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Context.—: In 2018 the College of American Pathologists Diagnostic Immunology and Flow Cytometry Committee designed and implemented a new plasma cell neoplasia flow cytometry proficiency testing program-PCNEO-to allow clinical flow cytometry laboratories to monitor and assess their performance compared with a peer group., Objective.—: To report the results from the first 4 years of the PCNEO program., Design.—: Program participants were sent 2 sets of challenges per year, each including 1 wet challenge and 2 dry challenges, with associated clinical and laboratory findings. The wet challenges were composed of myeloma cell line specimens (with or without dilution in preserved whole blood) for flow cytometric analysis. The dry (paper) challenges were composed of clinical case summaries and images of flow cytometric test results from various flow cytometry laboratories of committee members., Results.—: A total of 116 to 145 laboratories from 17 countries enrolled in the proficiency testing program. For the wet challenges, almost all participants (97%-100%; cumulative, 98.2%) correctly identified the presence of neoplastic plasma cell populations based on flow cytometric analysis of undiluted myeloma cell lines. Slightly fewer participants (89.0%-97.4%; cumulative, 95.2%) correctly identified the presence of neoplastic plasma cell populations based on flow cytometric analysis of diluted myeloma cell lines (10% or 50% dilutions into peripheral blood) intended to better represent a typical clinical sample. There was generally agreement among 80% or more of participants for positive or negative staining for CD38, CD138, CD19, CD20, and surface and cytoplasmic κ and λ light chains. Similarly, 84% to 100% of participants were able to correctly identify the presence of neoplastic plasma cell populations in paper challenges, including the presence of small, neoplastic plasma cell populations (0.01%-5.0% clonal plasma cells) and the presence of nonneoplastic plasma cell populations (correctly identified by 91%-96% of participants)., Conclusions.—: Participant performance in the new proficiency testing program was excellent overall, with the vast majority of participants able to perform flow cytometric analysis and identify neoplastic plasma cell populations and to identify small plasma cell clones or expanded populations of reactive plasma cells in dry challenge flow cytometry results. This program will allow laboratories to verify the accuracy of their testing program and test interpretations for the assessment of patients suspected of having a plasma cell neoplasm., Competing Interests: All authors are current or past members of the College of American Pathologists Diagnostic Immunology and Flow Cytometry Committee, except for Bashleben, who is an employee of the College of American Pathologists., (© 2024 College of American Pathologists.)

Purpose: This study investigated the effectiveness of algorithmic testing in hematopathology at the Brigham and Women's Hospital and Dana-Farber Cancer Institute (DFCI). The algorithm was predicated on test selection after an initial pathologic evaluation to maximize cost-effective testing, especially for expensive molecular and cytogenetic assays., Materials and Methods: Standard ordering protocols (SOPs) for 17 disease categories were developed and encoded in a decision support application. Six months of retrospective data from application beta testing was obtained and compared with actual testing practices during that timeframe. In addition, 2 years of prospective data were also obtained from patients at one community satellite site., Results: A total of 460 retrospective cases (before introduction of algorithmic testing) and 109 prospective cases (following introduction) were analyzed. In the retrospective data, 61.7% of tests (509 of 825) were concordant with the SOPs while 38.3% (316 of 825) were overordered and 30.8% (227 of 736) of SOP-recommended tests were omitted. In the prospective data, 98.8% of testing was concordant (244 of 247 total tests) with only 1.2% overordered tests (3 of 247) and 7.6% omitted tests (20 of 264 SOP-recommended tests; overall P < .001). The cost of overordered tests before implementing SOP indicates a potential annualized saving of $1,347,520 in US dollars (USD) in overordered testing at Brigham and Women's Hospital/DFCI. Only two of 316 overordered tests (0.6%) returned any additional information, both for extremely rare clinical circumstances., Conclusion: Implementation of SOPs dramatically improved test ordering practices, with a just right number of ancillary tests that minimizes cost and has no significant impact on acquiring key informative test results.

Waldenström macroglobulinemia (WM) is a rare subtype of non-Hodgkin lymphoma characterized by malignant lymphoplasmacytic cells in the bone marrow (BM). To dissect the pathophysiology of WM, we evaluated clonal cells by mapping of B cell lymphomagenesis with adaptive and innate immune tumor microenvironment (TME) in the BM of WM patients using mass cytometry (CyTOF). In-depth immunophenotypic profiling of WM cells exhibited profound expansion of clonal cells in both unswitched and switched memory B cells and also plasma cells with aberrant expression variations. WM B lymphomagenesis was associated with reduction of most B cell precursors assessed with the same clonally restricted light chain and phenotypic changes. The immune TME was infiltrated by mature monocytes, neutrophils and adaptive T cells, preferentially subsets of effector T helper, effector CTL and effector memory CTL cells that were associated with superior overall survival (OS), in contrast to progenitors of T cells and myeloid/monocytic lineage subsets that were suppressed in WM cohort. Moreover, decrease in immature B and NKT cells was related to worse OS in WM patients. Innate and adaptive immune subsets of WM TME were modulated by immune checkpoints, including PD-1/PD-L1&PD-L2, TIGIT/PVR, CD137/CD137-L, CTLA-4, BTLA and KIR expression. The response of ibrutinib treatment to the reduction of clonal memory B cell was associated with high levels of immature B cells and effector memory CTL cells. Our study demonstrates that CyTOF technology is a powerful approach for characterizing the pathophysiology of WM at various stages, predicting patient risk and monitoring the effectiveness of treatment strategies., (© 2022 The Authors. International Journal of Cancer published by John Wiley & Sons Ltd on behalf of UICC.)

To better characterize the heterogeneity of multiple myeloma (MM), we profiled plasma cells (PCs) and their B cell lymphopoiesis in the BM samples from patients with monoclonal gammopathy of undetermined significance, smoldering MM, and active MM by mass cytometry (CyTOF) analysis. Characterization of intra- and interneoplastic heterogeneity of malignant plasmablasts and PCs revealed overexpression of the MM SET domain (MMSET), Notch-1, and CD47. Variations in upregulation of B cell signaling regulators (IFN regulatory factor 4 [IRF-4], CXCR4, B cell lymphoma 6 [Bcl-6], c-Myc, myeloid differentiation primary response protein 88 [MYD88], and spliced X box-binding protein 1 [sXBP-1]) and aberrant markers (CD319, CD269, CD200, CD117, CD56, and CD28) were associated with different clinical outcomes in clonal PC subsets. In addition, prognosis was related to heterogeneity in subclonal expression of stemness markers, including neuroepithelial stem cell protein (Nestin), SRY-box transcription factor 2 (Sox2), Krüppel-like factor 4 (KLF-4), and Nanog. Furthermore, we have defined significantly elevated levels of MMSET, MYD88, c-Myc, CD243, Notch-1, and CD47 from hematopoietic stem cells to PCs in myeloma B cell lymphopoiesis, noted even in premalignant conditions, with variably modulated expression of B cell development regulators, including IRF-4, Bcl-2, Bcl-6, and sXBP-1; aberrant PC markers (such as CD52, CD44, CD200, CD81, CD269, CD117, and CXCR4); and stemness-controlling regulators, including Nanog, KLF-4, octamer-binding transcription factor 3/4 (Oct3/4), Sox2, and retinoic acid receptor α2 (RARα2). This study provides the rationale for precise molecular profiling of patients with MM by CyTOF technology to define disease heterogeneity and prognosis.

Novel drug discoveries have shifted the treatment paradigms of most hematological malignancies, including multiple myeloma (MM). However, this plasma cell malignancy remains incurable, and novel therapies are therefore urgently needed. Whole-genome transcriptome analyses in a large cohort of MM patients demonstrated that alterations in pre-mRNA splicing (AS) are frequent in MM. This manuscript describes approaches to identify disease-specific alterations in MM and proposes RNA-based therapeutic strategies to eradicate such alterations. As a "proof of concept", we examined the causes of aberrant HMMR (Hyaluronan-mediated motility receptor) splicing in MM. We identified clusters of single nucleotide variations (SNVs) in the HMMR transcript where the altered splicing took place. Using bioinformatics tools, we predicted SNVs and splicing factors that potentially contribute to aberrant HMMR splicing. Based on bioinformatic analyses and validation studies, we provided the rationale for RNA-based therapeutic strategies to selectively inhibit altered HMMR splicing in MM. Since splicing is a hallmark of many cancers, strategies described herein for target identification and the design of RNA-based therapeutics that inhibit gene splicing can be applied not only to other genes in MM but also more broadly to other hematological malignancies and solid tumors as well., (© 2023. The Author(s).)

Aggressive subtypes of non-Hodgkin lymphoma may uncommonly be referred to clinical oncologists for treatment of acute leukemia, due to an elevated or rapidly rising white blood cell count (WBC), with circulating neoplastic cells that morphologically resemble leukemic blasts seen in acute myeloid or lymphoblastic leukemia. We describe six cases of non-Hodgkin lymphoma that mimicked acute leukemia and were identified in the pathology records of the Brigham and Women's Hospital. The patients were older adults (mean age 70 years), who presented with leukocytosis (mean 79.7 × 10 9 /L) with circulating neoplastic cells (mean 57%), which mimicked leukemic blasts, thrombocytopenia, and anemia (4/6 patients). In each case, immunophenotypic analysis identified a population of mature B cells or mature T cells. We identified 15 additional cases of non-Hodgkin lymphoma in the literature that mimicked acute leukemia; considering all 21 cases, 11 had an appearance of acute lymphoblastic leukemia, 4 had an appearance of acute monocytic leukemia, and 6 had an appearance of acute leukemia unable to be further categorized. In general, patients exhibited poor overall survival. These cases illustrate the importance of comprehensive immunophenotypic analysis in the initial evaluation of hematolymphoid neoplasms, and that occasional cases of non-Hodgkin lymphomas can resemble acute leukemia at initial presentation., Competing Interests: Conflict of interestThe authors declare no competing interests., (© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2022.)

Oncogenic activated RAS mutations have been detected in 50% of de novo and 70% of relapsed multiple myeloma (MM) patients. Translocation t(11;14) involving IgH/CCDN1 and overexpression of cyclin-Ds are early events in MM pathogenesis, enhancing uncontrolled MM cell growth. We hypothesized that targeting both RAS/MAPK pathway molecules including Erk1/2 along with cyclin-Ds enhances MM cytotoxicity and minimizes side effects. Recent studies have demonstrated the high potency of Erk1/2 and CDK4/6 inhibitors in metastatic relapsed cancers, and here we tested anti-MM effects of the Erk1/2 + CDK4/6 inhibitor combination. Our studies showed strong synergistic (IC < 0.5) cytotoxicity of Erk1/2i + CDK4/6i in MM-cells. Erk1/2i + CDK4/6i treatment in a dose-dependent manner arrested MM-cells in the G0/G1 phase and activated mitochondrial apoptotic signaling. Our studies showed that Erk1/2i + CDK4/6i treatment-induced inhibition of key target molecules in Erk1/2 and CDK4/6 signaling, such as c-myc, p-RSK, p-S6, p-RB, and E2F1, suggesting on-target activity of these inhibitors. We identified Erk1/2i + CDK4/6i treatment associated five-gene signature which includes SNRPB and SLC25A5; these genes are involved in RNA processing and mitochondrial metabolism, respectively. Overall, our studies provide the preclinical framework for Erk1/2i + CDK4/6i combination clinical trials to target Ras+CDK pathways to improve patient outcome in MM., (© 2021. The Author(s).)

The COVID-19 pandemic has highlighted racial health disparities within the United States. Although social determinants of health are the most likely drivers of this disparity, it is possible that genetic traits enriched in the black population like sickle cell trait (SCT) could worsen the morbidity and mortality of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Patients admitted for SARS-CoV-2 infection who identified as black or African American were included in the study (n = 166). Blood remnants were tested for SCT, and clinical data were abstracted from the chart. There was no difference in mortality between those with SCT and those without. There was no difference in respiratory complications between groups, but those without SCT had a much higher burden of chronic lung disease (P = .004). Those with SCT had higher creatinine on admission (P = .004), but no difference in in-hospital renal complications (P = .532). Notably, 12% of the cohort had SCT, which is higher than the expected 7.31% (P = .025). Our study did not show any evidence of increased end organ damage, morbidity, or mortality from SARS-CoV-2 infection among patients with SCT but did show differences in admission creatinine and preexisting lung disease., (© 2021 by The American Society of Hematology.)

Chromosome 13q deletion [del(13q)], harboring the miR-15a/16-1 cluster, is one of the most common genetic alterations in mature B-cell malignancies, which originate from germinal center (GC) and post-GC B cells. Moreover, miR-15a/16 expression is frequently reduced in lymphoma and multiple myeloma (MM) cells without del(13q), suggesting important tumor-suppressor activity. However, the role of miR-15a/16-1 in B-cell activation and initiation of mature B-cell neoplasms remains to be determined. We show that conditional deletion of the miR-15a/16-1 cluster in murine GC B cells induces moderate but widespread molecular and functional changes including an increased number of GC B cells, percentage of dark zone B cells, and maturation into plasma cells. With time, this leads to development of mature B-cell neoplasms resembling human extramedullary plasmacytoma (EP) as well as follicular and diffuse large B-cell lymphomas. The indolent nature and lack of bone marrow involvement of EP in our murine model resembles human primary EP rather than MM that has progressed to extramedullary disease. We corroborate human primary EP having low levels of miR-15a/16 expression, with del(13q) being the most common genetic loss. Additionally, we show that, although the mutational profile of human EP is similar to MM, there are some exceptions such as the low frequency of hyperdiploidy in EP, which could account for different disease presentation. Taken together, our studies highlight the significant role of the miR-15a/16-1 cluster in the regulation of the GC reaction and its fundamental context-dependent tumor-suppression function in plasma cell and B-cell malignancies., (© 2021 by The American Society of Hematology.)

Context.—: Minimal residual disease (MRD) testing by flow cytometry is ubiquitous in hematolymphoid neoplasm monitoring, especially B-lymphoblastic leukemia (B-ALL), for which it provides predictive information and guides management. Major heterogeneity was identified in 2014. Subsequently, new Flow Cytometry Checklist items required documentation of the sensitivity determination method and required lower level of detection (LLOD) inclusion in final reports. This study assesses Laboratory Accreditation Program (LAP) participation and new checklist items' impact on flow cytometry MRD testing., Objectives.—: To survey flow cytometry laboratories about MRD testing for B-ALL and plasma cell myeloma. In particular, enumerate the laboratories performing MRD testing, the proportion performing assays with very low LLODs, and implementation of new checklist items., Design.—: Supplemental questions were distributed in the 2017-A mailing to 548 flow cytometry laboratories subscribed to the College of American Pathologists FL3 Proficiency Testing Survey (Flow Cytometry-Immunophenotypic Characterization of Leukemia/Lymphoma)., Results.—: The percentage of laboratories performing MRD studies has significantly decreased since 2014. Wide ranges of LLOD and collection event numbers were reported for B-ALL and plasma cell myeloma. Most laboratories determine LLOD by using dilutional studies and include it in final reports; a higher proportion of LAP participants used these practices than nonparticipants., Conclusions.—: Several MRD testing aspects vary among laboratories receiving FL3 Proficiency Testing materials. After the survey in 2014, new checklist items were implemented. As compared to 2014, fewer laboratories are performing MRD studies. While LLOD remains heterogeneous, a high proportion of LAP subscribers follow the new checklist requirements and, overall, target LLOD recommendations from disease-specific working groups are met., (© 2021 College of American Pathologists.)

Context.—: The diagnostic workup of lymphoma continues to evolve rapidly as experience and discovery led to the addition of new clinicopathologic entities and techniques to differentiate them. The optimal clinically effective, efficient, and cost-effective approach to diagnosis that is safe for patients can be elusive, in both community-based and academic practice. Studies suggest that there is variation in practice in both settings., Objective.—: To develop an evidence-based guideline for the preanalytic phase of testing, focusing on specimen requirements for the diagnostic evaluation of lymphoma., Design.—: The American Society for Clinical Pathology, the College of American Pathologists, and the American Society of Hematology convened a panel of experts in the laboratory workup of lymphoma to develop evidence-based recommendations. The panel conducted a systematic review of literature to address key questions. Using the Grading of Recommendations Assessment, Development, and Evaluation approach, recommendations were derived based on the available evidence, strength of that evidence, and key judgements as defined in the Grading of Recommendations Assessment, Development, and Evaluation Evidence to Decision framework., Results.—: Thirteen guideline statements were established to optimize specimen selection, ancillary diagnostic testing, and appropriate follow-up for safe and accurate diagnosis of indolent and aggressive lymphoma., Conclusions.—: Primary diagnosis and classification of lymphoma can be achieved with a variety of specimens. Application of the recommendations can guide decisions on specimen suitability, diagnostic capabilities, and correct use of ancillary testing. Disease prevalence in patient populations, availability of ancillary testing, and diagnostic goals should be incorporated into algorithms tailored to each practice environment., Competing Interests: Authors' disclosures of potential conflicts of interest and author contributions are found in the Appendix at the end of this article., (© 2021 College of American Pathologists.)

Objectives: The diagnostic workup of lymphoma continues to evolve rapidly as experience and discovery lead to the addition of new clinicopathologic entities and techniques to differentiate them. The optimal clinically effective, efficient, and cost-effective approach to diagnosis that is safe for patients can be elusive, in both community-based and academic practice. Studies suggest that there is variation in practice in both settings., The Aim of This Review Is to: develop an evidence-based guideline for the preanalytic phase of testing, focusing on specimen requirements for the diagnostic evaluation of lymphoma., Methods: The American Society for Clinical Pathology, the College of American Pathologists, and the American Society of Hematology convened a panel of experts in the laboratory workup of lymphoma to develop evidence-based recommendations. The panel conducted a systematic review of the literature to address key questions. Using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach, recommendations were derived based on the available evidence, the strength of that evidence, and key judgments as defined in the GRADE Evidence to Decision framework., Results: Thirteen guideline statements were established to optimize specimen selection, ancillary diagnostic testing, and appropriate follow-up for safe and accurate diagnosis of indolent and aggressive lymphoma., Conclusions: Primary diagnosis and classification of lymphoma can be achieved with a variety of specimens. Application of the recommendations can guide decisions about specimen suitability, diagnostic capabilities, and correct utilization of ancillary testing. Disease prevalence in patient populations, availability of ancillary testing, and diagnostic goals should be incorporated into algorithms tailored to each practice environment., (© American Society for Clinical Pathology, 2020. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Inclusion body myositis is a late onset treatment-refractory autoimmune disease of skeletal muscle associated with a blood autoantibody (anti-cN1A), an HLA autoimmune haplotype, and muscle pathology characterized by cytotoxic CD8+ T cell destruction of myofibres. Here, we report on translational studies of inclusion body myositis patient muscle compared with a diverse set of other muscle disease samples. Using available microarray data on 411 muscle samples from patients with inclusion body myositis (n = 40), other muscle diseases (n = 265), and without neuromuscular disease (normal, n = 106), we identified a signature of T-cell cytotoxicity in inclusion body myositis muscle coupled with a signature of highly differentiated CD8 T-cell effector memory and terminally differentiated effector cells. Further, we examined killer cell lectin-like receptor G1 (KLRG1) as a marker of this population of cells, demonstrated the correlation of KLRG1 gene expression with lymphocyte cytotoxicity across 28 870 human tissue samples, and identified the presence of KLRG1 on pathogenic inclusion body myositis muscle invading T cells and an increase in KLRG1 expressing T cells in inclusion body myositis blood. We examined inclusion body myositis muscle T-cell proliferation by Ki67 immunohistochemistry demonstrating that diseased muscle-invading T cells are minimally or non-proliferative, in accordance with known properties of highly differentiated or terminally differentiated T cells. We found low expression of KLRG1 on infection-protective human lymphoid tissue central memory T cells and autoimmune-protective human blood regulatory T cells. Targeting highly differentiated cytotoxic T cells could be a favourable approach to treatment of inclusion body myositis., (© The Author(s) (2019). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Objectives: We tested whether combined flow cytometric assessment of loss of blast heterogeneity and decreased hematogones is a diagnostically useful approach for evaluation of myelodysplastic syndrome (MDS)., Methods: Bone marrow samples from patients with known MDS were analyzed by 10-color flow cytometric immunophenotyping and compared with normal bone marrow samples., Results: There was loss of blast heterogeneity in patients with MDS compared with normal bone marrow samples, based on the relative size of the dominant blast population (83.0% vs 64.8%) and fewer hematogones (0.08% vs 1.39%). The size of the largest blast population divided by the fraction of hematogones (blast dominance-hematogone [BDH] index) was significantly larger in MDS compared with normal cases (27,084 vs 190, P < .0001; receiver operating characteristic area under the curve = 0.96)., Conclusions: The BDH index is more sensitive and specific than loss of blast heterogeneity or decrease in hematogones for detecting MDS in bone marrow samples and may be useful in clinical practice., (© American Society for Clinical Pathology, 2019. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Re-expression of the paralogous γ-globin genes (HBG1/2) could be a universal strategy to ameliorate the severe β-globin disorders sickle cell disease (SCD) and β-thalassemia by induction of fetal hemoglobin (HbF, α 2 γ 2 ) 1 . Previously, we and others have shown that core sequences at the BCL11A erythroid enhancer are required for repression of HbF in adult-stage erythroid cells but are dispensable in non-erythroid cells 2-6 . CRISPR-Cas9-mediated gene modification has demonstrated variable efficiency, specificity, and persistence in hematopoietic stem cells (HSCs). Here, we demonstrate that Cas9:sgRNA ribonucleoprotein (RNP)-mediated cleavage within a GATA1 binding site at the +58 BCL11A erythroid enhancer results in highly penetrant disruption of this motif, reduction of BCL11A expression, and induction of fetal γ-globin. We optimize conditions for selection-free on-target editing in patient-derived HSCs as a nearly complete reaction lacking detectable genotoxicity or deleterious impact on stem cell function. HSCs preferentially undergo non-homologous compared with microhomology-mediated end joining repair. Erythroid progeny of edited engrafting SCD HSCs express therapeutic levels of HbF and resist sickling, while those from patients with β-thalassemia show restored globin chain balance. Non-homologous end joining repair-based BCL11A enhancer editing approaching complete allelic disruption in HSCs is a practicable therapeutic strategy to produce durable HbF induction.

Objectives: Flow cytometry immunophenotyping is limited by poor resolution of T-cell clones. A newly described antibody was recently used to distinguish normal peripheral blood T cells from malignant T-cell clones. Here, we evaluate this antibody as a new diagnostic tool for detecting T-cell clonality in mature peripheral T-cell lymphomas., Methods: Immunostaining for the T-cell receptor β chain constant region 1 (TRBC1) along with routine T-cell markers was performed on 51 peripheral blood and two bone marrow samples submitted to the flow cytometry laboratory for suspected T-cell malignancy., Results: TRBC immunophenotyping identified malignant T-cell clones with 97% sensitivity and 91% specificity. Findings correlated with molecular T-cell clonality testing. In cases with equivocal molecular results, TRBC1 immunophenotyping provided additional diagnostic information., Conclusions: TRBC1 flow cytometric immunophenotyping is a robust and inexpensive method for identifying T-cell clonality that could easily be incorporated into routine flow cytometric practice., (© American Society for Clinical Pathology, 2019. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

EZH2 is a methyltransferase that plays an important tumorigenic role in various neoplasms. We previously found that EZH2 is expressed in a range of aggressive B-cell lymphomas (ABCLs), T-cell lymphomas, and histiocytic neoplasms, with differential expression of intracellular signaling molecules p-ERK, MYC, and p-STAT3, potential regulators of EZH2 expression. We studied EZH2 expression in nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), classic Hodgkin lymphoma (cHL), T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL), and B-cell Lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphomas and classic Hodgkin lymphoma (BCLu-DLBCL/cHL), as well as the coexpression of p-ERK, MYC, and p-STAT3 in these neoplasms. The neoplastic LP cells of NLPHL and Hodgkin/Reed-Sternberg cells of cHL were strongly positive for EZH2, as were the neoplastic cells in THRLBCL and BCLu-DLBCL/cHL. EZH2 expression correlated with proliferation rate, as assessed by Ki-67 staining. LP cells in NLPHL and Hodgkin/Reed-Sternberg cells in cHL were strongly positive for p-ERK, p-STAT3, and MYC, as were the neoplastic cells in THRLBCL and BCLu-DLBCL/cHL, in contrast to the differential expression of these molecules seen in ABCLs. These findings suggest that combined expression of p-ERK, MYC, and p-STAT3 is a useful immunohistochemical pattern for the diagnosis of EZH2-positive Hodgkin lymphomas and related lymphomas, in contrast to ABCLs. Furthermore, the overexpression of EZH2, in association with coexpression of tumorigenic signaling molecules, suggests an oncogenic role for this molecule in the development of Hodgkin lymphomas and related lymphomas. THRLBCL and BCLu-DLBCL/cHL appear to have a mechanism for the regulation of EZH2 expression that is similar to NLPHL and cHL and different from that of ABCLs. In addition, EZH2 and associated signaling cascades may serve as therapeutic targets for the treatment of Hodgkin lymphomas and related lymphomas.

Clinical uncertainty exists regarding which assay should be designated as the standard monitoring coagulation test for intravenous unfractionated heparin (UFH). Several studies have compared the use of activated partial thromboplastin time (aPTT) and antifactor-Xa (anti-Xa) and have come out with varying results. The correlation between these 2 tests varied, markedly from strong to weak. Some have demonstrated that monitoring with anti-Xa heparin assay leads to fewer dose adjustments, resulting in fewer laboratory tests, while others have not. In the current study, we evaluated the correlation between aPTT and anti-Xa values to guide clinical management of UFH, with the intention to develop a new correlation nomogram.

Background: Antiphospholipid antibody syndrome (APS) is characterized by laboratory evidence of antiphospholipid antibodies (aPL) [e.g. lupus anticoagulant (LA), anticardiolipin (ACL), and/or antiβ2-glycoprotein I (aB2GPI)] in a clinical setting of thrombosis or pregnancy morbidity. The International Society on Thrombosis and Haemostasis recommends two different testing modalities to detect LA. To evaluate these recommendations in a clinical setting, our hospital, a tertiary care center with a specialized coagulation laboratory, added the dilute Russell's viper venom time to be performed in parallel with the PTT-lupus anticoagulant to detect LA., Methods: Results of aPL testing were collected on all patients who had LA testing for one year. Chart review was performed to correlate LA results with ACL, aB2GPI, and clinical history., Results: Patients who were initially LA positive by both PTT-lupus anticoagulant and dilute Russell's viper venom time were more likely to be persistently positive. Patients who were positive for ACL and aB2GPI were likely to be positive by both LA methodologies. No single method was absolutely sensitive, as cases of APS were detected by PTTLA only, DRVVT only, and both methods., Conclusions: The addition of a second testing method for LA provides additional diagnostic information and may be helpful in stratifying risk of thrombosis.

T- and NK-cell lymphomas (TCL) are a heterogenous group of lymphoid malignancies with poor prognosis. In contrast to B-cell and myeloid malignancies, there are few preclinical models of TCLs, which has hampered the development of effective therapeutics. Here we establish and characterize preclinical models of TCL. We identify multiple vulnerabilities that are targetable with currently available agents (e.g., inhibitors of JAK2 or IKZF1) and demonstrate proof-of-principle for biomarker-driven therapies using patient-derived xenografts (PDXs). We show that MDM2 and MDMX are targetable vulnerabilities within TP53-wild-type TCLs. ALRN-6924, a stapled peptide that blocks interactions between p53 and both MDM2 and MDMX has potent in vitro activity and superior in vivo activity across 8 different PDX models compared to the standard-of-care agent romidepsin. ALRN-6924 induced a complete remission in a patient with TP53-wild-type angioimmunoblastic T-cell lymphoma, demonstrating the potential for rapid translation of discoveries from subtype-specific preclinical models.

EZH2 is an important enzymatic subunit of the epigenetic regulator polycomb repressive complex 2 (PRC2), which controls gene silencing through post-translational modification, and is overexpressed in various carcinomas and hematopoietic neoplasms. We found that the majority of cases of histiocytic and dendritic cell neoplasms, including histiocytic sarcoma, follicular dendritic cell sarcoma, Langerhans cell histiocytosis, and interdigitating dendritic cell sarcoma, show strong EZH2 expression by immunohistochemical staining, in contrast to benign histiocytic lesions and normal cellular counterparts, which did not show EZH2 expression, suggesting that this molecule may function as an oncogenic protein in these neoplasms. We correlated EZH2 expression with that of p-ERK1/2, MYC, and p-STAT3, potential regulators of EZH2, and found that 60-80% of these cases showed strong p-ERK1/2 expression, and only a minority of cases showed positivity for MYC or p-STAT3 in neoplastic cells. In cases of follicular dendritic cell sarcoma, Langerhans cell histiocytosis, histiocytic sarcoma, and interdigitating dendritic cell sarcoma with strong EZH2 expression, 90%, 89%, 70%, and 100% of cases showed co-expression of p-ERK1/2 with EZH2, respectively, while only a small percentage of these cases showed MYC or p-STAT3 co-expression with EZH2 (≤30%). These findings suggest that the p-ERK1/2 signaling cascade, but not the p-STAT3 and MYC signaling cascades, may regulate EZH2 expression in histiocytic and dendritic cell neoplasms, and that EZH2 and the p-ERK1/2 signaling cascade could serve as therapeutic targets for the treatment of these neoplasms. Interestingly, only a minority of cases of blastic plasmacytoid dendritic cell neoplasm exhibited high EZH2 expression, and only a minority of these cases showed p-ERK1/2 co-expression, suggesting that alternative mechanisms may contribute to tumorigenesis in this aggressive neoplasm.

Ectopic intrathyroidal thymic tissue is a benign lesion of nonthyroid origin occasionally found in the pediatric thyroid gland. Accurate diagnosis of such lesions is critical to avoid unnecessary biopsy or surgery. Twelve children referred to our center for the concern of thyroid nodules were found to have intrathyroidal thymic tissue. Most of the lesions had a classic sonographic appearance of a hypoechoic mass with sharp margins and multiple focal internal nonshadowing echogenicities identical to thymic tissue. Sonography and, in select cases, fine-needle aspiration can be used to diagnose benign thymic tissue within the thyroid and avoid unnecessary surgery., (© 2017 by the American Institute of Ultrasound in Medicine.)

Flow cytometry is ideally suited for the immunophenotypic analysis of T-cell neoplasia. This article covers the spectrum of flow cytometric findings associated with frequently encountered benign and neoplastic T-cell populations and details the most common immunophenotypic features associated with specific neoplasms of both immature and mature T cells., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Mast cells are present at a low frequency in bone marrow, rendering high-sensitivity multiparametric flow cytometric analysis an ideal method to assess antigen expression on mast cells. This article discusses the normal antigen expression profile of mast cells, established criteria to identify neoplastic mast cells, and new immunophenotypic markers and approaches to identify the presence of neoplastic mast cells in cases of mastocytosis., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Multiple myeloma (MM), a B cell malignancy characterized by clonal proliferation of plasma cells in the bone marrow, remains incurable despite the use of novel and conventional therapies. In this study, we demonstrated MM cell cytotoxicity triggered by realgar (REA; As 4 S 4 ) nanoparticles (NREA) versus Arsenic trioxide (ATO) against MM cell lines and patient cells. Both NREA and ATO showed in vivo anti-MM activity, resulting in significantly decreased tumour burden. The anti-MM activity of NREA and ATO is associated with apoptosis, evidenced by DNA fragmentation, depletion of mitochondrial membrane potential, cleavage of caspases and anti-apoptotic proteins. NREA induced G 2 /M cell cycle arrest and modulation of cyclin B1, p53 (TP53), p21 (CDKN1A), Puma (BBC3) and Wee-1 (WEE1). Moreover, NREA induced modulation of key regulatory molecules in MM pathogenesis including JNK activation, c-Myc (MYC), BRD4, and histones. Importantly, NREA, but not ATO, significantly depleted the proportion and clonogenicity of the MM stem-like side population, even in the context of the bone marrow stromal cells. Finally, our study showed that both NREA and ATO triggered synergistic anti-MM activity when combined with lenalidomide or melphalan. Taken together, the anti-MM activity of NREA was more potent compared to ATO, providing the preclinical framework for clinical trials to improve patient outcome in MM., (© 2017 John Wiley & Sons Ltd.)

Objectives: The importance of distinguishing mature B-cell lymphoproliferative disorders (B-LPDs) is highlighted by the distinct treatments used for and varying prognoses seen in association with these different diseases. Immunophenotyping allows for accurate and efficient differentiation of many B-LPDs. Recently, we showed that CD200 is highly expressed in hairy cell leukemia (HCL) but not in marginal zone lymphoma (MZL), lymphoplasmacytic lymphoma (LPL), or hairy cell leukemia-variant (HCL-v). Here, we assessed the usefulness of a flow cytometric panel combining CD200 and CD1d with CD25, CD103, and CD11c to distinguish CD10-, CD5- B-LPDs., Methods: We analyzed the expression of CD200 and CD1d by flow cytometric analysis in 79 cases of CD10-, CD5- mature B-LPDs., Results: Distinct patterns of CD200 and CD1d expression were seen in the examined B-LPDs. HCL showed bright positivity for CD200 along with positive staining for CD1d, whereas HCL-v showed low levels of expression for both markers. LPL demonstrated positive staining for CD200 in combination with dim to negative staining for CD1d. In contrast, MZL was commonly positive for CD1d and negative for CD200., Conclusions: Flow cytometric analysis of CD200 and CD1d, along with CD25, CD103, and CD11c, can aid in the diagnosis of CD10-, CD5- mature B-LPDs., (© American Society for Clinical Pathology, 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com)

T-cell transcription factor GATA-3, known to play a role in early T-cell development and in the development of T-cell neoplasms, is expressed at high levels in fetal and adult thymus, as well as in acute leukemias with T-cell differentiation, including T-lymphoblastic leukemia/lymphoma (22/22 cases), early T-cell precursor lymphoblastic leukemia (11/11 cases), and mixed-phenotype acute leukemia, T/myeloid (4/5 cases), but only rarely in acute myeloid leukemia/myeloid sarcoma (1/36 cases), and not in B-lymphoblastic leukemia (0/16 cases). In contrast, T-bet, the other T-cell transcription factor that controls Th1/Th2 T-cell fate, is not expressed to any significant extent in immature thymocytes or in cases of T-lymphoblastic leukemia or acute myeloid leukemia/myeloid sarcoma, but is expressed in most cases (15/16) of B-lymphoblastic leukemia and in mixed-phenotype acute leukemia, B/myeloid. GATA-3-positive acute leukemias with T-cell differentiation were also found to express proto-oncogene C-MYC, in an average of 52% of neoplastic cells, which, along with GATA-3, may contribute to leukemogenesis, as suggested by transgenic mouse models. We conclude that GATA-3 is a sensitive and specific marker for the diagnosis of acute leukemias with T-cell differentiation and may be a useful addition to the panel of immunophenotypic markers for the diagnostic evaluation of acute leukemias., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: The thyroid hormone-inactivating enzyme type 3 deiodinase (D3) is induced during hypertrophic and ischemic cardiomyopathy, leading to a state of local cardiac hypothyroidism. Whether D3 induction occurs in dilated cardiomyopathy is unknown., Methods: This study characterized changes in cardiac D3 and thyroid hormone signaling in a transgenic model of progressive dilated cardiomyopathy (TG9 mice)., Results: Cardiac D3 was dramatically induced 15-fold during the progression of dilated cardiomyopathy in TG9 mice. This D3 induction localized to cardiomyocytes and was associated with a decrease in myocardial thyroid hormone signaling., Conclusions: Cardiac D3 is induced in a mouse model of dilated cardiomyopathy, indicating that D3 induction may be a general response to diverse forms of cardiomyopathy.

Specific niches within the tumor bone marrow (BM) microenvironment afford a sanctuary for multiple myeloma (MM) clones due to stromal cell-tumor cell interactions, which confer survival advantage and drug resistance. Defining the sequelae of tumor cell interactions within the MM niches on an individualized basis may provide the rationale for personalized therapies. To mimic the MM niche, we here describe a new 3D co-culture ex-vivo model in which primary MM patient BM cells are co-cultured with mesenchymal stem cells (MSC) in a hydrogel 3D system. In the 3D model, MSC with conserved phenotype (CD73+CD90+CD105+) formed compact clusters with active fibrous connections, and retained lineage differentiation capacity. Extracellular matrix molecules, integrins, and niche related molecules including N-cadherin and CXCL12 are expressed in 3D MSC model. Furthermore, activation of osteogenesis (MMP13, SPP1, ADAMTS4, and MGP genes) and osteoblastogenic differentiation was confirmed in 3D MSC model. Co-culture of patient-derived BM mononuclear cells with either autologous or allogeneic MSC in 3D model increased proliferation of MM cells, CXCR4 expression, and SP cells. We carried out immune profiling to show that distribution of immune cell subsets was similar in 3D and 2D MSC model systems. Importantly, resistance to novel agents (IMiDs, bortezomib, carfilzomib) and conventional agents (doxorubicin, dexamethasone, melphalan) was observed in 3D MSC system, reflective of clinical resistance. This 3D MSC model may therefore allow for studies of MM pathogenesis and drug resistance within the BM niche. Importantly, ongoing prospective trials are evaluating its utility to inform personalized targeted and immune therapy in MM.

EZH2, a member of the polycomb protein group, is an important methyltransferase that is overexpressed in various neoplasms. We found that in small cell B-cell lymphomas, EZH2 is expressed in <40% of neoplastic cells, with heterogenous signal intensity. In aggressive B-cell lymphomas, 70-100% of tumor cells were positive for EZH2 expression with high signal intensity, which correlated with a high proliferation rate. We investigated the potential signaling molecules that regulate EZH2 overexpression in aggressive B-cell lymphomas and found that 80% of cases of EZH2-positive diffuse large B-cell lymphoma show high p-ERK1/2 expression (average ~57% tumor cell positivity). In contrast, only a small percentage of tumor cells (~10%) show p-ERK1/2 expression in Burkitt lymphoma and double hit lymphoma. On average, 91 and 76% of neoplastic cells were positive for MYC expression in Burkitt lymphoma and double hit lymphoma, respectively, while only 20% neoplastic cells were positive for MYC expression in diffuse large B-cell lymphoma. None of the aggressive B-cell lymphomas showed significant p-STAT3 expression in EZH2-overexpressed cases. The correlation of EZH2 expression with aggressive behavior and proliferation rate in B-cell neoplasms suggests that this molecule may function as an oncogenic protein in these neoplasms, with possible regulation by different signaling cascades in different types of aggressive B-cell lymphomas: p-ERK-related signaling in diffuse large B-cell lymphoma, and MYC-related signaling in Burkitt lymphoma and double hit lymphoma. Furthermore, EZH2 and associated signaling cascades may serve as therapeutic targets for the treatment of aggressive B-cell lymphomas.

We analyzed plasma cell populations in bone marrow samples from 353 patients with possible bone marrow involvement by a plasma cell neoplasm, using FLOCK (FLOw Clustering without K), an unbiased, automated, computational approach to identify cell subsets in multidimensional flow cytometry data. FLOCK identified discrete plasma cell populations in the majority of bone marrow specimens found by standard histologic and immunophenotypic criteria to be involved by a plasma cell neoplasm (202/208 cases; 97%), including 34 cases that were negative by standard flow cytometric analysis that included clonality assessment. FLOCK identified discrete plasma cell populations in only a minority of cases negative for involvement by a plasma cell neoplasm by standard histologic and immunophenotypic criteria (38/145 cases; 26%). Interestingly, 55% of the cases negative by standard analysis, but containing a FLOCK-identified discrete plasma cell population, were positive for monoclonal gammopathy by serum protein electrophoresis and immunofixation. FLOCK-identified and quantitated plasma cell populations accounted for 3.05% of total cells on average in cases positive for involvement by a plasma cell neoplasm by standard histologic and immunophenotypic criteria, and 0.27% of total cells on average in cases negative for involvement by a plasma cell neoplasm by standard histologic and immunophenotypic criteria (p<0.0001; area under the curve by ROC analysis=0.96). The presence of a FLOCK-identified discrete plasma cell population was predictive of the presence of plasma cell neoplasia with a sensitivity of 97%, compared with only 81% for standard flow cytometric analysis, and had specificity of 74%, PPV of 84% and NPV of 95%. FLOCK analysis, which has been shown to provide useful diagnostic information for evaluating patients with suspected systemic mastocytosis, is able to identify neoplastic plasma cell populations analyzed by flow cytometry, and may be helpful in the diagnostic evaluation of bone marrow samples for involvement by plasma cell neoplasia., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

SEE HOHLFELD AND SCHULZE-KOOPS DOI101093/BRAIN/AWW053 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Inclusion body myositis and T cell large granular lymphocytic leukaemia are rare diseases involving pathogenic cytotoxic CD8+ T cells. After encountering four patients with both disorders, we prospectively screened 38 patients with inclusion body myositis for the presence of expanded large granular lymphocyte populations by standard clinical laboratory methods (flow cytometry, examination of blood smears, and T cell receptor gene rearrangements), and performed muscle immunohistochemistry for CD8, CD57, and TIA1. Most (22/38; 58%) patients with inclusion body myositis had aberrant populations of large granular lymphocytes in their blood meeting standard diagnostic criteria for T cell large granular lymphocytic leukaemia. These T cell populations were clonal in 20/20 patients and stably present on follow-up testing in 15 patients a median of 350 days later. T cell aberrant loss of CD5 or gain of expression of CD16 and CD94 were common (19/42, 45%). In comparison, 2/15 (14%) age-matched patients with dermatomyositis, polymyositis, or necrotizing myopathy, and 0/20 (0%) age-matched healthy subjects had large granular lymphocyte expansions, with none of these patients having T cell aberrant expression of CD5, CD16 or CD94. Reduced blood CD4/CD8 ratio, increased blood CD8 count, and lymphocytosis were additional biomarkers highly correlated with flow cytometry-measured large granular lymphocyte expansions. Cross-sectional data suggested more aggressive disease in patients with such expansions than without. Muscle immunohistochemistry demonstrated invasion of large granular lymphocytes into muscle in 15/15 inclusion body myositis patients but in only 1/28 patients with dermatomyositis or polymyositis. The extent of CD8+ and CD57+ cells in inclusion body myositis muscle correlated with the size of blood large granular lymphocyte populations. Myofibre-invading cells expressed CD57, a marker of persistent T cell exposure to antigen and T cell aggressiveness. In many patients with inclusion body myositis, the autoimmune T cell expansion has evolved into a neoplastic-like or overtly neoplastic disorder, perhaps contributing to its relative refractoriness to immune-directed therapies previously reported., (© The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

More than 90% of drugs with preclinical activity fail in human trials, largely due to insufficient efficacy. We hypothesized that adequately powered trials of patient-derived xenografts (PDX) in mice could efficiently define therapeutic activity across heterogeneous tumors. To address this hypothesis, we established a large, publicly available repository of well-characterized leukemia and lymphoma PDXs that undergo orthotopic engraftment, called the Public Repository of Xenografts (PRoXe). PRoXe includes all de-identified information relevant to the primary specimens and the PDXs derived from them. Using this repository, we demonstrate that large studies of acute leukemia PDXs that mimic human randomized clinical trials can characterize drug efficacy and generate transcriptional, functional, and proteomic biomarkers in both treatment-naive and relapsed/refractory disease., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objectives: We validated the automatic nucleated RBC (nRBC) count on a Sysmex XE-5000 hematology analyzer (Sysmex Corporation, Kobe, Japan) and then evaluated the frequency of nRBCs in our patient population., Methods: We correlated automated nRBC enumeration by the Sysmex XE-5000 hematology analyzer on 463 peripheral blood (PB) samples with the manual nRBC count. Results from 360,504 consecutive blood samples were reviewed to determine the frequency of nRBCs in various patient populations in our hospital., Results: There was a strong correlation between the automated and manual nRBC count (Pearson's r = 0.97). Frequency of nRBCs varied in different patient populations and was significantly higher in the presence of other morphology flags or abnormal CBC parameters. Low-level nRBCs (0.2%-1.3%) were detected in 0.5% of samples with otherwise normal parameters., Conclusions: The automated method offers many advantages for high-throughput laboratories, including faster turnaround time, labor savings, and high reliability. Automated nRBC measurement allowed us to recognize a group of individuals who have low-level circulating nRBCs with otherwise normal CBC parameters. Nucleated RBC levels below 1.5% as detected by the automated count may be present in patients without increased erythropoiesis or a pathologic bone marrow process., (© American Society for Clinical Pathology, 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Many epithelial neoplasms can be analyzed by flow cytometry (FC), particularly from serous cavity effusion samples, using EpCAM, a cell adhesion molecule expressed on most normal epithelial cells and expressed at a higher level in most epithelial neoplasms. A simple 3-color flow cytometric panel can provide a high sensitivity and specificity compared to cytomorphology. FC provides more rapid immunophenotyping than conventional immunohistochemical staining, can identify rare malignant cells that could be missed by a cytological exam alone, and can be utilized to evaluate limited samples such as cerebrospinal fluid or fine-needle aspiration samples. Flow cytometric analysis for epithelial antigens can be combined with DNA ploidy analysis or assessment of the nucleus-to-cytoplasm ratio. Panels of flow cytometric markers are useful for the assessment of pediatric nonhematopoietic neoplasms, including neuroblastomas, primitive neuroectodermal tumors, Wilms' tumor, rhabdomyosarcomas, germ cell tumors, and hemangiopericytomas, as well as small-round-blue-cell tumors in adults, including small-cell carcinomas., (© 2016 S. Karger AG, Basel.)

Objectives: In our high-sensitivity flow cytometric approach for systemic mastocytosis (SM), we identified mast cell event clustering as a new diagnostic criterion for the disease., Methods: To objectively characterize mast cell gated event distributions, we performed cluster analysis using FLOCK, a computational approach to identify cell subsets in multidimensional flow cytometry data in an unbiased, automated fashion., Results: FLOCK identified discrete mast cell populations in most cases of SM (56/75 [75%]) but only a minority of non-SM cases (17/124 [14%]). FLOCK-identified mast cell populations accounted for 2.46% of total cells on average in SM cases and 0.09% of total cells on average in non-SM cases (P < .0001) and were predictive of SM, with a sensitivity of 75%, a specificity of 86%, a positive predictive value of 76%, and a negative predictive value of 85%., Conclusions: FLOCK analysis provides useful diagnostic information for evaluating patients with suspected SM, and may be useful for the analysis of other hematopoietic neoplasms., (Copyright© by the American Society for Clinical Pathology.)

Purpose: PD-1/PD-L1 signaling promotes tumor growth while inhibiting effector cell-mediated antitumor immune responses. Here, we assessed the impact of single and dual blockade of PD-1/PD-L1, alone or in combination with lenalidomide, on accessory and immune cell function as well as multiple myeloma cell growth in the bone marrow (BM) milieu., Experimental Design: Surface expression of PD-1 on immune effector cells, and PD-L1 expression on CD138(+) multiple myeloma cells and myeloid-derived suppressor cells (MDSC) were determined in BM from newly diagnosed (ND) multiple myeloma and relapsed/refractory (RR) multiple myeloma versus healthy donor (HD). We defined the impact of single and dual blockade of PD-1/PD-L1, alone and with lenalidomide, on autologous anti-multiple myeloma immune response and tumor cell growth., Results: Both ND and RR patient multiple myeloma cells have increased PD-L1 mRNA and surface expression compared with HD. There is also a significant increase in PD-1 expression on effector cells in multiple myeloma. Importantly, PD-1/PD-L1 blockade abrogates BM stromal cell (BMSC)-induced multiple myeloma growth, and combined blockade of PD-1/PD-L1 with lenalidomide further inhibits BMSC-induced tumor growth. These effects are associated with induction of intracellular expression of IFNγ and granzyme B in effector cells. Importantly, PD-L1 expression in multiple myeloma is higher on MDSC than on antigen-presenting cells, and PD-1/PD-L1 blockade inhibits MDSC-mediated multiple myeloma growth. Finally, lenalidomide with PD-1/PD-L1 blockade inhibits MDSC-mediated immune suppression., Conclusions: Our data therefore demonstrate that checkpoint signaling plays an important role in providing the tumor-promoting, immune-suppressive microenvironment in multiple myeloma, and that PD-1/PD-L1 blockade induces anti-multiple myeloma immune response that can be enhanced by lenalidomide, providing the framework for clinical evaluation of combination therapy., (©2015 American Association for Cancer Research.)

Fetal hemoglobin (HbF, α2γ2) induction is a well-validated strategy for sickle cell disease (SCD) treatment. Using a small-molecule screen, we found that UNC0638, a selective inhibitor of EHMT1 and EHMT2 histone methyltransferases, induces γ-globin expression. EHMT1/2 catalyze mono- and dimethylation of lysine 9 on histone 3 (H3K9), raising the possibility that H3K9Me2, a repressive chromatin mark, plays a role in silencing γ-globin expression. In primary human adult erythroid cells, UNC0638 and EHMT1 or EHMT2 short hairpin RNA-mediated knockdown significantly increased γ-globin expression, HbF synthesis, and the percentage of cells expressing HbF. At effective concentrations, UNC0638 did not alter cell morphology, proliferation, or erythroid differentiation of primary human CD34(+) hematopoietic stem and progenitor cells in culture ex vivo. In murine erythroleukemia cells, UNC0638 and Ehmt2 CRISPR/Cas9-mediated knockout both led to a marked increase in expression of embryonic β-globin genes Hbb-εy and Hbb-βh1. In primary human adult erythroblasts, chromatin immunoprecipitation followed by sequencing analysis revealed that UNC0638 treatment leads to genome-wide depletion in H3K9Me2 and a concomitant increase in the activating mark H3K9Ac, which was especially pronounced at the γ-globin gene region. In RNA-sequencing analysis of erythroblasts, γ-globin genes were among the most significantly upregulated genes by UNC0638. Further increase in γ-globin expression in primary human adult erythroid cells was achieved by combining EHMT1/2 inhibition with the histone deacetylase inhibitor entinostat or hypomethylating agent decitabine. Our data provide genetic and pharmacologic evidence that EHMT1 and EHMT2 are epigenetic regulators involved in γ-globin repression and represent a novel therapeutic target for SCD., (© 2015 by The American Society of Hematology.)