John E Dick

Ontario Institute for Cancer Research, Toronto, Ontario, Canada

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Publications (158)2128.01 Total impact

  • Experimental Hematology 08/2014; 42(8S):S51. · 2.81 Impact Factor
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    Experimental hematology; 08/2014
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    ABSTRACT: The hematopoietic system is a distributed tissue that consists of functionally distinct cell types continuously produced through hematopoietic stem cell (HSC) differentiation. Combining genomic and phenotypic data with high-content experiments, we have built a directional cell–cell communication network between 12 cell types isolated from human umbilical cord blood. Network structure analysis revealed that ligand production is cell type dependent, whereas ligand binding is promiscuous. Consequently, additional control strategies such as cell frequency modulation and compartmentalization were needed to achieve specificity in HSC fate regulation. Incorporating the in vitro effects (quiescence, self-renewal, proliferation, or differentiation) of 27 HSC binding ligands into the topology of the cell–cell communication network allowed coding of cell type-dependent feedback regulation of HSC fate. Pathway enrichment analysis identified intracellular regulatory motifs enriched in these cell type- and ligand-coupled responses. This study uncovers cellular mechanisms of hematopoietic cell feedback in HSC fate regulation, provides insight into the design principles of the human hematopoietic system, and serves as a foundation for the analysis of intercellular regulation in multicellular systems.
    Molecular Systems Biology 07/2014; 10(7). · 14.10 Impact Factor
  • John E Dick
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    ABSTRACT: Unearthing of the BRAF mutation in self-renewing hematopoietic stem cells reveals an unexpected origin for hairy cell leukemia-a mature B cell malignancy-and a potential new therapeutic target (Chung et al., this issue).
    Science translational medicine 05/2014; 6(238):238fs23. · 14.41 Impact Factor
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    ABSTRACT: Cancer stem cells or tumour-propagating cells (TPCs) have been identified for a number of cancers, but data pertaining to their existence in lymphoma so far remain elusive. We show for the first time that a small subset of cells purified from human anaplastic lymphoma kinase (ALK)-positive and -negative, anaplastic large cell lymphoma cell lines and primary patient tumours using the side population (SP) technique have serial tumour-propagating capacity both in vitro and in vivo; they give rise to both themselves and the bulk tumour population as well as supporting growth of the latter through the production of soluble factors. In vivo serial dilution assays utilising a variety of model systems inclusive of human cell lines, primary human tumours and nucleophosmin (NPM)-ALK-induced murine tumours demonstrate the TPC frequency to vary from as many as 1/54 to 1/1336 tumour cells. In addition, the SP cells express higher levels of pluripotency-associated transcription factors and are enriched for a gene expression profile consistent with early thymic progenitors. Finally, our data show that the SP cells express higher levels of the NPM-ALK oncogene and are sensitive to an ALK inhibitor.Oncogene advance online publication 12 May 2014; doi:10.1038/onc.2014.112.
    Oncogene 05/2014; · 8.56 Impact Factor
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    ABSTRACT: Historically, our understanding of mechanisms underlying human leukemogenesis are inferred from genetically engineered mouse models. Relatively few models that use primary human cells recapitulate the full leukemic transformation as assayed in xenografts and myeloid transformation is infrequent. We report a humanized experimental leukemia model where xenografts develop aggressive acute myeloid leukemia (AML) with disseminated myeloid sarcomas within 4 weeks following transplantation of cord blood transduced with vectors expressing BCR-ABL1 and a dominant negative isoform of IKAROS, Ik6. Ik6 induced transcriptional programs in BCR-ABL1 transduced progenitors that contained repressed B cell progenitor programs, along with strong stemness, proliferation, and granulocyte-monocytic progenitor signatures; a novel combination not induced in control groups. Thus, wild type IKAROS restrains stemness properties and has tumor suppressor activity in BCR-ABL1 initiated leukemia. Although IKAROS mutations/deletions are common in lymphoid transformation, they are found also at low frequency in AML that progress from a prior myeloproliferative neoplasms (MPN) state. Our experimental system provides an excellent model to gain insight into these rare cases of AML transformation and the properties conferred by IKAROS loss of function as a secondary mutation. More generally, our data point to the importance of deregulated stemness/lineage commitment programs in human myeloid leukemogenesis.Leukemia accepted article preview online, 05 May 2014; doi:10.1038/leu.2014.150.
    Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 05/2014; · 10.16 Impact Factor
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    ABSTRACT: The blood system is sustained by a pool of haematopoietic stem cells (HSCs) that are long-lived due to their capacity for self-renewal. A consequence of longevity is exposure to stress stimuli including reactive oxygen species (ROS), nutrient fluctuation and DNA damage. Damage that occurs within stressed HSCs must be tightly controlled to prevent either loss of function or the clonal persistence of oncogenic mutations that increase the risk of leukaemogenesis. Despite the importance of maintaining cell integrity throughout life, how the HSC pool achieves this and how individual HSCs respond to stress remain poorly understood. Many sources of stress cause misfolded protein accumulation in the endoplasmic reticulum (ER), and subsequent activation of the unfolded protein response (UPR) enables the cell to either resolve stress or initiate apoptosis. Here we show that human HSCs are predisposed to apoptosis through strong activation of the PERK branch of the UPR after ER stress, whereas closely related progenitors exhibit an adaptive response leading to their survival. Enhanced ER protein folding by overexpression of the co-chaperone ERDJ4 (also called DNAJB9) increases HSC repopulation capacity in xenograft assays, linking the UPR to HSC function. Because the UPR is a focal point where different sources of stress converge, our study provides a framework for understanding how stress signalling is coordinated within tissue hierarchies and integrated with stemness. Broadly, these findings reveal that the HSC pool maintains clonal integrity by clearance of individual HSCs after stress to prevent propagation of damaged stem cells.
    Nature 04/2014; · 42.35 Impact Factor
  • Antonija Kreso, John E Dick
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    ABSTRACT: Genetic analyses have shaped much of our understanding of cancer. However, it is becoming increasingly clear that cancer cells display features of normal tissue organization, where cancer stem cells (CSCs) can drive tumor growth. Although often considered as mutually exclusive models to describe tumor heterogeneity, we propose that the genetic and CSC models of cancer can be harmonized by considering the role of genetic diversity and nongenetic influences in contributing to tumor heterogeneity. We offer an approach to integrating CSCs and cancer genetic data that will guide the field in interpreting past observations and designing future studies.
    Cell stem cell 03/2014; 14(3):275-291. · 23.56 Impact Factor
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    ABSTRACT: In acute myeloid leukaemia (AML), the cell of origin, nature and biological consequences of initiating lesions, and order of subsequent mutations remain poorly understood, as AML is typically diagnosed without observation of a pre-leukaemic phase. Here, highly purified haematopoietic stem cells (HSCs), progenitor and mature cell fractions from the blood of AML patients were found to contain recurrent DNMT3A mutations (DNMT3A(mut)) at high allele frequency, but without coincident NPM1 mutations (NPM1c) present in AML blasts. DNMT3A(mut)-bearing HSCs showed a multilineage repopulation advantage over non-mutated HSCs in xenografts, establishing their identity as pre-leukaemic HSCs. Pre-leukaemic HSCs were found in remission samples, indicating that they survive chemotherapy. Therefore DNMT3A(mut) arises early in AML evolution, probably in HSCs, leading to a clonally expanded pool of pre-leukaemic HSCs from which AML evolves. Our findings provide a paradigm for the detection and treatment of pre-leukaemic clones before the acquisition of additional genetic lesions engenders greater therapeutic resistance.
    Nature 02/2014; · 42.35 Impact Factor
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    ABSTRACT: The hematopoietic system sustains regeneration throughout life by balancing self-renewal and differentiation. To stay poised for mature blood production, hematopoietic stem cells (HSCs) maintain low-level expression of lineage-associated genes, a process termed lineage priming. Here, we modulated expression levels of Inhibitor of DNA binding (ID) proteins to ask whether lineage priming affects self-renewal of human HSCs. We found that lentiviral overexpression of ID proteins in cord blood HSCs biases myeloerythroid commitment at the expense of lymphoid differentiation. Conversely, reducing ID2 expression levels increases lymphoid potential. Mechanistically, ID2 inhibits the transcription factor E47 to attenuate B-lymphoid priming in HSCs and progenitors. Strikingly, ID2 overexpression also results in a 10-fold expansion of HSCs in serial limiting dilution assays, indicating that early lymphoid transcription factors antagonize human HSC self-renewal. The relationship between lineage priming and self-renewal can be exploited to increase expansion of transplantable human HSCs and points to broader implications for other stem cell populations.
    Cell stem cell 01/2014; 14(1):94-106. · 23.56 Impact Factor
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    ABSTRACT: Constitutive heterozygous GATA2 mutation is associated with deafness, lymphedema, mononuclear cytopenias, infection, myelodysplasia (MDS) and AML. Here we describe a cross-sectional analysis of 24 patients and 6 relatives with 14 different frameshift or substitution mutations of GATA2. A pattern of mononuclear cytopenia (DCML deficiency) with elevated Flt3 ligand (Flt3L) was observed in all 20 patients phenotyped, including patients with Emberger's syndrome, monoMAC, and MDS. Four unaffected relatives had a normal phenotype indicating that cellular deficiency may evolve over time or is incompletely penetrant, while 2 developed subclinical cytopenias or elevated Flt3L. Patients with GATA2 mutation maintained higher hemoglobin, neutrophils and platelets and were younger than controls with acquired MDS and wild-type GATA2. Frame-shift mutations were associated with earlier age of clinical presentation than substitution mutations. Elevated Flt3L, loss of bone marrow progenitors and clonal myelopoiesis were early signs of disease evolution. Clinical progression was associated with increasingly elevated Flt3L, depletion of transitional B cells, CD56(bright) NK cells and naïve T cells and accumulation of terminally differentiated NK and CD8(+) memory T cells. These studies provide a framework for clinical and laboratory monitoring of patients with GATA2 mutation and may inform therapeutic decision making.
    Blood 12/2013; · 9.78 Impact Factor
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    ABSTRACT: The Lnk (Sh2b3) adaptor protein dampens the response of hematopoietic stem cells and progenitors (HSPCs) to a variety of cytokines by inhibiting JAK2 signaling. As a consequence, Lnk(-/-) mice develop hematopoietic hyperplasia, which progresses to a phenotype resembling the nonacute phase of myeloproliferative neoplasm. In addition, Lnk mutations have been identified in human myeloproliferative neoplasms and acute leukemia. We find that Lnk suppresses the development of radiation-induced acute B-cell malignancies in mice. Lnk-deficient HSPCs recover more effectively from irradiation than their wild-type counterparts, and this resistance of Lnk(-/-) HSPCs to radiation underlies the subsequent emergence of leukemia. A search for the mechanism responsible for radiation resistance identified the cytokine IL-11 as being critical for the ability of Lnk(-/-) HSPCs to recover from irradiation and subsequently become leukemic. In IL-11 signaling, wild-type Lnk suppresses tyrosine phosphorylation of the Src homology region 2 domain-containing phosphatase-2/protein tyrosine phosphatase nonreceptor type 11 and its association with the growth factor receptor-bound protein 2, as well as activation of the Erk MAP kinase pathway. Indeed, Src homology region 2 domain-containing phosphatase-2 has a binding motif for the Lnk Src Homology 2 domain that is phosphorylated in response to IL-11 stimulation. IL-11 therefore drives a pathway that enhances HSPC radioresistance and radiation-induced B-cell malignancies, but is normally attenuated by the inhibitory adaptor Lnk.
    Proceedings of the National Academy of Sciences 12/2013; · 9.81 Impact Factor
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    ABSTRACT: Tumor recurrence following treatment remains a major clinical challenge. Evidence from xenograft models and human trials indicates selective enrichment of cancer-initiating cells (CICs) in tumors that survive therapy. Together with recent reports showing that CIC gene signatures influence patient survival, these studies predict that targeting self-renewal, the key ‘stemness’ property unique to CICs, may represent a new paradigm in cancer therapy. Here we demonstrate that tumor formation and, more specifically, human colorectal CIC function are dependent on the canonical self-renewal regulator BMI-1. Downregulation of BMI-1 inhibits the ability of colorectal CICs to self-renew, resulting in the abrogation of their tumorigenic potential. Treatment of primary colorectal cancer xenografts with a small-molecule BMI-1 inhibitor resulted in colorectal CIC loss with long-term and irreversible impairment of tumor growth. Targeting the BMI-1–related self-renewal machinery provides the basis for a new therapeutic approach in the treatment of colorectal cancer.
    Nature Medicine 12/2013; · 28.05 Impact Factor
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    ABSTRACT: A locus on human chromosome 11q23 tagged by marker rs3802842 was associated with colorectal cancer in a genome-wide association study; this finding has been replicated in case-control studies worldwide. In order to identify biologic factors at this locus that are related to the etiopathology of colorectal cancer, we used microarray-based target selection methods, coupled to next-generation sequencing, to study 103 kb at the 11q23 locus. We genotyped 369 putative variants from 1030 patients with colorectal cancer (cases) and 1061 individuals without colorectal cancer (controls) from the Ontario Familial Colorectal Cancer Registry. Two previously uncharacterized genes, COLCA1 and COLCA2, were found to be co-regulated genes that are transcribed from opposite strands. Expression levels of COLCA1 and COLCA2 transcripts correlate with rs3802842 genotypes. In colon tissues, COLCA1 co-localizes with crystalloid granules of eosinophils and granular organelles of mast cells, neutrophils, macrophages, dendritic cells, and differentiated myeloid-derived cell lines. COLCA2 is present in the cytoplasm of normal epithelial, immune, and other cell lineages, as well as tumor cells. Tissue microarray analysis demonstrates the association of rs3802842 with lymphocyte density in the lamina propria (P=.014) and levels of COLCA1 in the lamina propria (P=.00016) and COLCA2 (tumor cells, P=.0041 and lamina propria, P = 6x10(-5) ). In conclusion, genetic, expression, and immunohistochemical data implicate COLCA1 and COLCA2 in the pathogenesis of colon cancer. Histologic analyses indicate the involvement of immune pathways. © 2013 Wiley Periodicals, Inc.
    International Journal of Cancer 10/2013; · 6.20 Impact Factor
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    ABSTRACT: Understanding how differentiation programs originate from the gene-expression 'landscape' of hematopoietic stem cells (HSCs) is crucial for the development of new clinical therapies. We mapped the transcriptional dynamics underlying the first steps of commitment by tracking transcriptome changes in human HSCs and eight early progenitor populations. We found that transcriptional programs were extensively shared, extended across lineage-potential boundaries and were not strictly lineage affiliated. Elements of stem, lymphoid and myeloid programs were retained in multilymphoid progenitors (MLPs), which reflected a hybrid transcriptional state. By functional single cell analysis, we found that the transcription factors Bcl-11A, Sox4 and TEAD1 (TEF1) governed transcriptional networks in MLPs, which led to B cell specification. Overall, we found that integrated transcriptome approaches can be used to identify previously unknown regulators of multipotency and show additional complexity in lymphoid commitment.
    Nature Immunology 05/2013; · 24.97 Impact Factor
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    ABSTRACT: Selective inhibition of protein methyltransferases is a promising new approach to drug discovery. An attractive strategy towards this goal is the development of compounds that selectively inhibit binding of the cofactor, S-adenosylmethionine, within specific protein methyltransferases. Here we report the three-dimensional structure of the protein methyltransferase DOT1L bound to EPZ004777, the first S-adenosylmethionine-competitive inhibitor of a protein methyltransferase with in vivo efficacy. This structure and those of four new analogues reveal remodelling of the catalytic site. EPZ004777 and a brominated analogue, SGC0946, inhibit DOT1L in vitro and selectively kill mixed lineage leukaemia cells, in which DOT1L is aberrantly localized via interaction with an oncogenic MLL fusion protein. These data provide important new insight into mechanisms of cell-active S-adenosylmethionine-competitive protein methyltransferase inhibitors, and establish a foundation for the further development of drug-like inhibitors of DOT1L for cancer therapy.
    Nature Communications 12/2012; 3:1288. · 10.74 Impact Factor
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    ABSTRACT: Intratumoral heterogeneity arises through evolution of genetically diverse subclones during tumor progression. However, whether cells within single genetic clones are functionally equivalent remains unknown. By combining DNA copy number alteration (CNA) profiling, sequencing, and lentiviral lineage tracking, we followed the repopulation dynamics of 150 single lentivirus-marked lineages from 10 human colorectal cancers through serial xenograft passages in mice. CNA and mutational analysis distinguished individual clones and showed that clones remained stable on serial transplantation. Despite this stability, the proliferation, persistence, and chemotherapy tolerance of lentivirally marked lineages were variable within each clone. Chemotherapy promoted dominance of previously minor or dormant lineages. Thus, apart from genetic diversity, tumor cells display inherent functional variability in tumor propagation potential, a mechanism that contributes both to cancer growth and therapy tolerance.
    Science 12/2012; · 31.48 Impact Factor
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    ABSTRACT: Despite efforts to understand and treat acute myeloid leukemia (AML), there remains a need for more comprehensive therapies to prevent AML-associated relapses. To identify new therapeutic strategies for AML, we screened a library of on- and off-patent drugs and identified the antimalarial agent mefloquine as a compound that selectively kills AML cells and AML stem cells in a panel of leukemia cell lines and in mice. Using a yeast genome-wide functional screen for mefloquine sensitizers, we identified genes associated with the yeast vacuole, the homolog of the mammalian lysosome. Consistent with this, we determined that mefloquine disrupts lysosomes, directly permeabilizes the lysosome membrane, and releases cathepsins into the cytosol. Knockdown of the lysosomal membrane proteins LAMP1 and LAMP2 resulted in decreased cell viability, as did treatment of AML cells with known lysosome disrupters. Highlighting a potential therapeutic rationale for this strategy, leukemic cells had significantly larger lysosomes compared with normal cells, and leukemia-initiating cells overexpressed lysosomal biogenesis genes. These results demonstrate that lysosomal disruption preferentially targets AML cells and AML progenitor cells, providing a rationale for testing lysosomal disruption as a novel therapeutic strategy for AML.
    The Journal of clinical investigation 12/2012; · 15.39 Impact Factor
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    ABSTRACT: Lifelong blood cell production is governed through the poorly understood integration of cell-intrinsic and -extrinsic control of hematopoietic stem cell (HSC) quiescence and activation. MicroRNAs (miRNAs) coordinately regulate multiple targets within signaling networks, making them attractive candidate HSC regulators. We report that miR-126, a miRNA expressed in HSC and early progenitors, plays a pivotal role in restraining cell-cycle progression of HSC in vitro and in vivo. miR-126 knockdown by using lentiviral sponges increased HSC proliferation without inducing exhaustion, resulting in expansion of mouse and human long-term repopulating HSC. Conversely, enforced miR-126 expression impaired cell-cycle entry, leading to progressively reduced hematopoietic contribution. In HSC/early progenitors, miR-126 regulates multiple targets within the PI3K/AKT/GSK3β pathway, attenuating signal transduction in response to extrinsic signals. These data establish that miR-126 sets a threshold for HSC activation and thus governs HSC pool size, demonstrating the importance of miRNA in the control of HSC function.
    Cell stem cell 11/2012; · 23.56 Impact Factor
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    ABSTRACT: Objective: A major limitation of current treatments for acute myelogenous leukemia (AML) is their inability to eradicate the leukemic stem cell (LSC) which is responsible for causing and propagating the disease. In addition radioimmunotherapy (RIT) suffers from dose‐limiting myelotoxicity. The chimeric mAb 360 recognizes CD123 in the absence of CD131, at unique exposed epitopes on LSCs but not on normal hematopoietic stem cells. Our aim was to construct 111In‐labeled 360 modified with nuclear localization sequence (NLS) containing peptides for nanometer‐micrometer Auger electron radiotherapy. Methods: MAb 360 was directly derivatized with DTPA then reacted with sulfo‐SMCC to introduce maleimide for conjugation to NLS containing peptides (CGYGPKKKRKVGG) and subsequently complexed with 111In (111In‐NLS‐360). Nuclear translocalization was measured by subcellular fractionation on primary AML specimens. Nine primary AML samples were inoculated and evaluated for AML engraftment into femurs of NOD/SCID mice. After 8‐weeks, mice were evaluated for hematological signs of leukemia and normal hematopoietic failure by complete blood counts. NOD/SCID mice engrafted with primary AML were treated with 500 μCi/mouse of 111In‐NLS‐ 360 for 72 h, targeting was monitored by micro‐single photon emission computerized tomography (SPECT; Bioscan NanoSPECT/CT) followed by harvesting of bone marrow (BM) cells and evaluated for CD45+CD123+CD131‐ population by flow cytometry. Results: 111In‐NLS‐360 exhibited enhanced (2‐6‐fold) nuclear uptake compared to non‐peptide modified 111In‐360 in 4/5 primary AML samples tested. After 8‐weeks, 4/9 samples produced high AML engraftment demonstrated by the percentage of CD45+CD123+CD131‐ cells. Mice that were able to engraft had decreases in white blood cell, red blood cell and platelet counts in whole blood. Harvested BM cells showed high percentage (60‐83%) of leukemic blasts and normal murine hematopoietic failure. MicroSPECT/CT demonstrated high specific uptake by 111In‐NLS‐360 vs isotype control into the BM (8.8 ± 1.4 vs 3.0 ± 0.1 %ID/g) of AML engrafted NOD/SCID mice at 72 h pi. CD45+CD123+CD131‐ cells were significantly reduced by 111In‐NLS‐360 compared to isotype control (47.2 ± 7.7 % vs 82.3 ± 1.8 %; P=7.92E‐06) Conclusions: The chimeric 111In‐NLS‐360 RIT strategy has the ability to deposit low‐energy ultra‐short range Auger electrons from 111In inside the nucleus of CD123+CD131‐ AML cells. In vivo studies with primary AML engrafting specimens demonstrated the ability of 111In‐NLS‐360 to track to BM sites of AML infiltration and reduce the CD45+CD123+CD131‐ population. Supported by the Canadian Institutes of Health Research.
    European journal of nuclear medicine and molecular imaging 10/2012; 39(Supplement 2):717. · 5.22 Impact Factor

Publication Stats

18k Citations
2,128.01 Total Impact Points


  • 2011–2014
    • Ontario Institute for Cancer Research
      Toronto, Ontario, Canada
  • 2004–2014
    • University Health Network
      • • Division of Cell and Molecular Biology
      • • Department of General Surgery
      Toronto, Ontario, Canada
  • 1994–2014
    • University of Toronto
      • • Department of Molecular Genetics
      • • Hospital for Sick Children
      Toronto, Ontario, Canada
  • 2009–2012
    • The Princess Margaret Hospital
      Toronto, Ontario, Canada
  • 1989–2000
    • SickKids
      Toronto, Ontario, Canada
  • 1999
    • The University of Western Ontario
      • Department of Microbiology and Immunology
      London, Ontario, Canada
  • 1993–1994
    • University of Guelph
      • Department of Clinical Studies
      Guelph, Ontario, Canada
  • 1992
    • UHN: Toronto General Hospital
      Toronto, Ontario, Canada
  • 1988
    • McGill University
      • Division of Hematology
      Montréal, Quebec, Canada