Kojo S J Elenitoba-Johnson

University of Pennsylvania, Filadelfia, Pennsylvania, United States

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Publications (128)722.31 Total impact

  • Aaron M Udager · Jonathan B McHugh · Kojo S J Elenitoba-Johnson · Noah A Brown

    No preview · Article · Dec 2015
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    ABSTRACT: Pan-NOTCH inhibitors are poorly tolerated in clinical trials because NOTCH signals are crucial for intestinal homeostasis. These inhibitors might also promote cancer because NOTCH can act as a tumor suppressor. We previously reported that the PIAS-like coactivator ZMIZ1 is frequently co-expressed with activated NOTCH1 in T cell acute lymphoblastic leukemia (T-ALL). Here, we show that similar to Notch1, Zmiz1 was important for T cell development and controlled the expression of certain Notch target genes, such as Myc. However, unlike Notch, Zmiz1 had no major role in intestinal homeostasis or myeloid suppression. Deletion of Zmiz1 impaired the initiation and maintenance of Notch-induced T-ALL. Zmiz1 directly interacted with Notch1 via a tetratricopeptide repeat domain at a special class of Notch-regulatory sites. In contrast to the Notch cofactor Maml, which is nonselective, Zmiz1 was selective. Thus, targeting the NOTCH1-ZMIZ1 interaction might combat leukemic growth while avoiding the intolerable toxicities of NOTCH inhibitors.
    Full-text · Article · Nov 2015 · Immunity
  • Nathanael G Bailey · Kojo S J Elenitoba-Johnson
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    ABSTRACT: Mature T-cell leukemias are a group of uncommon lymphoid neoplasms. These disorders have widely variable clinical features, ranging from indolent, slowly progressive processes to diseases with rapidly progressive courses, leading to death. Cytogenetic aberrations have long been identified in some of these diseases, and recent studies have found recurrent genetic mutations that contribute to their pathogenesis. Conventional multiagent chemotherapy lacks significant efficacy in this group of diseases and therapies vary from immunosuppression to treatment with monoclonal antibodies, antiviral agents, and hematopoietic stem cell transplantation. The recent expansion of knowledge regarding the underlying genetic basis of these disorders raises hope that new, more targeted therapeutic approaches will be available to patients in the near future.
    No preview · Article · Oct 2015 · Current Hematologic Malignancy Reports
  • Soo Jeong Nam · Sehui Kim · JiEun Kim · Megan S Lim · Kojo S J Elenitoba-Johnson · Chul Woo Kim · Yoon Kyung Jeon
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    ABSTRACT: Background: Napsin A is commonly expressed in pulmonary adenocarcinomas and some renal cell carcinomas. However, napsin A expression in lymphoid neoplasms has never been reported. Methods: Glycoproteomic analyses of lymphoma-derived cell lines revealed napsin A expression in anaplastic large cell lymphoma (ALCL) cells. We thus investigated napsin A expression in lymphoid neoplasms. A variety of lymphomas (n=672) and histiocytic tumors (n=55) was immunostained for napsin A using patient tissues. Results: In reactive lymphoid tissues, only a few histiocytes were positive for napsin A. ALK-positive ALCLs most frequently expressed napsin A (34.4%, 11/32 cases) at a rate that was significantly higher compared with ALK-negative ALCL (8.6%, 3/35; P=0.015). Napsin A expression was also observed in 13.4% (20/149) of diffuse large B-cell lymphomas (DLBCL), 11.1% (15/134) of Hodgkin lymphomas, 4.9% (2/41) of follicular lymphomas, 6% (4/67) of peripheral T-cell lymphomas, and 3.8% (1/26) of plasma cell neoplasms. Otherwise, napsin A was not detected in any other types of lymphomas or histiocytic neoplasms. Napsin A expression in systemic ALCL was associated with a higher international prognostic index. ALCL and DLBCL patients with napsin A expression tended to have poor prognosis. Conclusion: These results demonstrated that napsin A is aberrantly expressed in a subset of lymphomas. The biological significance of napsin A in lymphomas warrants further study.
    No preview · Article · Sep 2015 · Histology and histopathology
  • Anagh A Sahasrabuddhe · Kojo S J Elenitoba-Johnson
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    ABSTRACT: Deregulated proteolysis is increasingly being implicated in pathogenesis of lymphoma. In this review, we highlight the major cellular processes that are affected by deregulated proteolysis of critical substrates that promote lymphoproliferative disorders. Emerging evidence supports the role of aberrant proteolysis by the ubiquitin proteasome system (UPS) in lymphoproliferative disorders. Several UPS mediators are identified to be altered in lymphomagenesis. However, the precise role of their alteration and comprehensive knowledge of their target substrate critical for lymphomagenesis is far from complete. Many E3 ligase and deubiquitinases that contribute to regulated proteolysis of substrates critical for major cellular processes are altered in various lineages of lymphoma. Understanding of the proteolytic regulatory mechanisms of these major cellular pathways may offer novel biomarkers and targets for lymphoma therapy.
    No preview · Article · Jul 2015 · Current opinion in hematology
  • Amir Behdad · Helmut C. Weigelin · Kojo S.J. Elenitoba-Johnson · Bryan L. Betz
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    ABSTRACT: Diagnostic testing for CEBPA mutations is the standard of care for cytogenetically normal acute myeloid leukemia. Widespread implementation of this testing is hampered by technical challenges associated with the GC content of the gene, the variability of the mutations, and the complexity of the sequence analysis and variant interpretation. We developed a robust Sanger-sequencing test to detect CEBPA mutations in diagnostic acute myeloid leukemia specimens. Our experience with testing 2393 cases of suspected myeloid neoplasms is presented. NPM1, FLT3-internal tandem duplication (ITD), and FLT3-D835 mutation status were determined in parallel; 160 (6.7%) cases harbored CEBPA mutations, including 86 with a single mutation and 74 with double mutations. Nineteen single-mutant cases and 3 double-mutant cases showed only nucleotide substitutions that could not be detected by fragment-analysis-based tests. A subset of cases harbored double mutations with uneven mutant allele frequency and required careful interpretation because of possible leukemic heterogeneity. NPM1 and FLT3-ITD mutations were more frequent in single- compared with double-mutation cases (31% versus 5% for NPM1, and 28% versus 16% for FLT3-ITD). This sequencing-based assay provides an efficient and reliable CEBPA mutation testing platform, permitting detection of all mutations with immediate distinction of single- and double-mutation cases. Given the technical challenges, robust Sanger-sequencing assays continue to maintain an important role in clinical CEBPA testing despite the development of multigene next-generation sequencing assays.
    No preview · Article · Jan 2015 · Journal of Molecular Diagnostics
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    ABSTRACT: MALT1 is the only known paracaspase and is a critical mediator of B- and T-cell receptor signalling. The function of the MALT1 gene is subverted by oncogenic chimeric fusions arising from the recurrent t(11;18)(q21;q21) aberration, which is the most frequent translocation in mucosa-associated lymphoid tissue (MALT) lymphoma. API2-MALT1-positive MALT lymphomas manifest antibiotic resistance and aggressive clinical behaviour with poor clinical outcome. However, the mechanisms underlying API2-MALT1-induced MALT lymphomagenesis are not fully understood. Here we show that API2-MALT1 induces paracaspase-mediated cleavage of the tumour suppressor protein LIMA1. LIMA1 binding by API2-MALT1 is API2 dependent and proteolytic cleavage is dependent on MALT1 paracaspase activity. Intriguingly, API2-MALT1-mediated proteolysis generates a LIM domain-only (LMO)-containing fragment with oncogenic properties in vitro and in vivo. Importantly, primary MALT lymphomas harbouring the API2-MALT1 fusion uniquely demonstrate LIMA1 cleavage fragments. Our studies reveal a novel paracaspase-mediated oncogenic gain-of-function mechanism in the pathogenesis of MALT lymphoma.
    Full-text · Article · Jan 2015 · Nature Communications
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    Noah A Brown · Bryan L Betz · Helmut C Weigelin · Kojo S J Elenitoba-Johnson · Megan S Lim · Nathanael G Bailey
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    ABSTRACT: Detection of BRAF V600E mutations in hairy cell leukemia (HCL) has important diagnostic utility. In this study, we sought to compare immunohistochemistry with an antibody specific for this mutation to a sensitive molecular assay. The performance of the BRAF V600E-specific VE1 antibody was compared with that of allele-specific polymerase chain reaction (PCR) in 22 formalin-fixed, paraffin-embedded (FFPE) specimens with HCL involvement, along with nine splenic marginal zone lymphomas (SMZLs), 10 follicular lymphomas (FLs), 10 mantle cell lymphomas (MCLs), and 10 chronic lymphocytic leukemia/small lymphocytic lymphomas (CLL/SLLs). An additional 11 SMZLs, 100 FLs, 20 MCLs, 83 CLL/SLL specimens, and 49 reactive tonsils within tissue microarrays were stained with VE1. A BRAF V600E mutation was detected in 17 (77.3%) of 22 HCL cases by PCR. Immunohistochemistry demonstrated VE1 staining in 20 (90.9%) cases, identifying low-level (~1%) involvement in three HCL cases that were mutation negative by PCR. Evaluation of additional material from these patients confirmed the presence of BRAF V600E. Thirty-nine non-HCL cases were negative by both methods. Within tissue microarrays, weak false-positive staining was observed in two (0.8%) of 263 non-HCL cases. VE1 immunohistochemistry is more sensitive than allele-specific PCR in FFPE bone marrow specimens and can be applied to decalcified core biopsy specimens that are not appropriate for molecular techniques. Copyright© by the American Society for Clinical Pathology.
    Preview · Article · Jan 2015 · American Journal of Clinical Pathology

  • No preview · Conference Paper · Dec 2014
  • Xiaofei Chen · Thirunavukkarasu Velusamy · Fuzon Chung · Megan S Lim · Kojo S J Elenitoba-Johnson
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    ABSTRACT: Introduction: Enhancer of zeste homologue 2 (EZH2) is a critical enzymatic subunit of the polycomb repressive complex 2 (PRC2) which trimethylates histone H3 (H3K27) to mediate gene repression. EZH2 is aberrantly activated and overexpressed in several hematologic malignancies and is associated with aggressive clinical behavior. In particular, recurrent mutations targeting Y641 of EZH2 are common in germinal center derived lymphomas. Critically, the cellular machinery and mechanisms that regulate EZH2 by post-translational modification are not well understood. We have previously shown that β-transducin repeat containing protein (βTrCP) is the substrate specific adaptor for ubiquitin mediated degradation of EZH2, however the degron motif by which βTrCP recognizes EZH2 is unknown. In order to better understand the post-translational regulation of EZH2, we sought to identify the non-canonical degron motif that regulates EZH2 stability. Methods: βTrCP recognizes a phosphorylated consensus degron motif DpSG(X) pS in its substrates. To investigate the post-translational modifications regulating the half-life of EZH2 protein we generated a series of truncation and site directed mutants of βTrCP including deletion of 7 WD repeat domain and mutation of R474A. The afore mentioned βTrCP mutants were assessed for their interaction with EZH2. Having established the non-canonical degron (DpS KNVpS) in EZH2, to further characterize the role of this degron in EZH2-βTrCP interaction we generated several EZH2 mutants including site-directed deletion of putative degron motif (DSKNVS) or alanine substitution mutations of critical serine residues S601A and S605A alone or in combination. Using wild-type as well as EZH2 mutants we investigated their ability to interact with βTrCP and consequent lysine (K48) linked polyubiquitination on EZH2 using co-immunoprecipitation and western blotting techniques. Further we characterized the impact of the identified degron in EZH2 stability using cycloheximide chase mediated protein turnover analysis of wild type and EZH2 degron deletion and serine (S601A/S605A) substitution mutants. Moreover, we investigated the impact of increased stability of EZH2 on its H3K27 trimethylation activity using wild type and degron deletion and serine substitution mutants by western blot analysis. We also investigated the impact of increased stability of EZH2 via degron modification by analyzing its downstream target p21. Results: Extensive interaction between substrates and R474 and Y488 residues in the 7 WD repeat domain of βTrCP is critical for stable binding and this is mediated via the conserved degron motif. In co-immunoprecipitation experiments, the mutation of R474A or deletion of 7 WD repeat domain in βTrCP abrogated the EZH2-βTrCP interaction. Further, the deletion of the identified degron DSKNVS in EZH2 or substitution of critical serine residues residing within this degron abrogated EZH2-βTrCP interaction and consequent lysine K48-linked polyubiquitination and proteasomal degradation. Half-life measurements by cycloheximide chase experiments demonstrated that the degron deletion or substitution mutations exhibit increased protein stability as compared to wild type EZH2. Motif analysis revealed that the novel EZH2 degron harbors the GSK3β recognition and phosphorylation motif (DpSKNVpS) involved in the phosphorylation of several known βTrCP substrates. Therefore, we examined the involvement of GSK3β in EZH2-βTrCP interaction. Pharmacologic inhibition of GSK3β compromised EZH2-βTrCP interaction in a dose dependent manner. Further, deletion of the degron or alanine substitution mutation of the critical serine residues (S601A and S605A) within the degron increased H3K27 trimethylation activity of EZH2 and consequently increased its repression on its downstream target p21. Conclusion: In the present study, we identify the presence of a novel non-canonical degron and GSK3β-mediated phosphorylation of the site that regulates EZH2 stability and activity. Our studies demonstrate that βTrCP/GSK3β axis plays an important role in controlling H3K27 trimethylation activity by targeting EZH2 for degradation. We propose that this newly identified mechanism might help in designing novel therapeutic approaches for clinical management of hematologic malignancies driven by aberrant activity of EZH2. Disclosures: No relevant conflicts of interest to declare.
    No preview · Conference Paper · Dec 2014

  • No preview · Conference Paper · Dec 2014
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    ABSTRACT: Introduction: Enhancer of zeste homologue 2 (EZH2) is a critical enzymatic subunit of the polycomb repressive complex 2 (PRC2) which trimethylates histone H3 (H3K27) to mediate gene repression. EZH2 is aberrantly activated and overexpressed in several hematologic malignancies and is associated with aggressive clinical behavior. In particular, recurrent mutations targeting Y641 of EZH2 are common in germinal center derived lymphomas. Critically, the cellular machinery and mechanisms that regulate EZH2 by post-translational modification are not well understood. We have previously shown that β-transducin repeat containing protein (βTrCP) is the substrate specific adaptor for ubiquitin mediated degradation of EZH2, however the degron motif by which βTrCP recognizes EZH2 is unknown. In order to better understand the post-translational regulation of EZH2, we sought to identify the non-canonical degron motif that regulates EZH2 stability. Methods: βTrCP recognizes a phosphorylated consensus degron motif DpSG(X) pS in its substrates. To investigate the post-translational modifications regulating the half-life of EZH2 protein we generated a series of truncation and site directed mutants of βTrCP including deletion of 7 WD repeat domain and mutation of R474A. The afore mentioned βTrCP mutants were assessed for their interaction with EZH2. Having established the non-canonical degron (DpS KNVpS) in EZH2, to further characterize the role of this degron in EZH2-βTrCP interaction we generated several EZH2 mutants including site-directed deletion of putative degron motif (DSKNVS) or alanine substitution mutations of critical serine residues S601A and S605A alone or in combination. Using wild-type as well as EZH2 mutants we investigated their ability to interact with βTrCP and consequent lysine (K48) linked polyubiquitination on EZH2 using co-immunoprecipitation and western blotting techniques. Further we characterized the impact of the identified degron in EZH2 stability using cycloheximide chase mediated protein turnover analysis of wild type and EZH2 degron deletion and serine (S601A/S605A) substitution mutants. Moreover, we investigated the impact of increased stability of EZH2 on its H3K27 trimethylation activity using wild type and degron deletion and serine substitution mutants by western blot analysis. We also investigated the impact of increased stability of EZH2 via degron modification by analyzing its downstream target p21. Results: Extensive interaction between substrates and R474 and Y488 residues in the 7 WD repeat domain of βTrCP is critical for stable binding and this is mediated via the conserved degron motif. In co-immunoprecipitation experiments, the mutation of R474A or deletion of 7 WD repeat domain in βTrCP abrogated the EZH2-βTrCP interaction. Further, the deletion of the identified degron DSKNVS in EZH2 or substitution of critical serine residues residing within this degron abrogated EZH2-βTrCP interaction and consequent lysine K48-linked polyubiquitination and proteasomal degradation. Half-life measurements by cycloheximide chase experiments demonstrated that the degron deletion or substitution mutations exhibit increased protein stability as compared to wild type EZH2. Motif analysis revealed that the novel EZH2 degron harbors the GSK3β recognition and phosphorylation motif (DpSKNVpS) involved in the phosphorylation of several known βTrCP substrates. Therefore, we examined the involvement of GSK3β in EZH2-βTrCP interaction. Pharmacologic inhibition of GSK3β compromised EZH2-βTrCP interaction in a dose dependent manner. Further, deletion of the degron or alanine substitution mutation of the critical serine residues (S601A and S605A) within the degron increased H3K27 trimethylation activity of EZH2 and consequently increased its repression on its downstream target p21. Conclusion: In the present study, we identify the presence of a novel non-canonical degron and GSK3β-mediated phosphorylation of the site that regulates EZH2 stability and activity. Our studies demonstrate that βTrCP/GSK3β axis plays an important role in controlling H3K27 trimethylation activity by targeting EZH2 for degradation. We propose that this newly identified mechanism might help in designing novel therapeutic approaches for clinical management of hematologic malignancies driven by aberrant activity of EZH2. Disclosures: No relevant conflicts of interest to declare.
    Full-text · Conference Paper · Dec 2014
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    ABSTRACT: Ubiquitination of the αN-terminus of protein substrates has been reported sporadically since the early 1980s. However, the identity of an enzyme responsible for this unique ubiquitin (Ub) modification has only recently been elucidated. We show the Ub-conjugating enzyme (E2) Ube2w uses a unique mechanism to facilitate the specific ubiquitination of the α-amino group of its substrates that involves recognition of backbone atoms of intrinsically disordered N termini. We present the NMR-based solution ensemble of full-length Ube2w that reveals a structural architecture unlike that of any other E2 in which its C terminus is partly disordered and flexible to accommodate variable substrate N termini. Flexibility of the substrate is critical for recognition by Ube2w, and either point mutations in or the removal of the flexible C terminus of Ube2w inhibits substrate binding and modification. Mechanistic insights reported here provide guiding principles for future efforts to define the N-terminal ubiquitome in cells.
    Preview · Article · Dec 2014 · Nature Chemical Biology
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    ABSTRACT: The cutaneous CD30-positive lymphoproliferative spectrum of disorders (LPD) includes lymphomatoid papulosis (LYP) and primary cutaneous anaplastic large cell lymphoma (ALCL). Chromosomal translocations targeting tyrosine kinases in CD30-positive LPD have not been described. Using whole transcriptome sequencing, we identified a chimeric fusion involving NPM1 (5q35) and TYK2 (19p13) which encodes an NPM1- TYK2 protein containing the oligomerization domain of NPM1 and an intact catalytic domain in TYK2. Fluorescence in situ hybridization revealed NPM1-TYK2 fusions in 2 of 47 (4%) primary cases of CD30-positive LPDs and was absent in other mature T-cell neoplasms (n = 151). Functionally, NPM1-TYK2 induced constitutive TYK2, STAT1, STAT3 and STAT5 activation. Conversely, a kinase-defective NPM1-TYK2 mutant abrogated STAT1/3/5 signaling. Finally, shRNA-mediated silencing of TYK2 abrogated lymphoma cell growth. This is the first report of recurrent translocations involving TYK2 and highlights the novel therapeutic opportunities in the treatment of CD30-positive LPDs with TYK2 translocations.
    No preview · Article · Oct 2014 · Blood
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    ABSTRACT: Fbxo45 is an atypical E3 ubiquitin ligase, which specifically targets proteins for ubiquitin-mediated degradation. Fbxo45 ablation results in defective neuronal differentiation and abnormal formation of neural connections; however, the mechanisms underlying these defects are poorly understood. Using an unbiased mass spectrometry-based proteomic screen, we show here that N-cadherin is a novel interactor of Fbxo45. N-cadherin specifically interacts with Fbxo45 through two consensus motifs overlapping the site of calcium-binding and dimerization of the cadherin molecule. N-cadherin interaction with Fbxo45 is significantly abrogated by calcium treatment. Surprisingly, Fbxo45 depletion by RNAi-mediated silencing results in enhanced proteolysis of N-cadherin. Conversely, ectopic expression of Fbxo45 results in decreased proteolysis of N-cadherin. Fbxo45 depletion results in dramatic reduction in N-cadherin expression, impaired neuronal differentiation, and diminished formation of neuronal processes. Our studies reveal an unanticipated role for an F-box protein that inhibits proteolysis in the regulation of a critical biological process.
    Full-text · Article · Aug 2014 · Journal of Biological Chemistry
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    X Chen · A A Sahasrabuddhe · P Szankasi · F Chung · V Basrur · V M Rangnekar · M Pagano · M S Lim · K S J Elenitoba-Johnson
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    ABSTRACT: Prostate apoptosis response protein 4 (Par-4) also known as PRKC apoptosis WT1 regulator is a tumor suppressor that selectively induces apoptosis in cancer cells. However, its post-translational regulation by ubiquitin-mediated proteolysis and the cellular machinery that is responsible for its proteasomal degradation are unknown. Using immunopurification and an unbiased mass spectrometry-based approach, we show that Par-4 interacts with the SPRY-domain containing E3 ubiquitin ligase Fbxo45 through a short consensus sequence motif. Fbxo45 interacts with Par-4 in the cytoplasm and mediates its ubiquitylation and proteasomal degradation. Fbxo45 silencing results in stabilization of Par-4 with increased apoptosis. Importantly, a Par-4 mutant that is unable to bind Fbxo45 is stabilized and further enhances staurosporine-induced apoptosis. Co-expression of Fbxo45 with Par-4 protects cancer cells against Par-4-induced apoptosis. Our studies reveal that Fbxo45 is the substrate-receptor subunit of a functional E3 ligase for Par-4 that has a critical role in cancer cell survival.Cell Death and Differentiation advance online publication, 4 July 2014; doi:10.1038/cdd.2014.92.
    Full-text · Article · Jul 2014 · Cell Death and Differentiation
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    ABSTRACT: Langerhans cell histiocytosis (LCH) represents a clonal proliferation of Langerhans cells. BRAF V600E mutations have been identified in approximately 50% of cases. To discover other genetic mechanisms underlying LCH pathogenesis, we studied 8 cases of LCH using a targeted next generation sequencing platform. An E102_I103del mutation in MAP2K1 was identified in one BRAF wild-type case and confirmed by Sanger sequencing. Analysis of 32 additional cases using BRAF V600E allele-specific PCR and Sanger sequencing of MAP2K1 exons 2 and 3 revealed somatic, mutually exclusive BRAF and MAP2K1 mutations in a total of 18/40 (45.0%) and 11/40 (27.5%) cases, respectively. This is the first report of MAP2K1 mutations in LCH which occur in 50% of BRAF wild-type cases. The mutually exclusive nature of MAP2K1 and BRAF mutations implicates a critical role of oncogenic MAPK signaling in LCH. This finding may also have implications for the use of BRAF and MEK inhibitor therapy.
    Preview · Article · Jun 2014 · Blood
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    ABSTRACT: The comprehensive genetic alterations underlying the pathogenesis of T-Prolymphocytic Leukemia (T-PLL) are unknown. To address this, we performed whole genome sequencing (WGS), whole exome sequencing (WES), high-resolution copy number analysis and Sanger resequencing of a large cohort of T-PLL. WGS and WES identified novel mutations in recurrently altered genes not previously implicated in T-PLL including EZH2, FBXW10 and CHEK2. Strikingly, WGS and/or WES showed largely mutually-exclusive mutations affecting IL2RG, JAK1, JAK3 or STAT5B in 38 of 50 T-PLL genomes (76.0%). Notably, gain-of-function IL2RG mutations are novel and have not been reported in any form of cancer. Further, high frequency mutations in STAT5B have not been previously reported in T-PLL. Functionally, IL2RG-JAK1-JAK3-STAT5B mutations led to STAT5 hyperactivation, transformed Ba/F3 cells resulting in cytokine-independent growth and/or enhanced colony formation in Jurkat T-cells. Importantly, primary T-PLL cells exhibited constitutive activation of STAT5 and targeted pharmacological inhibition of STAT5 with pimozide induced apoptosis in primary T-PLL cells. These results for the first time provide a portrait of the mutational landscape of T-PLL and implicate deregulation of DNA repair and epigenetic modulators as well as high-frequency mutational activation of the IL2RG-JAK1-JAK3-STAT5B axis in the pathogenesis of T-PLL. These findings offer opportunities for novel targeted therapies in this aggressive leukemia.
    Full-text · Article · May 2014 · Blood
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    ABSTRACT: Deregulation of signaling pathways controlled by protein phosphorylation underlies the pathogenesis of hematological malignancies; however, the extent to which deregulated phosphorylation may be involved in B-cell non-Hodgkin lymphoma (B-NHL) pathogenesis is largely unknown. To identify phosphorylation events important in B-NHLs, we performed mass spectrometry-based, label-free, semiquantitative phosphoproteomic profiling of 11 cell lines derived from three B-NHL categories: Burkitt lymphoma, follicular lymphoma, and mantle-cell lymphoma. In all, 6579 unique phosphopeptides, corresponding to 1701 unique phosphorylated proteins, were identified and quantified. The data are available via ProteomeXchange with identifier PXD000658. Hierarchical clustering highlighted distinct phosphoproteomic signatures associated with each lymphoma subtype. Interestingly, germinal center-derived B-NHL cell lines were characterized by phosphorylation of proteins involved in the B-cell receptor signaling. Of these proteins, phosphoprotein associated with glycosphingolipid-enriched microdomains 1 (PAG1) was identified with the most phosphorylated tyrosine peptides in Burkitt lymphoma and follicular lymphoma. PAG1 knockdown resulted in perturbation of the tyrosine phosphosignature of B-cell receptor signaling components. Significantly, PAG1 knockdown increased cell proliferation and response to antigen stimulation of these germinal center-derived B-NHLs. These data provide a detailed annotation of phosphorylated proteins in human lymphoid cancer. Overall, our study revealed the utility of unbiased phosphoproteome interrogation in characterizing signaling networks that may provide insights into pathogenesis mechanisms in B-cell lymphomas.
    Full-text · Article · Mar 2014 · American Journal Of Pathology
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    ABSTRACT: Detection of high-frequency BRAF V600E mutations in hairy cell leukemia (HCL) has important diagnostic utility. However, the requisite analytic performance for a clinical assay to routinely detect BRAF V600E mutations in HCL has not been clearly defined. In this study, we sought to determine the level of analytic sensitivity needed for formalin-fixed, paraffin-embedded (FFPE) and frozen samples and to compare the performance of 2 allele-specific polymerase chain reaction (PCR) assays. Twenty-nine cases of classic HCL, including 22 FFPE bone marrow aspirates and 7 frozen specimens from blood or bone marrow were evaluated using a laboratory-developed allele-specific PCR assay and a commercially available allele-specific quantitative PCR assay-myT BRAF Ultra. Also included were 6 HCL variant and 40 non-HCL B-cell lymphomas. Two cases of classic HCL, 1 showing CD5 expression, were truly BRAF V600E-negative based on negative results by PCR and sequencing despite high-level leukemic involvement. Among the remaining 27 specimens, V600E mutations were detected in 88.9% (17/20 FFPE; 7/7 frozen) and 81.5% (15/20 FFPE; 7/7 frozen), for the laboratory-developed and commercial assays, respectively. No mutations were detected among the 46 non-HCL lymphomas. Both assays showed an analytic sensitivity of 0.3% involvement in frozen specimens and 5% in FFPE tissue. On the basis of these results, an assay with high analytic sensitivity is required for the clinical detection of V600E mutations in HCL specimens. Two allele-specific PCR assays performed well in both frozen and FFPE bone marrow aspirates, although detection in FFPE tissue required 5% or more involvement.
    No preview · Article · Feb 2014 · Applied immunohistochemistry & molecular morphology: AIMM / official publication of the Society for Applied Immunohistochemistry

Publication Stats

4k Citations
722.31 Total Impact Points

Institutions

  • 2015
    • University of Pennsylvania
      Filadelfia, Pennsylvania, United States
    • William Penn University
      Filadelfia, Pennsylvania, United States
  • 2007-2015
    • University of Michigan
      • Department of Pathology
      Ann Arbor, Michigan, United States
  • 2007-2014
    • Concordia University–Ann Arbor
      Ann Arbor, Michigan, United States
  • 2000-2008
    • University of Utah
      • • ARUP Institute for Clinical and Experimental Pathology
      • • Department of Pathology
      Salt Lake City, Utah, United States
    • Arup
      Londinium, England, United Kingdom
  • 2000-2007
    • University of Texas MD Anderson Cancer Center
      • • Department of Hematopathology
      • • Department of Pathology
      Houston, TX, United States
  • 2002
    • University of Toronto
      Toronto, Ontario, Canada
  • 1998
    • National Human Genome Research Institute
      Maryland, United States
  • 1997-1998
    • National Institutes of Health
      • Laboratory of Pathology
      베서스다, Maryland, United States
    • National Cancer Institute (USA)
      Maryland, United States
  • 1996
    • Rhode Island Hospital
      Providence, Rhode Island, United States