Erythrocyte possesses high sphingosine kinase 1 (SphK1) activity and is the major cell type supplying plasma sphingosine-1-phosphate, a signaling lipid regulating multiple physiological and pathological functions. Recent studies revealed that erythrocyte SphK1 activity is upregulated in sickle cell disease (SCD) and contributes to sickling and disease progression. However, how erythrocyte SphK1 activity is regulated remains unknown. Here we report that adenosine induces SphK1 activity in human and mouse sickle and normal erythrocytes in vitro. Next, using 4 adenosine receptor-deficient mice and pharmacological approaches, we determined that the A2B adenosine receptor (ADORA2B) is essential for adenosine-induced SphK1 activity in human and mouse normal and sickle erythrocytes in vitro. Subsequently, we provide in vivo genetic evidence that adenosine deaminase (ADA) deficiency leads to excess plasma adenosine and elevated erythrocyte SphK1 activity. Lowering adenosine by ADA enzyme therapy or genetic deletion of ADORA2B significantly reduced excess adenosine-induced erythrocyte SphK1 activity in ADA-deficient mice. Finally, we revealed that protein kinase A-mediated extracellular signal-regulated kinase 1/2 activation functioning downstream of ADORA2B underlies adenosine-induced erythrocyte SphK1 activity. Overall, our findings reveal a novel signaling network regulating erythrocyte SphK1 and highlight innovative mechanisms regulating SphK1 activity in normal and SCD.

Ribosomopathies are largely congenital diseases linked to defects in ribosomal proteins or biogenesis factors. Some of these disorders are characterized by hypoproliferative phenotypes such as bone marrow failure and anemia early in life, followed by elevated cancer risks later in life. This transition from hypo- to hyperproliferation presents an intriguing paradox in the field of hematology known as "Dameshek's riddle." Recent cancer sequencing studies also revealed somatically acquired mutations and deletions in ribosomal proteins in T-cell acute lymphoblastic leukemia and solid tumors, further extending the list of ribosomopathies and strengthening the association between ribosomal defects and oncogenesis. In this perspective, we summarize and comment on recent findings in the field of ribosomopathies. We explain how ribosomopathies may provide clues to help explain Dameshek's paradox and highlight some of the open questions and challenges in the field.

Treatment of Hodgkin lymphoma is associated with 2 major types of risk: that the treatment may fail to cure the disease or that the treatment will prove unacceptably toxic. Careful assessment of the amount of the lymphoma (tumor burden), its behavior (extent of invasion or specific organ compromise), and host related factors (age; coincident systemic infection; and organ dysfunction, especially hematopoietic, cardiac, or pulmonary) is essential to optimize outcome. Elaborately assembled prognostic scoring systems, such as the International Prognostic Factors Project score, have lost their accuracy and value as increasingly effective chemotherapy and supportive care have been developed. Identification of specific biomarkers derived from sophisticated exploration of Hodgkin lymphoma biology is bringing promise of further improvement in targeted therapy in which effectiveness is increased at the same time off-target toxicity is diminished. Parallel developments in functional imaging are providing additional potential to evaluate the efficacy of treatment while it is being delivered, allowing dynamic assessment of risk during chemotherapy and adaptation of the therapy in real time. Risk assessment in Hodgkin lymphoma is continuously evolving, promising ever greater precision and clinical relevance. This article explores the past usefulness and the emerging potential of risk assessment for this imminently curable malignancy.

This study aimed to compare the efficacy and safety of rituximab (RTX) plus recombinant human thrombopoietin (rhTPO) with RTX alone in patients with immune thrombocytopenia (ITP) who had failed to respond to corticosteroids or relapsed. Recruited patients were randomized at a ratio of 2:1 into 2 groups: the combination group (RTX + rhTPO, n = 77) and the monotherapy group (RTX, n = 38). Overall response was achieved in 79.2% of patients in the combination group vs 71.1% in the monotherapy group (P = .36), and the complete response (CR) rate was 45.4% in the combination group compared with 23.7% in the monotherapy group (P = .026). The combination group had significantly shorter time to response (TTR; median and range, 7 and 4-28 days) compared with the monotherapy group (28 and 4-90 days) (P < .01). There was no difference between these 2 groups in terms of the long-term response (P = .12). Our findings demonstrated that the combination of RTX and rhTPO significantly increased the CR rate and shortened TTR compared with RTX monotherapy in the treatment of corticosteroid-resistant or relapsed ITP but failed to show a beneficial effect on the long-lasting response. This study is registered at www.clinicaltrials.gov as #NCT01525836.

We present a programmable bioengineered 3-dimensional silk-based bone marrow niche tissue system that successfully mimics the physiology of human bone marrow environment allowing us to manufacture functional human platelets ex vivo. Using stem/progenitor cells, megakaryocyte function and platelet generation were recorded in response to variations in extracellular matrix components, surface topography, stiffness, coculture with endothelial cells, and shear forces. Millions of human platelets were produced and showed to be functional based on multiple activation tests. Using adult hematopoietic progenitor cells our system demonstrated the ability to reproduce key steps of thrombopoiesis, including alterations observed in diseased states. A critical feature of the system is the use of natural silk protein biomaterial allowing us to leverage its biocompatibility, nonthrombogenic features, programmable mechanical properties, and surface binding of cytokines, extracellular matrix components, and endothelial-derived proteins. This in turn offers new opportunities for the study of blood component production ex vivo and provides a superior tissue system for the study of pathologic mechanisms of human platelet production.

Postsurgical peritoneal adhesion bands are the most important causes of intestinal obstruction, pelvic pain, and female infertility. In this study, we used a mouse model of adhesion and compared the protective effect of activated protein C (APC) to that of the Food and Drug Administration-approved antiadhesion agent, sodium hyaluronate/carboxymethylcellulose (Seprafilm) by intraperitoneal administration of either APC or Seprafilm to experimental animals. Pathological adhesion bands were graded on day 7, and peritoneal fluid concentrations of tissue plasminogen activator (tPA), d-dimer, thrombin-antithrombin complex, and cytokines (IL-1β, IL-6, interferon-γ, tumor necrosis factor-α, transforming growth factor-β1) were evaluated. Inflammation scores were also measured based on histologic data obtained from peritoneal tissues. Relative to Seprafilm, intraperitoneal administration of human APC led to significantly higher reduction of postsurgical adhesion bands. Moreover, a markedly lower inflammation score was obtained in the adhesive tissues of the APC-treated group, which correlated with significantly reduced peritoneal concentrations of proinflammatory cytokines and an elevated tPA level. Further studies using variants of human APC with or without protease-activated receptor 1 (PAR1) signaling function and mutant mice deficient for either endothelial protein C receptor (EPCR) or PAR1 revealed that the EPCR-dependent signaling activity of APC is primarily responsible for its protective activity in this model. These results suggest APC has therapeutic potential for preventing postsurgical adhesion bands.

The combination of pomalidomide and low-dose dexamethasone (Pom-Dex) can be safely administered to patients with end-stage relapsed/refractory multiple myeloma (RRMM). However, we observed a shorter median progression-free survival (PFS) and overall survival (OS) in these patients when characterized with adverse cytogenetics (deletion 17p and translocation [4;14]) in the Intergroupe Francophone Myélome (IFM) 2009-02 trial. We then sought to determine whether MM with adverse cytogenetics would benefit more from Pom-Dex if exposed earlier in the multicenter IFM 2010-02 trial. The intention-to-treat population included 50 patients, with a median age of 63 years (38% were ≥65 years). Interestingly, there was a striking difference in time to progression (TTP), duration of response, and overall response rate (ORR) according to the presence of del(17p) compared with t(4;14) (TTP, 7.3 vs 2.8 months; duration of response, 8.3 vs 2.4 months; and ORR, 32% vs 15%). OS was prolonged after Pom-Dex, particularly in t(4;14), given the short TTP, suggesting that patients were rescued at relapse with further lines of therapy. Pom-Dex, a doublet immunomodulatory drug-based regimen, is active and well tolerated in adverse cytogenetic patients with early RRMM, particularly in those with del(17p), who are characterized by a high and rapid development of a refractoriness state and known for their poor prognosis. Future studies will determine the underlying mechanisms of Pom-Dex activity in del(17p). This trial is registered at www.clinicaltrials.gov as #NCT01745640.

Chemokine signaling is important for the seeding of different sites by hematopoietic stem cells (HSCs) during development. Serum response factor (SRF) controls multiple genes governing adhesion and migration, mainly by recruiting members of the myocardin-related transcription factor (MRTF) family of G-actin-regulated cofactors. We used vav-iCre to inactivate MRTF-SRF signaling early during hematopoietic development. In both Srf- and Mrtf-deleted animals, hematopoiesis in fetal liver and spleen is intact but does not become established in fetal bone marrow. Srf-null HSC progenitor cells (HSC/Ps) fail to effectively engraft in transplantation experiments, exhibiting normal proximal signaling responses to SDF-1, but reduced adhesiveness, F-actin assembly, and reduced motility. Srf-null HSC/Ps fail to polarize in response to SDF-1 and cannot migrate through restrictive membrane pores to SDF-1 or Scf in vitro. Mrtf-null HSC/Ps were also defective in chemotactic responses to SDF-1. Srf-null HSC/Ps exhibit substantial deficits in cytoskeletal gene expression. MRTF-SRF signaling is thus critical for expression of genes required for the response to chemokine signaling during hematopoietic development.

Hemophagocytic lymphohistiocytosis (HLH) is a rare syndrome of uncontrolled immune activation that has gained increasing attention during the last decade. The diagnosis of HLH is based on a constellation of clinical and laboratory abnormalities, including elevated serum ferritin levels. In the pediatric population, marked hyperferritinemia is specific for HLH. To determine what conditions are associated with profoundly elevated ferritin in the adult population, we performed a retrospective analysis in a large academic health care system. We identified 113 patients with serum ferritin levels higher than 50,000 µg/L. The most frequently observed conditions included renal failure, hepatocellular injury, infections, and hematologic malignancies. Our results suggest that marked hyperferritinemia can be seen in a variety of conditions and is not specific for HLH in adults.

Ibrutinib is a Bruton tyrosine kinase inhibitor approved for the treatment of patients with relapsed refractory chronic lymphocytic leukemia (RR-CLL). We describe the characteristics, causes of discontinuation, and outcomes in patients who discontinued treatment with ibrutinib. One hundred twenty-seven patients were enrolled in various clinical trials of ibrutinib, with or without rituximab, at our center. Thirty-three (26%) patients have discontinued ibrutinib to date. The majority of those patients had high-risk features: 94% with unmutated immunoglobulin heavy chain variable gene rearrangement, 58% with del(17p) by fluorescence in situ hybridization, and 54% with a complex karyotype. Causes of discontinuation were disease transformation (7), progressive CLL (7), stem cell transplantation (3), adverse events (11), serious adverse events/deaths (3), and miscellaneous reasons (2). Twenty five patients (76%) died after discontinuing ibrutinib; the median overall survival was 3.1 months after discontinuation. Most patients with RR-CLL who discontinued ibrutinib early were difficult to treat and had poor outcomes.

We have shown that human B-cell non-Hodgkin lymphomas (B-NHLs) express heat shock protein (HSP)H1/105 in function of their aggressiveness. Here, we now clarify its role as a functional B-NHL target by testing the hypothesis that it promotes the stabilization of key lymphoma oncoproteins. HSPH1 silencing in 4 models of aggressive B-NHLs was paralleled by Bcl-6 and c-Myc downregulation. In vitro and in vivo analysis of HSPH1-silenced Namalwa cells showed that this effect was associated with a significant growth delay and the loss of tumorigenicity when 10(4) cells were injected into mice. Interestingly, we found that HSPH1 physically interacts with c-Myc and Bcl-6 in both Namalwa cells and primary aggressive B-NHLs. Accordingly, expression of HSPH1 and either c-Myc or Bcl-6 positively correlated in these diseases. Our study indicates that HSPH1 concurrently favors the expression of 2 key lymphoma oncoproteins, thus confirming its candidacy as a valuable therapeutic target of aggressive B-NHLs.

The mechanisms underlying tyrosine kinase inhibitor (TKI) resistance in chronic myeloid leukemia (CML) patients lacking explanatory BCR-ABL1 kinase domain mutations are incompletely understood. To identify mechanisms of TKI resistance that are independent of BCR-ABL1 kinase activity, we introduced a lentiviral short hairpin RNA (shRNA) library targeting ∼5000 cell signaling genes into K562(R), a CML cell line with BCR-ABL1 kinase-independent TKI resistance expressing exclusively native BCR-ABL1. A customized algorithm identified genes whose shRNA-mediated knockdown markedly impaired growth of K562(R) cells compared with TKI-sensitive controls. Among the top candidates were 2 components of the nucleocytoplasmic transport complex, RAN and XPO1 (CRM1). shRNA-mediated RAN inhibition or treatment of cells with the XPO1 inhibitor, KPT-330 (Selinexor), increased the imatinib sensitivity of CML cell lines with kinase-independent TKI resistance. Inhibition of either RAN or XPO1 impaired colony formation of CD34(+) cells from newly diagnosed and TKI-resistant CML patients in the presence of imatinib, without effects on CD34(+) cells from normal cord blood or from a patient harboring the BCR-ABL1(T315I) mutant. These data implicate RAN in BCR-ABL1 kinase-independent imatinib resistance and show that shRNA library screens are useful to identify alternative pathways critical to drug resistance in CML.

Macrophage polarization between the M2 (repair, protumorigenic) and M1 (inflammatory) phenotypes is seen as a continuum of states. The detailed transcriptional events and signals downstream of colony-stimulating factor 1 receptor (CSF-1R) that contributes to amplification of the M2 phenotype and suppression of the M1 phenotype are largely unknown. Macrophage CSF-1R pTyr-721 signaling promotes cell motility and enhancement of tumor cell invasion in vitro. Combining analysis of cellular systems for CSF-1R gain of function and loss of function with bioinformatic analysis of the macrophage CSF-1R pTyr-721-regulated transcriptome, we uncovered microRNA-21 (miR-21) as a downstream molecular switch controlling macrophage activation and identified extracellular signal-regulated kinase1/2 and nuclear factor-κB as CSF-1R pTyr-721-regulated signaling nodes. We show that CSF-1R pTyr-721 signaling suppresses the inflammatory phenotype, predominantly by induction of miR-21. Profiling of the miR-21-regulated messenger RNAs revealed that 80% of the CSF-1-regulated canonical miR-21 targets are proinflammatory molecules. Additionally, miR-21 positively regulates M2 marker expression. Moreover, miR-21 feeds back to positively regulate its own expression and to limit CSF-1R-mediated activation of extracellular signal-regulated kinase1/2 and nuclear factor-κB. Consistent with an anti-inflammatory role of miRNA-21, intraperitoneal injection of mice with a miRNA-21 inhibitor increases the recruitment of inflammatory monocytes and enhances the peritoneal monocyte/macrophage response to lipopolysaccharide. These results identify the CSF-1R-regulated miR-21 network that modulates macrophage polarization.

Several non-Hodgkin lymphoma (NHL) subtypes, including diffuse large B-cell lymphoma (DLBCL), variably express CD30. This phase 2, open-label study evaluated the efficacy of brentuximab vedotin, an anti-CD30 antibody-drug conjugate, in relapsed/refractory CD30(+) NHL. This planned subset analysis of B-cell NHLs includes 49 patients with DLBCL and 19 with other B-cell NHLs. Objective response rate was 44% for DLBCL, including 8 (17%) complete remissions (CRs) with a median duration of 16.6 months thus far (range, 2.7 to 22.7+ months). There was no statistical correlation between response and level of CD30 expression; however, all responding patients had quantifiable CD30 by computer-assisted assessment of immunohistochemistry. DLBCL patients were generally refractory to first-line (76%) and most recent therapies (82%), and 44% of these refractory patients responded (15% CRs). Patients with other B-cell lymphomas also responded: 1 CR, 2 partial responses (PRs) of 6 with gray zone, 1 CR of 6 with primary mediastinal B-cell, and 1 CR of 3 with posttransplant lymphoproliferative disorder. Adverse events were consistent with known toxicities. The combination of brentuximab vedotin with rituximab was generally well tolerated and had activity similar to brentuximab vedotin alone. Overall, significant activity with brentuximab vedotin was observed in relapsed/refractory DLBCL, and responses occurred across a range of CD30 expression. This study was registered at www.clinicaltrials.gov as #NCT01421667.

Specific serum antibodies mediating humoral immunity and autoimmunity are provided by mature plasma cells (PC) residing in the bone marrow (BM), yet their dynamics and composition are largely unclear. We here characterize distinct subsets of human PC differing by CD19 expression. Unlike CD19(+) PC, CD19(-) PC were restricted to BM, expressed predominantly IgG, and they carried a prosurvival, distinctly mature phenotype, that is, HLA-DR(low)Ki-67(-)CD95(low)CD28(+)CD56(+/-), with increased BCL2 and they resisted their mobilization from the BM after systemic vaccination. Fewer mutations within immunoglobulin VH rearrangements of CD19(-) BMPC may indicate their differentiation in early life. Their resistance to in vivo B-cell depletion, that is, their independency from supply with new plasmablasts, is consistent with long-term stability of this PC subset in the BM. Moreover, CD19(-) PC were detectable in chronically inflamed tissues and secreted autoantibodies. We propose a multilayer model of PC memory in which CD19(+) and CD19(-) PC represent dynamic and static components, respectively, permitting both adaptation and stability of humoral immune protection.