Publications by authors named "Martin Guimond"

32 Publications

Modulating endothelial cells with EGFL7 to diminish aGVHD after allogeneic bone marrow transplantation in mice.

Blood Adv 2021 Oct 15. Epub 2021 Oct 15.

Hopital Maisonneuve-Rosemont, Canada.

Acute graft versus host (aGVHD) is the second cause of death after allogeneic-hematopoietic stem cell transplant (allo-HSCT) underscoring the need for novel therapies. Based on previous work that endothelial cell dysfunction is present in aGVHD and that epidermal growth factor-like domain 7 (EGFL7) plays a significant role in decreasing inflammation by repressing endothelial cell activation and T cell migration, we hypothesized that increasing EGFL7 levels after allo-HSCT will diminish the severity of aGVHD. Here, we show that treatment with recombinant EGFL7 (rEGFL7) in two different murine models of aGVHD decreases aGVHD severity and improves survival in recipient mice after allogeneic transplantation with respect to controls without affecting graft versus leukemia effect. Furthermore, we showed that rEGFL7 treatment results in higher thymocytes, T, B and dendritic cells in recipient mice after allo-HSCT. This study constitutes a proof of concept of the ability of rEGFL7 therapy to reduce GHVD severity and mortality after allo-HSCT.
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http://dx.doi.org/10.1182/bloodadvances.2021005498DOI Listing
October 2021

Persistence of Drug-Resistant Leukemic Stem Cells and Impaired NK Cell Immunity in CML Patients Depend on Antiproliferative and PP2A-Activating Functions.

Blood Cancer Discov 2020 Jul;1(1):48-67

Department of Haematology, Hammersmith Hospital, Imperial College London, London, United Kingdom.

Persistence of drug-resistant quiescent leukemic stem cells (LSC) and impaired natural killer (NK) cell immune response account for relapse of chronic myelogenous leukemia (CML). Inactivation of protein phosphatase 2A (PP2A) is essential for CML-quiescent LSC survival and NK cell antitumor activity. Here we show that has antiproliferative and PP2A-activating functions that are dose dependently differentially induced by CCND2/CDK6 and SET inhibition, respectively. is upregulated in CML LSCs and NK cells by bone marrow microenvironment (BMM) signals to induce quiescence and impair immune response, respectively. Conversely, BCR-ABL1 downregulates in CML progenitors to prevent growth arrest and PP2A-mediated apoptosis. Quiescent LSCs escape apoptosis by upregulating long noncoding RNA that uncouples and limits function to cytostasis. Genetic and pharmacologic modulation and/or PP2A-activating drug treatment restore NK cell activity, inhibit BMM-induced growth arrest, and selectively trigger LSC apoptosis and in patient-derived xenografts; hence, the importance of and PP2A activity for CML development and therapy.
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http://dx.doi.org/10.1158/0008-5472.BCD-19-0039DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7510943PMC
July 2020

Studying Peripheral T Cell Homeostasis in Mice: A Concise Technical Review.

Methods Mol Biol 2020 ;2111:267-283

Division Immunologie-Oncologie, Centre de Recherche de l'Hôpital Maisonneuve-Rosemont, Montréal, QC, Canada.

For several years, it was believed that the thymus was entirely responsible for maintaining T cell homeostasis. Today, it is well-known that homeostatic peripheral mechanisms are essential in order to maintain T cell numbers and diversity constant in the periphery. Naïve and memory T cells require continual access to self-peptide MHC class I and II molecules and/or cytokines to survive in the periphery. Under normal conditions, homeostatic resources are low, and lymphocytes undergo very slow proliferation and survive. Following T cell depletion, the bioavailability of homeostatic resources is significantly increased, and T cell proliferation is dramatically augmented. The development of lymphopenic mouse models has helped our current understanding of factors involved in the regulation of peripheral T cell homeostasis. In this minireview, we will give a brief overview about basic techniques used to study peripheral T cell homeostasis in mice.
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http://dx.doi.org/10.1007/978-1-0716-0266-9_21DOI Listing
January 2021

IL-7 Is the Limiting Homeostatic Factor that Constrains Homeostatic Proliferation of CD8 T Cells after Allogeneic Stem Cell Transplantation and Graft-versus-Host Disease.

Biol Blood Marrow Transplant 2019 04 19;25(4):648-655. Epub 2018 Dec 19.

Départment de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montréal, Québec, Canada; Division d'Hématologie-Oncologie, Centre de Recherche de l'Hôpital Maisonneuve-Rosemont, Montréal, Québec, Canada. Electronic address:

Immune reconstitution after allogeneic hematopoietic stem cell transplantation relies primarily on homeostatic proliferation (HP) of mature T lymphocytes, but this process is typically impaired during graft-versus-host disease (GVHD). We previously showed that low IL-7 levels combined with lack of dendritic cell (DC) regeneration constrain CD4 T cell HP during GVHD. However, it is not clear whether these alterations to the peripheral CD4 T cell niche also contribute to impair CD8 T cell regeneration during GVHD. We found that IL-7 therapy was sufficient for restoring CD8 T cell HP in GVHD hosts while forcing DC regeneration with Flt3-L had only a modest effect on CD8 T cell HP in IL-7 treated mice. Using bone marrow chimeras, we showed that HP of naïve CD8 T cells is primarily regulated by MHC class I on radio-resistant stromal cells, yet optimal recovery of CD8 T cell counts still requires expression of MHC class I on both radio-resistant and radio-sensitive hematopoietic cells. Thus, IL-7 level is the primary limiting factor that constrains naïve CD8 T cell HP during GVHD, and accessibility of MHC class I on stromal cells explains how IL-7 therapy, as a single agent, can induce robust CD8 T cell HP in the absence of DCs.
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http://dx.doi.org/10.1016/j.bbmt.2018.12.066DOI Listing
April 2019

Double-Negative T Cell Levels Correlate with Chronic Graft-versus-Host Disease Severity.

Biol Blood Marrow Transplant 2019 01 19;25(1):19-25. Epub 2018 Sep 19.

Research Center, Maisonneuve-Rosemont Hospital, Montreal, Quebec, Canada; Department of Microbiology, Infection, and Immunology, University of Montreal, Montreal, Quebec, Canada. Electronic address:

Chronic graft-versus-host disease (cGVHD) is a major complication, affecting 50% to 80% of long-term survivors of allogeneic hematopoietic stem cell transplantation. Current cGVHD therapies are neither specific nor curative, and patients are typically maintained for several months to years under immunosuppressive regimens that are associated with important side effects and increased susceptibility to life-threatening infections. As a result, continued investigation into the pathology of the disease and the search for novel diagnostic and therapeutic strategies to treat cGVHD remains a high priority. We report that the cellular dynamics of various immune cell subsets are related to cGVHD onset and severity in a cohort of allogeneic hematopoietic stem cell transplantation recipients. We document a decrease in the proportion of CD45RO CD4CD8 (double-negative [DN]) T cells at the onset of cGVHD, a time at which serum levels of B cell activating factor and B cells are increased. We also find that DN T cell levels are correlated with cGVHD severity. Our present findings are in line with the view that activated DN T cells exhibit their immunoregulatory potential by eliminating B cells in vivo. Taken together, these findings suggest that maintaining elevated DN T cell numbers before the onset of cGVHD may prevent pathological B cell responses.
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http://dx.doi.org/10.1016/j.bbmt.2018.09.008DOI Listing
January 2019

Restoring T Cell Homeostasis After Allogeneic Stem Cell Transplantation; Principal Limitations and Future Challenges.

Front Immunol 2018 18;9:1237. Epub 2018 Jun 18.

Division d'Hématologie-Oncologie, Centre de Recherche de l'Hôpital Maisonneuve-Rosemont, Montréal, QC, Canada.

For several leukemia patients, allogeneic stem cell transplantation (allogeneic-SCT) is the unique therapeutic modality that could potentially cure their disease. Despite significant progress made in clinical management of allogeneic-SCT, acute graft-versus-host disease (aGVHD) and infectious complications remain the second and third cause of death after disease recurrence. Clinical options to restore immunocompetence after allogeneic-SCT are very limited as studies have raised awareness about the safety with regards to graft-versus-host disease (GVHD). Preclinical works are now focusing on strategies to improve thymic functions and to restore the peripheral niche that have been damaged by alloreactive T cells. In this mini review, we will provide a brief overview about the adverse effects of GVHD on the thymus and the peripheral niche and the resulting negative outcome on peripheral T cell homeostasis. Finally, we will discuss the potential relevance of coordinating our studies on thymic rejuvenation and improvement of the peripheral lymphoid niche to achieve optimal T cell regeneration in GVHD patients.
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http://dx.doi.org/10.3389/fimmu.2018.01237DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6015883PMC
August 2019

Homeostatic cytokines in immune reconstitution and graft-versus-host disease.

Cytokine 2016 06 1;82:24-32. Epub 2016 Feb 1.

Maisonneuve-Rosemont Research Center, Montreal, Quebec, Canada; Department of Microbiology, Infectiology and Immunology, University of Montreal, Montreal, Quebec, Canada. Electronic address:

For numerous patients, allogeneic stem cell transplantation (SCT) is the only therapeutic option that could potentially cure their disease. Despite significant progress made in clinical management of allogeneic SCT, acute graft-versus-host disease (aGVHD) remains the second cause of death after disease recurrence. aGVHD is highly immunosuppressive and the adverse effect of allogeneic SCT on T cell regeneration is typically more important than the levels of immunosuppression normally seen after autologous SCT. In these patients, immune reconstitution often takes several years to occur and restoring immunocompetence after allogeneic SCT represents an important challenge, principally because clinical options are limited and current methods used to accelerate immune reconstitution are associated with increased GVHD. Interleukin-7 and IL-15 are both under clinical investigation and demonstrate the greatest potential on peripheral T cells regeneration in mice and humans. However, awareness has been raised about the use of IL-7 and IL-15 after allogeneic SCT with regards to potential adverse effects on aGVHD. In this review, we will discuss about recent progress made in lymphocyte regeneration, the critical role played by IL-7 and IL-15 in T cell homeostasis and how these cytokines could be used to improve immune reconstitution after allogeneic SCT.
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http://dx.doi.org/10.1016/j.cyto.2016.01.003DOI Listing
June 2016

Stromal-Derived Factor-1α and Interleukin-7 Treatment Improves Homeostatic Proliferation of Naïve CD4(+) T Cells after Allogeneic Stem Cell Transplantation.

Biol Blood Marrow Transplant 2015 Oct 4;21(10):1721-31. Epub 2015 Jul 4.

Department of Hematology-Oncology, Maisonneuve-Rosemont Hospital Research Center, Montréal, Québec, Canada; Department of Microbiology, Infectiology and Immunology, Faculty of Medicine, Université de Montréal, Montréal, Québec, Canada. Electronic address:

Graft-versus-host disease (GVHD) impairs immune reconstitution after allogeneic stem cell transplantation (allo-SCT) and effective therapies aimed at restoring T cell counts in GVHD patients have yet to be developed. During GVHD, CD4(+) T cell reconstitution is particularly affected and current models hold that GVHD insult to the peripheral lymphoid niche is responsible for this effect. Here, we show that naïve CD4(+) T cell homeostatic proliferation (HP) is lost during GVHD because of low systemic IL-7 and impaired dendritic cell (DC) regeneration. We assessed factors involved in DC differentiation and found that although fms-like tyrosine kinase 3 ligand (Flt3-L) levels were normal, stromal-derived factor-1α (SDF-1α) was diminished in the blood of GVHD mice. Unlike Flt3-L treatment, the administration of SDF-1α specifically increased CD8α(+) DC numbers and did not worsen GVHD. Importantly, CD4(+) T cell HP was enhanced only when IL-7 and SDF-1α or Flt3L were coadministered, confirming the crucial role of DCs and IL-7 in restoring CD4(+) T cell regeneration during GVHD. Altogether, our results indicate that CD8α(+) DCs are part of the peripheral niche that controls CD4(+) T cell HP and that their depletion, combined with low systemic IL-7, explains how GVHD constrains naïve CD4(+) T cell reconstitution after allo-SCT.
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http://dx.doi.org/10.1016/j.bbmt.2015.06.019DOI Listing
October 2015

Deficiency in the metabolite receptor SUCNR1 (GPR91) leads to outer retinal lesions.

Aging (Albany NY) 2013 Jun;5(6):427-44

Department of Ophthalmology, Hopital Maisonneuve-Rosemont Research Centre, University of Montreal, Montreal, Quebec, H1T 2M4, Canada.

Age-related macular degeneration (AMD) is a prominent cause of blindness in the Western world. To date, its molecular pathogenesis as well as the sequence of events leading to retinal degeneration remain largely ill-defined. While the invasion of choroidal neovessels in the retina is the primary mechanism that precipitates loss of sight, an earlier dry form precedes it. Here we provide the first evidence for the protective role of the Retinal Pigment Epithelium (RPE)-resident metabolite receptor, succinate receptor 1 (SUCNR1; G-Protein coupled Receptor-91 (GPR91), in preventing dry AMD-like lesions of the outer retina. Genetic analysis of 925 patients with geographic atrophy and 1199 AMD-free peers revealed an increased risk of developing geographic atrophy associated with intronic variants in theSUCNR1 gene. In mice, outer retinal expression of SUCNR1 is observed in the RPE as well as microglial cells and decreases progressively with age. Accordingly, Sucnr1-/- mice show signs of premature sub-retinal dystrophy with accumulation of oxidized-LDL, abnormal thickening of Bruch's membrane and a buildup of subretinal microglia. The accumulation of microglia in Sucnr1-deficient mice is likely triggered by the inefficient clearance of oxidized lipids by the RPE as bone marrow transfer of wild-type microglia into Sucnr1-/- mice did not salvage the patho-phenotype and systemic lipolysis was equivalent between wild-type and control mice. Our findings suggest that deficiency in SUCNR1 is a possible contributing factor to the pathogenesis of dry AMD and thus broaden our understanding of this clinically unmet need.
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http://dx.doi.org/10.18632/aging.100563DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3832265PMC
June 2013

TCR triggering modulates the responsiveness and homeostatic proliferation of CD4+ thymic emigrants to IL-7 therapy.

Blood 2013 Jun 23;121(23):4684-93. Epub 2013 Apr 23.

Maisonneuve-Rosemont Hospital Research Center, Montreal, QC, Canada.

Interleukin-7 (IL-7) is currently used in clinical trials to augment T-cell counts. Paradoxically, elevated systemic IL-7 found in lymphopenic humans is typically insufficient for CD4(+) T-cell regeneration, and thymopoiesis becomes critical in this process. Here we show that the proliferative effect of IL-7 is more pronounced on CD4(+)CD8(-) thymocytes compared with peripheral CD4(+) T cells. These cells express miR181a at higher levels and respond to lower concentrations of IL-7. As single-positive CD4(+) thymocytes (CD4(+)(SPT)) exit the thymus, they rapidly diminish their proliferation to IL-7 therapy, and this is mediated, at least in part, by major histocompatibility complex class II distribution outside the thymus. Interestingly, increasing T-cell receptor (TCR) stimulation augments IL-7 responsiveness and proliferation of peripheral CD4(+) T cells, whereas failure to stimulate TCR abrogates proliferation induced by IL-7. Finally, we demonstrated that IL-7 enhances the proliferation of CD4(+) T cells that undergo "slow proliferation" in lymphopenic hosts. To date, our results indicate that TCR signaling is a major controlling factor for CD4 responsiveness and proliferation to IL-7 therapy.
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http://dx.doi.org/10.1182/blood-2012-09-458174DOI Listing
June 2013

Val-boroPro accelerates T cell priming via modulation of dendritic cell trafficking resulting in complete regression of established murine tumors.

PLoS One 2013 12;8(3):e58860. Epub 2013 Mar 12.

Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.

Although tumors naturally prime adaptive immune responses, tolerance may limit the capacity to control progression and can compromise effectiveness of immune-based therapies for cancer. Post-proline cleaving enzymes (PPCE) modulate protein function through N-terminal dipeptide cleavage and inhibition of these enzymes has been shown to have anti-tumor activity. We investigated the mechanism by which Val-boroPro, a boronic dipeptide that inhibits post-proline cleaving enzymes, mediates tumor regression and tested whether this agent could serve as a novel immune adjuvant to dendritic cell vaccines in two different murine syngeneic murine tumors. In mice challenged with MB49, which expresses the HY antigen complex, T cell responses primed by the tumor with and without Val-boroPro were measured using interferon gamma ELISPOT. Antibody depletion and gene-deficient mice were used to establish the immune cell subsets required for tumor regression. We demonstrate that Val-boroPro mediates tumor eradication by accelerating the expansion of tumor-specific T cells. Interestingly, T cells primed by tumor during Val-boroPro treatment demonstrate increased capacity to reject tumors following adoptive transfer without further treatment of the recipient. Val-boroPro -mediated tumor regression requires dendritic cells and is associated with enhanced trafficking of dendritic cells to tumor draining lymph nodes. Finally, dendritic cell vaccination combined with Val-boroPro treatment results in complete regression of established tumors. Our findings demonstrate that Val-boroPro has antitumor activity and a novel mechanism of action that involves more robust DC trafficking with earlier priming of T cells. Finally, we show that Val-boroPro has potent adjuvant properties resulting in an effective therapeutic vaccine.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0058860PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3595211PMC
October 2013

Neuronal ER stress impedes myeloid-cell-induced vascular regeneration through IRE1α degradation of netrin-1.

Cell Metab 2013 Mar;17(3):353-71

Department of Ophthalmology, Maisonneuve-Rosemont Hospital Research Centre, University of Montreal, Montreal, QC H1T 2M4, Canada.

In stroke and proliferative retinopathy, despite hypoxia driven angiogenesis, delayed revascularization of ischemic tissue aggravates the loss of neuronal function. What hinders vascular regrowth in the ischemic central nervous system remains largely unknown. Using the ischemic retina as a model of neurovascular interaction in the CNS, we provide evidence that the failure of reparative angiogenesis is temporally and spatially associated with endoplasmic reticulum (ER) stress. The canonical ER stress pathways of protein kinase RNA-like ER kinase (PERK) and inositol-requiring enzyme-1α (IRE1α) are activated within hypoxic/ischemic retinal ganglion neurons, initiating a cascade that results in angiostatic signals. Our findings demonstrate that the endoribonuclease IRE1α degrades the classical guidance cue netrin-1. This neuron-derived cue triggers a critical reparative-angiogenic switch in neural macrophage/microglial cells. Degradation of netrin-1, by persistent neuronal ER stress, thereby hinders vascular regeneration. These data identify a neuronal-immune mechanism that directly regulates reparative angiogenesis.
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http://dx.doi.org/10.1016/j.cmet.2013.02.003DOI Listing
March 2013

Graft-versus-host disease impairs vaccine responses through decreased CD4+ and CD8+ T cell proliferation and increased perforin-mediated CD8+ T cell apoptosis.

J Immunol 2013 Feb 28;190(3):1351-9. Epub 2012 Dec 28.

Blood and Marrow Transplant Section, Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.

Tumor-targeted vaccines represent a strategy to enhance the graft-versus-leukemia effect after allogeneic blood and marrow transplantation (BMT). We have previously shown that graft-versus-host disease (GVHD) can negatively impact quantitative responses to vaccines. Using a minor histocompatibility Ag-mismatched BMT (B6 → B6 × C3H.SW) followed by adoptive transfer of HY-specific T cells and HY-expressing dendritic cells, we assessed whether GVHD induced by donor lymphocyte infusion (DLI) affects the persistence, proliferation, and survival of vaccine-responding, nonalloantigen reactive T cells. Both CD8(+) and CD4(+) HY-specific T cells undergo less vaccine-driven proliferation in allogeneic recipients with GVHD. Although vaccine-responding CD8(+) T cells show decreased IFN-γ and CD107a production, CD4(+) T cells exhibit increased programmed death 1 and T cell Ig mucin-like domain 3 expression. In addition, the degree of apoptosis in vaccine-responding CD8(+) T cells was higher in the presence of GVHD, but there was no difference in CD4(+) T cell apoptosis. Using Fas ligand-deficient or TRAIL-deficient DLI had no impact on apoptosis of HY-specific T cells. However, perforin-deficient alloreactive DLI induced significantly less apoptosis of vaccine-responding CD8(+) T cells and resulted in enhanced tumor protection. Thus, diminished vaccine responses during GVHD result from impaired proliferation of CD8(+) and CD4(+) T cells responding to vaccination, with an additional contribution from perforin-mediated CD8(+) T cell apoptosis. These results provide important insights toward optimizing vaccine responses after allogeneic BMT.
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http://dx.doi.org/10.4049/jimmunol.1200391DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3626171PMC
February 2013

IL-7-dependent B lymphocytes are essential for the anti-polysaccharide response and protective immunity to Streptococcus pneumoniae.

J Immunol 2010 Jul 26;185(1):525-31. Epub 2010 May 26.

Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.

Young children are impaired in their response to T cell-independent (TI) Ags, such as pneumococcal polysaccharide (PPS). B lymphopoeisis early in life is IL-7 independent, whereas in adults it is IL-7 dependent. Therefore, we hypothesized that IL-7-driven B lymphopoiesis plays a critical role in promoting Ab responses to TI Ags. Young but not adult mice are impaired in responses to PPS vaccination and to 4-hydroxy-3-nitrophenyl-acetyl-Ficoll, a widely studied model TI Ag, and B1b cells generate Ab responses to these Ags. In this paper, we show that, despite having B1b, B1a, and MZ B cells-all of which are involved in TI responses-young wild-type or adult mice deficient either in IL-7 or in IL-7Ralpha are severely impaired in anti-PPS responses and do not survive Streptococcus pneumoniae challenge, indicating IL-7-dependent B cells are required for TI immunity. Consistent with this, PPS immunization induced a robust TI response in young IL-7 transgenic mice that was comparable to adult wild-type responses. Moreover, immunized young or adult IL-7 transgenic mice were completely resistant to S. pneumoniae challenge. Our data indicate that activating the IL-7 signaling pathway could restore impaired TI responses in the young.
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http://dx.doi.org/10.4049/jimmunol.0902841DOI Listing
July 2010

Pharmacologic modulation of niche accessibility via tyrosine kinase inhibition enhances marrow and thymic engraftment after hematopoietic stem cell transplantation.

Blood 2010 May 15;115(20):4120-9. Epub 2010 Mar 15.

Pediatric Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.

Essential survival signals within hematopoietic stem cell (HSC) and thymic niches are mediated by receptor tyrosine kinases, which can be reversibly inhibited using clinically available drugs. We studied whether sunitinib, a multityrosine kinase inhibitor that inhibits KIT, enhances engraftment after bone marrow transplantation (BMT) in mice. Sunitinib diminished hematopoietic progenitor cell numbers, and sunitinib enhanced marrow, peripheral myeloid, and lymphoid engraftment after BMT in Rag1(-/-) mice. Sunitinib augmented HSC engraftment because recipients displayed increased myeloid and lymphoid engraftment and because sunitinib-treated recipients of purified HSCs showed enhanced engraftment of secondary hosts. However, sunitinib preferentially augmented T-cell engraftment with lesser effects on myeloid and HSC engraftment. Consistent with this, sunitinib preferentially depleted the early thymic progenitor subset in the thymus. Sunitinib did not increase engraftment in mice with deficient KIT signaling, and the pattern of more potent effects on T cell compared with HSC engraftment observed in sunitinib-treated hosts was also observed after BMT into KIT(W/Wv) mice. These results implicate KIT as a critical modulator of thymic niches. We conclude that transient, pharmacologic inhibition of KIT enhances accessibility of marrow and thymic niches, and provides a novel, noncytotoxic approach to accomplish engraftment after stem cell transplantation.
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http://dx.doi.org/10.1182/blood-2009-10-248898DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2875097PMC
May 2010

In vivo role of Flt3 ligand and dendritic cells in NK cell homeostasis.

J Immunol 2010 Mar 8;184(6):2769-75. Epub 2010 Feb 8.

Department of Molecular Virology, The Ohio State University, Columbus, OH43210, USA.

IL-15 is required for NK cell development and homeostasis in vivo. Because IL-15 is presented in trans via its high-affinity IL-15Ralpha-chain to cells expressing the IL-15Rbetagamma complex, we postulated that certain IL-15-bearing cells must be required for NK cell homeostasis. Using IL-15(WT/WT) and IL-15(-/-) mice, bone marrow chimeras with normal cellularity, and a selective depletion of CD11c(hi) dendritic cells (DCs), we demonstrate that ablation of the resting CD11c(hi) DC population results in a highly significant decrease in the absolute number of mature NK cells. In contrast, administration of Flt3 ligand increases the CD11c(hi) DC population, which, when expressing IL-15, significantly expands mature NK cells via enhanced survival and proliferation. In summary, a CD11c(hi) DC population expressing IL-15 is required to maintain NK cell homeostasis under conditions of normal cellularity and also is required to mediate Flt3 ligand-induced NK cell expansion in vivo.
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http://dx.doi.org/10.4049/jimmunol.0900685DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2924750PMC
March 2010

Harnessing the physiology of lymphopenia to support adoptive immunotherapy in lymphoreplete hosts.

Blood 2009 Oct 24;114(18):3831-40. Epub 2009 Aug 24.

Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA.

Lymphopenia enhances the effectiveness of adoptive immunotherapy by facilitating expansion of transferred T cells but also limits the T-cell repertoire available to mediate immune responses and, in humans, is associated with chronic immune dysfunction. Previous studies concluded that lymphopenia augments adoptive immunotherapy by diminishing Tregs and increasing homeostatic cytokines. We sought to determine whether targeted therapies that replicate the physiology of lymphopenia in lymphoreplete hosts could provide a similarly supportive milieu. Pmel-1 T cells were transferred to B16-bearing lymphopenic versus lymphoreplete mice receiving alphaCD25 and/or recombinant human interleukin-7. Although CD25-based Treg depletion was inefficient because of peripheral expansion of CD4+CD25-FOXP3+ cells, outcomes were better in alphaCD25-treated lymphoreplete hosts than in lymphopenic hosts, and adoptive immunotherapy was most effective in lymphoreplete hosts receiving alphaCD25 plus recombinant human interleukin-7. Lymphopenic hosts supported increased proliferation of adoptively transferred antigen-specific T cells, but cells transferred to lymphoreplete recipients receiving targeted therapies showed superior function. Further, determinant spreading was substantial in lymphoreplete hosts but absent in lymphopenic hosts. These results demonstrate that targeted therapies delivered to mimic the "physiology of lymphopenia" enhance the efficacy of adoptive immunotherapy in lymphoreplete hosts and provide a potentially superior alternative to the induction of lymphopenia.
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http://dx.doi.org/10.1182/blood-2009-03-212134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2773493PMC
October 2009

GVHD: a continuing barrier to the safety of allogeneic transplantation.

Biol Blood Marrow Transplant 2009 Jan;15(1 Suppl):162-8

Department of Hematology, Oncology, and Transplantation, University of Minnesota, Minneapolis, Minnesota, USA.

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http://dx.doi.org/10.1016/j.bbmt.2008.10.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2633357PMC
January 2009

Interleukin 7 signaling in dendritic cells regulates the homeostatic proliferation and niche size of CD4+ T cells.

Nat Immunol 2009 Feb 11;10(2):149-57. Epub 2009 Jan 11.

Pediatric Oncology Branch, National Cancer Institute, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.

Interleukin 7 (IL-7) and T cell antigen receptor signals have been proposed to be the main drivers of homeostatic T cell proliferation. However, it is not known why CD4(+) T cells undergo less-efficient homeostatic proliferation than CD8(+) T cells do. Here we show that systemic IL-7 concentrations increased during lymphopenia because of diminished use of IL-7 but that IL-7 signaling on IL-7 receptor-alpha-positive (IL-7Ralpha(+)) dendritic cells (DCs) in lymphopenic settings paradoxically diminished the homeostatic proliferation of CD4(+) T cells. This effect was mediated at least in part by IL-7-mediated downregulation of the expression of major histocompatibility complex class II on IL-7Ralpha(+) DCs. Our results indicate that IL-7Ralpha(+) DCs are regulators of the peripheral CD4(+) T cell niche and that IL-7 signals in DCs prevent uncontrolled CD4(+) T cell population expansion in vivo.
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http://dx.doi.org/10.1038/ni.1695DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2713006PMC
February 2009

The Mll partial tandem duplication: differential, tissue-specific activity in the presence or absence of the wild-type allele.

Blood 2008 Sep 10;112(6):2508-11. Epub 2008 Jul 10.

Department of Internal Medicine, Division of Hematology and Oncology, James Cancer Hospital and Solove Research Institute, The Ohio State University, Columbus, USA.

The partial tandem duplication of MLL (MLL-PTD) is found in 5% to 10% of patients with acute myeloid leukemia (AML) and normal cytogenetics. Its expression in leukemic blasts is coincident with a silenced wild-type (WT) MLL allele. We therefore generated mice expressing the Mll-PTD in the absence of Mll-WT. These Mll(PTD/-) mice die at birth unlike the normal life expectancy of Mll(PTD/WT), Mll(WT/-), and Mll(WT/WT) mice. Using Mll(WT/WT) fetal liver cells (FLC) as baseline, we compared Mll(PTD/-) with Mll(PTD/WT) FLC and found both had increased HoxA gene expression and granulocyte-macrophage colony-forming progenitor cells (CFU-GM); in contrast, only Mll(PTD/WT) FLC had increased pluripotent hemopoietic progenitors (CFU-GEMM). The similarities between Mll(PTD/WT) and Mll(PTD/-) mice suggest that the Mll-PTD mutation can up-regulate target genes in a dominant, gain-of-function fashion. The differences between these 2 genotypes suggest that in select tissues the Mll-PTD requires cooperation with the Mll-WT in the genesis of the observed abnormality.
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http://dx.doi.org/10.1182/blood-2008-01-134338DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2532816PMC
September 2008

Specific tumor suppressor function for E2F2 in Myc-induced T cell lymphomagenesis.

Proc Natl Acad Sci U S A 2007 Sep 19;104(39):15400-5. Epub 2007 Sep 19.

Human Cancer Genetics Program, Department of Molecular Virology, Immunology, and Medical Genetics, College of Medicine and Public Health, Ohio State University, Columbus, OH 43210, USA.

Deregulation of the Myc pathway and deregulation of the Rb pathway are two of the most common abnormalities in human malignancies. Recent in vitro experiments suggest a complex cross-regulatory relationship between Myc and Rb that is mediated through the control of E2F. To evaluate the functional connection between Myc and E2Fs in vivo, we used a bitransgenic mouse model of Myc-induced T cell lymphomagenesis and analyzed tumor progression in mice deficient for E2f1, E2f2, or E2f3. Whereas the targeted inactivation of E2f1 or E2f3 had no significant effect on tumor progression, loss of E2f2 accelerated lymphomagenesis. Interestingly, loss of a single copy of E2f2 also accelerated tumorigenesis, albeit to a lesser extent, suggesting a haploinsufficient function for this locus. The combined ablation of E2f1 or E2f3, along with E2f2, did not further accelerate tumorigenesis. Myc-overexpressing T cells were more resistant to apoptosis in the absence of E2f2, and the reintroduction of E2F2 into these tumor cells resulted in an increase of apoptosis and inhibition of tumorigenesis. These results identify the E2f2 locus as a tumor suppressor through its ability to modulate apoptosis.
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http://dx.doi.org/10.1073/pnas.0706307104DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2000495PMC
September 2007

Mll partial tandem duplication induces aberrant Hox expression in vivo via specific epigenetic alterations.

J Clin Invest 2006 Oct 14;116(10):2707-16. Epub 2006 Sep 14.

Department of Internal Medicine, Division of Hematology and Oncology, The Ohio State University, Columbus, Ohio 43220, USA.

We previously identified a rearrangement of mixed-lineage leukemia (MLL) gene (also known as ALL-1, HRX, and HTRX1), consisting of an in-frame partial tandem duplication (PTD) of exons 5 through 11 in the absence of a partner gene, occurring in approximately 4%-7% of patients with acute myeloid leukemia (AML) and normal cytogenetics, and associated with a poor prognosis. The mechanism by which the MLL PTD contributes to aberrant hematopoiesis and/or leukemia is unknown. To examine this, we generated a mouse knockin model in which exons 5 through 11 of the murine Mll gene were targeted to intron 4 of the endogenous Mll locus. Mll(PTD/WT) mice exhibit an alteration in the boundaries of normal homeobox (Hox) gene expression during embryogenesis, resulting in axial skeletal defects and increased numbers of hematopoietic progenitor cells. Mll(PTD/WT) mice overexpress Hoxa7, Hoxa9, and Hoxa10 in spleen, BM, and blood. An increase in histone H3/H4 acetylation and histone H3 lysine 4 (Lys4) methylation within the Hoxa7 and Hoxa9 promoters provides an epigenetic mechanism by which this overexpression occurs in vivo and an etiologic role for MLL PTD gain of function in the genesis of AML.
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http://dx.doi.org/10.1172/JCI25546DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1564428PMC
October 2006

Lymphopenia and interleukin-2 therapy alter homeostasis of CD4+CD25+ regulatory T cells.

Nat Med 2005 Nov 16;11(11):1238-43. Epub 2005 Oct 16.

Pediatric Oncology Branch, National Institutes of Health, 10 Center Drive, Bethesda, Maryland 20892, USA.

CD4(+)CD25(+) regulatory T (T(reg)) cells have a crucial role in maintaining immune tolerance. Mice and humans born lacking T(reg) cells develop severe autoimmune disease, and depletion of T(reg) cells in lymphopenic mice induces autoimmunity. Interleukin (IL)-2 signaling is required for thymic development, peripheral expansion and suppressive activity of T(reg) cells. Animals lacking IL-2 die of autoimmunity, which is prevented by administration of IL-2-responsive T(reg) cells. In light of the emerging evidence that one of the primary physiologic roles of IL-2 is to generate and maintain T(reg) cells, the question arises as to the effects of IL-2 therapy on them. We monitored T(reg) cells during immune reconstitution in individuals with cancer who did or did not receive IL-2 therapy. CD4(+)CD25(hi) cells underwent homeostatic peripheral expansion during immune reconstitution, and in lymphopenic individuals receiving IL-2, the T(reg) cell compartment was markedly increased. Mouse studies showed that IL-2 therapy induced expansion of existent T(reg) cells in normal hosts, and IL-2-induced T(reg) cell expansion was further augmented by lymphopenia. On a per-cell basis, T(reg) cells generated by IL-2 therapy expressed similar levels of FOXP3 and had similar potency for suppression compared to T(reg) cells present in normal hosts. These studies suggest that IL-2 and lymphopenia are primary modulators of CD4(+)CD25(+) T(reg) cell homeostasis.
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http://dx.doi.org/10.1038/nm1312DOI Listing
November 2005

Cytokine signals in T-cell homeostasis.

J Immunother 2005 Jul-Aug;28(4):289-94

Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892-1104, USA.

Thymic production of T cells declines rapidly with age, and therefore homeostatic cycling (HC) of mature lymphocytes plays an important role in maintaining stable numbers of mature T lymphocytes bearing sufficient repertoire diversity. Following lymphocyte depletion, HC changes in quality and magnitude, resulting in homeostatic peripheral expansion (HPE), a state of widespread T-cell cycling that serves to increase T-cell number and to maintain T-cell repertoire diversity to the greatest extent possible. Recent studies delineating the requirements for HC and HPE have shown that naive CD4+ cells and naive CD8+ cells require both IL7 and TCR engagement for survival, cycling, and homeostatic expansion, whereas CD8+ memory cells are maintained and expanded by cytokine signals alone, independent of TCR engagement. While basal levels of IL15 are sufficient for HC and HPE of CD8+ memory cells, supranormal levels of IL7 will also suffice. The requirements for memory CD4+ cells remain unclear, but current models hypothesize that either IL7 or TCR triggering may be sufficient. Thus, the changes in immune physiology that are present in lymphopenic hosts can be largely accounted for by cytokine-driven signals, especially those rendered by IL7 or IL15. As the alterations in immune physiology present in lymphopenic hosts may be conducive to stronger antitumor immune responsiveness, careful delineation of the factors responsible may be expected to give rise to approaches to augment the effectiveness of current antitumor immunotherapies.
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http://dx.doi.org/10.1097/01.cji.0000165356.03924.e7DOI Listing
October 2005

A human CD34(+) subset resides in lymph nodes and differentiates into CD56bright natural killer cells.

Immunity 2005 Mar;22(3):295-304

Department of Molecular Virology, Immunology, and Medical Genetics, College of Medicine and Public Health, The Ohio State University, Columbus, Ohio 43210, USA.

In humans, T cells differentiate in thymus and B cells develop in bone marrow (BM), but the natural killer (NK) precursor cell(s) and site(s) of NK development are unclear. The CD56bright NK subset predominates in lymph nodes (LN) and produces abundant cytokines compared to the cytolytic CD56dim NK cell that predominates in blood. Here, we identify a novel CD34dimCD45RA(+) hematopoietic precursor cell (HPC) that is integrin alpha4beta7bright. CD34dimCD45RA(+)beta7bright HPCs constitute <1% of BM CD34(+) HPCs and approximately 6% of blood CD34(+) HPCs, but >95% of LN CD34(+) HPCs. They reside in the parafollicular T cell regions of LN with CD56bright NK cells, and when stimulated by IL-15, IL-2, or activated LN T cells, they become CD56bright NK cells. The data identify a new NK precursor and support a model of human NK development in which BM-derived CD34dimCD45RA(+)beta7bright HPCs reside in LN where endogenous cytokines drive their differentiation to CD56bright NK cells in vivo.
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http://dx.doi.org/10.1016/j.immuni.2005.01.013DOI Listing
March 2005

The MLL partial tandem duplication: evidence for recessive gain-of-function in acute myeloid leukemia identifies a novel patient subgroup for molecular-targeted therapy.

Blood 2005 Jul 17;106(1):345-52. Epub 2005 Mar 17.

Department of Internal Medicine, Division of Hematology-Oncology, The Ohio State University, Columbus, OH 43210, USA.

MLL (ALL-1) chimeric fusions and MLL partial tandem duplications (PTD) may have mechanistically distinct contributions to leukemogenesis. Acute myeloid leukemia (AML) blasts with the t(9;11)(p22; q23) express MLL-AF9 and MLL wild-type (WT) transcripts, while normal karyotype AML blasts with the MLL(PTD/WT) genotype express MLL PTD but not the MLL WT. Silencing of MLL WT in MLL(PTD/WT) blasts was reversed by DNA methyltransferase (DNMT) and histone deacetylase (HDAC) inhibitors, and MLL WT induction was associated with selective sensitivity to cell death. Reduction of MLL PTD expression induced MLL WT and reduced blast colony-forming units, supporting opposing functions for MLL PTD and MLL WT whereby the MLL PTD contributes to the leukemic phenotype via a recessive gain-of-function. The coincident suppression of the MLL WT allele with the expression of the MLL PTD allele, along with the functional data presented here, supports the hypothesis that loss of WT MLL function via monoallelic repression contributes to the leukemic phenotype by the remaining mutant allele. These data from primary AML and the pharmacologic reversal of MLL WT silencing associated with a favorable alteration in the threshold for apoptosis suggest that these patients with poor prognosis may benefit from demethylating or histone deacetylase inhibitor therapy, or both.
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http://dx.doi.org/10.1182/blood-2005-01-0204DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1895129PMC
July 2005

Failed adoptive immunotherapy with tumor-specific T cells: reversal with low-dose interleukin 15 but not low-dose interleukin 2.

Cancer Res 2004 Nov;64(21):8062-7

Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University, Columbus, Ohio 43210, USA.

Adoptive immunotherapy with tumor-specific T cells has emerged as a valid approach for prevention or treatment of diseases, such as melanoma and EBV-associated lymphoma. As interleukin (IL) 15 promotes survival of CD8(+) memory CTLs, we hypothesized that it could be used to enhance antitumor immunity in vivo through the maintenance of adoptively transferred memory CTL. To test this, we treated mice bearing P1A(+) tumors with adoptively transferred T cells possessing a transgenic Valpha8(+) T-cell receptor specific for the P1A tumor antigen (called P1CTL). Mice were then randomized to receive daily low-dose IL-15 (0.5 microg/day) or PBS. Mice receiving the transgenic P1CTL and IL-15 experienced a significantly delayed tumor relapse or complete tumor regression (P < 0.002 compared with PBS), with a striking persistence of the CD8(+) Valpha8(+) P1CTL compared with mice receiving the CD8(+) Valpha8(+) P1CTL and PBS vehicle (26.3 versus 5.1% P < 10(-5)). Animals exhibiting complete tumor regression had a significant population of CD8(+) Valpha8(+) P1CTL (46%) that persisted with IL-15 treatment until 140 days after adoptive transfer and successfully defended them against tumor rechallenge without IL-15. Low-dose IL-2 afforded no protection over vehicle and resulted in lower percentages of T cells with an activated memory phenotype, lower Bcl-2 expression, and lower ex vivo antitumor cytotoxicity compared with mice treated with IL-15. Collectively, the data support the notion that exogenous low-dose IL-15 therapy can enhance and even reverse the limited efficacy of adoptively transferred tumor-specific T-cell therapy and may do so in a fashion that is superior and distinct from exogenous IL-2 therapy.
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http://dx.doi.org/10.1158/0008-5472.CAN-04-1860DOI Listing
November 2004

Donor-derived IL-15 is critical for acute allogeneic graft-versus-host disease.

Blood 2005 Jan 16;105(2):894-901. Epub 2004 Sep 16.

Division of Human Cancer Genetics, Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University, Columbus, OH, USA.

Interleukin-15 (IL-15) is a pleiotropic proinflammatory cytokine with inefficient posttranscriptional processing. We hypothesized that endogenous IL-15 could affect disease progression in the well-described C57Bl/6 (B6)-->(C57Bl/6 x DBA/2) F1 hybrid (B6D2F1) murine model of acute allogeneic graft-versus-host disease (GVHD). B6D2F1 allogeneic recipients received transplants of IL-15(-/-) B6 bone marrow cells or B6 bone marrow cells expressing a murine IL-15 transgene (IL-15 tg) modified for efficient translation and secretion. Mice that received transplants of IL-15(-/-) B6 bone marrow cells displayed a significantly longer median survival time (MST) compared with mice that received transplants of wild-type (wt) B6 bone marrow; in contrast, mice that received transplants of IL-15 tg B6 bone marrow cells had a dramatically decreased MST. This decrease in survival was associated with a substantial activation and expansion of effector-memory (CD44highCD62Llow) CD8+ T lymphocytes. Finally, in vivo depletion of either CD4+ or CD8+ T lymphocyte subsets significantly prolonged survival in mice receiving IL-15 tg B6 marrow, while depletion of both CD4+ and CD8+ T cells provided complete protection from acute GVHD. We thus show that acute GVHD is attenuated in the absence of donor bone marrow-derived IL-15 and conclude that donor-derived IL-15 is a critical mediator of T-cell function in acute GVHD.
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http://dx.doi.org/10.1182/blood-2004-05-1687DOI Listing
January 2005

Acute myeloid leukemia with complex karyotypes and abnormal chromosome 21: Amplification discloses overexpression of APP, ETS2, and ERG genes.

Proc Natl Acad Sci U S A 2004 Mar 8;101(11):3915-20. Epub 2004 Mar 8.

Human Cancer Genetics Program, Ohio State University Comprehensive Cancer Center, Columbus, OH 43210, USA.

Molecular mechanisms of leukemogenesis have been successfully unraveled by studying genes involved in simple rearrangements including balanced translocations and inversions. In contrast, little is known about genes altered in complex karyotypic abnormalities. We studied acute myeloid leukemia (AML) patients with complex karyotypes and abnormal chromosome 21. High-resolution bacterial artificial chromosome (BAC) array-based comparative genomic hybridization disclosed amplification predominantly in the 25- to 30-megabase (MB) region that harbors the APP gene (26.3 MB) and at position 38.7-39.1 MB that harbors the transcription factors ERG and ETS2. Using oligonucleotide arrays, APP was by far the most overexpressed gene (mean fold change 19.74, P = 0.0003) compared to a control group of AML with normal cytogenetics; ERG and ETS2 also ranked among the most highly expressed chromosome 21 genes. Overexpression of APP and ETS2 correlated with genomic amplification, but high APP expression occurred even in a subset of AML patients with normal cytogenetics (10 of 64, 16%). APP encodes a glycoprotein of unknown function previously implicated in Alzheimer's disease, but not in AML. We hypothesize that APP and the transcription factors ERG and ETS2 are altered by yet unknown molecular mechanisms involved in leukemogenesis. Our results highlight the value of molecularly dissecting leukemic cells with complex karyotypes.
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http://dx.doi.org/10.1073/pnas.0400272101DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC374344PMC
March 2004
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