Hematology
Abstract
The complex process of platelet formation originates with the hematopoietic stem cell, which differentiates through the myeloid lineage, matures, and releases proplatelets into the BM sinusoids. How formed platelets maintain a low basal activation state in the circulation remains unknown. We identify Lepr+ stromal cells lining the BM sinusoids as important contributors to sustaining low platelet activation. Ablation of murine Lepr+ cells led to a decreased number of platelets in the circulation with an increased activation state. We developed a potentially novel culture system for supporting platelet formation in vitro using a unique population of CD51+PDGFRα+ perivascular cells, derived from human umbilical cord tissue, which display numerous mesenchymal stem cell (MSC) properties. Megakaryocytes cocultured with MSCs had altered LAT and Rap1b gene expression, yielding platelets that are functional with low basal activation levels, a critical consideration for developing a transfusion product. Identification of a regulatory cell that maintains low baseline platelet activation during thrombopoiesis opens up new avenues for improving blood product production ex vivo.
Authors
Avital Mendelson, Ana Nicolle Strat, Weili Bao, Peter Rosston, Georgia Fallon, Sophie Ohrn, Hui Zhong, Cheryl Lobo, Xiuli An, Karina Yazdanbakhsh
Abstract
Advances in genomic medicine have elucidated an increasing number of genetic etiologies for patients with common variable immunodeficiency (CVID). However, there is heterogeneity in clinical and immunophenotypic presentations and a limited understanding of the underlying pathophysiology of many cases. The primary defects in CVID may extend beyond the adaptive immune system, and the combined defect in both the myeloid and lymphoid compartments suggests the mechanism may involve bone marrow output and earlier progenitors. Using the methylation profile of the human androgen receptor (AR) gene as a surrogate epigenetic marker for bone marrow clonality, we examined the hematopoietic compartments of patients with CVID. Our data show that clonal hematopoiesis is common among patients with adult-onset CVID who do not have associated noninfectious complications. Nonblood tissues did not show a skewed AR methylation status, supporting a model of an acquired clonal hematopoietic event. Attenuation of memory B cell differentiation into long-lived plasma cells (CD20–CD27+CD38+CD138+) was associated with marked changes in the postdifferentiation methylation profile, demonstrating the functional consequence of clonal hematopoiesis on humoral immunity in these patients. This study sheds light on a potential etiology of a subset of patients with CVID, and the findings suggest that it is a stage of an acquired lymphocyte maturation disorder.
Authors
Gabriel K. Wong, Sara Barmettler, James M. Heather, David Millar, Sarah A. Penny, Aarnoud Huissoon, Alex Richter, Mark Cobbold
Abstract
BACKGROUND. Autologous stem-cell transplantation (ASCT) is the standard treatment for R/R B-NHL, while chimeric antigen receptor T (CAR-T) therapy targeting CD19 emerges as an alternative strategy. Here we report a comparative analysis of the two strategies in a single center. METHODS. We performed a prospective single-arm study of CAR-T therapy in 29 patients with R/R B-NHL and compared the outcomes with contemporaneous 27 patients who received ASCT. NHL was diagnosed by histopathological assessments, and the safety and efficacy were compared. RESULTS. The CAR-T group exhibited better rates of CR (48.0% vs. 20.8%, P=0.046) and one-year OS (74.4% vs. 44.5%, P=0.044) compared with the ASCT group. Subpopulation analysis showed that patients with IPI scores ≥ 3 achieved significantly higher ORR and CR rates in the CAR-T group than in the ASCT group (ORR: 72.0% vs. 10.0%, P=0.002; CR: 38.9% vs 0% P=0.030, respectively). The most common severe adverse events in the CAR-T group were cytokine release syndrome, neurotoxicity and infection compared with cytopenia, gastrointestinal toxicity and infection in the ASCT group. Additionally, the incidence of non-hematologic severe adverse events (SAEs) was markedly lower in the CAR-T group than in the ASCT group (20.7% vs. 48.1% P=0.030). CONCLUSION. CAR-T therapy exhibited superior clinical outcomes in safety and efficacy over ASCT in patients with R/R B-NHL, suggesting CAR-T may be a recommended alternative to ASCT.
Authors
Caixia Li, Ying Zhang, Changfeng Zhang, Jia Chen, Xiaoyan Lou, Xiaochen Chen, Liqing Kang, Nan Xu, Minghao Li, Jingwen Tan, Xiuli Sun, Jin Zhou, Zhen Yang, Xiangping Zong, Pu Wang, Ting Xu, Changju Qu, Haiwen Huang, Zhengming Jin, Lei Yu, Depei Wu
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
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