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Aim: This study was to explore role of immune landscape and the immune cells in acute lymphoblastic leukemia (ALL) progression., Background: The most prevalent genetic alteration in childhood ALL is the ETV6-RUNX1 fusion. The increased proliferation of B progenitor cells could expedite the disease's progression due to irregularities in the cell cycle. Nevertheless, the mechanisms by which particular cell clusters influence the cell cycle and promote the advancement of ALL are still not well understood., Objective: This study was to explore role of immune landscape and the immune cells in ALL progression., Methods: Single-cell RNA sequencing (scRNA-seq) data of ETV6-RUNX1 and healthy pediatric samples obtained from GSE132509 were clustered and annotated using the Seurat package, and differentially highly expressed genes identified in each cluster were analyzed using DAVID for pathway annotation. Chromosome amplification and deletion were analyzed using the inferCNV package. SCENIC evaluated the regulation of transcription factors and target gene formation in cells. cellphoneDB and CellChat were served to infer ligand-receptor pairs that mediate interactions between subpopulations. The role of the target gene in regulating ALL progression was assessed using RT-qPCR, Transwell and scratch healing assays., Results: The bone marrow mononuclear cells (BMMCs) from ETV6-RUNX1 and healthy pediatric samples in GSE132509 were divided into 11 clusters, and B cell cluster 1 was identified as B progenitor cell, which was amplified on chromosome 6p. B progenitor cells were divided into seven clusters. Expression levels of amplified genes in chromosome 6p of B progenitor cell cluster 5 were the highest, and its specific highly expressed genes were annotated to pathways promoting cell cycle progression. Regulons formed in B progenitor cell cluster 5 were all involved in promoting cell cycle progression, so it was regarded as the B progenitor cell cluster that drives cell cycle progression. The key regulator of the B progenitor cell is E2F1, which promotes the migration and invasion ability of the cell line HAP1. The major ligand-receptor pairs that mediate the communication of B progenitor cell cluster 5 with cytotoxic NK/T cells or naive T cells included FAM3C-CLEC2D, CD47-SIRPG, HLAE-KLRC2, and CD47-KLRC2. HLAE-KLRC1 and TGFB1-(TGFBR1+TGFBR2)., Conclusion: This study outlined the immune cell landscape of ETV6-RUNX1 ALL and identified chromosome 6p amplification in B progenitor cells, described the major B progenitor cell cluster driving cell cycle progression and its potential regulatory mechanisms on NK cells and T cells, providing cellular and molecular insights into ETV6-RUNX1 ALL., Competing Interests: The authors declare that they have no competing interests., (© 2024 Qu et al.)

Pro-B- and pre-B-cells are consecutive entities in early B-cell development, representing cells of origin for B-cell precursor acute lymphoid leukemia (BCP-ALL). Normal B-cell differentiation is critically regulated by specific transcription factors (TFs). Accordingly, TF-encoding genes are frequently deregulated or mutated in BCP-ALL. Recently, we described TF-codes which delineate physiological activities of selected groups of TF-encoding genes in hematopoiesis including B-cell development. Here, we exploited these codes to uncover regulatory connections between particular TFs in pro-B- and pre-B-cells via an analysis of developmental TFs encoded by NKL and TALE homeobox genes and by ETS and T-box genes. Comprehensive expression analyses in BCP-ALL cell lines helped identify validated models to study their mutual regulation in vitro. Knockdown and overexpression experiments and subsequent RNA quantification of TF-encoding genes in selected model cell lines revealed activating, inhibitory or absent connections between nine TFs operating in early B-cell development, including HLX, MSX1, IRX1, MEIS1, ETS2, ERG, SPIB, EOMES, and TBX21. In addition, genomic profiling revealed BCP-ALL subtype-specific copy number alterations of ERG at 21q22, while a deletion of the TGFbeta-receptor gene TGFBR2 at 3p24 resulted in an upregulation of EOMES . Finally, we combined the data to uncover gene regulatory networks which control normal differentiation of early B-cells, collectively endorsing more detailed evaluation of BCP-ALL subtypes.

Little is known about the transition mechanisms that govern early lymphoid lineage progenitors from common lymphoid progenitors (CLP). Pellino2 (PELI2) is a newly discovered E3 ubiquitin ligase, which plays important roles in inflammation and the immune system. However, the physiological and molecular roles of PELI2 in the differentiation of immune cells are largely unknown. Here, by using a conditional knockout mouse model, we demonstrated that PELI2 is required for early B-cell development and stressed hematopoiesis. PELI2 interacted with and stabilized PU.1 via K63-polyubiquitination to regulate IL-7R expression. The defects of B-cell development induced by PELI2 deletion were restored by overexpression of PU.1. Similarly, PELI2 promoted TCF3 protein stability via K63-polyubiquitination to regulate IL-7R expression, which is required for the proliferation of B-cell precursor acute lymphoblastic leukemia (BCP-ALL) cells. These results underscore the significance of PELI2 in both normal B lymphopoiesis and malignant B-cell acute lymphoblastic leukemia via the regulation of IL-7R expression, providing a potential therapeutic approach for BCP-ALL.

Involvement of the cervix with acute lymphoblastic leukaemia (ALL) is extremely rare. In this case report, we discuss an unmarried woman in her early 20s, who presented in the emergency with lower abdominal pain and irregular vaginal bleeding for 1 month. Clinical examination and imaging revealed a large cervical mass probably neoplastic with obstructive uropathy. On evaluation, she was diagnosed incidentally with CALLA-positive precursor B cell ALL in peripheral blood flow cytometry. Involvement of B cell ALL in cervical mass was confirmed by histopathological examination of cervical biopsy and immunohistochemistry markers. Her history was not suggestive of signs and symptoms pertaining to leukaemia. Literature is sparse with only a few cases reporting cervical leukaemic infiltration. The present case report is a rarest case where the primary/initial presentation of precursor B cell ALL was seen with cervical involvement and obstructive uropathy mimicking characteristics of advanced cervical malignancy., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: The specific mechanisms driving autoimmunity in Graves' disease (GD) remain largely unknown. Kappa-deleting recombination excision circles (KRECs) are circular DNA molecules generated during B cell maturation in the bone marrow which provide a measure of B cell production and proliferation. We aimed to investigate the association between KRECs and B cell subpopulations, with thyroid status and clinical outcome in GD patients., Methods: Kappa-deleting recombination excision circles were measured by quantitative real-time PCR using a triple-insert plasmid control in 132 GD patients and 140 healthy controls. In addition, KRECs in GD patients on withdrawal of antithyroid drug (ATD) and 6-10 weeks later were analysed according to a clinical outcome at 1 year. Flow cytometry was performed on isolated CD19+ B cells to quantitate 7 B lymphocyte subpopulations in 65 GD patients., Results: Circulating KRECs were higher in GD vs. controls (P = 1.5 × 10-9) and demonstrated a positive correlation to thyroid hormones and autoantibodies (free thyroxine: P = 2.14 × 10-5, rho = .30; free triiodothyronine: P = 1.99 × 10-7, rho = .37; thyroid stimulating hormone receptor autoantibodies: P = 1.36 × 10-5, rho = .23). Higher KRECs in GD patients 6-10 weeks after ATD withdrawal were associated with relapse of hyperthyroidism at 1 year (P = .04). The KRECs were positively correlated to the total CD19+ B cell count (P = 3.2 × 10-7)., Conclusions: This study reports a robust association between KRECs and GD, highlighting the importance of B cells in the pathogenesis of GD and the influence of thyroid status on B cell activity. The findings indicate a potential role for KRECs as a marker of disease activity and outcome in GD., (© The Author(s) 2023. Published by Oxford University Press on behalf of European Society of Endocrinology.)

Large B-cell lymphoma of immune-privileged sites (LBCL-IP) arise in immune sanctuaries including the testis and central nervous system (CNS). After initially reaching complete response, relapses occur in almost 50% of patients, typically at other immune-privileged sites. Resolution of the clonal relationships and evolutionary patterns of LBCL-IP is required to understand the unique clinical behavior. We collected a unique set of 33 primary-relapse LBCL-IP sample pairs and performed next-generation sequencing for copy number, mutation, translocation, and immunoglobulin clonality analysis. All LBCL-IP sample pairs were clonally related, and both tumors developed from a common progenitor cell (CPC) with MYD88 and TBL1XR1 mutations and/or BCL6 translocations in 30/33 cases, indicating that these are early genetic events. This was succeeded by intermediate genetic events including shared, as well as unique alterations in targets of aberrant somatic hypermutation (aSHM), CD79B mutations, and 9p21.3/CDKN2A loss. Genetic alterations in genes involved in immune escape (HLA, CD274/PDCD1LG2) were predominantly unique in primary and relapse samples and thus considered late genetic events. Together, this study indicates that primary and relapsed LBCL-IP follow an early parallel evolutionary pattern where the CPC contains genetic alterations that support prolonged survival/proliferation and retention in a memory B-cell state, followed by germinal center reentry, aSHM and immune escape., Significance: Genomic analyses reveal that primary and relapse LBCL-IP originate from a common progenitor cell with a small set of genetic alterations, followed by extensive parallel diversification, elucidating the clonal evolution of LBCL-IP., (©2023 American Association for Cancer Research.)

Borderline rejection (BL) in renal transplantation is associated with decreased allograft survival, yet many patients with BL maintain stable graft function. Identifying patients with early BL at risk for shortened allograft survival would allow for timely targeted therapeutic intervention aimed at improving outcomes. 851/1187 patients transplanted between 2013-18 underwent early biopsy (0-4 mos). 217/851 (25%) had BL and were compared to 387/851 without significant inflammation (NI). Serial surveillance and for-cause biopsies and seven-year follow-up were used to evaluate histological and clinical progression. To identify high-risk patients, we examined clinical/histological parameters using regression and non-linear dimensionality reduction (tSNE) and a biomarker based on peripheral blood transitional-1 B cell (T1B) IL-10/TNFα ratio. Compared to NI, early BL was associated with increased progression to late acute rejection (AR; 5-12 mos), premature interstitial fibrosis and tubular atrophy (IFTA) and decreased seven-year graft survival. However, decreased graft survival was limited to BL patients who progressed to late AR or IFTA, and was not influenced by treatment. Although tSNE clustered patients into groups based on clinical factors, the ability of these factors to risk stratify BL patients was modest. In contrast, a low T1B IL-10/TNFα ratio at 3 months identified BL patients at high risk for progression to AR (ROC AUC 0.87) and poor 7-yr graft survival (52% vs. 92%, p=0.003), while BL patients with a high ratio had similar graft survival to patients with NI (91%, p=NS). Thus, progressive early allograft inflammation manifested as BL that progresses to late AR in the first post-transplant year represents a high-risk clinical state for poor allograft outcomes. Such high-risk status can be predicted by the T1B IL-10/TNFα ratio before irreversible scarring sets in, thus allowing timely risk stratification., (Copyright © 2022 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Homeobox genes encode transcription factors regulating basic developmental processes. They are arranged according to sequence similarities of their conserved homeobox in 11 classes, including TALE. Recently, we have reported the so-called TALE-code. This gene signature describes physiological expression patterns of all active TALE-class homeobox genes in the course of hematopoiesis. The TALE-code allows the evaluation of deregulated TALE homeobox genes in leukemia/lymphoma. Here, we extended the TALE-code to include the stages of pro-B-cells and pre-B-cells in early B-cell development. Detailed analysis of the complete lineage of B-cell differentiation revealed expression of TALE homeobox genes IRX1 and MEIS1 exclusively in pro-B-cells. Furthermore, we identified aberrant expression of IRX2, IRX3 and MEIS1 in patients with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) which originates from early B-cell progenitors. The data showed correlated activities of deregulated TALE-class members with particular BCP-ALL subtype markers, namely IRX2 with TCF3/E2A-fusions, IRX3 with ETV6/TEL-fusions, and MEIS1 with KMT2A/MLL-fusions. These correlations were also detected in BCP-ALL cell lines which served as experimental models. We performed siRNA-mediated knockdown experiments and reporter gene assays to analyze regulatory connections. The results showed mutual activation of IRX1 and TCF3. In contrast, IRX2 directly repressed wild-type TCF3 while the fusion gene TCF3::PBX1 lost the binding site for IRX2 and remained unaltered. IRX3 mutually activated fusion gene ETV6::RUNX1 while activating itself by aberrantly expressed transcription factor KLF15. Finally, KMT2A activated MEIS1 which in turn supported the expression of IRX3. In summary, we revealed normal TALE homeobox gene expression in early B-cell development and identified aberrant activities of IRX2, IRX3 and MEIS1 in particular subtypes of BCP-ALL. Thus, these TALE homeobox genes may serve as novel diagnostic markers and therapeutic targets.

Background: An atypical form of Burkitt leukemia/lymphoma (BL), BL with a phenotype of precursor B-cells (preBLL), is listed in the WHO Classification. Recent reports suggested that preBLL and classical BL could be distinguished by the differences in IG-MYC translocation architecture and an additional mutated genes profile. The characteristics of classical BL are IG-MYC by aberrant somatic hypermutation or class switch recombination, and BL-specific gene mutations such as MYC, ID3, and CCND3. Meanwhile, preBLL is characterized by IG-MYC due to aberrant VDJ recombination and mutations in NRAS and KRAS. However, it is not clear whether all preBLL cases can be differentiated. This report investigated the molecular characteristics of an infant preBLL case, with a more advanced stage of maturity than typical preBLL., Case: The patient showed BL-like morphology with IGH-MYC rearrangement. In the immunophenotyping, CD20 and surface immunoglobulin were negative, whereas other markers were consistent with BL. To evaluate the genetic contribution, we performed whole-exome sequencing. The breakpoint analysis revealed the IG-MYC occurred due to an aberrant VDJ recombination. Meanwhile, additional somatic mutations were detected in FBXO11, one of the mutant genes specific to BL. In the analysis of the specimen in complete remission, mutation in KRAS, frequently mutated in preBLL, was detected with low frequency, suggesting somatic mosaicism., Conclusion: The present case showed the characteristics of both typical preBLL and classical BL. Because preBLL includes atypical cases such as the present case, further studies are required to elucidate preBLL features., (© 2021 The Authors. Cancer Reports published by Wiley Periodicals LLC.)

Background: The aberrant distribution of peripheral B cell subsets is associated with the pathogenesis of a variety of inflammatory and autoimmune diseases. However, the distribution of peripheral B cell subsets in patients with idiopathic dilated cardiomyopathy (DCM) remains to be elucidated., Methods: Twenty-seven patients with idiopathic DCM (DCM group), 18 control patients with heart failure (HF group) and 21 healthy individuals (HC group) were included in this study. Peripheral B cell subsets were analysed using multicolour flow cytometry. The plasma β1 adrenergic receptor (β1-AR) autoantibody titre was determined using ELISA. Additionally, clinical features were also collected., Results: Compared with the HF and HC groups, the percentage of B1 cells was significantly decreased, whereas the percentage of transitional B cells (Tr) was significantly increased in the DCM group. Notably, the percentage of B1 cells was significantly lower in patients with β1-AR autoantibody-positive DCM than in β1-AR autoantibody-negative patients. The correlation analysis showed that the percentage of B1 cells was negatively correlated with N-terminal pro-brain natriuretic peptide (NT-proBNP) levels and positively correlated with the left ventricular ejection fraction in patients with DCM., Conclusion: As shown in the present study, the percentage of B1 cells in the peripheral blood of patients with idiopathic DCM is abnormally decreased, especially in β1-AR autoantibody-positive patients, while the percentage of Tr cells is significantly increased, indicating that B1 cells and Tr cells may be implicated in the pathogenesis of idiopathic DCM. The decrease in the percentage of B1 cells is directly related to the severity of DCM., (© 2022. The Author(s).)

Interleukin-7 receptor α (encoded by IL7R) is essential for lymphoid development. Whether acute lymphoblastic leukemia (ALL)-related IL7R gain-of-function mutations can trigger leukemogenesis remains unclear. Here, we demonstrate that lymphoid-restricted mutant IL7R, expressed at physiological levels in conditional knock-in mice, establishes a pre-leukemic stage in which B-cell precursors display self-renewal ability, initiating leukemia resembling PAX5 P80R or Ph-like human B-ALL. Full transformation associates with transcriptional upregulation of oncogenes such as Myc or Bcl2, downregulation of tumor suppressors such as Ikzf1 or Arid2, and major IL-7R signaling upregulation (involving JAK/STAT5 and PI3K/mTOR), required for leukemia cell viability. Accordingly, maximal signaling drives full penetrance and early leukemia onset in homozygous IL7R mutant animals. Notably, we identify 2 transcriptional subgroups in mouse and human Ph-like ALL, and show that dactolisib and sphingosine-kinase inhibitors are potential treatment avenues for IL-7R-related cases. Our model, a resource to explore the pathophysiology and therapeutic vulnerabilities of B-ALL, demonstrates that IL7R can initiate this malignancy., (© 2021. The Author(s).)

Cell adhesion to stromal support and the associated intracellular signaling are central to drug resistance, therefore blocking both has been effective in increasing drug sensitization in leukemia. The stromal Ser/Thr protein kinase C (PKC) has been found to be important for conferring protection to leukemic cells. We aimed at elucidating the intracellular signals connected to cell adhesion and to stromal PKC. We found that NF-κB and Akt were up-regulated in mesenchymal stem cells (MSC) after binding of B-cell acute lymphoblastic leukemia (B-ALL) cells. Nevertheless, Akt inhibition did not induce B-ALL cell detachment. In spite of a clear activation of the NF-κB signaling pathway after B-ALL cell binding (up-regulation NF-κB1/2, and down-regulation of the IKBε and IKBα inhibitors) and an important reduction in cell adhesion after NF-κB inhibition, sensitization to the drug treatment was not observed. This was opposite to the PKC inhibitors Enzastaurin and HKPS, a novel chimeric peptide inhibitor, that were able to increase sensitization to dexamethasone, methotrexate, and vincristine. PLCγ1, Erk1/2, and CREB appear to be related to PKC signaling and PKC effect on drug sensitization since they were contra-regulated by HKPS when compared to dexamethasone-treated cells. Additionally, PKC inhibition by HKPS, but not by Enzastaurin, in MSC reduced the activity of three ABC transporters in leukemic cells treated with dexamethasone, a new indirect mechanism to increase sensitization to drug treatment in B-ALL cells. Our results show the validity of targeting the functional characteristic acquired and modulated during cell-to-cell interactions occurring in the leukemic niche.

Objectives: This study aims to retrospectively assess C-lectin-like molecule 1 (CLL-1) bimodal expression on CD34+ blasts in acute myeloid leukemia (AML) patients (total N = 306) and explore potential CLL-1 bimodal associations with leukemia and patient-specific characteristics., Methods: Flow cytometry assays were performed to assess the deeper immunophenotyping of CLL-1 bimodality. Cytogenetic analysis was performed to characterize the gene mutation on CLL-1-negative subpopulation of CLL-1 bimodal AML samples., Results: The frequency of a bimodal pattern of CLL-1 expression of CD34 + blasts ranged from 8% to 65% in the different cohorts. Bimodal CLL-1 expression was most prevalent in patients with MDS-related AML (P = .011), ELN adverse risk (P = .002), NPM1 wild type (WT, P = .049), FLT3 WT (P = .035), and relatively low percentages of leukemia-associated immunophenotypes (P = .006). Additional immunophenotyping analysis revealed the CLL-1 - subpopulation may consist of pre-B cells, immature myeloblasts, and hematopoietic stem cells. Furthermore, (pre)-leukemic mutations were detected in both CLL-1 + and CLL-1 - subfractions of bimodal samples (N = 3)., Conclusions: C-lectin-like molecule 1 bimodality occurs in about 25% of AML patients and the CLL-1 - cell population still contains malignant cells, hence it may potentially limit the effectiveness of CLL-1-targeted therapies and warrant further investigation., (© 2021 Genentech Inc. European Journal of Haematology published by John Wiley & Sons Ltd.)

PCR of TCR/Ig gene rearrangements is considered the method of choice for minimal residual disease (MRD) quantification in BCP-ALL, but flow cytometry analysis of leukemia-associated immunophenotypes (FCM-MRD) is faster and biologically more informative. FCM-MRD performed in 18 laboratories across seven countries was used for risk stratification of 1487 patients with BCP-ALL enrolled in the NOPHO ALL2008 protocol. When no informative FCM-marker was available, risk stratification was based on real-time quantitative PCR. An informative FCM-marker was found in 96.2% and only two patients (0.14%) had non-informative FCM and non-informative PCR-markers. The overall 5-year event-free survival was 86.1% with a cumulative incidence of relapse (CIR 5y ) of 9.5%. FCM-MRD levels on days 15 (HzR 4.0, p < 0.0001), 29 (HzR 2.7, p < 0.0001), and 79 (HzR 3.5, p < 0.0001) associated with hazard of relapse adjusted for age, cytogenetics, and WBC. The early (day 15) response associated with CIR 5y adjusted for day 29 FCM-MRD, with higher levels in adults (median 2.4 × 10 -2 versus 5.2 × 10 -3 , p < 0.0001). Undetectable FCM- and/or PCR-MRD on day 29 identified patients with a very good outcome (CIR 5y  = 3.2%). For patients who did not undergo transplantation, day 79 FCM-MRD > 10 -4 associated with a CIR 5y  = 22.1%. In conclusion, FCM-MRD performed in a multicenter setting is a clinically useful method for MRD-based treatment stratification in BCP-ALL.

Accurate knowledge of expression patterns/levels of commonly used MRD markers in regenerative normal-B-cell-precursors (BCP) is highly desirable to distinguish leukemic-blasts from regenerative-BCP for multicolor flow cytometry (MFC)-based measurable residual disease (MRD) assessment in B-lymphoblastic leukemia (B-ALL). However, the data highlighting therapy-related immunophenotypic-shift in regenerative-BCPs is scarce and limited to small cohort. Herein, we report the in-depth evaluation of immunophenotypic shift in regenerative-BCPs from a large cohort of BALL-MRD samples. Ten-color MFC-MRD analysis was performed in pediatric-BALL at the end-of-induction (EOI), end-of-consolidation (EOC), and subsequent-follow-up (SFU) time-points. We studied normalized-mean fluorescent intensity (nMFI) and coefficient-of-variation of immunofluorescence (CVIF) of CD10, CD19, CD20, CD34, CD38, and CD45 expression in regenerative-BCP (early, BCP1 and late, BCP2) from 200 BALL-MRD samples, and compared them with BCP from 15 regenerating control (RC) TALL-MRD samples and 20 treatment-naïve bone-marrow control (TNSC) samples. Regenerative-BCP1 showed downregulation in CD10 and CD34 expression with increased CVIF and reduced nMFI (p < 0.001), upregulation of CD20 with increased nMFI (p = 0.014) and heterogeneous CD45 expression with increased CVIF (p < 0.001). Immunophenotypic shift was less pronounced in the BCP2 compared to BCP1 compartment with increased CVIF in all but CD45 (p < 0.05) and reduced nMFI only in CD45 expression (p = 0.005). Downregulation of CD10/CD34 and upregulation of CD20 was higher at EOI than EOC and SFU time-points (p < 0.001). Regenerative-BCPs are characterized by the significant immunophenotypic shift in commonly used B-ALL-MRD markers, especially CD10 and CD34 expression, as compared to treatment-naïve BCPs. Therefore, the templates/database for BMRD analysis must be developed using regenerative-BCP., (© 2020 International Clinical Cytometry Society.)

A 62-year-old woman, who had a 16-year history of JAK2 V617F -mutated myeloproliferative neoplasm (MPN), developed Burkitt leukemia (BL) 16 months after treatment with ruxolitinib to control hydroxyurea-refractory conditions. BL cells were CD10 + , CD19 + , CD20 - , CD34 - , cytoplasmic CD79a + , and TdT + , and lacked surface immunoglobulins but expressed the cytoplasmic μ heavy chain. In the bone marrow, nuclear MYC + BL cells displaced the MPN tissues. t(8;14)(q24;q32) occurred at a CG dinucleotide within MYC exon 1 and at the IGHJ3 segment, and an N-like segment was inserted at the junction. The V-D-J sequence of the non-translocated IGH allele had the unmutated configuration. DNA from peripheral blood at a time of the course of MPN exhibited homozygous JAK2 V617F mutation, while that at BL development included both JAK2 V617F and wild-type DNAs. Although the association between JAK1/2 inhibitor therapy for MPN and secondary development of aggressive B-cell neoplasm remains controversial, this report suggests that, in selected patients, close monitoring of clonal B-cells in the BM is required before and during treatment with JAK1/2 inhibitors.

Genes encoding B lineage-restricted transcription factors are frequently mutated in B-lymphoid leukemias, suggesting a close link between normal and malignant B-cell development. One of these transcription factors is early B-cell factor 1 (EBF1), a protein of critical importance for lineage specification and survival of B-lymphoid progenitors. Here, we report that impaired EBF1 function in mouse B-cell progenitors results in reduced expression of Myc. Ectopic expression of MYC partially rescued B-cell expansion in the absence of EBF1 both in vivo and in vitro. Using chromosome conformation analysis in combination with ATAC-sequencing, chromatin immunoprecipitation-sequencing, and reporter gene assays, six EBF1-responsive enhancer elements were identified within the Myc locus. CRISPR-Cas9-mediated targeting of EBF1-binding sites identified one element of key importance for Myc expression and pro-B cell expansion. These data provide evidence that Myc is a direct target of EBF1. Furthermore, chromatin immunoprecipitation-sequencing analysis revealed that several regulatory elements in the Myc locus are targets of PAX5. However, ectopic expression of PAX5 in EBF1-deficient cells inhibits the cell cycle and reduces Myc expression, suggesting that EBF1 and PAX5 act in an opposing manner to regulate Myc levels. This hypothesis is further substantiated by the finding that Pax5 inactivation reduces requirements for EBF1 in pro-B-cell expansion. The binding of EBF1 and PAX5 to regulatory elements in the human MYC gene in a B-cell acute lymphoblastic leukemia cell line indicates that the EBF1:PAX5:MYC regulatory loop is conserved and may control both normal and malignant B-cell development., (© 2021 by The American Society of Hematology.)

Background: Impaired B-cell receptor (BCR) function has been associated with the progress of several B-cell malignancies. The spleen tyrosine kinase (SYK) represents a potential therapeutic target in a subset of B-cell neoplasias. In precursor B-acute lymphoblastic leukemia (B-ALL), the pathogenic role and therapeutic potential of SYK is still controversially discussed. We evaluate the application of the SYK inhibitor entospletinib (Ento) in pre- and pro-B-ALL cell lines, characterizing the biologic and molecular effects., Methods: SYK expression was characterized in pre-B-ALL (NALM-6) and pro-B-ALL cell lines (SEM and RS4;11). The cell lines were exposed to different Ento concentrations and the cell biological response analyzed by proliferation, metabolic activity, apoptosis induction, cell-cycle distribution and morphology. BCR pathway gene expression and protein modulations were further characterized., Results: Ento significantly induced anti-proliferative and pro-apoptotic effects in NALM-6 and SEM, while barely affecting RS4;11. Targeted RNAseq revealed pronounced gene expression modulation only in NALM-6, while Western Blot analyses demonstrated that vital downstream effector proteins, such as pAKT, pERK, pGSK3β, p53 and BCL-6, were affected by Ento exposure in the inhibitor-sensitive cell lines., Conclusion: Different acting modes of Ento, independent of pre-BCR dependency, were characterized, unexpected in SEM. Accordingly, SYK classifies as a potential target structure in a subset of pro-B-ALLs.

EBF1 and PAX5 mutations are associated with the development of B progenitor acute lymphoblastic leukemia (B-ALL) in humans. To understand the molecular networks driving leukemia in the Ebf1 +/- Pax5 +/- (dHet) mouse model for B-ALL, we interrogated the transcriptional profiles and chromatin status of leukemic cells, preleukemic dHet pro-B, and wild-type pro-B cells with the corresponding EBF1 and Pax5 cistromes. In dHet B-ALL cells, many EBF1 and Pax5 target genes encoding pre-BCR signaling components and transcription factors were down-regulated, whereas Myc and genes downstream from IL-7 signaling or associated with the folate pathway were up-regulated. We show that blockade of IL-7 signaling in vivo and methotrexate treatment of leukemic cells in vitro attenuate the expansion of leukemic cells. Single-cell RNA-sequencing revealed heterogeneity of leukemic cells and identified a subset of wild-type pro-B cells with reduced Ebf1 and enhanced Myc expression that show hallmarks of dHet B-ALL cells. Thus, EBF1 and Pax5 may safeguard early stage B cells from transformation to B-ALL by limiting IL-7 signaling, folate metabolism and Myc expression., (© 2020 Ramamoorthy et al.; Published by Cold Spring Harbor Laboratory Press.)

Epidemiological studies of atomic-bomb survivors have revealed an increased risk of lymphoid neoplasm (i.e. acute lymphoblastic leukemia) associated with radiation exposure. In particular, children are more susceptible to radiation-induced precursor lymphoid neoplasm than adults. Although ~75% of human lymphoid tumors are B-cell neoplasms, the carcinogenic risk associated with each stage of differentiation of B-cells after radiation exposure is poorly understood. Therefore, we irradiated mice at infancy or in young adulthood to investigate the effect of age at exposure on the risk of developing B-cell neoplasms. Histopathology was used to confirm the presence of lymphoid neoplasms, and the population of B-cell neoplasms was classified into the precursor B-cell (pro-B and pre-B cell) type and mature B-cell type, according to immunophenotype. The data revealed that precursor B-cell neoplasms were induced soon after radiation exposure in infancy or young adulthood, resulting in a greater risk of developing the neoplasms. This was particularly the case for the pro-B cell type after young adult exposure. Our findings suggest that exposure to radiation at young age increases the risk of developing precursor B-cell neoplasms in humans., (© The Author(s) 2020. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.)

Background: Measurable residual disease (MRD) assessment using multicolor flow cytometry (MFC) has become the center point of pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL) risk stratification and therapeutic management. The addition of new markers can improve the accuracy and applicability of MFC-based MRD assay further. Herein, we evaluated the utility of a new marker, CD304/neuropilin-1, in the assessment of MFC-based MRD., Methods: Expression patterns of CD304 were studied in leukemic blasts from BCP-ALL patients and in normal precursor B cells (NPBC) from uninvolved non-BCP-ALL bone marrow samples using 10-color MFC. MRD was monitored at end-of-induction (EOI; Days 35-40) and end-of-consolidation (Day 78-80) time points., Results: We studied CD304 expression in 300 pediatric BCP-ALL patients and found it positive in BCP-ALL blasts in 41.7% of diagnostic samples. It was significantly associated with ETV6-RUNX1 (p < .001) as well as BCR-ABL1 (p = .019) and inversely associated with TCF3-PBX1 fusion gene (p = .0012). It was found clearly negative in NPBC. EOI-MRD was detectable in 152/300 (50.7%; ≥0.01% in 35.33% and <0.01% in 15.33%) samples, in which CD304 was positive in 72/152 (47.4%) diagnostic and 63/152 (41.4%) MRD samples. It was positive in 45.7% (21/46) of low-level (<0.01%) MRD samples. In comparison with diagnostic samples, its expression was retained in 68.06% (49/72), lost in 31.94% (23/72), and gained in 14/80 (17.5%) of EOI-MRD samples., Conclusions: CD304 is commonly expressed in leukemic blasts of BCP-ALL. It is very useful in distinguishing residual disease from hematogones and is a fairly dependable marker. Hence, it is a valuable addition for enhancing the sensitivity and applicability of MFC-based MRD assay in BCP-ALL., (© 2020 International Clinical Cytometry Society.)

The tumor microenvironment is a dynamic and interactive supporting network of various components, including blood vessels, cytokines, chemokines, and immune cells, which sustain the tumor cell's survival and growth. Murine models of lymphoma are useful to study tumor biology, the microenvironment, and mechanisms of response to therapy. Lymphomas are heterogeneous hematologic malignancies, and the complex microenvironment from which they arise and their multifaceted genetic basis represents a challenge for the generation and use of an appropriate murine model. So, it is important to choose the correct methodology. Recently, we supported the first evidence on the pro-oncogenic action of IBTK in Myc-driven B cell lymphomagenesis in mice, inhibiting apoptosis in the pre-cancerous stage. We used the transgenic Eμ-myc mouse model of non-Hodgkin's lymphoma and Ibtk hemizygous mice to evaluate the tumor development of Myc-driven lymphoma. Here, we report that the allelic loss of Ibtk alters the immunophenotype of Myc-driven B cell lymphomas, increasing the rate of pre-B cells and affecting the tumor microenvironment in Eμ-myc mice. In particular, we observed enhanced tumor angiogenesis, increasing pro-angiogenic and lymphangiogenic factors, such as VEGF, MMP-9, CCL2, and VEGFD, and a significant recruitment of tumor-associated macrophages in lymphomas of Ibtk +/- Eμ-myc compared to Ibtk +/+ Eμ-myc mice. In summary, these results indicate that IBTK haploinsufficiency promotes Myc tumor development by modifying the tumor microenvironment.

Background: Burkitt leukemia (BL) with the precursor B-cell immunophenotype is a rarely reported condition. The prognosis of such patients is similar to that of classic BL. However, the combination of chromosomal translocations associated with bcl-2 and c-myc rearrangement has a poor prognosis., Observations: An 11-year-old child presented with fever and weakness. Bone marrow aspiration showed morphologically L1 type blasts and flow cytometry analysis was compatible with precursor B-cell immunophenotype. Cytogenetic analysis revealed a combination of t(8;14) and t(14;l8)., Conclusions: The combination of t(8;14) and t(14;l8) can exhibit different immunophenotypical and morphologic features in leukemias.

B-cell progenitors (hematogones) are markedly decreased or completely absent in the bone marrows of myelodysplastic syndromes (MDS), and the finding is considered as an important feature in MDS flow cytometry immunophenotyping. We studied CD34+ hematogones as a proportion of total CD34+ cells in 160 treatment naïve low grade primary MDS patients, consecutively collected over a two-year period. While confirming that the median CD34 + hematogones was significantly decreased (1.08%, 0%, to 67.86%), we observed variably preserved CD34 + hematogones in some MDS patients. Using a 5% cutoff, a total of 46 (29%) MDS patients had ≥5% CD34 + hematogones, significantly overrepresented by MDS with ring sideroblasts (RS) (MDS-RS) (18/40, 45%, vs. 28/120, 23%, P = 0.015). While we did not observe unique features among MDS-RS, mutations were noticeably absent in a significant number of MDS without RS (37% vs. 14%, P = 0.013), including TP53 mutations (0% vs.16.5%, P = 0.021) if ≥5% CD34 + hematogones were present. Although the follow up was short (18.5 months, 0 to 151.0), a better overall survival was observed in MDS with ≥5% CD34 + hematogones, either as a group (P = 0.008) or among patients with no RS (P = 0.028). In multivariate analysis, reduced hematogones remained to be significant hazard (P = 0.015). In summary, preserved CD34 + hematogones (≥5%) are seen in over a quarter of primary low-grade MDS and these cases are overrepresented by MDS with RS or MDS with no detectable mutations. The finding is new, and this phenomenon may in part attribute to preservation of B-cell differentiation of CD34+ progenitors, and it is associated with a better prognosis in low grade MDS patients. © 2019 International Clinical Cytometry Society., (© 2019 International Clinical Cytometry Society.)

Background: Optimal discrimination between leukemic blasts and normal B-cell precursors (BCP) is critical for treatment monitoring in BCP acute lymphoblastic leukemia (ALL); thus identification of markers differentially expressed on normal BCP and leukemic blasts is required., Methods: Multicenter analysis of CD73, CD86 and CD304 expression levels was performed in 282 pediatric BCP-ALL patients vs. normal bone marrow BCP, using normalized median fluorescence intensity (nMFI) values., Results: CD73 was expressed at abnormally higher levels (vs. pooled normal BCP) at diagnosis in 71/108 BCP-ALL patients (66%), whereas CD304 and CD86 in 119/202 (59%) and 58/100 (58%) patients, respectively. Expression of CD304 was detected at similar percentages in common-ALL and pre-B-ALL, while found at significantly lower frequencies in pro-B-ALL. A significant association (p = 0.009) was found between CD304 expression and the presence of the ETV6-RUNX1 fusion gene. In contrast, CD304 showed an inverse association with MLL gene rearrangements (p = 0.01). The expression levels of CD73, CD86 and CD304 at day 15 after starting therapy (MRD15) were stable or higher than at diagnosis in 35/37 (95%), 40/56 (71%) and 19/41 (46%) cases investigated, respectively. This was also associated with an increased mean nMFI at MRD15 vs. diagnosis of +24 and +3 nMFI units for CD73 and CD86, respectively. In addition, gain of expression of CD73 and CD86 at MRD15 for cases that were originally negative for these markers at diagnosis was observed in 16% and 18% of cases, respectively. Of note, CD304 remained aberrantly positive in 63% of patients, despite its levels of expression decreased at follow-up in 54% of cases., Conclusions: Here we show that CD73, CD86 and CD304 are aberrantly (over)expressed in a substantial percentage of BCP-ALL patients and that their expression profile remains relatively stable early after starting therapy, supporting their potential contribution to improved MRD analysis by flow cytometry., (Copyright © 2018. Published by Elsevier B.V.)

Introduction: Osimertinib is approved for advanced EGFR-mutated NSCLC, and identification of on-target mechanisms of resistance (i.e., EGFR C797S) to this third-generation EGFR inhibitor are evolving. Whether durable control of subsequently osimertinib-resistant NSCLC with the EGFR-sensitizing mutation (SM)/C797S is possible with first-generation EGFR inhibitors (such as gefitinib or erlotinib) remains underreported, as does the resultant acquired resistance profile., Methods: We used N-ethyl-N-nitrosourea mutagenesis to determine the profile of EGFR SM/C797S preclinical models exposed to reversible EGFR inhibitors. In addition, we retrospectively probed a case of EGFR SM lung adenocarcinoma treated with first-line osimertinib, followed by second-line erlotinib in the setting of EGFR SM/C797S., Results: Use of N-ethyl-N-nitrosourea mutagenesis against the background of EGFR L858R/C797S in conjunction with administration of gefitinib revealed preferential outgrowth of cells with EGFR L858R/T790M/C797S. A patient with EGFR delE746&#95;T751insV NSCLC was treated with osimertinib with sustained response for 10 months before acquiring EGFR C797S. The patient was subsequently treated with erlotinib, with response for a period of 4 months, but disease progression ensued. Liquid biopsy disclosed EGFR delE746&#95;T751insV with T790M and C797S present in cis., Conclusion: EGFR SM NSCLC can acquire resistance to osimertinib through development of the EGFR C797S mutation. In this clinical scenario, the tumor may respond transiently to reversible first-generation EGFR inhibitors (gefitinib or erlotinib), but evolving mechanisms of on-target resistance-in clinical specimens and preclinical systems-indicate that EGFR C797S along with EGFR T790M can evolve. This report adds to the growing understanding of tumor evolution or adaptability to sequential EGFR inhibition and augments support for exploring combination therapies to delay or prevent on-target resistance., (Copyright © 2019 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.)

Background: MNNG HOS transforming gene (MET) exon 14 mutations in lung cancer, including exon 14 skipping and point mutations, have been attracting the attention of thoracic oncologists as new therapeutic targets. Tumors with these mutations almost always acquire resistance, which also occurs in other oncogene-addicted lung cancers. However, the resistance mechanisms and treatment strategies are not fully understood., Methods: We generated Ba/F3 cells expressing MET exon 14 mutations by retroviral gene transfer. The sensitivities of these cells to eight MET-tyrosine kinase inhibitors (TKIs) were determined using a colorimetric assay. In addition, using N-ethyl-N-nitrosourea mutagenesis, we generated resistant clones, searched for secondary MET mutations, and then examined the sensitivities of these resistant cells to different TKIs., Results: Ba/F3 cells transfected with MET mutations grew in the absence of interleukin-3, indicating their oncogenic activity. These cells were sensitive to all MET-TKIs except tivantinib. We identified a variety of secondary mutations. D1228 and Y1230 were common sites for resistance mutations for type I TKIs, which bind the active form of MET, whereas L1195 and F1200 were common sites for type II TKIs, which bind the inactive form. In general, resistance mutations against type I were sensitive to type II, and vice versa., Conclusions: MET-TKIs inhibited the growth of cells with MET exon 14 mutations. We also identified mutation sites specific for TKI types as resistance mechanisms and complementary activities between type I and type II inhibitors against those mutations. These finding should provide relevant clinical implication for treating patients with lung cancer harboring MET exon 14 mutations., (Copyright © 2019 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.)

Juvenile myelomonocytic leukemia (JMML) has a poor prognosis in general, with hematopoietic stem cell transplant (HSCT) remaining the standard of care for cure. The hypomethylating agent, azacitidine, has been used as a bridging therapy to transplant. However, no patients have been treated with azacitidine without an HSCT post azacitidine. We report on an infant with JMML with somatic KRAS G12A mutation and monosomy 7 who achieved sustained remission following azacitidine monotherapy. He also developed an aberrant B-lymphoblast population which declined with similar kinetics as his JMML-associated abnormalities, suggesting that a B-lymphoblast population in JMML does not always progress to acute leukemia., (© 2019 Wiley Periodicals, Inc.)

CD30 is expressed on a variety of B-cell lymphomas, such as Hodgkin lymphoma, primary effusion lymphoma, and a diffuse large B-cell lymphoma subgroup. In normal tissues, CD30 is expressed on some activated B and T lymphocytes. However, the physiological function of CD30 signaling and its contribution to the generation of CD30 + lymphomas are still poorly understood. To gain a better understanding of CD30 signaling in B cells, we studied the expression of CD30 in different murine B-cell populations. We show that B1 cells expressed higher levels of CD30 than B2 cells and that CD30 was upregulated in IRF4 + plasmablasts (PBs). Furthermore, we generated and analyzed mice expressing a constitutively active CD30 receptor in B lymphocytes. These mice displayed an increase in B1 cells in the peritoneal cavity (PerC) and secondary lymphoid organs as well as increased numbers of plasma cells (PCs). TI-2 immunization resulted in a further expansion of B1 cells and PCs. We provide evidence that the expanded B1 population in the spleen included a fraction of PBs. CD30 signals seemed to enhance PC differentiation by increasing activation of NF-κB and promoting higher levels of phosphorylated STAT3 and STAT6 and nuclear IRF4. In addition, chronic CD30 signaling led to B-cell lymphomagenesis in aged mice. These lymphomas were localized in the spleen and PerC and had a B1-like/plasmablastic phenotype. We conclude that our mouse model mirrors chronic B-cell activation with increased numbers of CD30 + lymphocytes and provides experimental proof that chronic CD30 signaling increases the risk of B-cell lymphomagenesis., (© 2019 by The American Society of Hematology.)

Approximately 10% of NUP98-PHF23 (NP23) mice develop an aggressive acute lymphoblastic leukemia of B-1 lymphocyte progenitor origin (pro-B1 ALL), accompanied by somatic frameshift mutations of the BCL6 interacting corepressor ( Bcor ) gene, most commonly within a 9-bp "hotspot" in Bcor exon 8. To determine whether experimentally engineered Bcor mutations would lead to pro-B1 ALL, we used clustered, regularly interspaced, short palindromic repeats-associated protein 9 to introduce a Bcor frameshift mutation into NP23 hematopoietic stem and progenitor cells through the use of Bcor small guide RNAs ( Bcor sgRNAs). Recipient mice transplanted with NP23 bone marrow or fetal liver cells that had been transduced with a Bcor sgRNA developed pro-B1 ALL, characterized by a B-1 progenitor immunophenotype, clonal Igh gene rearrangement, and Bcor indel mutation, whereas control recipients did not. Similar to a subset of human B-cell precursor ALL, the murine pro-B1 ALL had acquired somatic mutations in Jak kinase genes. JAK inhibitors (ruxolitinib and tofacitinib) inhibited the growth of pro-B1 ALL cell lines established from Bcor sgRNA/NP23 recipients at clinically achievable concentrations (100 nM). Our results demonstrate that Bcor mutations collaborate with NP23 to induce pro-B1 ALL, and that JAK inhibitors are potential therapies for pro-B1 ALL.

The advent of CD19-specific chimeric antigen receptor (CAR) T cells has proven to be a powerful asset in the arsenal of cancer immunotherapy of acute lymphoblastic leukemia and certain B cell lymphomas. However, a sizable portion of patients treated with CD19-CAR T cells relapse with CD19-negative cancer cells, necessitating the quest for back-up antigens. Chondroitin sulfate proteoglycan 4 (CSPG4) expression has been reported on leukemic blasts bearing the ill-fated MLL 11q23 rearrangement. We aimed at exploring the use of CSPG4-specific CAR T cells against mixed-lineage leukemia (MLL)-rearranged leukemic blasts, using the precursor B cell leukemia cell line KOPN8 (MLL-MLLT1 translocation) as a model. First, we confirmed CSPG4 expression on KOPN8 cells. Bulk T cells electroporated with mRNA encoding a CSPG4-specific CAR upregulated activation markers and secreted the Th1 cytokines TNF and IFNγ in an antigen-specific manner upon co-culture with KOPN8 cells. More importantly, CSPG4-specific CAR T cells evinced specific degranulation towards KOPN8 cells and specifically lysed KOPN8 target cells in chromium lysis experiments. CSPG4 is a well-established CAR target in cutaneous melanoma. Here, we provide proof-of-principle data for the use of CSPG4-specific CAR T cells against MLL-translocated leukemias.

We describe an unusual case of pre-B lymphoblastic leukaemia presenting with a unilateral maxillary sinus mass in which biopsies of the primary mass and the bone marrow demonstrated conflicting immunophenotyping results. The extramedullary mass was consistent with a precursor B-cell malignancy, while the bone marrow was initially reported as a possible mature B-cell malignancy. The treatments for the two are fundamentally different, which necessitated a delay in the initiation of his chemotherapy until a clear diagnosis was made. Mixed lineage leukaemia gene rearrangement was confirmed by fluorescence in situ hybridisation in both the primary mass and bone marrow, which unified the diagnosis as pre-B acute lymphoblastic leukaemia given the common cytogenetic feature., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

Transformation of hematopoietic stem cells by the BCR-FGFR1 fusion kinase found in a variant of stem cell leukemia/lymphoma (SCLL) syndrome leads to development of B-lymphomas in syngeneic mice and humans. In this study, we show that the relatively rapid onset of this leukemia is potentially related to oncogenic domains within the BCR component. BCR recruited a guanidine nucleotide exchange factor (GEF) domain to the fusion kinase to facilitate activation of small GTPases such as the Ras homology gene family, member A (RHOA). Deletion of this GEF domain increased leukemogenesis, enhanced cell survival and proliferation, and promoted stem cell expansion and lymph node metastasis. This suggests that, in an SCLL context, the presence of the endogenous GEF motif leads to reduced leukemogenesis. Indeed, loss of the GEF domain suppressed activation of RHOA and PTEN, leading to increased activation of AKT. Loss of the GEF domain enhanced cell proliferation and invasion potential, which was also observed in cells in which RHOA is knocked down, supported by the observation that overexpression of RHOA leads to reduced viability and invasion. In vivo depletion of RHOA in SCLL cells significantly increased disease progression and shortened latency. Collectively, these data show that the BCR GEF domain affects phenotypes associated with progression of SCLL through suppression of RHOA signaling. SIGNIFICANCE: RHOA activation is a critical event in the progression of BCR-FGFR1-driven leukemogenesis in stem cell leukemia and lymphoma syndrome and is regulated by the BCR GEF domain., (©2018 American Association for Cancer Research.)

Granulocyte-colony stimulating factor receptor (G-CSFR) controls myeloid progenitor proliferation and differentiation to neutrophils. Mutations in CSF3R (encoding G-CSFR) have been reported in patients with chronic neutrophilic leukemia (CNL) and acute myeloid leukemia (AML); however, despite years of research, the malignant downstream signaling of the mutated G-CSFRs is not well understood. Here, we used a quantitative phospho-tyrosine analysis to generate a comprehensive signaling map of G-CSF induced tyrosine phosphorylation in the normal versus mutated (proximal: T618I and truncated: Q741x) G-CSFRs. Unbiased clustering and kinase enrichment analysis identified rapid induction of phospho-proteins associated with endocytosis by the wild type G-CSFR only; while G-CSFR mutants showed abnormal kinetics of canonical Stat3, Stat5, and Mapk phosphorylation, and aberrant activation of Bruton's Tyrosine Kinase (Btk). Mutant-G-CSFR-expressing cells displayed enhanced sensitivity (3-5-fold lower IC50) for ibrutinib-based chemical inhibition of Btk. Primary murine progenitor cells from G-CSFR-Q741x knock-in mice validated activation of Btk by the mutant receptor and retrovirally transduced human CD34 + umbilical cord blood cells expressing mutant receptors displayed enhanced sensitivity to Ibrutinib. A significantly lower clonogenic potential was displayed by both murine and human primary cells expressing mutated receptors upon ibrutinib treatment. Finally, a dramatic synergy was observed between ibrutinib and ruxolinitib at lower dose of the individual drug. Altogether, these data demonstrate the strength of unsupervised proteomics analyses in dissecting oncogenic pathways, and suggest repositioning Ibrutinib for therapy of myeloid leukemia bearing CSF3R mutations. Phospho-tyrosine data are available via ProteomeXchange with identifier PXD009662.

After infection with Trypanosoma cruzi , the etiologic agent of Chagas disease, immunosuppression, and apoptosis of mature lymphocytes contribute to the establishment of the parasite in the host and thereby to persistence and pathology in the chronic stage of infection. In a systemic mouse model of experimental Chagas disease, we have demonstrated a strong depletion of mature B cells in the spleen during the first 2 weeks of infection. Remarkably, the decrease in this cell population commenced already in the bone marrow from infected mice and was a concomitant of an increased apoptosis in pro- and pre-B cell populations. Pro- and pre-B cells in the bone marrow showed a significant reduction accompanied by a functional disturbance of bone marrow-derived stromal cells resulting in diminished levels of IL-7, an essential factor for the development of B cell precursors. Ex vivo , stromal cells isolated from the bone marrow of infected mice had a strikingly impaired capacity to maintain the development of pro- and pre-B cells obtained from uninfected animals. Together, the reduction of an active humoral immune response during acute Chagas disease suggests to be an initial immune evasion mechanism of the parasite to establish persistent infection. Therefore, prevention of B cell depletion by rescuing the stromal cells during this early phase, could give rise to new therapeutic approaches.

Runt-related transcription factor 1 (RUNX1) is a well-known master regulator of hematopoietic lineages but its mechanisms of action are still not fully understood. Here, we found that RUNX1 localizes on active chromatin together with Far Upstream Binding Protein 1 (FUBP1) in human B-cell precursor lymphoblasts, and that both factors interact in the same transcriptional regulatory complex. RUNX1 and FUBP1 chromatin localization identified c-KIT as a common target gene. We characterized two regulatory regions, at +700 bp and +30 kb within the first intron of c-KIT, bound by both RUNX1 and FUBP1, and that present active histone marks. Based on these regions, we proposed a novel FUBP1 FUSE-like DNA-binding sequence on the +30 kb enhancer. We demonstrated that FUBP1 and RUNX1 cooperate for the regulation of the expression of the oncogene c-KIT. Notably, upregulation of c-KIT expression by FUBP1 and RUNX1 promotes cell proliferation and renders cells more resistant to the c-KIT inhibitor imatinib mesylate, a common therapeutic drug. These results reveal a new mechanism of action of RUNX1 that implicates FUBP1, as a facilitator, to trigger transcriptional regulation of c-KIT and to regulate cell proliferation. Deregulation of this regulatory mechanism may explain some oncogenic function of RUNX1 and FUBP1.

The WHO Classification of Tumours of Haematopoietic and Lymphoid Tissue notes instances of Burkitt lymphoma/leukemia (BL) with IG- MYC rearrangement displaying a B-cell precursor immunophenotype (termed herein "preBLL"). To characterize the molecular pathogenesis of preBLL, we investigated 13 preBLL cases (including 1 cell line), of which 12 were analyzable using genome, exome, and targeted sequencing, imbalance mapping, and DNA methylation profiling. In 5 patients with reads across the IG- MYC breakpoint junctions, we found evidence that the translocation derived from an aberrant VDJ recombination, as is typical for IG translocations arising in B-cell precursors. Genomic changes like biallelic IGH translocations or VDJ rearrangements combined with translocation into the VDJ region on the second allele, potentially preventing expression of a productive immunoglobulin, were detected in 6 of 13 cases. We did not detect mutations in genes frequently altered in BL, but instead found activating NRAS and/or KRAS mutations in 7 of 12 preBLLs. Gains on 1q, recurrent in BL and preB lymphoblastic leukemia/lymphoma (pB-ALL/LBL), were detected in 7 of 12 preBLLs. DNA methylation profiling showed preBLL to cluster with precursor B cells and pB-ALL/LBL, but apart from BL. We conclude that preBLL genetically and epigenetically resembles pB-ALL/LBL rather than BL. Therefore, we propose that preBLL be considered as a pB-ALL/LBL with recurrent genetic abnormalities.

Adoptive transfer of patient-derived T cells modified to express chimeric antigen receptors (CARTs) has demonstrated dramatic success in relapsed/refractory pre-B-cell acute lymphoblastic leukemia (ALL), but response and durability of remission requires exponential CART expansion and persistence. Tumors are known to affect T-cell function, but this has not been well studied in ALL and in the context of chimeric antigen receptor (CAR) expression. Using TCF3/PBX1 and MLL-AF4-driven murine ALL models, we assessed the impact of progressive ALL on T-cell function in vivo. Vaccines protect against TCF3/PBX1.3 but were ineffective when administered after leukemia injection, suggesting immunosuppression induced early during ALL progression. T cells from leukemia-bearing mice exhibited increased expression of inhibitory receptors, including PD1, Tim3, and LAG3, and were dysfunctional following adoptive transfer in a model of T-cell receptor (TCR)-dependent leukemia clearance. Although expression of inhibitory receptors has been linked to TCR signaling, pre-B-cell ALL induced inhibitory receptor expression, at least in part, in a TCR-independent manner. Finally, introduction of a CAR into T cells generated from leukemia-bearing mice failed to fully reverse poor in vivo function.

Synthetic glucocorticoids (GCs) are used to treat lymphoid cancers, but many patients develop resistance to treatment, especially to GC. By identifying genes that influence sensitivity to GC-induced cell death, we found that histone methyltransferases G9a and G9a-like protein (GLP), two glucocorticoid receptor (GR) coactivators, are required for GC-induced cell death in acute lymphoblastic leukemia (B-ALL) cell line Nalm6. We previously established in a few selected genes that automethylated G9a and GLP recruit heterochromatin protein 1γ (HP1γ) as another required coactivator. Here, we used a genome-wide analysis to show that HP1γ is selectively required for GC-regulated expression of the great majority of GR target genes that require G9a and GLP. To further address the importance of G9a and GLP methylation in this process and in cell physiology, we found that JIB-04, a selective JmjC family lysine demethylase inhibitor, increased G9a methylation and thereby increased G9a binding to HP1γ. This led to increased expression of GR target genes regulated by G9a, GLP and HP1γ and enhanced Nalm6 cell death. Finally, the KDM4 lysine demethylase subfamily demethylates G9a in vitro, in contrast to other KDM enzymes tested. Thus, inhibiting G9a/GLP demethylation potentially represents a novel method to restore sensitivity of treatment-resistant B-ALL tumors to GC-induced cell death.

Background: Normal B lymphoid maturation occurs in bone marrow (BM) throughout life, but immature B-cell progenitors (BCPs) are more numerous in children than in adults. To assess the normal values according to age became important as BCPs are decreased in myelodysplastic syndromes and have been considered an important diagnostic and prognostic feature in these clonal disorders., Methods: in a multicenter retrospective study from the Brazilian Group of Flow Cytometry we analyzed the variation of BCPs in normal BM according to age and technical peculiarities of each laboratory. We analysed of 45 BM donors and 89 cases examined for elucidation of transitory reactive cytopenias presenting a normal BM immunophenotyping. BCPs were enumerated as CD19 + /CD34 + /CD45 dim /CD10 + cells (panel 1) or CD19 + /CD34 + /CD45 dim cells (panel 2) among the total nucleated non-erythroid cells and as percentage of CD34 + cells., Results: we included 134 cases. Panel 1 was applied in 88 cases and panel 2 was used in 46. Age range: 10 months to 89 years. In a multiple regression, % BCPs/total nucleated cells was an exponential function of age. Age explained alone 49.4% of the variance, while 'panel used' explained 1.8% and 'laboratory' explained 0.7%. Age explained only 24.9% of the variance of BCPs/CD34 + cells., Conclusions: in normal individuals, BM B-cell precursors varied mainly according to age, but were also dependent on technical peculiarities of operators and equipments. Analysis by phenotype and as percentage of total nucleated cells was more accurate and less susceptible to variation than evaluating % BCPs/total CD34 + cells. © 2017 International Clinical Cytometry Society., (© 2017 International Clinical Cytometry Society.)

Introduction: The survival of patients with EGFR mutation-positive lung cancer has dramatically improved since the introduction of EGFR tyrosine kinase inhibitors (EGFR-TKIs). Recently, osimertinib showed significantly prolonged progression-free survival than first-generation EGFR-TKI in first-line treatment, suggesting that a paradigm change that would move osimetinib to first-line treatment is indicated. We performed N-ethyl-N-nitrosourea (ENU) mutagenesis screening to uncover the resistant mechanism in first- and second-line osimertinib treatment., Methods: Ba/F3 cells harboring EGFR activating-mutation with or without secondary resistant mutation were exposed to ENU for 24 hours to introduce random mutations and selected with gefitinib, afatinib, or osimertinib. Mutations of emerging resistant cells were assessed., Results: The resistance of T790M and C797S to gefitinib and osimertinib, respectively, was prevalent in the mutagenesis screening with the Ba/F3 cells harboring activating-mutation alone. From C797S/activating-mutation expressing Ba/F3, the additional T790M was a major resistant mechanism in gefitinib and afatinib selection and the additional T854A and L792H were minor resistance mechanisms only in afatinib selection. However, the additional T854A or L792H mediated resistance to all classes of EGFR-TKI. Surprisingly, no resistant clone due to secondary mutation emerged from activating-mutation alone in the gefitinib + osimertinib selection., Conclusions: We showed the resistance mechanism to EGFR-TKI focusing on first- and second-line osimertinib using ENU mutagenesis screening. Additional T854A and L792H on C797S/activating-mutation were found as afatinib resistance and not as gefitinib resistance. Thus, compared to afatinib, the first-generation EGFR-TKI might be preferable as second-line treatment to C797S/activating-mutation emerging after first-line osimertinib treatment., (Copyright © 2018 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.)

Context: It has been shown that hesperidin induces apoptosis in NALM-6 cells through inhibition of nuclear factor-kappa B (NF-κB) activation., Aims: To investigate the effect of hesperidin on inhibition of NF-κB activation through blocking phosphoinositide 3-kinase (PI3K)/Akt pathway as a main target in cancer treatment, in NALM-6 cells., Materials and Methods: NALM-6 cells were incubated with two concentrations of hesperidin (25, 50 μM) in the presence or absence of insulin (100 nM), as a potent activator of Akt. The cytotoxic activity of hesperidin was determined by 3-(4,5-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptotic death was measured by ELISA test using cell death detection ELISA Plus kit. To assay the effect of hesperidin on Akt pathway, the phosphorylation levels of Akt, inhibitor of kappa B alpha (IκBα), and glycogen synthase kinase-3 beta (GSK-3β) and expression level of IκB kinase alpha (IKKα) were determined by Western blot analysis., Results: Hesperidin (both concentrations) significantly reduced cells survival in the presence and absence of insulin compared to untreated cells in a time-dependent manner (P < 0.05). Hesperidin also significantly increased apoptosis in NALM-6 cells even in hyperinsulinemia condition (P < 0.0001). Hesperidin inhibited insulin-induced phosphorylation and activation of Akt, IκBα, and GSK-3β and decreased expression of IKKα., Conclusion: The results of this study demonstrated that cytotoxic and proapoptotic actions of hesperidin are partly mediated through the suppression of PI3K3/Akt/IKK signaling pathway. So, hesperidin might act as a chemotherapeutic agent by targeting cell survival pathways., Competing Interests: There are no conflicts of interest

Antigen receptor gene assembly is accomplished in developing lymphocytes by the V(D)J recombination reaction, which can be separated into two steps: DNA cleavage by the recombination-activating gene (RAG) nuclease and joining of DNA double strand breaks (DSBs) by components of the nonhomologous end joining (NHEJ) pathway. Deficiencies for NHEJ factors can result in immunodeficiency and a propensity to accumulate genomic instability, thus highlighting the importance of identifying all players in this process and deciphering their functions. Bcl2 transgenic v-Abl kinase-transformed pro-B cells provide a pseudo-physiological cellular system to study V(D)J recombination. Treatment of v-Abl/Bcl2 pro-B cells with the Abl kinase inhibitor Imatinib leads to G1 cell cycle arrest, the rapid induction of Rag1/2 gene expression and V(D)J recombination. In this system, the Bcl2 transgene alleviates Imatinib-induced apoptosis enabling the analysis of induced V(D)J recombination. Although powerful, the use of mouse models carrying the Bcl2 transgene for the generation of v-Abl pro-B cell lines is time and money consuming. Here, we describe a method for generating v-Abl/Bcl2 pro-B cell lines from wild type mice and for performing gene knock-out using episomal CRISPR/Cas9 targeting vectors. Using this approach, we generated distinct NHEJ-deficient pro-B cell lines and quantified V(D)J recombination levels in these cells. Furthermore, this methodology can be adapted to generate pro-B cell lines deficient for any gene suspected to play a role in V(D)J recombination, and more generally DSB repair., (Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.)

Despite advances in treatment, children with acute lymphoblastic leukemia (ALL) still experience drug resistance and relapse. Several gene mutations are involved in the onset of this disease and resistance to therapy. The present study examines the incidence of IKZF1, CDKN2A/B, PAX5, EBF1, ETV6, BTG1, RB1, JAK2, and Xp22.33 gene deletions/duplications associated with pediatric ALL in Iran and investigates the possible effect of these mutations on drug resistance. Three-year disease-free survival (3DFS) was evaluated for children diagnosed with Philadelphia negative precursor-B-cell ALL hospitalized at Sayed-al-Shohada Hospital, Isfahan-Iran, from January 2009 until December 2012. DNA was extracted from bone marrow slides, and ALL correlated gene deletions and duplications were measured using Multiplex Ligation-dependent Probe Amplification (MLPA) method. The correlation between gene mutations and 3DFS was then assessed. Among the nine aforementioned investigated genes, 63% of samples showed at least one gene mutation. At least two concomitant genomic mutations were observed in 42% of samples. Pax5 deletion was the most prevalent gene mutation observed in 45% of cases, and showed significant negative impact on response to treatment. CDKN2A/B (9p21.3) gene deletion, and ETV6 (12p13.2) gene duplication also demonstrated negative effect on patient survival and contributed to a worse prognosis if concomitant with Pax5 gene deletion. ALL patients with one of the gene deletions including Pax5  and CDKN2A/B (9p21.3) or ETV6 (12p13.2) gene duplication are classified as high-risk patients and need more intensified protocols of treatment to improve their chance of survival.