Hematology
Abstract
Adeno-associated-viral (AAV) vector liver-directed gene therapy (GT) for hemophilia B (HB) is limited by a vector-dose-dependent hepatotoxicity. Recently, this obstacle has been partially circumvented by the use of a hyperactive factor IX (FIX) variant, R338L (Padua), which has an eightfold increased specific activity compared to FIX-WT. FIX-R338L has emerged as the standard for HB GT. However, the underlying mechanism of its hyperactivity is undefined; as such, safety concerns of unregulated coagulation and the potential for thrombotic complications have not been fully addressed. To this end, we evaluated the enzymatic and clotting activity as well as the activation, inactivation, and cofactor-dependence of FIX-R338L relative to FIX-WT. We observed that the high-specific-activity of FIX-R338L requires factor VIIIa (FVIIIa) cofactor. In a novel system utilizing emicizumab, a FVIII-mimicking bispecific antibody, the hyperactivity of both recombinant FIX-R338L and AAV-mediated-transgene-expressed FIX-R338L from HB GT subjects is ablated without FVIIIa activity. We conclude that the molecular regulation of activation, inactivation, and cofactor-dependence of FIX-R338L is similar to FIX-WT, but that the FVIIIa-dependent hyperactivity of FIX-R338L is the result of a faster rate of factor X activation. This mechanism helps mitigate safety concerns of unregulated coagulation and supports the expanded use of FIX-R338L in HB therapy.
Authors
Benjamin J. Samelson-Jones, Jonathan D. Finn, Lindsey A. George, Rodney M. Camire, Valder R. Arruda
Abstract
Inhibition of Bruton tyrosine kinase (BTK) is a breakthrough therapy for certain B cell lymphomas and B cell chronic lymphatic leukemia. Covalent BTK inhibitors (e.g., ibrutinib) bind to cysteine C481, and mutations of this residue confer clinical resistance. This has led to the development of noncovalent BTK inhibitors that do not require binding to cysteine C481. These new compounds are now entering clinical trials. In a systematic BTK mutagenesis screen, we identify residues that are critical for the activity of noncovalent inhibitors. These include a gatekeeper residue (T474) and mutations in the kinase domain. Strikingly, co-occurrence of gatekeeper and kinase domain lesions (L512M, E513G, F517L, L547P) in cis results in a 10- to 15-fold gain of BTK kinase activity and de novo transforming potential in vitro and in vivo. Computational BTK structure analyses reveal how these lesions disrupt an intramolecular mechanism that attenuates BTK activation. Our findings anticipate clinical resistance mechanisms to a new class of noncovalent BTK inhibitors and reveal intramolecular mechanisms that constrain BTK’s transforming potential.
Authors
Shenqiu Wang, Sayan Mondal, Chunying Zhao, Marjan Berishaj, Phani Ghanakota, Connie Lee Batlevi, Ahmet Dogan, Venkatraman E. Seshan, Robert Abel, Michael R. Green, Anas Younes, Hans-Guido Wendel
Abstract
Many cytokines and chemokines that are important for hematopoiesis activate the PI3K signaling pathway. Because this pathway is frequently mutated and activated in cancer, PI3K inhibitors have been developed for the treatment of several malignancies, and are now being tested in the clinic in combination with chemotherapy. However, the role of PI3K in adult hematopoietic stem cells (HSCs), particularly during hematopoietic stress, is still unclear. We previously showed that the individual PI3K catalytic isoforms P110α or P110β have dispensable roles in HSC function, suggesting redundancy between PI3K isoforms in HSCs. We now demonstrate that simultaneous deletion of P110α and P110δ in double knockout (DKO) HSCs uncovers their redundant requirement in HSC cycling after 5-fluorouracil (5-FU) chemotherapy administration. In contrast, DKO HSCs are still able to exit quiescence in response to other stress stimuli, such as LPS. We found that DKO HSCs and progenitors have impaired sensing of inflammatory signals ex vivo, and that levels of IL1-β and MIG are higher in the bone marrow after LPS than after 5-FU administration. Furthermore, exogenous in vivo administration of IL1-β can induce cell cycle entry of DKO HSCs. Our findings have important clinical implications for the use of PI3K inhibitors in combination with chemotherapy.
Authors
Shayda Hemmati, Taneisha Sinclair, Meng Tong, Boris Bartholdy, Rachel O. Okabe, Kristina Ames, Leanne Ostrodka, Tamanna Haque, Imit Kaur, Taylor S. Mills, Anupriya Agarwal, Eric M. Pietras, Jean J. Zhao, Thomas M. Roberts, Kira Gritsman
Abstract
Monosomy 7 or deletion of 7q (del(7q)) are common clonal cytogenetic abnormalities associated with high grade myelodysplastic syndrome (MDS) arising in inherited and acquired bone marrow failure. Current non-transplant approaches to treat marrow failure may be complicated by stimulation of clonal outgrowth. To study the biological consequences of del(7q) within the context of a failing marrow, we generated induced pluripotent stem cells (iPSCs) derived from patients with Shwachman Diamond Syndrome (SDS), a bone marrow failure disorder with MDS predisposition, and genomically engineered a 7q deletion. The TGFβ pathway was the top differentially regulated pathway in transcriptomic analysis of SDS versus SDSdel(7q) iPSCs. SMAD2 phosphorylation was increased in SDS relative to wild type cells consistent with hyperactivation of the TGFbeta pathway in SDS. Phospho-SMAD2 levels were reduced following 7q deletion in SDS cells and increased upon restoration of 7q diploidy. Inhibition of the TGFbeta pathway rescued hematopoiesis in SDS-iPSCs and in bone marrow hematopoietic cells from SDS patients while it had no impact on the SDSdel(7q) cells. These results identified a potential targetable vulnerability to improve hematopoiesis in an MDS-predisposition syndrome, and highlight the importance of the germline context of somatic alterations to inform precision medicine approaches to therapy.
Authors
Melisa Ruiz-Gutierrez, Özge Vargel Bölükbaşi, Gabriela Alexe, Andriana G. Kotini, Kaitlyn Ballotti, Cailin E. Joyce, David W. Russell, Kimberly Stegmaier, Kasiani Myers, Carl D. Novina, Eirini P. Papapetrou, Akiko Shimamura
Abstract
The bone marrow microenvironment (BMME) contributes to the regulation of hematopoietic stem cell (HSC) function, though its role in age-associated lineage skewing is poorly understood. Here we show that dysfunction of aged marrow macrophages (Mφs) directs HSC platelet-bias. Mφs from the marrow of aged mice and humans exhibited an activated phenotype, with increased expression of inflammatory signals. Aged marrow Mφs also displayed decreased phagocytic function. Senescent neutrophils, typically cleared by marrow Mφs, were markedly increased in aged mice, consistent with functional defects in Mφ phagocytosis and efferocytosis. In aged mice, Interleukin 1B (IL1B) was elevated in the bone marrow and caspase 1 activity, which can process pro-IL1B, was increased in marrow Mφs and neutrophils. Mechanistically, IL1B signaling was necessary and sufficient to induce a platelet bias in HSCs. In young mice, depletion of phagocytic cell populations or loss of the efferocytic receptor Axl expanded platelet-biased HSCs. Our data support a model wherein increased inflammatory signals and decreased phagocytic function of aged marrow Mφs induce the acquisition of platelet bias in aged HSCs. This work highlights the instructive role of Mφs and IL1B in the age-associated lineage-skewing of HSCs, and reveals the therapeutic potential of their manipulation as antigeronic targets.
Authors
Benjamin J. Frisch, Corey M. Hoffman, Sarah E. Latchney, Mark W. LaMere, Jason Myers, John Ashton, Allison J. Li, Jerry Saunders, James Palis, Archibald S. Perkins, Amanda McCabe, Julianne N. Smith, Kathleen E. McGrath, Fatima Rivera-Escalera, Andrew McDavid, Jane L. Liesveld, Vyacheslav A. Korshunov, Michael R. Elliott, Katherine C. MacNamara, Michael W. Becker, Laura M. Calvi
Abstract
Hypoxic tumor niches are chief causes of treatment resistance and tumor recurrence. Sickle erythrocytes’ (SSRBCs’) intrinsic oxygen-sensing functionality empowers them to access such hypoxic niches wherein they form microaggregates that induce focal vessel closure. In search of measures to augment the scale of SSRBC-mediated tumor vaso-occlusion, we turned to the vascular disrupting agent, combretastatin A-4 (CA-4). CA-4 induces selective tumor endothelial injury, blood stasis, and hypoxia but fails to eliminate peripheral tumor foci. In this article, we show that introducing deoxygenated SSRBCs into tumor microvessels treated with CA-4 and sublethal radiation (SR) produces a massive surge of tumor vaso-occlusion and broadly propagated tumor infarctions that engulfs treatment-resistant hypoxic niches and eradicates established lung tumors. Tumor regression was histologically corroborated by significant treatment effect. Treated tumors displayed disseminated microvessels occluded by tightly packed SSRBCs along with widely distributed pimidazole-positive hypoxic tumor cells. Humanized HbS-knockin mice (SSKI) but not HbA-knockin mice (AAKI) showed a similar treatment response underscoring SSRBCs as the paramount tumoricidal effectors. Thus, CA-4-SR–remodeled tumor vessels license SSRBCs to produce an unprecedented surge of tumor vaso-occlusion and infarction that envelops treatment-resistant tumor niches resulting in complete tumor regression. Strategically deployed, these innovative tools constitute a major conceptual advance with compelling translational potential.
Authors
Chiao-Wang Sun, Li-Chen Wu, Mamta Wankhede, Dezhi Wang, Jutta Thoerner, Lawrence Woody, Brian S. Sorg, Tim M. Townes, David S. Terman
Abstract
Multiple myeloma (MM) is an incurable plasma cell malignancy with frequent treatment failures and relapses, suggesting the existence of pathogenic myeloma stem/progenitor populations. However, the identity of MM stem cells remains elusive. We used a murine model of MM with transgenic overexpression of the unfolded protein response sensor X-box binding protein 1 (XBP1s) in the B cell compartment to define MM stem cells. We herein report that a post–germinal center, pre–plasma cell population significantly expands as MM develops. This population has the following characteristics: (a) cell surface phenotype of B220+CD19+IgM–IgD–CD138–CD80+sIgG–AA4.1+FSChi; (b) high expression levels of Pax5 and Bcl6 with intermediate levels of Blimp1 and XBP1s; (c) increased expression of aldehyde dehydrogenase, Notch1, and c-Kit; and (d) ability to efficiently reconstitute antibody-producing capacity in B cell–deficient mice in vivo. We thus have defined a plasma cell progenitor population that resembles myeloma stem cells in mice. These results provide potentially novel insights into MM stem cell biology and may contribute to the development of novel stem cell–targeted therapies for the eradication of MM.
Authors
Joshua Kellner, Caroline Wallace, Bei Liu, Zihai Li
Abstract
Background: Protein disulfide isomerase (PDI) is a thiol isomerase secreted by vascular cells that is required for thrombus formation. Quercetin flavonoids inhibit PDI activity and block platelet accumulation and fibrin generation at the site of a vascular injury in mouse models but the clinical effect of targeting extracellular PDI in humans has not been studied. Methods: We conducted a multi-center phase 2 trial of sequential dosing cohorts to evaluate the efficacy of targeting PDI with isoquercetin to reduce hypercoagulability in cancer patients at high risk for thrombosis. Patients received isoquercetin at 500 mg (cohort A, N=28) or 1000 mg (cohort B, N=29) daily for 56 days with laboratory assays performed at baseline and end-of-study, along with bilateral lower extremity compression ultrasound. The primary efficacy endpoint was a reduction in D-dimer and the primary clinical endpoint included pulmonary embolism or proximal deep vein thrombosis. Results: The administration of isoquercetin 1000 mg decreased D-dimer plasma concentrations by a median of -21.9% (P=0.0002). There were no primary VTE events or major hemorrhages observed in either cohort. Isoquercetin increased PDI inhibitory activity in plasma (37.0% in cohort A, N=25, P<0.001; 73.3% in cohort B, N=22, P<0.001, respectively). Corroborating the antithrombotic efficacy, we also observed a significant decrease in platelet-dependent thrombin generation (cohort A median decrease -31.1%, P=0.007; cohort B median decrease -57.2%, P=0.004) and circulating soluble P-selectin at the 1000 mg isoquercetin dose (median decrease -57.9%, P<0.0001). Conclusions: Isoquercetin represents first-in-class inhibitor of PDI demonstrating efficacy in improving markers of coagulation in advanced cancer patients. Trial Registration: Clinicaltrials.gov NCT02195232
Authors
Jeffrey I. Zwicker, Benjamin L. Schlechter, Jack D. Stopa, Howard Liebman, Anita Aggarwal, Maneka Puligandla, Thomas Caughey, Kenneth A. Bauer, Nancy Kuemmerle, Ellice Wong, Ted Wun, Marilyn McLaughlin, Manuel Hidalgo, Donna Neuberg, Bruce Furie, Robert Flaumenhaft
Abstract
New techniques for single-cell analysis have led to insights into hematopoiesis and the immune system, but the ability of these techniques to cross-validate and reproducibly identify the biological variation in diverse human samples is currently unproven. We therefore performed a comprehensive assessment of human bone marrow cells using both single-cell RNA sequencing and multiparameter flow cytometry from 20 healthy adult human donors across a broad age range. These data characterize variation between healthy donors as well as age-associated changes in cell population frequencies. Direct comparison of techniques revealed discrepancy in the quantification of T lymphocyte and natural killer cell populations. Orthogonal validation of immunophenotyping using mass cytometry demonstrated a strong correlation with flow cytometry. Technical replicates using single-cell RNA sequencing matched robustly, while biological replicates showed variation. Given the increasing use of single-cell technologies in translational research, this resource serves as an important reference data set and highlights opportunities for further refinement.
Authors
Karolyn A. Oetjen, Katherine E. Lindblad, Meghali Goswami, Gege Gui, Pradeep K. Dagur, Catherine Lai, Laura W. Dillon, J. Philip McCoy, Christopher S. Hourigan
Abstract
BACKGROUND. Hypophosphatemia can complicate intravenous iron therapy, but no head-to-head trials compared the effects of newer intravenous iron formulations on risks and mediators of hypophosphatemia. METHODS. In a randomized, double-blinded, controlled trial of adults with iron deficiency anemia from February 2016 to January 2017, we compared rates of hypophosphatemia in response to a single FDA-approved course of ferric carboxymaltose (n = 1,000) or ferumoxytol (n = 997). To investigate pathophysiological mediators of intravenous iron-induced hypophosphatemia, we nested within the parent trial a physiological substudy (ferric carboxymaltose, n = 98; ferumoxytol, n = 87) in which we measured fibroblast growth factor 23 (FGF23), calcitriol, and parathyroid hormone (PTH) at baseline and 1, 2, and 5 weeks later. RESULTS. The incidence of hypophosphatemia was significantly higher in the ferric carboxymaltose versus the ferumoxytol group (<2.0 mg/dl, 50.8% vs. 0.9%; <1.3 mg/dl, 10.0% vs. 0.0%; P < 0.001), and hypophosphatemia persisted through the end of the 5-week study period in 29.1% of ferric carboxymaltose–treated patients versus none of the ferumoxytol-treated patients (P < 0.001). Ferric carboxymaltose, but not ferumoxytol, increased circulating concentrations of biologically active FGF23 (mean within-patient percentage change from baseline to week 2 peak: +302.8 ± 326.2% vs. +10.1 ± 61.0%; P < 0.001), which was significantly associated with contemporaneous hypophosphatemia, renal phosphate wasting, and decreased serum calcitriol and calcium, and increased PTH concentrations. CONCLUSIONS. Ferric carboxymaltose rapidly increases biologically active FGF23 in patients with iron deficiency anemia. Paralleling hereditary and other acquired syndromes of hypophosphatemic rickets/osteomalacia, ferric carboxymaltose–induced FGF23 elevation triggers a pathophysiological cascade of renal phosphate wasting, calcitriol deficiency, and secondary hyperparathyroidism that frequently culminates in hypophosphatemia. TRIAL REGISTRATION. ClinicalTrials.gov, NCT02694978 FUNDING. AMAG Pharmaceuticals, Inc. Role of the funding source: This study was supported by AMAG Pharmaceuticals, Inc. The academic investigators designed the clinical trial, performed the analyses, and authored the manuscript with input from the coauthors from AMAG Pharmaceuticals, Inc.
Authors
Myles Wolf, Glenn M. Chertow, Iain C. Macdougall, Robert Kaper, Julie Krop, William Strauss
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