia/neutropenia as the most common reversible grade 3/4 toxicity (41.9/39.5%). These data suggest that weekly docetaxel plus carboplatin may be an important therapeutic second-line treatment option for patients with DRPC.

• Free iron ions decrease indoleamine 2,3-dioxygenase expression and reduce IFNgamma-induced inhibition of Chlamydia trachomatis infection.

  Authors: Birgit Krausse-Opatz, Ulrike Wittkop, Frank M Gutzki, Cornelia Schmidt, Barbara Jürgens-Saathoff, Sabine Meier, Bibiana Beckmann, Osamu Takikawa, Michael A Morgan, Dimitrios Tsikas, Dirk O Stichtenoth, Annette D Wagner, Henning Zeidler, Lars Köhler

  Microbial pathogenesis. 04/2009;

  Interferon-gamma (IFNgamma)-mediated indoleamine 2,3-dioxygenase (IDO) expression, important in innate immunity, immune suppression, and tolerance, can be counteracted by ferrous iron (FeSO(4)).Interferon-gamma (IFNgamma)-mediated indoleamine 2,3-dioxygenase (IDO) expression, important in innate immunity, immune suppression, and tolerance, can be counteracted by ferrous iron (FeSO(4)). Elevation of intracellular iron levels during stimulation with IFNgamma impeded IFNgamma-induced IDO mRNA and protein expression in HEp-2 cells. Decreased IDO expression was accompanied by decreased tryptophan degradation. Accordingly, IFNgamma-mediated suppressing effects on Chlamydia trachomatis (CT) infection were reduced or even abolished in the presence of FeSO(4). Conversely, lowering intracellular iron levels by deferoxamine (DFO) did not increase IFNgamma-induced IDO expression but potentiated Chlamydia-suppressing effects by lowering intracellular iron availability. Additionally, DFO led to a CT-induced IDO expression in HEp-2 cells not treated with IFNgamma. In summary, this study demonstrates that iron acts as a regulatory element for modulating IDO expression, in addition to its function as an essential element for chlamydial growth. This may represent an important control mechanism of IDO expression at the transcriptional level.

• Staining of Chlamydia trachomatis elementary bodies: a suitable method for identifying infected human monocytes by flow cytometry.

  Authors: Karen Schnitger, Florence Njau, Ulrike Wittkop, Andrea Liese, Jens G Kuipers, Andreas Thiel, Michael A Morgan, Henning Zeidler, Annette D Wagner

  Journal of microbiological methods. 05/2007; 69(1):116-21.

  Persistence of Chlamydia trachomatis (C. trachomatis) in the joint is the most frequent cause of reactive arthritis following urogenital tract infection. The resulting changes of host cell antigen-Persistence of Chlamydia trachomatis (C. trachomatis) in the joint is the most frequent cause of reactive arthritis following urogenital tract infection. The resulting changes of host cell antigen- and cytokine-expression are not precisely understood. We developed and evaluated a direct cytometric approach to visualize in vitro C. trachomatis-infected monocytes. Infectious elementary bodies (EBs) of C. trachomatis serovar K were labelled by incubation with 5-(and-6)-carboxyfluorescein diacetate succinimidyl ester (CFSE). Afterwards, human peripheral blood monocytes were cultured with the CFSE-labelled EBs and analysed by flow cytometry. Real-time polymerase chain reaction (PCR) was used to demonstrate intracellular uptake and viability of CFSE-labelled C. trachomatis by the determination of gene expression. Labelling EBs with CFSE may become a valuable tool for studying the interaction between C. trachomatis and the host cell.

• Targeting vascular endothelial growth factor (VEGF)-receptor-signaling in renal cell carcinoma.

  Authors: Christoph W M Reuter, Michael A Morgan, Viktor Grünwald, Thomas R W Herrmann, Martin Burchardt, Arnold Ganser

  World journal of urology. 04/2007; 25(1):59-72.

  Metastatic renal cell carcinoma (RCC) is resistant to conventional chemotherapy. Combined data for a variety of immunotherapies resulted in an overall chance of partial (PR) or complete remissionMetastatic renal cell carcinoma (RCC) is resistant to conventional chemotherapy. Combined data for a variety of immunotherapies resulted in an overall chance of partial (PR) or complete remission (CR) of only 12.9%. There is a clear need for novel, more effective therapies to prevent relapse, control metastases and improve overall survival. Improved understanding of RCC disease biology has led to the introduction of molecularly targeted treatment strategies in these cancers. Von Hippel-Lindau (VHL) gene inactivation is observed in most clear cell renal carcinoma, resulting in vascular endothelial growth factor (VEGF) over-expression and driving the malignant phenotype. This review discusses the efficacy of novel therapies targeting the VEGF receptor (VEGFR) (e.g. anti-VEGF antibodies, VEGFR tyrosine kinase inhibitors, mTOR inhibitors), some of which were recently approved by the Food and Drug Administration/European Medicines Evaluation Agency (FDA/EMEA) and represent the new treatment standards in RCC patients.

• Going from genes to proteins in myelodysplastic syndromes.

  Authors: Arnold Ganser, Michael A Morgan, Eva M Weissinger

  Proceedings of the National Academy of Sciences of the United States of America. 02/2007; 104(4):1109-10.

• Molecularly targeted therapies in myelodysplastic syndromes and acute myeloid leukemias.

  Authors: Michael A Morgan, Christoph W M Reuter

  Annals of hematology. 04/2006; 85(3):139-63.

  Although there has been significant progress in acute myeloid leukemia (AML) treatment in younger adults during the last decade, standard induction therapy still fails to induce remission in up toAlthough there has been significant progress in acute myeloid leukemia (AML) treatment in younger adults during the last decade, standard induction therapy still fails to induce remission in up to 40% of AML patients. Additionally, relapses are common in 50-70% of patients who achieve a complete remission, and only 20-30% of patients enjoy long-term disease-free survival. The natural history of myelodysplastic syndrome (MDS) is variable, with about half of the patients dying from cytopenic complications, and an additional 20-30% transforming to AML. The advanced age of the majority of MDS patients limits the therapeutic strategies often to supportive care. To address these shortcomings, much effort has been directed toward the development of novel treatment strategies that target the evolution and proliferation of malignant clones. Presented here is an overview of molecularly targeted therapies currently being tested in AML and MDS patients, with a focus on FMS-like tyrosine kinase 3 inhibitors, farnesyltransferase inhibitors, antiangiogenesis agents, DNA hypomethylation agents, and histone deacetylase inhibitors.

• Candida kefyr as an emerging pathogen causing nosocomial bloodstream infections in neutropenic leukemia patients.

  Authors: Christoph W M Reuter, Michael A Morgan, Franz-Christoph Bange, Florian Gunzer, Matthias Eder, Bernd Hertenstein, Arnold Ganser

  Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 12/2005; 41(9):1365-6.

• Combining prenylation inhibitors causes synergistic cytotoxicity, apoptosis and disruption of RAS-to-MAP kinase signalling in multiple myeloma cells.

  Authors: Michael A Morgan, Tarkan Sebil, Erdem Aydilek, Dietrich Peest, Arnold Ganser, Christoph W M Reuter

  British journal of haematology. 10/2005; 130(6):912-25.

  The high incidence of activating RAS mutations, coupled with accumulating evidence linking RAS to multiple myeloma (MM) pathogenesis, indicate that novel therapies utilising inhibitors of RASThe high incidence of activating RAS mutations, coupled with accumulating evidence linking RAS to multiple myeloma (MM) pathogenesis, indicate that novel therapies utilising inhibitors of RAS prenylation and signalling may be successful in the management of this disease. While preclinical studies investigating prenylation inhibitors, such as lovastatin, farnesyltransferase inhibitors (FTI) and geranylgeranyltransferase inhibitors (GGTI), have been promising, recent phase I/II clinical trials with FTI R115777 were disappointing, suggesting resistance to FTI monotherapy. To address this issue, the effects of FTI, GGTI and lovastatin alone and in combination were analysed in MM cell lines and primary cells. FTI treatment blocked H-RAS processing, but was ineffective at inhibiting K- and N-RAS prenylation because of alternative geranylgeranylation of these isoforms. However, combinations of FTI and GGTI or lovastatin were found to synergistically inhibit MM cell proliferation, migration, K- and N-RAS processing, RAS-to-mitogen-activated protein kinase signalling and to induce apoptosis. In contrast to FTI, lovastatin and some GGTI were found to cause intracellular accumulation of Rho proteins. Our results suggest that clinical efficacy of prenylation inhibitors in MM are limited by alternative prenylation of several small G-proteins, such as RhoB, K- and N-RAS. Furthermore, strategies combining FTI with GGTI or statins may provide greater efficacy in MM treatment.

• Gene silencing mediated by small interfering RNAs in mammalian cells.

  Authors: Michaela Scherr, Michael A Morgan, Matthias Eder

  Current medicinal chemistry. 03/2003; 10(3):245-56.

  RNA interference (RNAi) as a protecting mechanism against invasion by foreign genes was first described in C. elegans and has subsequently been demonstrated in diverse eukaryotes such as insects,RNA interference (RNAi) as a protecting mechanism against invasion by foreign genes was first described in C. elegans and has subsequently been demonstrated in diverse eukaryotes such as insects, plants, fungi and vertebrates. RNAi is the mechanism of sequence-specific, post-transcriptional gene silencing initiated by double-stranded RNAs (dsRNA) homologous to the gene being suppressed. dsRNAs are processed by Dicer, a cellular ribonuclease III, to generate duplexes of about 21 nt with 3'-overhangs (small interfering RNA, siRNA) which mediate sequence-specific mRNA degradation. In mammalian cells siRNA molecules are capable of specifically silencing gene expression without induction of the unspecific interferon response pathway. Thus, siRNAs have become a new and powerful alternative to other genetic tools such as antisense oligonucleotides and ribozymes to analyze loss-of-function phenotypes. Application of siRNA duplexes to interfere with the expression of a specific gene requires knowledge of target accessibility, highly effective delivery of siRNAs into target cells and for some applications long-term siRNA expression. Effective strategies to deliver siRNAs to target cells in cell culture include transduction by physical or chemical transfection. An alternative strategy uses the endogenous expression of siRNAs by various Pol III promoter expression cassettes that allow transcription of functional siRNAs or their precursors. This review summarizes some genetic and biochemical aspects of RNAi, the delivery and application of siRNAs to target cells, the kinetics of RNAi and the utility of siRNAs as analytical and potential therapeutic tools.

• Free iron ions decrease indoleamine 2,3-dioxygenase expression and reduce IFNγ-induced inhibition of Chlamydia trachomatis infection

  Authors: Birgit Krausse-Opatz, Ulrike Wittkop, Frank M. Gutzki, Cornelia Schmidt, Barbara Jürgens-Saathoff, Sabine Meier, Bibiana Beckmann, Osamu Takikawa, Michael A. Morgan, Dimitrios Tsikas, Dirk O. Stichtenoth, Annette D. Wagner, Henning Zeidler, Lars Köhler

  Microbial Pathogenesis.

  Interferon-γ (IFNγ)-mediated indoleamine 2,3-dioxygenase (IDO) expression, important in innate immunity, immune suppression, and tolerance, can be counteracted by ferrous iron (FeSO4). Elevation ofInterferon-γ (IFNγ)-mediated indoleamine 2,3-dioxygenase (IDO) expression, important in innate immunity, immune suppression, and tolerance, can be counteracted by ferrous iron (FeSO4). Elevation of intracellular iron levels during stimulation with IFNγ impeded IFNγ-induced IDO mRNA and protein expression in HEp-2 cells. Decreased IDO expression was accompanied by decreased tryptophan degradation. Accordingly, IFNγ-mediated suppressing effects on Chlamydia trachomatis (CT) infection were reduced or even abolished in the presence of FeSO4. Conversely, lowering intracellular iron levels by deferoxamine (DFO) did not increase IFNγ-induced IDO expression but potentiated Chlamydia-suppressing effects by lowering intracellular iron availability. Additionally, DFO led to a CT-induced IDO expression in HEp-2 cells not treated with IFNγ. In summary, this study demonstrates that iron acts as a regulatory element for modulating IDO expression, in addition to its function as an essential element for chlamydial growth. This may represent an important control mechanism of IDO expression at the transcriptional level.