Publications by authors named "Richard A Wells"

48 Publications

Intracellular ROS profile in hematopoietic progenitors of MDS patients: association with blast count and iron overload.

Hematology 2021 Dec;26(1):88-95

Biological Sciences, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Canada.

Reactive oxygen species (ROS) are under scrutiny as a participant in the pathophysiology of myelodysplastic syndrome (MDS) and the progression of MDS to acute myeloid leukemia (AML). Measurement of intracellular ROS (iROS) is particularly important since iROS is a direct indicator of cellular health and integrity. We developed a technique to measure standardize iROS (siROS) level in lymphocytes and bone marrow (BM) CD34 hematopoietic progenitors using the fluorescent probe dichlorofluorescein (DCF). We then quantified the siROS in 38 consecutive BM specimens from 27 MDS patients over the course of 10 months. Disease outcome of these patients were also assessed. High serum ferritin, high blast count and poor IPSS were associated with inferior survival and AML progression in this cohort. High blast MDS patients had lower siROS in their BM CD34+ cells than those of low blast patients, consistent with increased reliance on glycolysis and enhanced ROS defense in high blast MDS. We also observed narrower siROS distribution in the BM CD34+ cells of high blast patients, suggesting that loss of heterogeneity in ROS content accompanies the clonal evolution of MDS. Furthermore, we observed a strong correlation between CD34+ cells siROS and serum ferritin level in high blast patients. In one case, iron chelation therapy (ICT) resulted in parallel decreases in serum ferritin and CD34 cells siROS. Our findings established the siROS profile in early hematopoietic cells of MDS patients and its relationship with blast count and iron overload.
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http://dx.doi.org/10.1080/16078454.2020.1870373DOI Listing
December 2021

The effects of secondary iron overload and iron chelation on a radiation-induced acute myeloid leukemia mouse model.

BMC Cancer 2021 May 6;21(1):509. Epub 2021 May 6.

Biological Sciences, Sunnybrook Research Institute Sunnybrook Health Sciences Centre, Toronto, ON, Canada.

Background: Patients with myelodysplastic syndrome (MDS) require chronic red blood cell (RBC) transfusion due to anemia. Multiple RBC transfusions cause secondary iron overload and subsequent excessive generation of reactive oxygen species (ROS), which leads to mutations, cell death, organ failure, and inferior disease outcomes. We hypothesize that iron loading promotes AML development by increasing oxidative stress and disrupting important signaling pathways in the bone marrow cells (BMCs). Conversely, iron chelation therapy (ICT) may reduce AML risk by lowering iron burden in the iron-loaded animals.

Methods: We utilized a radiation-induced acute myeloid leukemia (RI-AML) animal model. Iron overload was introduced via intraperitoneal injection of iron dextran, and iron chelation via oral gavage of deferasirox. A total of 86 irradiated B6D2F1 mice with various levels of iron burden were monitored for leukemia development over a period of 70 weeks. The Kaplan-Meier estimator was utilized to assess AML free survival. In addition, a second cohort of 30 mice was assigned for early analysis at 5 and 7 months post-irradiation. The BMCs of the early cohort were assessed for alterations of signaling pathways, DNA damage response and gene expression. Statistical significance was established using Student's t-test or ANOVA.

Results: Iron loading in irradiated B6D2F1 mice accelerated RI-AML development. However, there was a progressive decrease in AML risk for irradiated mice with increase in iron burden from 7.5 to 15 to 30 mg. In addition, ICT decreased AML incidence in the 7.5 mg iron-loaded irradiated mice, while AML onset was earlier for the 30 mg iron-loaded irradiated mice that received ICT. Furthermore, analysis of BMCs from irradiated mice at earlier intervals revealed accelerated dysregulation of signaling pathways upon iron loading, while ICT partially mitigated the effects.

Conclusions: We concluded that iron is a promoter of leukemogenesis in vivo up to a peak iron dose, but further iron loading decreases AML risk by increasing cell death. ICT can partially mitigate the adverse effects of iron overload, and to maximize its benefit this intervention should be undertaken prior to the development of extreme iron overload.
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http://dx.doi.org/10.1186/s12885-021-08259-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8103632PMC
May 2021

Pharmacokinetic and pharmacodynamic effects of ravulizumab and eculizumab on complement component 5 in adults with paroxysmal nocturnal haemoglobinuria: results of two phase 3 randomised, multicentre studies.

Br J Haematol 2020 11 24;191(3):476-485. Epub 2020 May 24.

Clinical Haematology at Peter MacCallum Cancer Centre, The Royal Melbourne Hospital and University of Melbourne, Melbourne, Australia.

Ravulizumab, a novel long-acting complement component 5 (C5) inhibitor administered every 8 weeks (q8w), was non-inferior to eculizumab for all efficacy outcomes in two randomised, open-label, phase 3 trials in C5 inhibitor-naïve (Study 301) and eculizumab-experienced (Study 302) adult patients with paroxysmal nocturnal haemoglobinuria (PNH). This pre-specified analysis characterised ravulizumab pharmacokinetics (PK), pharmacodynamics (PD; free C5 levels), and PD differences between medications (Study 301, n = 246; Study 302, n = 195). Ravulizumab PK parameters were determined using non-compartmental analysis. Serum free C5 was quantified with a Gyros-based fluorescence assay (ravulizumab) and an electrochemiluminescence ligand-binding assay (eculizumab). Ravulizumab PK parameters were numerically comparable in both studies; the median time to maximum concentrations ranged from 2·3 to 2·8 and 2·3 to 2·6 h in studies 301 and 302, respectively. Ravulizumab steady-state serum concentrations were achieved immediately after the first dose and sustained throughout treatment. For ravulizumab, the mean (SD) post hoc terminal elimination half-life was 49·7 (8·9) days. Serum free C5 concentrations <0·5 µg/ml were achieved after the first ravulizumab dose and sustained throughout treatment in both studies. In a minority of patients, free C5 concentrations <0·5 µg/ml were not consistently achieved with eculizumab in either study. Ravulizumab q8w was more consistent in providing immediate, complete, sustained C5 inhibition than eculizumab every-2-weeks in patients with PNH.
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http://dx.doi.org/10.1111/bjh.16711DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7687070PMC
November 2020

The management and outcomes of patients with myelodysplastic syndrome with persistent severe thrombocytopenia: An observational single centre registry study.

Leuk Res 2019 01 11;76:76-81. Epub 2018 Dec 11.

Department of Hematology/Oncology, Odette Cancer Center, Sunnybrook Health Sciences Centre, Canada; Department of Medicine, University of Toronto, Toronto, ON, Canada. Electronic address:

Background: Severe thrombocytopenia affects 10% of patients with myelodysplastic syndrome (MDS) and is associated with poor outcomes. The role for prophylactic platelet transfusions in the outpatient setting is unknown.

Objective/methods: To audit treatments, bleeding rates, and transfusion requirements of patients with MDS and persistent severe thrombocytopenia (PST) registered in a prospective MDS registry at our center.

Results: 99 (17%) of 586 total registry patients had PST; 28 were treated with tranexamic acid alone (TXA), 39 with TXA and prophylactic platelet transfusions (PROPH), 19 with PROPH alone, and 13 were untreated. Median duration of PST was 27 weeks and median overall survival was 0.9 years (95% CI 0.7-1.2). During the PST, 6% (6/99) of patients had a grade 4 bleeding event, from which 4 died. Platelet count at the time of grade 4 bleeding ranged from 2 to 19 × 10/L. 66% (27/41) of patients on TXA alone or untreated required no therapeutic platelet transfusions and experienced no grade 3-4 bleeds. There were no significant differences in grade 3-4 bleeding rates between groups.

Conclusions: Patients with MDS and PST had low rates of major bleeding but poor overall survival. Disparities in clinical practice likely relate to patient and provider heterogeneity and the lack of published evidence. The benefit of TXA and/or prophylactic platelet transfusions would be best evaluated by a randomized controlled trial.
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http://dx.doi.org/10.1016/j.leukres.2018.12.002DOI Listing
January 2019

The orphan nuclear receptor EAR-2 (NR2F6) inhibits hematopoietic cell differentiation and induces myeloid dysplasia in vivo.

Biomark Res 2018 7;6:36. Epub 2018 Dec 7.

3Department of Medical Biophysics, University of Toronto, Sunnybrook Research Institute, Toronto, ON M4N 3M5 Canada.

Background: In patients with myelodysplastic syndrome (MDS), bone marrow cells have an increased predisposition to apoptosis, yet MDS cells outcompete normal bone marrow (BM)-- suggesting that factors regulating growth potential may be important in MDS. We previously identified v-Erb A related-2 (EAR-2, NR2F6) as a gene involved in control of growth ability.

Methods: Bone marrow obtained from C57BL/6 mice was transfected with a retrovirus containing EAR-2-IRES-GFP. Ex vivo transduced cells were flow sorted. In some experiments cells were cultured in vitro, in other experiments cells were injected into lethally irradiated recipients, along with non-transduced bone marrow cells. Short-hairpin RNA silencing EAR-2 was also introduced into bone marrow cells cultured ex vivo.

Results: Here, we show that EAR-2 inhibits maturation of normal BM in vitro and in vivo and that EAR-2 transplant chimeras demonstrate key features of MDS. Competitive repopulation of lethally irradiated murine hosts with EAR-2-transduced BM cells resulted in increased engraftment and increased colony formation in serial replating experiments. Recipients of EAR-2-transduced grafts had hypercellular BM, erythroid dysplasia, abnormal localization of immature precursors and increased blasts; secondary transplantation resulted in acute leukemia. Animals were cytopenic, having reduced numbers of erythrocytes, monocytes and granulocytes. Suspension culture confirmed that EAR-2 inhibits granulocytic and monocytic differentiation, while knockdown induced granulocytic differentiation. We observed a reduction in the number of BFU-E and CFU-GM colonies and the size of erythroid and myeloid colonies. Serial replating of transduced hematopoietic colonies revealed extended replating potential in EAR-2-overexpressing BM, while knockdown reduced re-plating ability. EAR-2 functions by recruitment of histone deacetylases, and inhibition of differentiation in 32D cells is dependent on the DNA binding domain.

Conclusions: This data suggest that NR2F6 inhibits maturation of normal BM in vitro and in vivo and that the NR2F6 transplant chimera system demonstrates key features of MDS, and could provide a mouse model for MDS.
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http://dx.doi.org/10.1186/s40364-018-0149-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6286615PMC
December 2018

Iron overload in myelodysplastic syndromes: Evidence based guidelines from the Canadian consortium on MDS.

Leuk Res 2018 11 19;74:21-41. Epub 2018 Sep 19.

Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.

In 2008 the first evidence-based Canadian consensus guideline addressing the diagnosis, monitoring and management of transfusional iron overload in patients with myelodysplastic syndromes (MDS) was published. The Canadian Consortium on MDS, comprised of hematologists from across Canada with a clinical and academic interest in MDS, reconvened to update these guidelines. A literature search was updated in 2017; topics reviewed include mechanisms of iron overload induced cellular damage, evidence for clinical endpoints impacted by iron overload including organ dysfunction, infections, marrow failure, overall survival, acute myeloid leukemia progression, and endpoints around hematopoietic stem-cell transplant. Evidence for an impact of iron reduction on the same endpoints is discussed, guidelines are updated, and areas identified where evidence is suboptimal. The guidelines address common questions around the diagnosis, workup and management of iron overload in clinical practice, and take the approach of who, when, why and how to treat iron overload in MDS. Practical recommendations for treatment and monitoring are made. Evidence levels and grading of recommendations are provided for all clinical endpoints examined.
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http://dx.doi.org/10.1016/j.leukres.2018.09.005DOI Listing
November 2018

How we treat paroxysmal nocturnal hemoglobinuria: A consensus statement of the Canadian PNH Network and review of the national registry.

Eur J Haematol 2019 Jan 25;102(1):36-52. Epub 2018 Oct 25.

Division of Hematology & Thromboembolism, McMaster University, Hamilton, Ontario, Canada.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare hematologic disease characterized by intravascular hemolysis, thrombophilia, and marrow failure. Its phenotype is due to absent or reduced expression of GPI-linked complement regulators and subsequent sensitivity of hematopoietic cells to complement-mediated damage and lysis. Introduction of the terminal complement inhibitor eculizumab drastically improved outcomes in PNH patients; however, despite this improvement, there remain several challenges faced by PNH patients and physicians who care for them. One of the most important is increasing awareness of the heterogeneity with which patients can present, which can lead to significant delays in recognition. Data from the Canadian PNH Registry are presented to demonstrate the variety of presenting symptoms. In Canada, geography precludes consolidation of care to just a few centers, so management is distributed across academic hospitals, linked together as the Canadian PNH Network. The Network over the last several years has developed educational programs and clinical checklists and has worked to standardize access to diagnostics across the country. Herein, we address some of the common diagnostic and therapeutic challenges faced by PNH physicians and give our recommendations. Gaps in knowledge are also addressed, and where appropriate, consensus opinion is provided.
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http://dx.doi.org/10.1111/ejh.13176DOI Listing
January 2019

Ravulizumab (ALXN1210) in patients with paroxysmal nocturnal hemoglobinuria: results of 2 phase 1b/2 studies.

Blood Adv 2018 09;2(17):2176-2185

Department of Hematology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.

Ravulizumab (ALXN1210), a humanized monoclonal antibody to complement component C5, was engineered from eculizumab to have a substantially longer terminal half-life, permitting longer dosing intervals for paroxysmal nocturnal hemoglobinuria (PNH) treatment. Two phase 1b/2 multicenter open-label studies evaluated efficacy and safety of multiple doses and regimens of ravulizumab in PNH patients naive to complement-inhibitor treatment. Patients in study 103 (n = 13) received ravulizumab 900 mg (lower trough exposure) or 1800 mg every 4 weeks (higher trough exposure); those in study 201 (n = 26) received 1000 mg every 4, 1600 mg every 6, 2400 mg every 8, or 5400 mg every 12 weeks. Trough exposure levels with study 201 dosing regimens were similar to the study 103 900-mg every-4-weeks regimen. Rapid sustained reduction of plasma lactate dehydrogenase (LDH) occurred across all cohorts (73%-90% at end point vs baseline). A greater proportion of patients had normalized LDH (<234 U/L) at least once from days 29 to 253 in the higher- (85.7%) vs lower-trough-exposure (50.0%-83.3%) cohorts; the weighted average of the proportion of instances of LDH normalization from days 29 to 253 was highest in higher- vs lower-trough-exposure cohorts (62.3% vs 31.4%-54.5%). No patients in the higher-trough-exposure cohort, but 1 to 2 patients in all lower-trough-exposure cohorts, experienced breakthrough hemolysis. Ravulizumab improved quality of life (QoL) measures in all cohorts. Two patients experienced meningococcal infections; both recovered and continued in the study. In summary, ravulizumab provided rapid and sustained reduction in complement-mediated hemolysis and improved QoL at dosing intervals up to 12 weeks. This trial was registered at www.clinicaltrials.gov as #NCT02598583 (study 103) and NCT02605993 (study 201).
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http://dx.doi.org/10.1182/bloodadvances.2018020644DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6134221PMC
September 2018

An inflammatory environment containing TNFα favors Tet2-mutant clonal hematopoiesis.

Exp Hematol 2018 03 28;59:60-65. Epub 2017 Nov 28.

Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario, Canada. Electronic address:

Clonal hematopoiesis of aging and indeterminate potential (ARCH or CHIP), driven mainly by mutations in DNMT3A and TET2, is an emerging public health issue, affecting at least 10-15% of adults older than 65 years. CHIP is associated with increased risks of de novo and therapy-related hematological neoplasms and serves as a reservoir for leukemic relapse. CHIP is also associated with increased all-cause mortality and risk of cardio-metabolic disease. The latter association may be explained, at least in part, by the effects of inactivating mutations in TET2 on progeny macrophages. We and others have shown recently that TET2-deficient macrophages are hyperinflammatory and this may exacerbate processes such as atherosclerosis. We postulated an inflammatory state associated with TET2 inactivation and/or unhealthy aging may also favor TET2-mutant hematopoietic stem and progenitor cell (HSPC) expansion. Herein, we demonstrate a clonogenic advantage for Tet2-knockout murine and TET2-mutant human HSPCs in an in vitro environment that contains the proinflammatory cytokine tumor necrosis factor-alpha (TNFα). This phenotype emerges on chronic TNFα exposure and is associated with myeloid skewing and resistance to apoptosis. To our knowledge, this is the first evidence to suggest that TET2 mutations promote clonal dominance with aging by conferring TNFα resistance to sensitive bone marrow progenitors while also propagating such an inflammatory environment. Normalizing the immune environment may present a novel strategy to control or eradicate mutant CHIP clones.
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http://dx.doi.org/10.1016/j.exphem.2017.11.002DOI Listing
March 2018

A predictive model of response to erythropoietin stimulating agents in myelodysplastic syndrome: from the Canadian MDS patient registry.

Ann Hematol 2017 Dec 3;96(12):2025-2029. Epub 2017 Oct 3.

Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, Ontario, M4N 3M5, Canada.

Prediction of response to erythropoietin stimulating agents (ESAs) in anemic MDS patients is often based on the Nordic score. We wished to validate the Nordic score (IWG 2006 response criteria) in a larger cohort and determine if other variables such as IPSS/IPSS-R, ferritin, LDH, and a novel European ESA response score (Santini 2013) were of prognostic importance. We analyzed 208 ESA-treated MDS patients (WHO 2008 criteria) from a prospective registry. Ninety-four and 93% had lower risk scores by IPSS (low/int - 1) and IPSS-R (low/very low), respectively. Erythroid response was achieved in 94 patients (47%); responses were similar with erythropoietin (50%) and darbepoetin (39%; p = 0.2). The Nordic and European scores were both validated on univariate analysis. Variables independently predictive of response in multivariate analysis were low-risk IPSS score (OR 0.1, p = 0.0016) and serum EPO level < 100 mIU/mL (OR 8.7, p < 0.0001). We propose a new ESA response score, consisting of (a) IPSS low score (1 point) and (b) serum EPO levels < 100 mIU/ml (2 points), yielding scores ranging from 0 to 3, with response rates varying from 17 to 81%. The Nordic score has validity but we observed lower than the expected response rates in the best risk group. Our proposed scoring system appears more discriminating but needs validation.
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http://dx.doi.org/10.1007/s00277-017-3137-0DOI Listing
December 2017

Tet2 restrains inflammatory gene expression in macrophages.

Exp Hematol 2017 11 18;55:56-70.e13. Epub 2017 Aug 18.

Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario, Canada. Electronic address:

Tet methylcytosine dioxygenase 2 (TET2) is one of the earliest and most frequently mutated genes in clonal hematopoiesis of indeterminate potential (CHIP) and myeloid cancers, including myelodysplastic syndromes (MDS) and chronic myelomonocytic leukemia (CMML). TET2 catalyzes the oxidation of 5-methylcytosine to 5-hydroxymethylcytosine, leading to DNA demethylation, and also affects transcription by recruiting histone modifiers. Inactivating TET2 mutations cause epigenetic dysregulation, clonal hematopoietic stem cell (HSC) dominance, and monocytic lineage skewing. Here, we found that Tet2 was the most highly expressed Tet enzyme in murine macrophage (MΦ) differentiation. Tet2 transcription was further induced by lipopolysaccharide (LPS), but not interleukin (IL)-4, stimulation, potentially in a nuclear factor κβ-dependent manner. Tet2 loss did not affect early LPS gene responses in vitro, but increased Il-1b, Il-6, and Arginase 1 (Arg1) mRNA expression at later stages of stimulation in bone-marrow-derived MΦs (BMMΦs). Tet2-deficient peritoneal MΦs, however, demonstrated profound, constitutive expression of LPS-induced genes associated with an inflammatory state in vivo. In contrast, Tet2 deficiency did not affect alternative MΦ gene expression significantly in response to IL-4. These results suggested impaired resolution of inflammation in the absence of Tet2 both in vitro and in vivo. For the first time, we also detected TET2 mutations in BMMΦs from MDS and CMML patients and assayed their effects on LPS responses, including their potential influence on human IL-6 expression. Our results show that Tet2 restrains inflammation in murine MΦs and mice, raising the possibility that loss of TET2 function in MΦs may alter the immune environment in the large elderly population with TET2-mutant CHIP and in TET2-mutant myeloid cancer patients.
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http://dx.doi.org/10.1016/j.exphem.2017.08.001DOI Listing
November 2017

Overall survival in lower IPSS risk MDS by receipt of iron chelation therapy, adjusting for patient-related factors and measuring from time of first red blood cell transfusion dependence: an MDS-CAN analysis.

Br J Haematol 2017 10 5;179(1):83-97. Epub 2017 Jul 5.

Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada.

Analyses suggest iron overload in red blood cell (RBC) transfusion-dependent (TD) patients with myleodysplastic syndrome (MDS) portends inferior overall survival (OS) that is attenuated by iron chelation therapy (ICT) but may be biassed by unbalanced patient-related factors. The Canadian MDS Registry prospectively measures frailty, comorbidity and disability. We analysed OS by receipt of ICT, adjusting for these patient-related factors. TD International Prognostic Scoring System (IPSS) low and intermediate-1 risk MDS, at RBC TD, were included. Predictive factors for OS were determined. A matched pair analysis considering age, revised IPSS, TD severity, time from MDS diagnosis to TD, and receipt of disease-modifying agents was conducted. Of 239 patients, 83 received ICT; frailty, comorbidity and disability did not differ from non-ICT patients. Median OS from TD was superior in ICT patients (5·2 vs. 2·1 years; P < 0·0001). By multivariate analysis, not receiving ICT independently predicted inferior OS, (hazard ratio for death 2·0, P = 0·03). In matched pair analysis, OS remained superior for ICT patients (P = 0·02). In this prospective, non-randomized analysis, receiving ICT was associated with superior OS in lower IPSS risk MDS, adjusting for age, frailty, comorbidity, disability, revised IPSS, TD severity, time to TD and receiving disease-modifying agents. This provides additional evidence that ICT may confer clinical benefit.
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http://dx.doi.org/10.1111/bjh.14825DOI Listing
October 2017

Patient-related factors independently impact overall survival in patients with myelodysplastic syndromes: an MDS-CAN prospective study.

Br J Haematol 2016 07 15;174(1):88-101. Epub 2016 Mar 15.

Toronto General Hospital, University Health Network, Toronto, ON, Canada.

Unlabelled: Little is known about the effects of frailty, disability and physical functioning on the clinical outcomes for myelodysplastic syndromes (MDS). We investigated the predictive value of these factors on overall survival (OS) in 445 consecutive patients with MDS and chronic monomyelocytic leukaemia (CMML) enrolled in a multi-centre prospective national registry. Frailty, comorbidity, instrumental activities of daily living, disability, quality of life, fatigue and physical performance measures were evaluated at baseline and were added as covariates to conventional MDS-related factors as predictors of OS in Cox proportional hazards models. The median age was 73 years, and 79% had revised International Prognostic Scoring System (IPSS-R) risk scores of intermediate or lower. Frailty correlated only modestly with comorbidity. OS was significantly shorter for patients with higher frailty and comorbidity scores, any disability, impaired grip strength and timed chair stand tests. By multivariate analysis, the age-adjusted IPSS-R, frailty (Hazard ratio 2·7 (95% confidence interval [CI] 1·7-4·2), P < 0·0001) and Charlson comorbidity score (Hazard ratio 1·8 (95% CI 1·1-2·8), P = 0·01) were independently prognostic of OS. Incorporation of frailty and comorbidity scores improved risk stratification of the IPSS-R by 30% and 5%, respectively. These data demonstrate for the first time, the importance of considering frailty in prognostic models and a potential target for therapeutic intervention in optimizing clinical outcomes in older MDS patients.

Trial Registration: ClinicalTrials.gov Identifier: NCT02537990.
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http://dx.doi.org/10.1111/bjh.14033DOI Listing
July 2016

Myelodysplastic syndrome.

CMAJ 2016 Jul 4;188(10):751. Epub 2016 Jan 4.

Division of Medical Oncology and Hematology, Odette Cancer Centre (Wells, Buckstein); Department of Family Medicine (Rezmovitz), Sunnybrook Health Sciences Centre, Toronto, Ont.

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http://dx.doi.org/10.1503/cmaj.151077DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4938687PMC
July 2016

Lenalidomide and metronomic melphalan for CMML and higher risk MDS: a phase 2 clinical study with biomarkers of angiogenesis.

Leuk Res 2014 Jul 5;38(7):756-63. Epub 2014 Apr 5.

Department of Medical Oncology/Hematology, Odette Cancer and Sunnybrook Health Sciences Center, Toronto, Canada; Department of Biological Sciences, Sunnybrook Research Institute, Toronto, Canada.

Metronomic, low dose chemotherapy may have anti-angiogenic effects and augment the effects of lenalidomide in MDS and CMML. We evaluated the clinical efficacy, tolerability and anti-angiogenic effects of melphalan 2mg and lenalidomide 10mg for 21 days/28 in CMML (n=12) and higher risk MDS (n=8) patients in a prospective phase II study. The primary endpoint was overall response and secondary endpoints included survival, progression-free survival, toxicity and biomarkers of angiogenesis. The median age was 73 years, 55% were pretreated and transfusion dependent. The overall response rate was 3(15%) of 19 evaluable patients but 25% in CMML and 33% in pCMML. Dose reductions and/or delays were common due to myelosuppression. Transient spikes in circulating endothelial cells that declined below baseline were seen in responders and patients with CMML, suggesting anti-angiogenic activity. In conclusion, lenalidomide and metronomic low dose melphalan demonstrate signals of clinical and possible anti-angiogenic activity in patients with pCMML that require future validation. This trial was registered at clinicaltrial.gov under # NCT00744536.
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http://dx.doi.org/10.1016/j.leukres.2014.03.022DOI Listing
July 2014

Initial transfusion intensity predicts survival in myelodysplastic syndrome.

Leuk Lymphoma 2014 Oct 24;55(10):2296-300. Epub 2014 Feb 24.

Molecular and Cellular Biology, Sunnybrook Research Institute , Toronto, ON , Canada.

We evaluated 52 patients with myelodysplastic syndrome (MDS) who had received at least one red blood cell (RBC) transfusion. In the 4-week period following the first transfusion, 24 patients (group 1) required no transfusion, while 28 (group 2) required transfusion of two or more units of RBCs. Survival was greater in group 1 (440 weeks vs. 167 weeks, p < 0.01), even when only international prognostic scoring system (IPSS) low and intermediate-1 risk patients were analyzed (median overall survival 491 vs. 170 weeks, p < 0.05), independent of age, IPSS and progression to acute myeloid leukemia (AML). The intensity of transfusion required in the first few weeks after the first transfusion predicts disease severity and correlates with survival.
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http://dx.doi.org/10.3109/10428194.2013.878934DOI Listing
October 2014

The aryl hydrocarbon receptor nuclear translocator (ARNT) modulates the antioxidant response in AML cells.

Leuk Res 2013 Dec 22;37(12):1750-6. Epub 2013 Oct 22.

The J. Douglas Crashley MDS Research Laboratory, Sunnybrook Research Institute, 2075 Bayview Avenue, Toronto, ON M4N 3M5, Canada.

We observed AML cell lines vary in their sensitivity to induction of apoptosis by troglitazone (TG), which induces apoptosis through the generation of intracellular reactive oxygen species (ROS). TG-resistant cell lines had increased abundance of ARNT transcripts and protein. Expression of ARNT in TG-sensitive cells made these cells resistant to both TG and daunorubicin. ARNT-expressing cells had increased expression of SOD2 and Nrf2 transcripts and elevated intracellular GSH concentration. Our results indicate that ARNT expression in AML cells augments antioxidant response and confers resistance to ROS inducers. This suggests ARNT may modulate ROS signaling and drug response in AML.
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http://dx.doi.org/10.1016/j.leukres.2013.10.010DOI Listing
December 2013

The orphan nuclear receptor Ear-2 (Nr2f6) is a novel negative regulator of T cell development.

Exp Hematol 2014 Jan 2;42(1):46-58. Epub 2013 Oct 2.

Department of Medical Biophysics, University of Toronto, Toronto, Canada; Biological Sciences, Sunnybrook Research Institute, Toronto, Canada; Department of Medicine, University of Toronto, Toronto, Canada; Department of Medical Oncology, Myelodysplastic Syndromes Program, Toronto Sunnybrook Regional Cancer Centre, Toronto, Canada. Electronic address:

We describe a novel role for the orphan nuclear receptor Ear-2 in regulating T cell development. Retrovirus-mediated overexpression of Ear-2 (EAR-2++) in a bone marrow (BM) transplantation assay resulted in limited T cell development and a greater than tenfold decrease in thymus size and cellularity relative to controls. Ear-2-transduced murine BM hematopoietic stem cells (HSCs) in OP9-DL1 cultures showed a proliferation deficit during days 1-5 after induction of differentiation, which corresponded to increased expression of the cell cycle regulators p21 (cdkn1a) and p27 (cdkn1b), as well as increased expression of Hes1, Notch3, Egr1, and Scl (Tal1) and decreased expression of Gli1, Gfi-1, HoxA9, PU.1, Nrarp, and Tcf1. In addition, there was a block in differentiation at the DN4 to double-positive (DP) transition accompanied by an increase in apoptosis, similar to the deficit seen in the RORγt null mouse. Gene expression profiling revealed that, like the RORγt-deficient mouse, EAR-2++ DP cells had decreased expression of BclXL and increased expression of the proapoptosis gene Bad. In addition, EAR-2++ DP cells had decreased expression of Bcl11b, PU.1, and HoxA9, and increased expression of Id2. Based on these findings, we conclude that EAR-2++ cells were able to migrate to, but not fully repopulate, the thymus because of a cell-intrinsic defect in the proliferation of DN1 cells followed by a block in differentiation from the DN4 to DP stage of T cell development. We conclude that Ear-2 is a novel negative regulator of T-cell development and that downregulation of Ear-2 is indispensable for the proliferation of DN1 cells and the survival of DN4-DP cells.
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http://dx.doi.org/10.1016/j.exphem.2013.09.010DOI Listing
January 2014

Income and outcome in myelodysplastic syndrome: the prognostic impact of SES in a single-payer system.

Leuk Res 2013 Nov 8;37(11):1495-501. Epub 2013 Sep 8.

MDS Research Program, Medical Oncology/Hematology, Sunnybrook Odette Cancer Centre, 2075 Bayview Avenue, Toronto, ON M4N 3M5, Canada.

We examined the prognostic impact of SES, estimated by census median household income, in 312 adult MDS patients. Age, progression to AML, use of recombinant erythropoietin, WHO diagnosis and IPSS risk category were independent predictors of survival but there was no association between SES and survival. Unexpectedly, progression to AML was more prevalent in the highest income quartile (HR 3.96 for highest vs. lowest; p=0.0032). The previously demonstrated association of low SES with poor outcome MDS in the United States may have been driven primarily by reduced access to care rather than other SES-linked factors such as co-morbidity.
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http://dx.doi.org/10.1016/j.leukres.2013.08.021DOI Listing
November 2013

TP53 suppression promotes erythropoiesis in del(5q) MDS, suggesting a targeted therapeutic strategy in lenalidomide-resistant patients.

Proc Natl Acad Sci U S A 2013 Oct 16;110(40):16127-32. Epub 2013 Sep 16.

H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612.

Stabilization of p53 in erythroid precursors in response to nucleosomal stress underlies the hypoplastic anemia in myelodysplastic syndromes (MDS) with chromosome 5q deletion [del(5q)]. We investigated whether cenersen, a clinically active 20-mer antisense oligonucleotide complementary to TP53 exon10, could suppress p53 expression and restore erythropoiesis in del(5q) MDS. Cenersen treatment of ribosomal protein S-14-deficient erythroblasts significantly reduced cellular p53 and p53-up-regulated modulator of apoptosis expression compared with controls, accompanied by a significant reduction in apoptosis and increased cell proliferation. In a two-stage erythroid differentiation assay, cenersen significantly suppressed nuclear p53 in bone marrow CD34+ cells isolated from patients with del(5q) MDS, whereas erythroid burst recovery increased proportionally to the magnitude of p53 suppression without evidence of del(5q) clonal suppression (r = -0.6; P = 0.005). To explore the effect of p53 suppression on erythropoiesis in vivo, dexamethasone, a glucocorticoid receptor-dependent p53 antagonist, was added to lenalidomide treatment in eight lower-risk, transfusion-dependent, del(5q) MDS patients with acquired drug resistance. Transfusion independence was restored in five patients accompanied by expansion of erythroid precursors and decreased cellular p53 expression. We conclude that targeted suppression of p53 could support effective erythropoiesis in lenalidomide-resistant del(5q) MDS.
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http://dx.doi.org/10.1073/pnas.1311055110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3791697PMC
October 2013

Generation of high-titer viral preparations by concentration using successive rounds of ultracentrifugation.

J Transl Med 2011 Aug 17;9:137. Epub 2011 Aug 17.

Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 2M9, Canada.

Background: Viral vectors provide a method of stably introducing exogenous DNA into cells that are not easily transfectable allowing for the ectopic expression or silencing of genes for therapeutic or experimental purposes. However, some cell types, in particular bone marrow cells, dendritic cells and neurons are difficult to transduce with viral vectors. Successful transduction of such cells requires preparation of highly concentrated viral stocks, which permit a high virus concentration and multiplicity of infection (MOI) during transduction. Pseudotyping with the vesicular stomatitis virus G (VSV-G) envelope protein is common practice for both lentiviral and retroviral vectors. The VSV-G glycoprotein adds physical stability to retroviral particles, allowing concentration of virus by high-speed ultracentrifugation. Here we describe a method report for concentration of virus from large volumes of culture supernatant by means of successive rounds of ultracentrifugation into the same ultracentrifuge tube.

Method: Stable retrovirus producer cell lines were generated and large volumes of virus-containing supernatant were produced. We then tested the transduction ability of virus following varying rounds of concentration by ultra-centrifugation. In a second series of experiments lentivirus-containing supernatant was produced by transient transfection of 297T/17 cells and again we tested the transduction ability of virus following multiple rounds of ultra-centrifugation.

Results: We report being able to centrifuge VSV-G coated retrovirus for as many as four rounds of ultracentrifugation while observing an additive increase in viral titer. Even after four rounds of ultracentrifugation we did not reach a plateau in viral titer relative to viral supernatant concentrated to indicate that we had reached the maximum tolerated centrifugation time, implying that it may be possible to centrifuge VSV-G coated retrovirus even further should it be necessary to achieve yet higher titers for specific applications. We further report that VSV-G coated lentiviral particles may also be concentrated by successive rounds of ultracentrifugation (in this case four rounds) with minimal loss of transduction efficiency.

Conclusion: This method of concentrating virus has allowed us to generate virus of sufficient titers to transduce bone marrow cells with both retrovirus and lentivirus, including virus carrying shRNA constructs.
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http://dx.doi.org/10.1186/1479-5876-9-137DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3175463PMC
August 2011

Correlation among nuclear localization of NuMA-RARα, deregulation of gene expression and leukemic phenotype of hCG-NuMA-RARα transgenic mice.

Leuk Res 2011 May 21;35(5):670-6. Epub 2011 Jan 21.

Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada.

Acute promyelocytic leukemia (APL) is a model system of aberrant transcription in cancer. We sought to elucidate the mechanism of action of the variant fusion NuMA-RARα in APL, using the hCG-NuMA-RARα transgenic model. We report that subcellular localization of NuMA-RARα in transgenic mice is dependent upon its protein expression and transgene dosage. Subcellular localization of the fusion is inversely correlated with extent of gene deregulation at the mRNA level for Cebpα, Cebpɛ and Pu.1. Finally, we report that phenotype onset is correlated with NuMA-RARα copy number; mice with higher copy number developing disease later than those with lower copy number.
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http://dx.doi.org/10.1016/j.leukres.2010.12.009DOI Listing
May 2011

5-Azacytidine in myelodysplastic syndromes: a clinical practice guideline.

Cancer Treat Rev 2011 Apr 29;37(2):160-7. Epub 2010 Jun 29.

Myelodysplastic Syndromes Program, The Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.

Background: Myelodysplastic syndrome (MDS) is a clonal disorder of hematopoiesis that results in peripheral blood cytopenias and a marked propensity to progress to acute myelogenous leukemia. With 40,000-76,000 new cases per year in the USA, MDS is the commonest of the hematological malignancies and represents a significant burden of morbidity and premature death. Although supportive or palliative measures such as blood transfusion have long been the mainstay of management of MDS, disease-modifying medical therapies have recently become available. The most extensively characterized of these is 5-azacytidine (5-Aza); however, no consensus exists on how this agent should be deployed in MDS.

Methods: An overarching search of the literature identified 7019 citations investigating the treatment or management of MDS. Of those, six clinical articles of prospective phase 2-3 study design or meta-analyses were selected for inclusion in a systematic review of the evidence.

Conclusions: The Canadian Consortium on Evidence-Based Care in MDS recommends 5-Aza as first line therapy in all MDS patients with IPSS high-intermediate and high risk scores including WHO-defined AML (20-30% blasts) who cannot proceed immediately to allogeneic stem cell transplant. 5-Aza is not recommended as first line therapy with MDS patients with IPSS Low and Low-intermediate risk scores as there is no evidence that it alters the natural history of the disease nor is superior to standard therapy. The MDS consortium does not recommend combining 5-Aza with other agents at this time outside the context of a clinical trial.
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http://dx.doi.org/10.1016/j.ctrv.2010.05.006DOI Listing
April 2011

Cross-Talk between PPARs and the Partners of RXR: A Molecular Perspective.

PPAR Res 2009 20;2009:925309. Epub 2009 Dec 20.

Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada M5G 2M9.

The PPARs are integral parts of the RXR-dependent signaling networks. Many other nuclear receptor subfamily 1 members also require RXR as their obligatory heterodimerization partner and they are often co-expressed in any given tissue. Therefore, the PPARs often complete with other RXR-dependent nuclear receptors and this competition has important biological implications. Thorough understanding of this cross-talk at the molecular level is crucial to determine the detailed functional roles of the PPARs. At the level of DNA binding, most RXR heterodimers bind selectively to the well-known "DR1 to 5" DNA response elements. As a result, many heterodimers share the same DR element and must complete with each other for DNA binding. At the level of heterodimerization, the partners of RXR share the same RXR dimerization interface. As a result, individual nuclear receptors must complete with each other for RXR to form functional heterodimers. Cross-talk through DNA binding and RXR heterodimerization present challenges to the study of these nuclear receptors that cannot be adequately addressed by current experimental approaches. Novel tools, such as engineered nuclear receptors with altered dimerization properties, are currently being developed. These tools will enable future studies to dissect specific RXR heterodimers and their signaling pathways.
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http://dx.doi.org/10.1155/2009/925309DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2801013PMC
July 2011

Identification of miR-145 and miR-146a as mediators of the 5q- syndrome phenotype.

Nat Med 2010 Jan 8;16(1):49-58. Epub 2009 Nov 8.

British Columbia Cancer Agency Research Centre, Vancouver, British Columbia, Canada.

5q- syndrome is a subtype of myelodysplastic syndrome characterized by severe anemia and variable neutropenia but normal or high platelet counts with dysplastic megakaryocytes. We examined expression of microRNAs (miRNAs) encoded on chromosome 5q as a possible cause of haploinsufficiency. We show that deletion of chromosome 5q correlates with loss of two miRNAs that are abundant in hematopoietic stem/progenitor cells (HSPCs), miR-145 and miR-146a, and we identify Toll-interleukin-1 receptor domain-containing adaptor protein (TIRAP) and tumor necrosis factor receptor-associated factor-6 (TRAF6) as respective targets of these miRNAs. TIRAP is known to lie upstream of TRAF6 in innate immune signaling. Knockdown of miR-145 and miR-146a together or enforced expression of TRAF6 in mouse HSPCs resulted in thrombocytosis, mild neutropenia and megakaryocytic dysplasia. A subset of mice transplanted with TRAF6-expressing marrow progressed either to marrow failure or acute myeloid leukemia. Thus, inappropriate activation of innate immune signals in HSPCs phenocopies several clinical features of 5q- syndrome.
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http://dx.doi.org/10.1038/nm.2054DOI Listing
January 2010

Iron overload in myelodysplastic syndromes.

Expert Rev Hematol 2009 Jun;2(3):215-8

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http://dx.doi.org/10.1586/ehm.09.23DOI Listing
June 2009

Estimating the prevalence of myelodysplastic syndromes in patients with unexplained cytopenias: a retrospective study of 322 bone marrows.

Leuk Res 2009 Oct 17;33(10):1313-8. Epub 2009 Mar 17.

MDS Research Program, Department of Hematology/Oncology, Odette Cancer Center, Sunnybrook Health Sciences Center, Toronto, Ontario, Canada.

Although unexplained anemia is common in the elderly, the prevalence of MDS is poorly defined. We reviewed 2267 bone marrows reviewed at our center between the years 2002 and 2005. Of these, 322 met our criteria for inclusion (14%). Seventy-three patients (22.6%) had a confirmed diagnosis of MDS and 32 (9.9%) had suspected MDS. Confirmed or suspected MDS was more likely in patients aged >65 (31.5% and 11%, respectively). Age, MCV, LDH and RDW were independently predictive of MDS. Extrapolation of our findings to the elderly anemic individuals in the community suggests MDS prevalence may be higher than previously postulated.
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http://dx.doi.org/10.1016/j.leukres.2009.02.010DOI Listing
October 2009