Systemic bacterial infection induces a hematopoietic response program termed "emergency granulopoiesis" that is characterized by increased de novo bone marrow (BM) neutrophil production. How loss of local immune control and bacterial dissemination is sensed and subsequently translated into the switch from steady-state to emergency granulopoiesis is, however, unknown. Using tissue-specific myeloid differentiation primary response gene 88 (Myd88)-deficient mice and in vivo lipopolysaccharide (LPS) administration to model severe bacterial infection, we here show that endothelial cells (ECs) but not hematopoietic cells, hepatocytes, pericytes, or BM stromal cells, are essential cells for this process. Indeed, ECs from multiple tissues including BM express high levels of Tlr4 and Myd88 and are the primary source of granulocyte colony-stimulating factor (G-CSF), the key granulopoietic cytokine, after LPS challenge or infection with Escherichia coli. EC-intrinsic MYD88 signaling and subsequent G-CSF production by ECs is required for myeloid progenitor lineage skewing toward granulocyte-macrophage progenitors, increased colony-forming unit granulocyte activity in BM, and accelerated BM neutrophil generation after LPS stimulation. Thus, ECs catalyze the detection of systemic infection into demand-adapted granulopoiesis.
Waldenström macroglobulinemia (WM) is a distinct B-cell lymphoproliferative disorder for which clearly defined criteria for the diagnosis, initiation of therapy, and treatment strategy have been proposed as part of the consensus panels of International Workshops on WM (IWWM). As part of the IWWM-7 and based on recently published and ongoing clinical trials, the panels updated treatment recommendations. Therapeutic strategy in WM should be based on individual patient and disease characteristics (age, comorbidities, need for rapid disease control, candidacy for autologous transplantation, cytopenias, IgM-related complications, hyperviscosity, and neuropathy). Mature data show that rituximab combinations with cyclophosphamide/dexamethasone, bendamustine, or bortezomib/dexamethasone provided durable responses and are indicated for most patients. New monoclonal antibodies (ofatumumab), second-generation proteasome inhibitors (carfilzomib), mammalian target of rapamycin inhibitors, and Bruton's tyrosine kinase inhibitors are promising and may expand future treatment options. A different regimen is typically recommended for relapsed or refractory disease. In selected patients with relapsed disease after long-lasting remission, reuse of a prior effective regimen may be appropriate. Autologous stem cell transplantation may be considered in young patients with chemosensitive disease and in newly diagnosed patients with very-high-risk features. Active enrollment of patients with WM in clinical trials is encouraged.
When blood vessels are cut, the forces in the bloodstream increase and change character. The dark side of these forces causes hemorrhage and death. However, von Willebrand factor (VWF), with help from our circulatory system and platelets, harnesses the same forces to form a hemostatic plug. Force and VWF function are so closely intertwined that, like members of the Jedi Order in the movie Star Wars who learn to use "the Force" to do good, VWF may be considered the Jedi knight of the bloodstream. The long length of VWF enables responsiveness to flow. The shape of VWF is predicted to alter from irregularly coiled to extended thread-like in the transition from shear to elongational flow at sites of hemostasis and thrombosis. Elongational force propagated through the length of VWF in its thread-like shape exposes its monomers for multimeric binding to platelets and subendothelium and likely also increases affinity of the A1 domain for platelets. Specialized domains concatenate and compact VWF during biosynthesis. A2 domain unfolding by hydrodynamic force enables postsecretion regulation of VWF length. Mutations in VWF in von Willebrand disease contribute to and are illuminated by VWF biology. I attempt to integrate classic studies on the physiology of hemostatic plug formation into modern molecular understanding, and point out what remains to be learned.
Treatment outcomes for older patients with acute myeloid leukemia (AML) have remained dismal. This randomized, phase 2 trial in AML patients not considered suitable for intensive induction therapy compared low-dose cytarabine (LDAC) with or without volasertib, a highly potent and selective inhibitor of polo-like kinases. Eighty-seven patients (median age 75 years) received LDAC 20 mg twice daily subcutaneously days 1-10 or LDAC + volasertib 350 mg IV days 1 + 15 every 4 weeks. Response rate (complete remission and complete remission with incomplete blood count recovery) was higher for LDAC + volasertib vs LDAC (31.0% vs 13.3%; odds ratio, 2.91; P = .052). Responses in the LDAC + volasertib arm were observed across all genetic groups, including 5 of 14 patients with adverse cytogenetics. Median event-free survival was significantly prolonged by LDAC + volasertib compared with LDAC (5.6 vs 2.3 months; hazard ratio, 0.57; 95% confidence interval, 0.35-0.92; P = .021); median overall survival was 8.0 vs 5.2 months, respectively (hazard ratio, 0.63; 95% confidence interval, 0.40-1.00; P = .047). LDAC + volasertib led to an increased frequency of adverse events that was most pronounced for neutropenic fever/infections and gastrointestinal events; there was no increase in the death rate at days 60 + 90. This study was registered at www.clinicaltrials.gov as #NCT00804856.
Recent genomic studies have provided a refined genetic map of acute lymphoblastic leukemia (ALL) and increased the number of potential prognostic markers. Therefore, we integrated copy-number alteration data from the 8 most commonly deleted genes, subordinately, with established chromosomal abnormalities to derive a 2-tier genetic classification. The classification was developed using 809 ALL97/99 patients and validated using 742 United Kingdom (UK)ALL2003 patients. Good-risk (GR) genetic features included ETV6-RUNX1, high hyperdiploidy, normal copy-number status for all 8 genes, isolated deletions affecting ETV6/PAX5/BTG1, and ETV6 deletions with a single additional deletion of BTG1/PAX5/CDKN2A/B. All other genetic features were classified as poor risk (PR). Three-quarters of UKALL2003 patients had a GR genetic profile and a significantly improved event-free survival (EFS) (94%) compared with patients with a PR genetic profile (79%). This difference was driven by a lower relapse rate (4% vs 17%), was seen across all patient subgroups, and was independent of other risk factors. Even genetic GR patients with minimal residual disease (>0.01%) at day 29 had an EFS in excess of 90%. In conclusion, the integration of genomic and cytogenetic data defines 2 subgroups with distinct responses to treatment and identifies a large subset of children suitable for treatment deintensification.
Acute myeloid leukemia (AML) with t(8;21) (q22;q22) is considered to have favorable risk; however, nearly half of t(8;21) patients are not cured, and recent studies have highlighted remarkable genetic heterogeneity in this subset of AML. Here we identify somatic mutations in additional sex combs-like 2 (ASXL2) in 22.7% (25/110) of patients with t(8;21), but not in patients with inv(16)/t(16;16) (0/60) or RUNX1-mutated AML (0/26). ASXL2 mutations were similarly frequent in adults and children t(8;21) and were mutually exclusive with ASXL1 mutations. Although overall survival was similar between ASXL1 and ASXL2 mutant t(8;21) AML patients and their wild-type counterparts, patients with ASXL1 or ASXL2 mutations had a cumulative incidence of relapse of 54.6% and 36.0%, respectively, compared with 25% in ASXL1/2 wild-type counterparts (P = .226). These results identify a high-frequency mutation in t(8;21) AML and identify the need for future studies to investigate the clinical and biological relevance of ASXL2 mutations in this unique subset of AML.
Although the accumulation of highly-differentiated and granzyme B (GrB)-expressing CD8+CD28– T cells has been associated with aging, the mechanism for their enrichment and contribution to immune function remains poorly understood. Here we report a novel B-cell subset expressing 4-1BBL, which increases with age in humans, rhesus macaques, and mice, and with immune reconstitution after chemotherapy and autologous progenitor cell transplantation. These cells (termed 4BL cells) induce GrB+CD8+ T cells by presenting endogenous antigens and using the 4-1BBL/4-1BB axis. We found that the 4BL cells increase antitumor responses in old mice, which may explain in part the paradox of retarded tumor growth in the elderly. 4BL cell accumulation and its capacity to evoke the generation of GrB+CD8+ T cells can be eliminated by inducing reconstitution of B cells in old mice, suggesting that the age-associated skewed cellular immune responses are reversible. We propose that 4BL cells and the 4-1BBL signaling pathway are useful targets for improved effectiveness of natural antitumor defenses and therapeutic immune manipulations in the elderly.
The comprehensive genetic alterations underlying the pathogenesis of T-cell prolymphocytic leukemia (T-PLL) are unknown. To address this, we performed whole-genome sequencing (WGS), whole-exome sequencing (WES), high-resolution copy-number analysis, and Sanger resequencing of a large cohort of T-PLL. WGS and WES identified novel mutations in recurrently altered genes not previously implicated in T-PLL including EZH2, FBXW10, and CHEK2. Strikingly, WGS and/or WES showed largely mutually exclusive mutations affecting IL2RG, JAK1, JAK3, or STAT5B in 38 of 50 T-PLL genomes (76.0%). Notably, gain-of-function IL2RG mutations are novel and have not been reported in any form of cancer. Further, high-frequency mutations in STAT5B have not been previously reported in T-PLL. Functionally, IL2RG-JAK1-JAK3-STAT5B mutations led to signal transducer and activator of transcription 5 (STAT5) hyperactivation, transformed Ba/F3 cells resulting in cytokine-independent growth, and/or enhanced colony formation in Jurkat T cells. Importantly, primary T-PLL cells exhibited constitutive activation of STAT5, and targeted pharmacologic inhibition of STAT5 with pimozide induced apoptosis in primary T-PLL cells. These results for the first time provide a portrait of the mutational landscape of T-PLL and implicate deregulation of DNA repair and epigenetic modulators as well as high-frequency mutational activation of the IL2RG-JAK1-JAK3-STAT5B axis in the pathogenesis of T-PLL. These findings offer opportunities for novel targeted therapies in this aggressive leukemia.
Anaplastic lymphoma kinase (ALK)-negative anaplastic large cell lymphoma (ALCL) is a CD30-positive T-cell non-Hodgkin lymphoma that morphologically resembles ALK-positive ALCL but lacks chromosomal rearrangements of the ALK gene. The genetic and clinical heterogeneity of ALK-negative ALCL has not been delineated. We performed immunohistochemistry and fluorescence in situ hybridization on 73 ALK-negative ALCLs and 32 ALK-positive ALCLs and evaluated the associations among pathology, genetics, and clinical outcome. Chromosomal rearrangements of DUSP22 and TP63 were identified in 30% and 8% of ALK-negative ALCLs, respectively. These rearrangements were mutually exclusive and were absent in ALK-positive ALCLs. Five-year overall survival rates were 85% for ALK-positive ALCLs, 90% for DUSP22-rearranged ALCLs, 17% for TP63-rearranged ALCLs, and 42% for cases lacking all 3 genetic markers (P < .0001). Hazard ratios for death in these 4 groups after adjusting for International Prognostic Index and age were 1.0 (reference group), 0.58, 8.63, and 4.16, respectively (P = 7.10 x 10–5). These results were similar when restricted to patients receiving anthracycline-based chemotherapy, as well as to patients not receiving stem cell transplantation. Thus, ALK-negative ALCL is a genetically heterogeneous disease with widely disparate outcomes following standard therapy. DUSP22 and TP63 rearrangements may serve as predictive biomarkers to help guide patient management.
Targeting B-cell receptor (BCR) signaling in chronic lymphocytic leukemia (CLL) has been successful with durable remissions observed with several targeted therapeutics. Protein kinase C-β (PKC-β) is immediately downstream of BCR and has been shown to be essential to CLL cell survival and proliferation in vivo. We therefore evaluated sotrastaurin (AEB071), an orally administered potent PKC inhibitor, on CLL cell survival both in vitro and in vivo. AEB071 shows selective cytotoxicity against B-CLL cells in a dose-dependent manner. Additionally, AEB071 attenuates BCR-mediated survival pathways, inhibits CpG-induced survival and proliferation of CLL cells in vitro, and effectively blocks microenvironment-mediated survival signaling pathways in primary CLL cells. Furthermore, AEB071 alters β-catenin expression, resulting in decreased downstream transcriptional genes as c-Myc, Cyclin D1, and CD44. Lastly, our preliminary in vivo studies indicate beneficial antitumor properties of AEB071 in CLL. Taken together, our results indicate that targeting PKC-β has the potential to disrupt signaling from the microenvironment contributing to CLL cell survival and potentially drug resistance. Future efforts targeting PKC with the PKC inhibitor AEB071 as monotherapy in clinical trials of relapsed and refractory CLL patients are warranted.
Chronic myeloid leukemia (CML) stem cell survival is not dependent on BCR-ABL protein kinase and treatment with ABL tyrosine kinase inhibitors cures only a minority of CML patients, thus highlighting the need for novel therapeutic targets. The Janus kinase (JAK)2/signal transducer and activator of transcription (STAT)5 pathway has recently been explored for providing putative survival signals to CML stem/progenitor cells (SPCs) with contradictory results. We investigated the role of this pathway using the JAK2 inhibitor, ruxolitinib (RUX). We demonstrated that the combination of RUX, at clinically achievable concentrations, with the specific and potent tyrosine kinase inhibitor nilotinib, reduced the activity of the JAK2/STAT5 pathway in vitro relative to either single agent alone. These effects correlated with increased apoptosis of CML SPCs in vitro and a reduction in primitive quiescent CML stem cells, including NOD.Cg-PrkdcscidIL2rgtm1Wjl /SzJ mice repopulating cells, induced by combination treatment. A degree of toxicity toward normal SPCs was observed with the combination treatment, although this related to mature B-cell engraftment in NOD.Cg-PrkdcscidIL2rgtm1Wjl /SzJ mice with minimal effects on primitive CD34+ cells. These results support the JAK2/STAT5 pathway as a relevant therapeutic target in CML SPCs and endorse the current use of nilotinib in combination with RUX in clinical trials to eradicate persistent disease in CML patients.
The oncomir microRNA-125b (miR-125b) is upregulated in a variety of human neoplastic blood disorders and constitutive upregulation of miR-125b in mice can promote myeloid and B-cell leukemia. We found that miR-125b promotes myeloid and B-cell neoplasm by inducing tumorigenesis in hematopoietic progenitor cells. Our study demonstrates that miR-125b induces myeloid leukemia by enhancing myeloid progenitor output from stem cells as well as inducing immortality, self-renewal, and tumorigenesis in myeloid progenitors. Through functional and genetic analyses, we demonstrated that miR-125b induces myeloid and B-cell leukemia by inhibiting interferon regulatory factor 4 (IRF4) but through distinct mechanisms; it induces myeloid leukemia through repressing IRF4 at the messenger RNA (mRNA) level without altering the genomic DNA and induces B-cell leukemia via genetic deletion of the gene encoding IRF4.
Our knowledge of the genetic basis of myelodysplastic syndromes (MDS) and myelodysplastic/myeloproliferative neoplasms (MDS/MPN) has considerably improved. To define genotype/phenotype relationships of clinical relevance, we studied 308 patients with MDS, MDS/MPN, or acute myeloid leukemia evolving from MDS. Unsupervised statistical analysis, including the World Health Organization classification criteria and somatic mutations, showed that MDS associated with SF3B1-mutation (51 of 245 patients, 20.8%) is a distinct nosologic entity irrespective of current morphologic classification criteria. Conversely, MDS with ring sideroblasts with nonmutated SF3B1 segregated in different clusters with other MDS subtypes. Mutations of genes involved in DNA methylation, splicing factors other than SF3B1, and genes of the RAS pathway and cohesin complex were independently associated with multilineage dysplasia and identified a distinct subset (51 of 245 patients, 20.8%). No recurrent mutation pattern correlated with unilineage dysplasia without ring sideroblasts. Irrespective of driver somatic mutations, a threshold of 5% bone marrow blasts retained a significant discriminant value for identifying cases with clonal evolution. Comutation of TET2 and SRSF2 was highly predictive of a myeloid neoplasm characterized by myelodysplasia and monocytosis, including but not limited to, chronic myelomonocytic leukemia. These results serve as a proof of concept that a molecular classification of myeloid neoplasms is feasible.
Loss-of-function mutation in the heme oxygenase 1 (Hmox1) gene causes a rare and lethal disease in children, characterized by severe anemia and intravascular hemolysis, with damage to endothelia and kidneys. Previously, we found that macrophages engaged in recycling of red cells were depleted from the tissues of Hmox1–/– mice, which resulted in intravascular hemolysis and severe damage to the endothelial system, kidneys, and other organs. Here, we report that subablative bone marrow transplantation (BMT) has a curative effect for disease in Hmox1–/– animals as a result of restoration of heme recycling by repopulation of the tissues with wild-type macrophages. Although engraftment was transient, BMT reversed anemia, normalized blood chemistries and iron metabolism parameters, and prevented renal damage. The largest proportion of donor-derived cells was observed in the livers of transplanted animals. These cells, identified as Kupffer cells with high levels of Hmox1 expression, persisted months after transient engraftment of the donor bone marrow and were responsible for the full restoration of heme-recycling ability in Hmox1–/– mice and reversing Hmox1-deficient phenotype. Our findings suggest that BMT or the development of specific cell therapies to repopulate patients’ tissues with wild-type or reengineered macrophages represent promising approaches for HMOX1 deficiency treatment in humans.
Activated protein C (APC) resistance, often associated with the factor V (FV) Leiden mutation, is the most common risk factor for venous thrombosis. We observed increased APC resistance in carriers of fibrinogen gene (FGG) haplotype 2, which is associated with reduced levels of the alternatively spliced fibrinogen ' chain. This finding prompted us to study the effects of fibrinogen and its ' chain on APC resistance. Fibrinogen, and particularly the A/' isoform, improved the response of plasma to added APC in the thrombin generation-based assay. Similarly, a synthetic peptide mimicking the C-terminus of the fibrinogen ' chain, which binds thrombin and inhibits its activities, greatly increased the APC sensitivity of normal and FV Leiden plasma, likely due to its ability to inhibit thrombin-mediated activation of FV and FVIII. Although the fibrinogen ' peptide also inhibited protein C activation by the thrombin/thrombomodulin complex, it still increased the sensitivity of plasma to endogenously formed APC when thrombin generation was measured in the presence of soluble thrombomodulin. We conclude that fibrinogen, and particularly fibrinogen ', increases plasma APC sensitivity. The fibrinogen ' peptide might form the basis for pharmacologic interventions to counteract APC resistance.