ABSTRACT
Erythropoietic protoporphyria (EPP) is a rare genetic disease in which patients experience acute phototoxic reactions after sunlight exposure. It is caused by a deficiency in ferrochelatase (FECH) in the heme biosynthesis pathway. Most patients exhibit a loss-of-function mutation in trans to an allele bearing a SNP that favors aberrant splicing of transcripts. One viable strategy for EPP is to deploy splice-switching oligonucleotides (SSOs) to increase FECH synthesis, whereby an increase of a few percent would provide therapeutic benefit. However, successful application of SSOs in bone marrow cells is not described. Here, we show that SSOs comprising methoxyethyl-chemistry increase FECH levels in cells. We conjugated one SSO to three prototypical targeting groups and administered them to a mouse model of EPP in order to study their biodistribution, their metabolic stability and their FECH splice-switching ability. The SSOs exhibited distinct distribution profiles, with increased accumulation in liver, kidney, bone marrow and lung. However, they also underwent substantial metabolism, mainly at their linker groups. An SSO bearing a cholesteryl group increased levels of correctly spliced FECH transcript by 80% in the bone marrow. The results provide a promising approach to treat EPP and other disorders originating from splicing dysregulation in the bone marrow.
Subject(s)
Ferrochelatase/genetics , Oligonucleotides/administration & dosage , Protoporphyria, Erythropoietic/metabolism , RNA Splicing , Albumins/metabolism , Animals , Bone Marrow/metabolism , COS Cells , Chlorocebus aethiops , Disease Models, Animal , Ferrochelatase/metabolism , Humans , K562 Cells , Mice , Oligonucleotides/blood , Oligonucleotides/chemistry , Oligonucleotides/pharmacokinetics , Polymorphism, Single Nucleotide , Protoporphyria, Erythropoietic/genetics , Protoporphyria, Erythropoietic/therapy , RNA Splice Sites , Tissue DistributionABSTRACT
Physiological processes in multicellular organisms depend on the function and interactions of specialized cell types operating in context. Some of these cell types are rare and thus obtainable only in minute quantities. For example, tissue-specific stem and progenitor cells are numerically scarce, but functionally highly relevant, and fulfill critical roles in development, tissue maintenance, and disease. Whereas low numbers of cells are routinely analyzed by genomics and transcriptomics, corresponding proteomic analyses have so far not been possible due to methodological limitations. Here we describe a sensitive and robust quantitative technique based on data-independent acquisition mass spectrometry. We quantified the proteome of sets of 25,000 human hematopoietic stem/multipotent progenitor cells (HSC/MPP) and three committed progenitor cell subpopulations of the myeloid differentiation pathway (common myeloid progenitors, megakaryocyte-erythrocyte progenitors, and granulocyte-macrophage progenitors), isolated by fluorescence-activated cell sorting from five healthy donors. On average, 5,851 protein groups were identified per sample. A subset of 4,131 stringently filtered protein groups was quantitatively compared across the 20 samples, defining unique signatures for each subpopulation. A comparison of proteomic and transcriptomic profiles indicated HSC/MPP-specific divergent regulation of biochemical functions such as telomerase maintenance and quiescence-inducing enzymes, including isocitrate dehydrogenases. These are essential for maintaining stemness and were detected at proteome, but not transcriptome, level. The method is equally applicable to almost any rare cell type, including healthy and cancer stem cells or physiologically and pathologically infiltrating cell populations. It thus provides essential new information toward the detailed biochemical understanding of cell development and functionality in health and disease.
Subject(s)
Hematopoietic Stem Cells/metabolism , Mass Spectrometry/methods , Proteomics , Gene Ontology , HEK293 Cells , Humans , Proteome/metabolism , Transcriptome/genetics , Trypsin/metabolismABSTRACT
The pathogenesis of acquired myeloperoxidase (MPO) deficiency, a rare phenomenon observed in patients with Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), is unknown. MPO is a glycoprotein (GP) chaperoned by calreticulin (CALR) in the endoplasmic reticulum. Mutations in CALR are frequently found in patients with myelofibrosis (MF) and essential thrombocythemia (ET) with nonmutated Janus kinase 2 (JAK2). We hypothesized that acquired MPO deficiency in MPN could be associated with the presence of CALR mutations. A cohort of 317 patients with MPN (142 polycythemia vera [PV], 94 ET, and 81 MF) was screened for MPO deficiency. MPO deficiency was observed in 6/81 MF patients (7.4%), but not in PV or ET patients. Susceptibility to infections had been documented in 2/6 (33%) MPO-deficient patients. Five out of 6 patients with MPO deficiency carried a homozygous CALR mutation and were also deficient in eosinophilic peroxidase (EPX). In contrast, 1 patient with MF, a JAK2-V617F mutation, and MPO deficiency, carried 2 previously reported MPO mutations and showed normal EPX activity. Patients with homozygous CALR mutations had reduced MPO protein, but normal MPO messenger RNA (mRNA) levels supporting a posttranscriptional defect in MPO production. Finally, we demonstrate in vitro that in the absence of CALR, immature MPO protein precursors are degraded in the proteasome. Therefore, 4 decades after the first description of acquired MPO deficiency in MPN, we provide the molecular correlate associated with this phenomenon and evidence that CALR mutations can affect the biosynthesis of GPs.
Subject(s)
Calreticulin/genetics , Metabolism, Inborn Errors/genetics , Mutation , Primary Myelofibrosis/genetics , Animals , Cells, Cultured , Cohort Studies , Homozygote , Humans , Metabolism, Inborn Errors/pathology , Mice , Mice, Knockout , Peroxidase/genetics , Peroxidase/metabolism , Primary Myelofibrosis/complications , Primary Myelofibrosis/pathology , Proteasome Endopeptidase Complex/metabolism , ProteolysisSubject(s)
Acute Kidney Injury/diagnosis , Acute Kidney Injury/etiology , Antineoplastic Combined Chemotherapy Protocols/adverse effects , Creatinine/blood , Leukemia, Myeloid, Acute/complications , Preoperative Care , Adolescent , Adult , Aged , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Biomarkers , Female , Glomerular Filtration Rate , Hematopoietic Stem Cell Transplantation , Humans , Leukemia, Myeloid, Acute/drug therapy , Male , Middle Aged , Preoperative Care/adverse effects , Preoperative Care/methods , Prognosis , Retrospective Studies , Young AdultSubject(s)
Antibodies, Monoclonal , Lymph Nodes/immunology , Animals , Humans , Immune System , MiceABSTRACT
Over the last decades, incrementally improved xenograft mouse models, supporting the engraftment and development of a human hemato-lymphoid system, have been developed and now represent an important research tool in the field. The most significant contributions made by means of humanized mice are the identification of normal and leukemic hematopoietic stem cells, the characterization of the human hematopoietic hierarchy, and their use as preclinical therapy models for malignant hematopoietic disorders. Successful xenotransplantation depends on three major factors: tolerance by the mouse host, correct spatial location, and appropriately cross-reactive support and interaction factors such as cytokines and major histocompatibility complex molecules. Each of these can be modified. Experimental approaches include the genetic modification of mice to faithfully express human support factors as non-cross-reactive cytokines, to create free niche space, the co-transplantation of human mesenchymal stem cells, the implantation of humanized ossicles or other stroma, and the implantation of human thymic tissue. Besides the source of hematopoietic cells, the conditioning regimen and the route of transplantation also significantly affect human hematopoietic development in vivo. We review here the achievements, most recent developments, and the remaining challenges in the generation of pre-clinically-predictive systems for human hematology and immunology, closely resembling the human situation in a xenogeneic mouse environment.
Subject(s)
Hematopoietic System/immunology , Lymphatic System/immunology , Mesenchymal Stem Cell Transplantation , Thymus Gland/transplantation , Animals , Heterografts , Humans , Mice , Mice, SCID , Thymus Gland/immunologyABSTRACT
Previous chemotherapy research has focused almost exclusively on apoptosis. Here, a standard frontline drug combination of cytarabine and idarubicin induces distinct features of caspase-independent, poly(ADP-ribose) polymerase 1 (PARP-1)-mediated programmed cell death "parthanatos" in acute myeloid leukemia (AML) cell lines (n = 3/10 tested), peripheral blood mononuclear cells from healthy human donors (n = 10/10 tested), and primary cell samples from patients with AML (n = 18/39 tested, French-American-British subtypes M4 and M5). A 3-fold improvement in survival rates is observed in the parthanatos-positive versus -negative patient groups (hazard ratio [HR] = 0.28-0.37, p = 0.002-0.046). Manipulation of PARP-1 activity in parthanatos-competent cells reveals higher drug sensitivity in cells that have basal PARP-1 levels as compared with those subjected to PARP-1 overexpression or suppression. The same trends are observed in RNA expression databases and support the conclusion that PARP-1 can have optimal levels for favorable chemotherapeutic responses.
Subject(s)
Leukemia , Poly(ADP-ribose) Polymerase Inhibitors , Humans , Apoptosis , Cell Line , Leukocytes, Mononuclear , Poly(ADP-ribose) Polymerase Inhibitors/pharmacology , Poly(ADP-ribose) Polymerase Inhibitors/therapeutic useABSTRACT
Polycythemia vera (PV) is a hematopoietic stem cell neoplasm driven by somatic mutations in JAK2, leading to increased red blood cell (RBC) production uncoupled from mechanisms that regulate physiological erythropoiesis. At steady-state, bone marrow macrophages promote erythroid maturation, whereas splenic macrophages phagocytose aged or damaged RBCs. The binding of the anti-phagocytic ("don't eat me") CD47 ligand expressed on RBCs to the SIRPα receptor on macrophages inhibits phagocytic activity protecting RBCs from phagocytosis. In this study, we explore the role of the CD47-SIRPα interaction on the PV RBC life cycle. Our results show that blocking CD47-SIRPα in a PV mouse model due to either anti-CD47 treatment or loss of the inhibitory SIRPα-signal corrects the polycythemia phenotype. Anti-CD47 treatment marginally impacted PV RBC production while not influencing erythroid maturation. However, upon anti-CD47 treatment, high-parametric single-cell cytometry identified an increase of MerTK+ splenic monocyte-derived effector cells, which differentiate from Ly6Chi monocytes during inflammatory conditions, acquire an inflammatory phagocytic state. Furthermore, in vitro, functional assays showed that splenic JAK2 mutant macrophages were more "pro-phagocytic," suggesting that PV RBCs exploit the CD47-SIRPα interaction to escape innate immune attacks by clonal JAK2 mutant macrophages.
Subject(s)
Polycythemia Vera , Animals , Mice , CD47 Antigen/metabolism , Disease Models, Animal , Macrophages , Monocytes/metabolism , Phagocytosis , Phenotype , Polycythemia Vera/genetics , Polycythemia Vera/metabolismABSTRACT
Myelofibrosis is a hematopoietic stem cell disorder belonging to the myeloproliferative neoplasms. Myelofibrosis patients frequently carry driver mutations in either JAK2 or Calreticulin (CALR) and have limited therapeutic options. Here, we integrate ex vivo drug response and proteotype analyses across myelofibrosis patient cohorts to discover targetable vulnerabilities and associated therapeutic strategies. Drug sensitivities of mutated and progenitor cells were measured in patient blood using high-content imaging and single-cell deep learning-based analyses. Integration with matched molecular profiling revealed three targetable vulnerabilities. First, CALR mutations drive BET and HDAC inhibitor sensitivity, particularly in the absence of high Ras pathway protein levels. Second, an MCM complex-high proliferative signature corresponds to advanced disease and sensitivity to drugs targeting pro-survival signaling and DNA replication. Third, homozygous CALR mutations result in high endoplasmic reticulum (ER) stress, responding to ER stressors and unfolded protein response inhibition. Overall, our integrated analyses provide a molecularly motivated roadmap for individualized myelofibrosis patient treatment.
Subject(s)
Myeloproliferative Disorders , Primary Myelofibrosis , Humans , Primary Myelofibrosis/drug therapy , Primary Myelofibrosis/genetics , Myeloproliferative Disorders/genetics , Mutation , Hematopoietic Stem Cells/metabolism , Homozygote , Calreticulin/genetics , Calreticulin/metabolism , Janus Kinase 2/metabolismABSTRACT
Aging facilitates the expansion of hematopoietic stem cells (HSCs) carrying clonal hematopoiesis-related somatic mutations and the development of myeloid malignancies, such as myeloproliferative neoplasms (MPNs). While cooperating mutations can cause transformation, it is unclear whether distinct bone marrow (BM) HSC-niches can influence the growth and therapy response of HSCs carrying the same oncogenic driver. Here we found different BM niches for HSCs in MPN subtypes. JAK-STAT signaling differentially regulates CDC42-dependent HSC polarity, niche interaction and mutant cell expansion. Asymmetric HSC distribution causes differential BM niche remodeling: sinusoidal dilation in polycythemia vera and endosteal niche expansion in essential thrombocythemia. MPN development accelerates in a prematurely aged BM microenvironment, suggesting that the specialized niche can modulate mutant cell expansion. Finally, dissimilar HSC-niche interactions underpin variable clinical response to JAK inhibitor. Therefore, HSC-niche interactions influence the expansion rate and therapy response of cells carrying the same clonal hematopoiesis oncogenic driver.
Subject(s)
Myeloproliferative Disorders , Neoplasms , Humans , Aged , Myeloproliferative Disorders/genetics , Myeloproliferative Disorders/therapy , Myeloproliferative Disorders/pathology , Bone Marrow/pathology , Bone Marrow/physiology , Hematopoietic Stem Cells/pathology , Bone and Bones/pathology , Tumor Microenvironment/geneticsABSTRACT
Polycythemia vera (PV) is a stem cell disorder characterized by hyperproliferation of the myeloid lineages and the presence of an activating JAK2 mutation. To elucidate mechanisms controlling PV stem and progenitor cell biology, we applied a recently developed highly sensitive data-independent acquisition mass spectrometry workflow to purified hematopoietic stem and progenitor cell (HSPC) subpopulations of patients with chronic and progressed PV. We integrated proteomic data with genomic, transcriptomic, flow cytometry, and in vitro colony formation data. Comparative analyses revealed added information gained by proteomic compared with transcriptomic data in 30% of proteins with changed expression in PV patients. Upregulated biological pathways in hematopoietic stem and multipotent progenitor cells (HSC/MPPs) of PV included mammalian target of rapamycin (MTOR), STAT, and interferon signaling. We further identified a prominent reduction of clusterin (CLU) protein expression and a corresponding activation of nuclear factor-κB (NF-κB) signaling in HSC/MPPs of untreated PV patients compared with controls. Reversing the reduction of CLU and inhibiting NF-κB signaling decreased proliferation and differentiation of PV HSC/MPPs in vitro. Upon progression of PV, we identified upregulation of LGALS9 and SOCS2 protein expression in HSC/MPPs. Treatment of patients with hydroxyurea normalized the expression of CLU and NF-κB2 but not of LGALS9 and SOCS2. These findings expand the current understanding of the molecular pathophysiology underlying PV and provide new potential targets (CLU and NF-κB) for antiproliferative therapy in patients with PV.
Subject(s)
Polycythemia Vera , Cell Proliferation , Hematopoietic Stem Cells , Humans , Janus Kinase 2/genetics , NF-kappa B , Polycythemia Vera/diagnosis , Polycythemia Vera/genetics , ProteomicsABSTRACT
Calreticulin (CALR) is an endoplasmic reticulum (ER)-retained chaperone that assists glycoproteins in obtaining their structure. CALR mutations occur in patients with myeloproliferative neoplasms (MPNs), and the ER retention of CALR mutants (CALR MUT) is reduced due to a lacking KDEL sequence. Here, we investigate the impact of CALR mutations on protein structure and protein levels in MPNs by subjecting primary patient samples and CALR-mutated cell lines to limited proteolysis-coupled mass spectrometry (LiP-MS). Especially glycoproteins are differentially expressed and undergo profound structural alterations in granulocytes and cell lines with homozygous, but not with heterozygous, CALR mutations. Furthermore, homozygous CALR mutations and loss of CALR equally perturb glycoprotein integrity, suggesting that loss-of-function attributes of mutated CALR chaperones (CALR MUT) lead to glycoprotein maturation defects. Finally, by investigating the misfolding of the CALR glycoprotein client myeloperoxidase (MPO), we provide molecular proof of protein misfolding in the presence of homozygous CALR mutations.
Subject(s)
Calreticulin , Myeloproliferative Disorders , Humans , Calreticulin/genetics , Calreticulin/chemistry , Calreticulin/metabolism , Mutation/genetics , Homozygote , Molecular Chaperones/genetics , Molecular Chaperones/metabolism , Proteome/metabolismABSTRACT
Erythropoietic protoporphyria (EPP) is a rare disease in which patients experience severe light sensitivity. It is caused by a deficiency of ferrochelatase (FECH), the last enzyme in heme biosynthesis (HBS). The lack of FECH causes accumulation of its photoreactive substrate protoporphyrin IX (PPIX) in patients' erythrocytes. Here, we explored an approach for the treatment of EPP by decreasing PPIX synthesis using small-molecule inhibitors directed to factors in the HBS pathway. We generated a FECH-knockout clone from K562 erythroleukemia cells, which accumulates PPIX and undergoes oxidative stress upon light exposure. We used these matched cell lines to screen a set of publicly available inhibitors of factors in the HBS pathway. Inhibitors of the glycine transporters GlyT1 and GlyT2 lowered levels of PPIX and markers of oxidative stress selectively in K56211B4 cells, and in primary erythroid cultures from an EPP patient. Our findings open the door to investigation of glycine transport inhibitors for HBS disorders.
Subject(s)
Glycine Plasma Membrane Transport Proteins/antagonists & inhibitors , Protoporphyria, Erythropoietic/drug therapy , Protoporphyrins/pharmacology , Cells, Cultured , Erythrocytes/drug effects , Erythrocytes/metabolism , Glycine Plasma Membrane Transport Proteins/metabolism , Humans , K562 Cells , Molecular Structure , Protoporphyria, Erythropoietic/metabolismABSTRACT
Neuropathological and experimental evidence suggests that the cell-to-cell transfer of α-synuclein has an important role in the pathogenesis of Parkinson's disease (PD). However, the mechanism underlying this phenomenon is not fully understood. We undertook a small interfering RNA (siRNA), genome-wide screen to identify genes regulating the cell-to-cell transfer of α-synuclein. A genetically encoded reporter, GFP-2A-αSynuclein-RFP, suitable for separating donor and recipient cells, was transiently transfected into HEK cells stably overexpressing α-synuclein. We find that 38 genes regulate the transfer of α-synuclein-RFP, one of which is ITGA8, a candidate gene identified through a recent PD genome-wide association study (GWAS). Weighted gene co-expression network analysis (WGCNA) and weighted protein-protein network interaction analysis (WPPNIA) show that those hits cluster in networks that include known PD genes more frequently than expected by random chance. The findings expand our understanding of the mechanism of α-synuclein spread.
Subject(s)
Cell Communication/physiology , Genome-Wide Association Study/methods , Protein Interaction Maps/physiology , alpha-Synuclein/metabolism , HumansABSTRACT
The application and integration of molecular profiling technologies create novel opportunities for personalized medicine. Here, we introduce the Tumor Profiler Study, an observational trial combining a prospective diagnostic approach to assess the relevance of in-depth tumor profiling to support clinical decision-making with an exploratory approach to improve the biological understanding of the disease.
Subject(s)
Neoplasms/genetics , Neoplasms/metabolism , Clinical Decision-Making/methods , Computational Biology/methods , Decision Support Systems, Clinical , Humans , Precision Medicine/methods , Prospective StudiesABSTRACT
The engraftment potential of myeloproliferative neoplasms in immunodeficient mice is low. We hypothesized that the physiological expression of human cytokines (macrophage colony-stimulating factor, interleukin-3, granulocyte-macrophage colony-stimulating factor, and thrombopoietin) combined with human signal regulatory protein α expression in Rag2-/-Il2rγ-/- (MISTRG) mice might provide a supportive microenvironment for the development and maintenance of hematopoietic stem and progenitor cells (HSPC) from patients with primary, post-polycythemia or post-essential thrombocythemia myelofibrosis (MF). We show that MISTRG mice, in contrast to standard immunodeficient NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ and Rag2-/-Il2rγ-/- mice, supported engraftment of all patient samples investigated independent of MF disease stage or risk category. Moreover, MISTRG mice exhibited significantly higher human MF engraftment levels in the bone marrow, peripheral blood, and spleen and supported secondary repopulation. Bone marrow fibrosis development was limited to 3 of 14 patient samples investigated in MISTRG mice. Disease-driving mutations were identified in all xenografts, and targeted sequencing revealed maintenance of the primary patient sample clonal composition in 7 of 8 cases. Treatment of engrafted mice with the current standard-of-care Janus kinase inhibitor ruxolitinib led to a reduction in human chimerism. In conclusion, the established MF patient-derived xenograft model supports robust engraftment of MF HSPCs and maintains the genetic complexity observed in patients. The model is suited for further testing of novel therapeutic agents to expedite their transition into clinical trials.
Subject(s)
Hematopoietic Stem Cells , Heterografts , Primary Myelofibrosis , Animals , Humans , Mice , Mice, Inbred BALB C , Mice, Inbred NOD , Primary Myelofibrosis/geneticsSubject(s)
Immune Checkpoint Inhibitors , Macrophages , Humans , Macrophages/immunology , Macrophages/metabolism , Immune Checkpoint Inhibitors/therapeutic use , Immune Checkpoint Inhibitors/pharmacology , Animals , Immunotherapy/methods , Neoplasms/immunology , Neoplasms/therapy , Neoplasms/drug therapyABSTRACT
The sphingosine-1-phosphate (S1P) receptor S1PR2 and its downstream adaptor Gα13 are recurrently mutationally inactivated in the germinal center B-cell subtype of diffuse large B-cell lymphoma (DLBCL) and are silenced by the S1PR2 repressor FOXP1 in the activated B-cell like subtype of the disease. Loss of S1PR2 signaling relieves the germinal center confinement that is maintained by an S1P gradient and allows cells to resist S1P-induced apoptosis. We have shown previously that S1PR2 expression is induced in normal B cells through a newly described transforming growth factor-ß (TGF-ß)/TGF-ßRII/SMAD1 signaling axis that is inactivated in >85% of DLBCL patients. DLBCL cell lines lacking S1PR2, TGFBRII, or SMAD1 as the result of genomic editing all have a strong growth advantage in vitro, as well as in subcutaneous and orthotopic xenotransplantation models. Here, we show that the TGF-ß signaling pathway in DLBCL is blocked at the level of SMAD1 in DLBCL cell lines and patient samples by hypermethylation of CpG-rich regions surrounding the SMAD1 transcription start site. The pharmacologic restoration of SMAD1 expression by the demethylating agent decitabine (DAC) sensitizes cells to TGF-ß-induced apoptosis and reverses the growth of initially SMAD1- cell lines in ectopic and orthotopic models. This effect of DAC is reduced in a SMAD1-knockout cell line. We further show that DAC restores SMAD1 expression and reduces the tumor burden in a novel patient-derived orthotopic xenograft model. The combined data lend further support to the concept of an altered epigenome as a major driver of DLBCL pathogenesis.
Subject(s)
Antineoplastic Agents/pharmacology , DNA Demethylation/drug effects , Gene Expression Regulation, Neoplastic/drug effects , Lymphoma, Large B-Cell, Diffuse/genetics , Lymphoma, Large B-Cell, Diffuse/metabolism , Signal Transduction/drug effects , Smad1 Protein/genetics , Smad1 Protein/metabolism , Animals , Antineoplastic Agents/therapeutic use , Apoptosis/drug effects , Apoptosis/genetics , Cell Line, Tumor , Disease Models, Animal , Gene Silencing , Humans , Immunohistochemistry , Lymphoma, Large B-Cell, Diffuse/drug therapy , Lymphoma, Large B-Cell, Diffuse/pathology , Mice , Xenograft Model Antitumor AssaysABSTRACT
Neutrophils are the most abundant innate immune cells and the first line of defense against many pathogenic microbes, including the human fungal pathogen Candida albicans. Among the neutrophils' arsenal of effector functions, neutrophil extracellular traps (NETs) are thought to be of particular importance for trapping and killing the large fungal filaments by means of their web-like structures that consist of chromatin fibers decorated with proteolytic enzymes and host defense proteins. Peptidylarginine deiminase 4 (PAD4)-mediated citrullination of histones in activated neutrophils correlates with chromatin decondensation and extrusion and is widely accepted to act as an integral process of NET induction (NETosis). However, the requirement of PAD4-mediated histone citrullination for NET release during C. albicans infection remains unclear. In this study, we show that although PAD4-dependent neutrophil histone citrullination is readily induced by C. albicans, PAD4 is dispensable for NETosis in response to the fungus and other common NET-inducing stimuli. Moreover, PAD4 is not required for antifungal immunity during mucosal and systemic C. albicans infection. Our results demonstrate that PAD4 is dispensable for C. albicans-induced NETosis, and they highlight the limitations of using histone citrullination as a marker for NETs and PAD4-/- mice as a model of NET-deficiency.
ABSTRACT
The clinical and biological relevance of a paraprotein that newly arises after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in non-myeloma patients is unknown. In this study, the incidence, the course, and the clinical impact of paraproteins found after allo-HSCT were investigated in a cohort of 383 non-myeloma patients. Paraproteinemia after allo-HSCT was more frequent (52/383 patients, 14%) than the reported incidence of monoclonal gammopathy of unknown significance (MGUS) in age-matched healthy subjects and, in contrast to MGUS, did not correlate with age. In most patients (32/52, 62%), the paraprotein appeared transiently within the first year after allo-HSCT with a median duration of 6.0 months. Post-allo-HSCT paraproteinemia was significantly associated with graft versus host disease (GvHD) and correlated with a survival benefit within the first year, but not after five years following allo-HSCT. Importantly, patients with post-allo-HSCT paraproteinemia did not progress into a plasma cell myeloma as observed for MGUS inferring a distinct pathogenic mechanism. Skewing of lymphocyte subpopulations and alterations in cytokine levels in GvHD may explain the expansion of a specific plasma cell subset in non-myeloma patients undergoing allo-HSCT. Our data suggests that paraproteinemia after allo-HSCT is a reactive phenomenon rather than the consequence of clonal plasma cell transformation.