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The standardized EuroFlow protocol, including CD19 as primary B-cell marker, enables highly sensitive and reliable minimal residual disease (MRD) assessment in B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) patients treated with chemotherapy. We developed and validated an alternative gating strategy allowing reliable MRD analysis in BCP-ALL patients treated with CD19-targeting therapies. Concordant data were obtained in 92% of targeted therapy patients who remained CD19-positive, whereas this was 81% in patients that became (partially) CD19-negative. Nevertheless, in both groups median MRD values showed excellent correlation with the original MRD data, indicating that, despite higher interlaboratory variation, the overall MRD analysis was correct., The EuroFlow Consortium received support from the FP6-2004-LIFESCIHEALTH-5 programme of the European Commission (grant LSHB-CT-2006-018708) as Specific Targeted Research Project (STREP). The EuroFlow Consortium is part of the European Scientific Foundation for Hemato-Oncology (ESLHO), a Scientific Working Group (SWG) of the European Hematology Association (EHA). TS and LS were supported by a Scientific Grant from the Medical University of Silesia Nr. PCN-1-050/K/0/K.

© The Author(s) 2020., Precise classification of acute leukemia (AL) is crucial for adequate treatment. EuroFlow has previously designed an AL orientation tube (ALOT) to guide toward the relevant classification panel and final diagnosis. In this study, we designed and validated an algorithm for automated (database-supported) gating and identification (AGI tool) of cell subsets within samples stained with ALOT. A reference database of normal peripheral blood (PB, n = 41) and bone marrow (BM; n = 45) samples analyzed with the ALOT was constructed, and served as a reference for the AGI tool to automatically identify normal cells. Populations not unequivocally identified as normal cells were labeled as checks and were classified by an expert. Additional normal BM (n = 25) and PB (n = 43) and leukemic samples (n = 109), analyzed in parallel by experts and the AGI tool, were used to evaluate the AGI tool. Analysis of normal PB and BM samples showed low percentages of checks ( 0.95 for all cell types in PB and r2 > 0.75 in BM) and resulted in highly concordant classification of leukemic cells by our previously published automated database-guided expert-supervised orientation tool for immunophenotypic diagnosis and classification of acute leukemia (Compass tool). Similar data were obtained using alternative, commercially available tubes, confirming the robustness of the developed tools. The AGI tool represents an innovative step in minimizing human intervention and requirements in expertise, toward a “sample-in and result-out” approach which may result in more objective and reproducible data analysis and diagnostics. The AGI tool may improve quality of immunophenotyping in individual laboratories, since high percentages of checks in normal samples are an alert on the quality of the internal procedures., The EuroFlow Consortium received support from the FP6- 2004-LIFESCIHEALTH-5 program of the European Commission (grant LSHB-CT-2006-018708) as Specific Targeted Research Project (STREP). The Prague team received support from the grant number NV18-03-00343. The Salamanca team received support from the Instituto de Salud Carlos III (ISCIII) (PI16/00787-FEDER) and from Agencia Estatal de Investigación (RTC-2016-4865-1-FEDER), Ministerio de Economía y Competitividad, Madrid, Spain. AHD is supported from the program DI-17-09591 from Agencia Estatal de Investigación, Ministerio de Ciencia, Innovación y Universidades, Madrid, Spain. SB is supported from the program PTQ16-08364 from Agencia Estatal de Investigación, Ministerio de Ciencia, Innovación y Universidades, Madrid, Spain. Medical University of Silesia in Katowice team was supported by the Strategmed III PersonALL grant [No. 304586/5/NCBR/2017] from the Polish National Center of Research and Development. The EuroFlow Consortium is part of the European Scientific Foundation for Hemato-Oncology (ESLHO), a Scientific Working Group (SWG) of the European Hematology Association (EHA).

We prospectively examined whether surface expression of Cytokine Receptor-Like Factor 2 (CRLF2) on leukemic blasts is associated with survival and induction treatment response in pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL) patients. Flow cytometric analysis of bone marrow-derived leukemia cells revealed that 7.51% (29/286) of 386 pediatric BCP-ALL patients were CRLF2-positive (CRLF2pos) at diagnosis. The median minimal residual disease (MRD) was lower in CRLF2pos than CRLF2-negative (CRLF2neg) patients on day 15 (MRD15) after induction therapy [0.01% (0.001-0.42%) vs. 0.45% (0.05-3.50%); p=0.001]. By contrast, the MRD15 was higher in Ikaros family Zinc Finger Protein 1 (IKZF1)-deleted BCP-ALL patients than in BCP-ALL patients without IKZF1 deletions [1.18% (0.06-12.0%) vs 0.33% (0.03-2.6%); p=0.003]. Subgroup analysis showed that MRD15 levels were lower in IKZF1Δ/CRLF2pos patients than in IKZF1Δ/CRLF2neg patients [0.1% (0.02-5.06%) vs. 2.9% (0.25-12%); p=0.005]. Furthermore, MRD15 levels were higher in IKZF1WT/CRLF2neg patients than in IKZF1WT/CRLF2pos patients [0.40% (0.04-2.7%) vs. 0.001% (0.001-0.01%)]. Despite the low MRD15 levels, IKZF1Δ/CRLF2pos patients showed poorer relapse-free survival (RFS) than other patient groups (p=0.003). These findings demonstrate that surface CRLF2 expression is associated with increased risk of relapse in pediatric BCP-ALL patients harboring IKZF1 deletions.

Chromosomal rearrangements of the human MLL/KMT2A gene are associated with infant, pediatric, adult and therapy-induced acute leukemias. Here we present the data obtained from 2345 acute leukemia patients. Genomic breakpoints within the MLL gene and the involved translocation partner genes (TPGs) were determined and 11 novel TPGs were identified. Thus, a total of 135 different MLL rearrangements have been identified so far, of which 94 TPGs are now characterized at the molecular level. In all, 35 out of these 94 TPGs occur recurrently, but only 9 specific gene fusions account for more than 90% of all illegitimate recombinations of the MLL gene. We observed an age-dependent breakpoint shift with breakpoints localizing within MLL intron 11 associated with acute lymphoblastic leukemia and younger patients, while breakpoints in MLL intron 9 predominate in AML or older patients. The molecular characterization of MLL breakpoints suggests different etiologies in the different age groups and allows the correlation of functional domains of the MLL gene with clinical outcome. This study provides a comprehensive analysis of the MLL recombinome in acute leukemia and demonstrates that the establishment of patient-specific chromosomal fusion sites allows the design of specific PCR primers for minimal residual disease analyses for all patients.

This commentary discusses particularities of application of the EuroFlow standardization of flow cytometric analyses on three different flow cytometers. The EuroFlow consortium developed a fully standardized approach for flow cytometric immunophenotyping of hematological malignancies and primary immunodeficiencies. Standardized instrument setup is an essential part of EuroFlow standardization. Initially, the EuroFlow Consortium developed and optimized a step-by-step standard operating procedure (SOP) to setup 8-color BD FACSCanto II flow cytometer (Canto), with the later inclusion of Navios (Beckman Coulter) and BD FACSLyric (Lyric). Those SOPs were developed to enable standardized and fully comparable fluorescence measurements in the three flow cytometers. In Canto and Navios, mean fluorescence intensity (MFI) of a reference peak of Rainbow beads calibration particles is used to set up photomultiplier (PMT) voltages for each detector channel in individual instruments to reach the same MFI across distinct instruments. In turn, a new feature of Lyric instruments allows to share collection of attributes that are used to place the positive population at the same position among instruments in the form of assays, as one of its components integrated in the Cytometer Setup and Tracking (CS&T) module. The EuroFlow Lyric assays thus allow for standardized acquisition of 8-color EuroFlow panels on Lyric without the need to setup the PMT voltages on the individual instruments manually. In summary, the standardized instrument setup developed by EuroFlow enables cross-platform inter- and intra-laboratory standardization of flow cytometric measurements. This commentary provides a perspective on the modifications of the standardized EuroFlow instrument setup of Canto, Navios and Lyric instruments that are described in detail in individual instrument-specfic SOPs available at the EuroFlow website., TK and MN were supported by Ministry of Health of the Czech Republic, grant nr. NV18-03-00343, Ministry of Education, Youth and Sports of the Czech Republic, NPU I project nr.LO1604 and EU-Prague project CZ.2.16/3.1.00/24505. JFM and AO were supported by CB16/12/00400 grant (CIBER-ONC, Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain and FONDOS FEDER).

Fluorochrome selection is a key step in designing multi-color antibody panels. The list of available fluorochromes is continuously growing, fitting current needs in clinical flow cytometry to simultaneously use more markers to better define multiple leukocyte subpopulations in a single tube. Several criteria guide fluorochrome selection: i) the fluorescence profiles (excitation and emission), ii) relative brightness, iii) fluorescence overlap, iv) fluorochrome stability, and v) reproducible conjugation to antibodies. Here we used 75 samples (45 bone marrow and 30 blood) to illustrate EuroFlow strategies for evaluation of compatible fluorochromes, and how the results obtained guide fluorochrome selection as a critical step in the antibody-panel building process. Our results allowed identification of optimal fluorescence profiles (e.g. higher fluorescence intensity and/or resolution with limited fluorescence overlap into neighbor channels) for brilliant violet (BV)421 and BV510 in the violet laser and allophycocyanin (APC) hilite 7 (H7) or APC C750 in the red laser vs. other candidate fluorochromes generally applied for the same detectors and here evaluated. Moreover, evaluation of the same characteristics for another group of fluorochromes (e.g. BV605, BV650, PE CF594, AF700 or APC AF700) guided selection of the most appropriate fluorochrome conjugates to be combined in a multi-color antibody panel. Albeit this is a demanding approach, it could be successfully applied for selection of fluorochrome combinations for the EuroFlow antibody panels for diagnosis, classification and monitoring of hematological malignancies and primary immunodeficiencies. Consequently, sets of 8-, 10- and 12-color fluorochrome combinations are proposed as frame of reference for initial antibody panel design., This work was supported by CB16/12/00400 grant (CIBER-ONC, Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain and FONDOS FEDER) and grant PI16/00787 from Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain. TK and KR were supported by project NPU LO1604 and EU-Prague project CZ.2.16/3.1.00/24505.

A fully-standardized EuroFlow 8–color antibody panel and laboratory procedure was stepwise designed to measure minimal residual disease (MRD) in B-cell precursor (BCP) acute lymphoblastic leukemia (ALL) patients with a sensitivity of £10, comparable to real-time quantitative polymerase chain reaction (RQ-PCR)–based MRD detection via antigen-receptor rearrangements. Leukocyte markers and the corresponding antibodies and fluorochromes were selected based on their contribution in separating BCP-ALL cells from normal/regenerating BCP cells in multidimensional principal component analyses. After 5 multicenter design-test-evaluate-redesign phases with a total of 319 BCP-ALL patients at diagnosis, two 8-color antibody tubes were selected, which allowed separation between normal and malignant BCP cells in 99% of studied patients. These 2 tubes were tested with a new erythrocyte bulk-lysis protocol allowing acquisition of high cell numbers in 377 bone marrow follow-up samples of 178 BCP-ALL patients. Comparison with RQ-PCR–based MRD data showed a clear positive relation between the percentage concordant cases and the number of cells acquired. For those samples with >4 million cells acquired, concordant results were obtained in 93% of samples. Most discordances were clarified upon high-throughput sequencing of antigen-receptor rearrangements and blind multicenter reanalysis of flow cytometric data, resulting in an unprecedented concordance of 98% (97% for samples with MRD < 0.01%). In conclusion, the fully standardized EuroFlow BCP-ALL MRD strategy is applicable in >98% of patients with sensitivities at least similar to RQ-PCR (£10), if sufficient cells (>4 3 10, preferably more) are evaluated., E.F. was supported by the Grant Agency of the Czech Republic (project of Centre of Excellence No. P302/12/G101). L.S., T.S., and P.T. were supported by European Research Area Network (ERA-NET) PrioMedChild, grant 40-41800-98-027. E.M. was supported by Ministry of Health of the Czech Republic, grant 15-28525A. M.K. was supported by the University Hospital Motol, Prague, Czech Republic (00064203). E.S.d.C., Q.L., and A.O. acknowledge the Bilateral Cooperation Program between Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brasília, Brazil) and Dirección General de Políticas Universitárias–Ministério de Educación, Cultura y Deportes (Madrid, Spain) (311/15). E.S.d.C. acknowledges Research Foundation of the State of Rio de Janeiro, Rio de Janeiro, Brazil (E26/110.105/2014, E26/102.191/2013) and Conselho Nacional de Desenvolvimento Científico e Tecnológico–CNPQ of Brazil (400194/2014-7). G.G., C.B., and P.B. were supported by Fondazione Tettamanti.

© 2019 The Authors., In recent years the volume and complexity of flow cytometry data has increased substantially. This has led to a greater number of identifiable cell populations in a single measurement. Consequently, new gating strategies and new approaches for cell population definition are required. Here we describe how the EuroFlow Lymphoid Screening Tube (LST) reference data base for peripheral blood (PB) samples was designed, constructed and validated for automated gating of the distinct lymphoid (and myeloid) subsets in PB of patients with chronic lymphoproliferative disorders (CLPD). A total of 46 healthy/reactive PB samples which fulfilled pre-defined technical requirements, were used to construct the LST-PB reference data base. In addition, another set of 92 PB samples (corresponding to 10 healthy subjects, 51 B-cell CLPD and 31 T/NK-cell CLPD patients), were used to validate the automated gating and cell-population labeling tools with the Infinicyt software. An overall high performance of the LST-PB data base was observed with a median percentage of alarmed cellular events of 0.8% in 10 healthy donor samples and of 44.4% in CLPD data files containing 49.8% (range: 1.3–96%) tumor cells. The higher percent of alarmed cellular events in every CLPD sample was due to aberrant phenotypes (75.6% cases) and/or to abnormally increased cell counts (86.6% samples). All 18 (22%) data files that only displayed numerical alterations, corresponded to T/NK-cell CLPD cases which showed a lower incidence of aberrant phenotypes (41%) vs B-cell CLPD cases (100%). Comparison between automated vs expert-bases manual classification of normal (r2 = 0.96) and tumor cell populations (rho = 0.99) showed a high degree of correlation. In summary, our results show that automated gating of cell populations based on the EuroFlow LST-PB data base provides an innovative, reliable and reproducible tool for fast and simplified identification of normal vs pathological B and T/NK lymphocytes in PB of CLPD patients., This work was supported by the CB16/12/00400 and CB16/12/00369 grants, CIBER-ONC, Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain and FONDOS FEDER; DTS 15/00119 grant, Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain and FONDOS FEDER; and, RETOS (RTC–2016–4865–1) grant, Sociedad de la Acción Estratégica de Economía y Sociedad Digital-Impulso Tecnológico; Ministerio de Economía y Competitividad, Madrid, Spain.

The germline variant at rs3824662 in GATA3 is a risk locus for Philadelphia-like acute lymphoblastic leukemia (Ph-like ALL), the biological subtype of B-cell precursor (BCP)-ALL defined by a distinct gene expression profile and the presence of specific somatic aberrations including rearrangements of CRLF2. In this study, we investigated whether rs3824662 in GATA3 associates with CRLF2 expression in leukemic cells and predicts prognosis in pediatric BCP-ALL patients treated according to the ALL Intercontinental Berlin-Frankfurt-Munster (IC BFM) 2009 (n = 645) and the ALL IC BFM 2002 (n = 216) protocols. High expression of CRLF2 was observed at both protein and mRNA levels (fourfold higher in AA than in CA + CC) among GATA3 AA variant carriers, independent of the presence of P2RY8-CRLF2 fusion. Additionally, the AA variant at rs3824662 was a significant factor affecting minimal residual disease level at the end of induction phase and overall survival regardless of the risk group and the protocol. The germline variant at rs3824662 in GATA3 is a prognostic factor which associates with CRLF2 expression in leukemic cells supporting the hypothesis that GATA3 may have a regulatory effect on the CRLF2 pathway in pediatric BCP-ALL.

Background To investigate the effects of obesity on CD47, phosphatidylserine (PS) exposure, and Caspase-8 and Caspase-3 activities in erythrocytes. Methods The study included 25 morbidly obese patients and 20 healthy people as the control group. We evaluated CD47 expression on the red blood cell (RBC) membrane surface and eryptosis markers such as PS externalization and caspase activity using flow cytometric analyses. Results CD47 expression on the RBC surface was significantly lower in obese patients than in the control group (P = 0.000001). We did not find significant differences in the Caspase-3 and Caspase-8 activities between the obese and nonobese control groups. Additionally, we did not find differences in PS exposure on erythrocyte membranes. The fibrinogen levels were higher in the obese group than they were in the control group (P = 0.00002). Correlations between CD47 expression and body mass index (r = −0.65; P = 0.0004), waist circumference (r = −0.54; P = 0.0052), and fibrinogen (r = 0.57; P = 0.0024) were found. Univariate analyses revealed that body mass index, waist circumference, hip circumference, and fibrinogen levels were potential predictors of CD47 expression. Multivariate analyses found that fibrinogen levels (β = 0.4708; P = 0.045) independently predicted CD47 expression. Conclusions The study demonstrated that CD47 expression is decreased on the surface of RBCs in obese subjects. These changes in CD47 expression on the RBC surface may be an adaptive response to hyperfibrinogenemia associated with obesity. © 2015 International Clinical Cytometry Society

Flow cytometric detection of minimal residual disease (MRD) in children with B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) requires immunophenotypic discrimination between residual leukaemic cells and B-cell precursors (BCPs) which regenerate during therapy intervals. In this study, EuroFlow-based 8-colour flow cytometry and innovative analysis tools were used to first characterize the immunophenotypic maturation of normal BCPs in bone marrow (BM) from healthy children, resulting in a continuous multiparametric pathway including transition stages. This pathway was subsequently used as a reference to characterize the immunophenotypic maturation of regenerating BCPs in BM from children treated for BCP-ALL. We identified pre-B-I cells that expressed low or dim CD34 levels, in contrast to the classical CD34 pre-B-I cell immunophenotype. These CD34 pre-B-I cells were relatively abundant in regenerating BM (11–85% within pre-B-I subset), while hardly present in healthy control BM (9–13% within pre-B-I subset; P = 0·0037). Furthermore, we showed that some of the BCP-ALL diagnosis immunophenotypes (23%) overlapped with CD34 pre-B-I cells. Our results indicate that newly identified CD34 pre-B-I cells can be mistaken for residual BCP-ALL cells, potentially resulting in false-positive MRD outcomes. Therefore, regenerating BM, in which CD34 pre-B-I cells are relatively abundant, should be used as reference frame in flow cytometric MRD measurements., The research for this manuscript was (in part) performed within the framework of the Erasmus Postgraduate School Molecular Medicine and was financially supported by PrioMedChild, project 40-41800-98-027. This study was performed within the EuroFlow Consortium, the EU-supported LSHB-CT2006-018708 FP6 Specific Targeted Research Project, which obtained sustainability based on income from the development of intellectual property and related patents, which have been licensed to industry. The work was supported through AZV (15-28525A) to EM and to MN.

We prospectively examined whether surface expression of Cytokine Receptor-Like Factor 2 (CRLF2) on leukemic blasts is associated with survival and induction treatment response in pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL) patients. Flow cytometric analysis of bone marrow-derived leukemia cells revealed that 7.51% (29/286) of 386 pediatric BCP-ALL patients were CRLF2-positive (CRLF2pos) at diagnosis. The median minimal residual disease (MRD) was lower in CRLF2pos than CRLF2-negative (CRLF2neg) patients on day 15 (MRD15) after induction therapy [0.01% (0.001-0.42%) vs. 0.45% (0.05-3.50%); p=0.001]. By contrast, the MRD15 was higher in Ikaros family Zinc Finger Protein 1 (IKZF1)-deleted BCP-ALL patients than in BCP-ALL patients without IKZF1 deletions [1.18% (0.06-12.0%) vs 0.33% (0.03-2.6%); p=0.003]. Subgroup analysis showed that MRD15 levels were lower in IKZF1Δ/CRLF2pos patients than in IKZF1Δ/CRLF2neg patients [0.1% (0.02-5.06%) vs. 2.9% (0.25-12%); p=0.005]. Furthermore, MRD15 levels were higher in IKZF1WT/CRLF2neg patients than in IKZF1WT/CRLF2pos patients [0.40% (0.04-2.7%) vs. 0.001% (0.001-0.01%)]. Despite the low MRD15 levels, IKZF1Δ/CRLF2pos patients showed poorer relapse-free survival (RFS) than other patient groups (p=0.003). These findings demonstrate that surface CRLF2 expression is associated with increased risk of relapse in pediatric BCP-ALL patients harboring IKZF1 deletions.

Although a growing body of data links mutations in the perforin gene with increased susceptibility to hematologic malignancies, no studies discuss their influence on the clinical course of such diseases. The present study examines the impact of perforin gene variation on the clinical outcome in acute lymphoblastic leukemia (ALL) patients. The study enrolled 312 children aged 1-18 years, treated for ALL. PRF1 gene variants were analyzed through direct DNA sequencing. Variation in rs885822 was found to be associated with overall survival: patients carrying the GG genotype demonstrated a significantly increased risk of death compared to those carrying the A allele, independently of ALL risk groups (HR 3.13, 95%CI 1.16-7.8, p = 0.014). The effect was even more pronounced in high-risk ALL patients (p = 0.006). On the other hand, the presence of the rs35947132 minor A allele was slightly protective with regard to overall prognosis (p = 0.047). No differences in relapse-free survival were observed with regard to genotypes. The results of the study may imply that perforin gene variation has a role in modifying mortality in childhood ALL.

Flow cytometry has become a highly valuable method to monitor minimal residual disease (MRD) and evaluate the depth of complete response (CR) in bone marrow (BM) of multiple myeloma (MM) after therapy. However, current flow-MRD has lower sensitivity than molecular methods and lacks standardization. Here we report on a novel next generation flow (NGF) approach for highly sensitive and standardized MRD detection in MM. An optimized 2-tube 8-color antibody panel was constructed in five cycles of design-evaluation-redesign. In addition, a bulk-lysis procedure was established for acquisition of ⩾107 cells/sample, and novel software tools were constructed for automatic plasma cell gating. Multicenter evaluation of 110 follow-up BM from MM patients in very good partial response (VGPR) or CR showed a higher sensitivity for NGF-MRD vs conventional 8-color flow-MRD -MRD-positive rate of 47 vs 34% (P=0.003)-. Thus, 25% of patients classified as MRD-negative by conventional 8-color flow were MRD-positive by NGF, translating into a significantly longer progression-free survival for MRD-negative vs MRD-positive CR patients by NGF (75% progression-free survival not reached vs 7 months; P=0.02). This study establishes EuroFlow-based NGF as a highly sensitive, fully standardized approach for MRD detection in MM which overcomes the major limitations of conventional flow-MRD methods and is ready for implementation in routine diagnostics., This work has been supported by the International Myeloma Foundation-Black Swan Research Initiative, the Red Temática de Investigación Cooperativa en Cáncer (RTICC); grant SA079U14 from the Consejería de Educación, Junta de Castilla y León, Valladolid, Spain and; grant DTS15/00119 from Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain.

The inactivation of tumor suppressor genes located within 9p21 locus (CDKN2A, CDKN2B) occurs in up to 30% of children with B-cell precursor acute lymphoblastic leukemia (BCP-ALL), but its independent prognostic significance remains controversial. In order to investigate the prognostic impact of deletions and promoter methylation within 9p21, 641 children with newly diagnosed BCP-ALL using methylation specific multiplex ligation-dependent probe amplification (MS-MLPA) were investigated. A total of 169 (26.4%) microdeletions in 9p21 were detected, of which 71 were homozygous. Patients with CDKN2A homozygous deletions were older at diagnosis (p

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivative Works 3.0 Unported License.-- EuroFlow Consortium (EU-FP6, LSHB-CT-2006-018708): et al., The EU-supported EuroFlow Consortium aimed at innovation and standardization of immunophenotyping for diagnosis and classification of hematological malignancies by introducing 8-color flow cytometry with fully standardized laboratory procedures and antibody panels in order to achieve maximally comparable results among different laboratories. This required the selection of optimal combinations of compatible fluorochromes and the design and evaluation of adequate standard operating procedures (SOPs) for instrument setup, fluorescence compensation and sample preparation. Additionally, we developed software tools for the evaluation of individual antibody reagents and antibody panels. Each section describes what has been evaluated experimentally versus adopted based on existing data and experience. Multicentric evaluation demonstrated high levels of reproducibility based on strict implementation of the EuroFlow SOPs and antibody panels. Overall, the 6 years of extensive collaborative experiments and the analysis of hundreds of cell samples of patients and healthy controls in the EuroFlow centers have provided for the first time laboratory protocols and software tools for fully standardized 8-color flow cytometric immunophenotyping of normal and malignant leukocytes in bone marrow and blood; this has yielded highly comparable data sets, which can be integrated in a single database., The research activities of the EuroFlow Consortium were supported by the European Commission (grant STREP EU-FP6, LSHB-CT-2006-018708, entitled ‘Flow cytometry for fast and sensitive diagnosis and follow-up of hematological malignancies’) and the following national grants: Spanish Network of Cancer Research Centers (ISCIII RTICC-RD06/0020/0035-FEDER), FIS 08/90881 from the ‘Fondo de Investigación Sanitaria’, Ministerio de Ciencia e Innovación (Madrid, Spain), SA016-A-09 from the Consejería de Educación, Junta de Castilla y León, Valladolid, Spain, and PIB2010BZ-00565 from the Dirección General de Cooperación Internacional y Relaciones Institucionales, Secretaría de Estado de Investigación, Ministerio de Ciencia e Innovación (Madrid, Spain). T Kalina, E Mejstrikova and O Hrusak were supported by the Czech Ministry of Education Grant No. MSM0021620813, Czech Ministry of Health grant NT/12425-4 and TK is supported as an ISAC Scholar by The International Society for Advancement of Cytometry.

Nijmegen breakage syndrome (NBS) is an autosomal recessive chromosomal instability disorder characterized by a high incidence of pediatric hematologic malignancies. Majority of patients affected are of Slavic origin and share the same founder mutation of 657del5 within the NBN gene encoding protein involved in DNA double-strand breaks (DSB) repair. We report a case of a pediatric patient with NBS, who developed t(9;11)/AF9-MLL-positive AML as a second malignancy after successful treatment of T-NHL. The coexistence of NBN and MLL mutations suggests that the profound dysfunction of NBN may promote alterations of MLL that is mediated by error-prone non-homologous end joining pathway particularly in patients treated with DNA topoisomerase II inhibitors.

Nowadays, the presence of specific genetic aberrations is progressively used for classification and treatment stratification, because acute leukemias with the same oncogenetic aberration generally form a clinically and diagnostically homogenous disease entity with comparable prognosis. Many oncogenetic aberrations in acute leukemias result in a fusion gene, which is transcribed into fusion transcripts and translated into fusion proteins, which are assumed to play a critical role in the oncogenetic process. Fusion gene aberrations are detected by karyotyping, FISH, or RT-PCR analysis. However, these molecular genetic techniques are laborious and time consuming, which is in contrast to flow cytometric techniques. Therefore we developed a flow cytometric immunobead assay for detection of fusion proteins in lysates of leukemia cell samples by use of a bead-bound catching antibody against one side of the fusion protein and fluorochrome-conjugated detection antibody. So far, we have been able to design such fusion protein immunobead assays for BCR-ABL, PML-RARA, TEL-AML1, E2A-PBX1, MLL-AF4, AML1-ETO and CBFB-MYH11. The immunobead assay for detection of fusion proteins can be performed within 3 to 4 hours in a routine diagnostic setting, without the need of special equipment other than a flow cytometer. The novel immunobead assay will enable fast and easy classification of acute leukemia patients that express fusion proteins. Such patients can be included at an early stage in the right treatment protocols, much faster than by use of current molecular techniques. The immunobead assay can be run in parallel to routine immunophenotyping and is particularly attractive for clinical settings without direct access to molecular diagnostics. © 2010 Elsevier Ltd. All rights reserved., The research and development of the flow cytometric immunobead assay and the EuroFlow Consortium were supported by the European Commission (grant STREP EU-FP6, LSHB-CT-2006- 018708).

An increasing number of evidences suggest a genetic predisposition in acute lymphoblastic leukemia (ALL) that might favor the occurrence of the driver genetic alterations. Such genetic background might also translate into phenotypic alterations of residual hematopoietic cells. Whether such phenotypic alterations are present in bone marrow (BM) cells from childhood B-cell precursor (BCP)-ALL remains to be investigated. Here we analyzed the immunophenotypic profile of BM and peripheral blood (PB) maturing/matured neutrophils from 118 children with BCP-ALL and their relationship with the features of the disease. Our results showed altered neutrophil phenotypes in most (77%) BCP-ALL cases. The most frequently altered marker was CD10 (53%), followed by CD33 (34%), CD13 (15%), CD15/CD65 (10%) and CD123 (7%). Of note, patients with altered neutrophil phenotypes had younger age (p = 0.03) and lower percentages of BM maturing neutrophils (p = 0.004) together with greater BM lymphocyte (p = 0.04), and mature B-cell (p = 0.03) counts. No significant association was found between an altered neutrophil phenotype and other disease features. These findings point out the potential existence of an altered residual hematopoiesis in most childhood BCP-ALL cases., This work was supported by the following grants: Bilateral Cooperation Program between Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES (Brasília/Brazil) and Dirección General de Políticas Universitárias – Ministério de Educación, Cultura y Deportes - DPGU (Madrid/Spain) (311/15) and RD12/0036/0048 from RETICS, (Instituto de Salud Carlos III, Ministerio de Economia y Competitividad, Madrid, Spain and Fondos FEDER); Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro of Brazil (E26/110.105/2014; E26/102.191/2013); Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPQ of Brazil (400194/2014–7). EO and DNRG were both supported by grants from CAPES (Brazil). NLD was partly supported by a grant from CNPQ (Brazil). TS and LS were supported by the internal grants from the Medical University of Silesia (Katowice, Poland).

To investigate the effects of obesity on CD47, phosphatidylserine (PS) exposure, and Caspase-8 and Caspase-3 activities in erythrocytes.The study included 25 morbidly obese patients and 20 healthy people as the control group. We evaluated CD47 expression on the red blood cell (RBC) membrane surface and eryptosis markers such as PS externalization and caspase activity using flow cytometric analyses.CD47 expression on the RBC surface was significantly lower in obese patients than in the control group (P = 0.000001). We did not find significant differences in the Caspase-3 and Caspase-8 activities between the obese and nonobese control groups. Additionally, we did not find differences in PS exposure on erythrocyte membranes. The fibrinogen levels were higher in the obese group than they were in the control group (P = 0.00002). Correlations between CD47 expression and body mass index (r = -0.65; P = 0.0004), waist circumference (r = -0.54; P = 0.0052), and fibrinogen (r = 0.57; P = 0.0024) were found. Univariate analyses revealed that body mass index, waist circumference, hip circumference, and fibrinogen levels were potential predictors of CD47 expression. Multivariate analyses found that fibrinogen levels (β = 0.4708; P = 0.045) independently predicted CD47 expression.The study demonstrated that CD47 expression is decreased on the surface of RBCs in obese subjects. These changes in CD47 expression on the RBC surface may be an adaptive response to hyperfibrinogenemia associated with obesity. © 2015 International Clinical Cytometry Society.

Nijmegen breakage syndrome (NBS) is an autosomal recessive chromosomal instability disorder characterized by a high incidence of pediatric hematologic malignancies. Majority of patients affected are of Slavic origin and share the same founder mutation of 657del5 within the NBN gene encoding protein involved in DNA double-strand breaks (DSB) repair. We report a case of a pediatric patient with NBS, who developed t(9;11)/AF9-MLL-positive AML as a second malignancy after successful treatment of T-NHL. The coexistence of NBN and MLL mutations suggests that the profound dysfunction of NBN may promote alterations of MLL that is mediated by error-prone non-homologous end joining pathway particularly in patients treated with DNA topoisomerase II inhibitors.

A better description of the leukemia cell surface proteome (surfaceome) is a prerequisite for the development of diagnostic and therapeutic tools. Insights into the complexity of the surfaceome have been limited by the lack of suitable methodologies. We combined a leukemia xenograft model with the discovery-driven chemoproteomic Cell Surface Capture technology to explore the B-cell precursor acute lymphoblastic leukemia (BCP-ALL) surfaceome; 713 cell surface proteins, including 181 CD proteins, were detected through combined analysis of 19 BCP-ALL cases. Diagnostic immunophenotypes were recapitulated in each case, and subtype specific markers were detected. To identify new leukemia-associated markers, we filtered the surfaceome data set against gene expression information from sorted, normal hematopoietic cells. Nine candidate markers (CD18, CD63, CD31, CD97, CD102, CD157, CD217, CD305, and CD317) were validated by flow cytometry in patient samples at diagnosis and during chemotherapy. CD97, CD157, CD63, and CD305 accounted for the most informative differences between normal and malignant cells. The ALL surfaceome constitutes a valuable resource to assist the functional exploration of surface markers in normal and malignant lymphopoiesis. This unbiased approach will also contribute to the development of strategies that rely on complex information for multidimensional flow cytometry data analysis to improve its diagnostic applications.

Chromosomal rearrangements of the human MLL (mixed lineage leukemia) gene are associated with high-risk infant, pediatric, adult and therapy-induced acute leukemias. We used long-distance inverse-polymerase chain reaction to characterize the chromosomal rearrangement of individual acute leukemia patients. We present data of the molecular characterization of 1590 MLL-rearranged biopsy samples obtained from acute leukemia patients. The precise localization of genomic breakpoints within the MLL gene and the involved translocation partner genes (TPGs) were determined and novel TPGs identified. All patients were classified according to their gender (852 females and 745 males), age at diagnosis (558 infant, 416 pediatric and 616 adult leukemia patients) and other clinical criteria. Combined data of our study and recently published data revealed a total of 121 different MLL rearrangements, of which 79 TPGs are now characterized at the molecular level. However, only seven rearrangements seem to be predominantly associated with illegitimate recombinations of the MLL gene (≈ 90%): AFF1/AF4, MLLT3/AF9, MLLT1/ENL, MLLT10/AF10, ELL, partial tandem duplications (MLL PTDs) and MLLT4/AF6, respectively. The MLL breakpoint distributions for all clinical relevant subtypes (gender, disease type, age at diagnosis, reciprocal, complex and therapy-induced translocations) are presented. Finally, we present the extending network of reciprocal MLL fusions deriving from complex rearrangements.

Introduction Germline variant at rs3824662 in GATA3 gene was associated with early response to treatment as well as relapse risk in childhood BCP-ALL treated with COG protocols. This effect resulted from the strong link between the GATA3 polymorphism and the presence of somatic defects in leukemic cells including IKZF1 deletions, CRLF2 rearrangements and JAK2 gene mutations, which promote aggressive course of the disease. Aims The study aimed to evaluate an association between GATA3 gene polymorphism and clinical and biological features of pediatric BCP-ALL treated with the BFM backbone protocols. Methods Between November 2010 and June 2016, 957 consecutive children with newly diagnosed BCP-ALL were enrolled into the study. 822 patients treated according to ALL-IC BFM2009 protocol (n=594) and ALL-IC BFM2002 protocol (n=228) in 15 centers of the Polish Pediatric Leukemia/Lymphoma Study Group were enrolled into the study (median age 4.5 yrs, median follow-up time 2.5 yrs). Patients with BCR-ABL1 and MLL gene rearrangements were excluded from the analysis. The rs3824662 polymorphism of the GATA3 gene was genotyped using TaqMan probes. GATA3 mRNA expression level in leukemic cell was evaluated in BCP-ALL cases using qPCR with FAM-MGB probes (n=136). Targeted copy number screening of selected 23 loci was performed using the P335-B2 SALSA MLPA kit (MRC-Holland, Netherlands) in n=807 available DNA leukemia samples. MRD at day 15 and 33 was measured by flow cytometry with EuroFlow 8-color antibody panels. Results In the study group genotypes distribution withinrs3824662 of GATA3 was as follows: AA: n=44 (5.4%); CA: n=266 (32.4%); CC: n=512 (62.3%). Median MRD15 and MRD33 were 0.31% and 0.001% respectively. IKZF1 deletion were found in 18%, PAX5 in 20%, PAR1 in 12%, CDKN2A in 24%, CDKN2B 20%, BTG1 in 6.3%, ETV6 in 21%, EBF1 in 4% and RB1 in 6% of cases. Leukemic cells harbouring AA variant withinrs3824662 showed GATA3 mRNA expression 1.6 and 2.2 times higher compared to cells with CA and CC variants respectively, with the difference close to significant (ANOVA p=0.06). The presence of AA variant was not related to any gene deletion apart from microdeletions of the pseudoautosomal region PAR1 (Xp22 and Yp11) which occurred more frequently in AA carriers as compared to CA and CC carriers (11/41 vs. 34/242 vs. 52/468, p=0.013). We did not find any association of clinical features such as initial WBC, steroid response, sex and age at diagnosis among BCP-ALL patients with GATA3 genotype. However, AA carriers had a higher risk for MRD>10% at day 15 OR (95%CI)=3.93 (1.37-11.23) as well as MRD>0.01% at day 33, OR(95%CI)=2.95 (1.12-7.73) as compared CC carriers. Cox model of survival analysis was done for variables with univariate significance of p Conclusions We showed that carriers of AA genotype in GATA3 are prone to develop PAR1 -deleted BCP-ALL. Moreover our study confirmed an association of GATA3 AA rs3824662 homozygosity with poor early response to treatment as well as risk of death among pediatric BCP-ALL patients treated with the BFM backbone protocols. Disclosures Madzio: National Science Centre: Research Funding.

Background Juvenile myelomonocytic leukemia (JMML) is a lethal myeloproliferative disease (MPD) of young childhood characterized by an overproduction of myelomonocytic cells and an increased in vitro sensitivity of hematopoietic progenitors to granulocyte-macrophage colony-stimulating factor [GM-CSF] (Emanuel PD et al, Blood 1991). Diagnostic criteria for JMML are currently well-established and based on clinical features and laboratory findings. However, in some patients diagnosis of JMML vs other overlapping disease entities, still remains a challenge, immunophenotyping being not part of the diagnostic work-up of JMML. Here, we aimed at detailed characterization of the CD34+ cell compartment in JMML bone marrow (BM) using the standardized EuroFlow myeloid panel in combination with innovative EuroFlow software maturation tools. Our major goal was to determine the potential utility of immunophenotyping of CD34 cells in the diagnostic work-up of JMML. Methods Overall, we analyzed BM cells from 10 JMML patients at diagnosis (age range: 0-7 years), 17 control subjects (age range: 0-15 years) and 5 patients (age range: 0-5 years) with a suspected diagnosis of JMML that was subsequently not confirmed following standardized EuroFlow antibody combinations: 1) cyCD3/ CD45/ cyMPO/ cyCD79a/ CD34/ CD19 / CD7/smCD3 (for early lineage assignement); 2) HLADR/CD45/CD16/CD13/CD34/CD117/CD11b/CD10 (neutrophilic maturation); 3) HLADR/CD45/CD35/CD64/CD34/CD117/CD300e (IREM2)/CD14 (monocytic maturation); 4) HLADR/CD45/CD36/CD105/CD34/CD117/CD33/CD71 (erythroid vs plasmacytoid dendritic cell maturation). Samples were processed and analyzed according to the Euroflow standard operating protocols (van Dongen JJM et al, Leukemia 2012, Kalina T et al, Leukemia 2012). Data analysis was specifically focused on the immunophenotypic profile of CD34+ gated cells. Results Within the CD34+ BM cell compartment the proportion (mean % ± 1SD) of granulocytic and monocytic precursors were not significantly different in JMML as compared to controls: 33% ± 15% vs 25% ± 12% (p = 0.16) and 14% ± 6.3% vs 12% ± 7.1% (p = 0.68) respectively. Otherwise we observed a slightly decreased in erythroid CD34+ progenitors in JMML vs controls (1.0% ± 1.2% vs 2.8% ± 1.7%, p Conclusions CD34+ precursor cells from JMML patients display a unique immunophenotypic profile characterized by an inverted ratio of CD19+ B/CD7+ lymphoid precursors, associated with unusual marker coexpressions, which might contribute to fast and more precise diagnostic work-up of JMML. Further studies in larger patient series are required to confirm our observations. Disclosures Biondi: Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Advisory Board; BMS: Membership on an entity's Board of Directors or advisory committees; Cellgene: Other: Advisory Board.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivative Works 3.0 Unported License.-- EuroFlow Consortium: et al., The PML-RARA fusion protein is found in approximately 97% of patients with acute promyelocytic leukemia (APL). APL can be associated with life-threatening bleeding complications when undiagnosed and not treated expeditiously. The PML-RARA fusion protein arrests maturation of myeloid cells at the promyelocytic stage, leading to the accumulation of neoplastic promyelocytes. Complete remission can be obtained by treatment with all-trans-retinoic acid (ATRA) in combination with chemotherapy. Diagnosis of APL is based on the detection of t(15;17) by karyotyping, fluorescence in situ hybridization or PCR. These techniques are laborious and demand specialized laboratories. We developed a fast (performed within 4-5 h) and sensitive (detection of at least 10% malignant cells in normal background) flow cytometric immunobead assay for the detection of PML-RARA fusion proteins in cell lysates using a bead-bound anti-RARA capture antibody and a phycoerythrin-conjugated anti-PML detection antibody. Testing of 163 newly diagnosed patients (including 46 APL cases) with the PML-RARA immunobead assay showed full concordance with the PML-RARA PCR results. As the applied antibodies recognize outer domains of the fusion protein, the assay appeared to work independently of the PML gene break point region. Importantly, the assay can be used in parallel with routine immunophenotyping for fast and easy diagnosis of APL., The research and development of the flow cytometric immunobead assay and the EuroFlow Consortium were supported by the European Commission (grant STREP EU-FP6, LSHB-CT-2006-018708; Flow cytometry for fast and sensitive diagnosis and follow-up of hematological malignancies).

EuroFlow Consortium (EU-FP6, LSHB-CT-2006-018708): et al., This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivative Works 3.0 Unported License., Most consensus leukemia lymphoma antibody panels consist of lists of markers based on expert opinions, but they have not been validated. Here we present the validated EuroFlow 8-color antibody panels for immunophenotyping of hematological malignancies. The single-tube screening panels and multi-tube classification panels fit into the EuroFlow diagnostic algorithm with entries defined by clinical and laboratory parameters. The panels were constructed in 2-7 sequential design-evaluation-redesign rounds, using novel Infinicyt software tools for multivariate data analysis. Two groups of markers are combined in each 8-color tube: (i) backbone markers to identify distinct cell populations in a sample, and (ii) markers for characterization of specific cell populations. In multi-tube panels, the backbone markers were optimally placed at the same fluorochrome position in every tube, to provide identical multidimensional localization of the target cell population(s). The characterization markers were positioned according to the diagnostic utility of the combined markers. Each proposed antibody combination was tested against reference databases of normal and malignant cells from healthy subjects and WHO-based disease entities, respectively. The EuroFlow studies resulted in validated and flexible 8-color antibody panels for multidimensional identification and characterization of normal and aberrant cells, optimally suited for immunophenotypic screening and classification of hematological malignancies., We are grateful to Dr Jean-Luc Sanne of the European Commission for his support and monitoring of the EuroFlow project. The research activities of the EuroFlow Consortium were supported by the European Commission (grant STREP EU-FP6, LSHB-CT-2006-018708, entitled ‘Flow cytometry for fast and sensitive diagnosis and follow-up of hematological malignancies’) and the following national grants: Spanish Network of Cancer Research Centers (ISCIII RTICC-RD06/0020/0035-FEDER), FIS 08/90881 and FIS PS09/02430 from the ‘Fondo de Investigación Sanitaria’, Ministerio de Ciencia e Innovación (Madrid, Spain); GR37 EDU/894/2009 and SA016-A-09 from the Consejería de Educación, Junta de Castilla y León (Valladolid, Spain); PIB2010BZ-00565 from the Dirección General de Cooperación Internacional y Relaciones Institucionales, Secretaría de Estado de Investigación, Ministerio de Ciencia e Innovación (Madrid, Spain); Ministry of Health Czech Republic (NT/12425-4 and NS/10480-3); and Charles University grant No. 23010 and UNCE No. 204012; Tomas Kalina is supported as an ‘ISAC Scholar’ by the International Society for Advancement of Cytometry (ISAC); Andy Rawstron was supported by Leukemia and Lymphoma Research (LLR).

Abstract 2700 Objective: Infant acute lymphoblastic leukemia (ALL) is characterized by distinct biological and clinical features. In this study, we aimed at detailed evaluation of infant ALL immunophenotype based on the large cohort of patients treated homogeneously on INTERFANT'99 protocol. Patients and Methods: We were able to obtain sufficient flow cytometry based immunophenotypic data from 286 (130 boys and 156 girls) of 483 infant ALL cases treated on INTERFANT'99 protocols. The distribution of patient and leukemia characteristics as well as clinical outcome were very similar to the entire study cohort (Pieters et al, Lancet 2007; 370: 240–250). The positivity for a certain antigen was defined at the cut-off value of >20% of cells expressing this antigen. In B-cell precursor ALL (BCP-ALL), evaluated antigens included CD10, CD20, CD34, myeloid markers (CD13, CD33, CD15 and/or CD65) and NG2 antigen assessed with 7.1 antibody. The strength of association between characteristics (patient's age and gender, initial white blood count [WBC], CNS involvement, presence of MLL gene rearrangements, prednisone response [PR]) and antigen expression was analyzed with Fisher exact test adjusted for multiple comparisons. Univariate analysis of outcome by immunophenotype was based on event free survival (EFS) and compared by log-rank test. Multivariate analysis was performed using Cox model in MLL-rearranged cases. P values < 0.05 were considered to be significant. Results: Altogether, 272 cases of infant BCP-ALL and 14 of infant T-ALL were analyzed. Most BCP-ALL cases were CD10 negative (66%), CD20 negative (88%), CD34 positive (60%), and NG2 positive (58%). Co-expression of myeloid antigens was less frequent and concerned CD13 in 8%, CD33 in 17%, CD15 in 31%, and CD65 in 28%. CD10 negativity and NG2 expression were significantly more frequent in younger infants, patients with initial high leukocytosis and with MLL rearrangements. CD34 expression was observed more frequently in younger infants, while CD20 positivity was significantly associated with lower initial leukocytosis and absence of MLL rearrangement. For myeloid antigen expression, the only significant association was more frequent CNS involvement in infants with CD13+ and/or CD33+ BCP-ALL. Analysis of outcome showed significantly better prognosis for CD10 positivity (4-year EFS of 56.3 as compared to 37.2 for CD10 negative BCP-ALL), absence of NG2 expression (4-year EFS of 63.9 as compared to 34.9 for NG2 positive BCP-ALL) and CD33 negativity (4-year EFS of 47.6 as compared to 27.7 for CD33 positive BCP-ALL). There was also a trend towards better outcome in CD20 positive infant BCP-ALL. While CD10 negativity and NG2 positivity were associated with well-known high-risk features, prognostic significance of CD33 expression is somewhat more difficult to explain. Of note, CD10 negativity was not associated to a worst outcome in MLL-rearranged patients. Moreover, in this subset, multivariate analysis showed that none of the markers analyzed had independent prognostic significance, after adjustment for sex, age at diagnosis, WBC and PR. In rare infant T-ALL cases, we observed equal distribution to different immunophenotypic subgroups as defined by EGIL classification. Conclusion: Infant BCP-ALL has distinct immunophenotypic features. However, immunophenotype has no independent prognostic relevance when MLL, age, WBC, PR and other factors are included. Disclosures: No relevant conflicts of interest to declare.

Chalcones exhibit chemopreventive and antitumor effects. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a naturally occurring anticancer agent that induces apoptosis in cancer cells and is not toxic to normal cells. We examined the cytotoxic and apoptotic effect of five chalcones in combination with TRAIL on prostate cancer cells. The cytotoxicity was evaluated by the MTT and LDH assays. The apoptosis was determined using flow cytometry with annexin V-FITC. Our study showed that all five tested chalcones: chalcone, licochalcone-A, isobavachalcone, xanthohumol, butein markedly augmented TRAIL-mediated apoptosis and cytotoxicity in prostate cancer cells and confirmed the significant role of chalcones in chemoprevention of prostate cancer.

Embryonic stem (ES) cells represent an attractive tool not only for the study of the development of various cell types but also as a potential source of cells for transplantation. Previous studies suggested a role of the signal transduction protein SRC homology 2(SH2) protein of Beta-cells (SHB) for the development of both pancreatic 3-cells and blood vessels. SHB is an SH2 domain-containing adapter protein involved in the generation of signaling complexes in response to activation of a variety of receptors, several of which have been implicated in developmental processes. Moreover, microarray analysis of ES cells expressing mutant SHB has revealed decreased expression of several genes of developmental importance. Here, we present protocols that may be used for transfection of mouse ES cells and to study the differentiation of ES cell-derived embryoid bodies (EBs) into the pancreatic Beta-cell lineage as well as into vascular structures with special reference to the effect of SHB. Moreover, we also provide a protocol that may be used for enrichment by fluorescence-activated cell sorting of specific cell lineages in EBs.

BACKGROUND Cytotoxic treatment in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) patients induces a dramatic decrease in B-cell precursor (BCP) and mature B-cell numbers, followed by regeneration of BCPs in the bone marrow (BM) and subsequent replenishment of mature B-cells in the peripheral blood (PB) in between treatment blocks and after stop of treatment. To understand the degree of B-cell recovery after such dramatic changes, we first evaluated the composition of the B-cell population in the BM and PB of pediatric BCP-ALL patients during and after therapy. Secondly, we investigated whether the immunophenotypic maturation of BCPs in regenerating BM is similar to normal BCP development or whether such regeneration induces immunophenotypic aberrancies, which could potentially hamper minimal residual disease (MRD) detection. Finally, we assessed whether compensatory proliferation plays a role during B-cell regeneration, since enhanced proliferation might limit the B-cell receptor diversity and consequently may affect susceptibility to infections during and after therapy. METHODS For immunophenotypic characterization of different B-cell subsets, 8-color flow cytometry was performed on fresh BM and PB samples at different time points after start of therapy (DCOG ALL11-protocol). To study BCP maturation, a multidimensional maturation pathway based on 5 backbone markers was designed and the expression pattern of several differentiation markers during this maturation pathway was evaluated. To assess proliferation in BCP subsets, BM samples were stained with subset-specific antibodies and DRAQ5 for cell cycle analysis. The proliferation history of sorted pre-B-II-small and immature subsets in BM and sorted mature B-cell subsets in PB was assessed by performing a kappa-deleting recombination excision circle (KREC)-assay. RESULTS BCP regeneration occurred mainly at day 78, month 5 and after stop of therapy. The BCP compartment in regenerating BM at time points during therapy showed a shift towards the most immature stages. In PB, mature B-cell numbers decreased after start of therapy and newly generated mature B-cells subsets reappeared at month 5 and after stop of therapy. Importantly, the BCP maturation pathway with its expression patterns of CD10, CD34, CD58, CD66c, CD38, CD123, CD9, CD81, CD24, TdT, Igκ and Igλ was comparable between regenerating BM and BM of healthy individuals, albeit that a shift in the relative BCP subset distribution was observed in regenerating BM. As expected, most proliferation in BM of healthy controls occurred in the pre-B-II-large subset (68% ±11% (mean ±SD) proliferating cells). Comparable percentages of proliferating pre-B-II-large cells were found in regenerating BM: 74%±10% at day 78, 72%±10% at month 5 and 63% (preliminary data, n=1) at one year after stop of therapy (month 36). Also pre-B-I cells showed some proliferation, with no significant differences between normal and regenerating BM (Figure 1). If present, the pre-B-II-small and immature BCP subsets showed no proliferation in regenerating and normal BM. KREC-analysis of sorted pre-B-II-small and immature subsets confirmed that no cell divisions had occurred after IGK-rearrangement in normal BM as well as regenerating BM at month 5 and month 36. Low numbers of pre-B-II-small and immature cells precluded KREC-analysis at day 78. KREC-analysis of the various mature B-cell subsets in PB showed no significant difference in proliferation history between PB of patients at different time points during or after therapy and PB of healthy controls. CONCLUSIONS In BCP-ALL patients, the B-cell compartment is drastically affected during treatment. Subsequent regeneration of BCPs and mature B-cells occurs at different time points during therapy and after stop of therapy. Immunophenotypically, BCP maturation in regenerating BM is similar to normal B-cell differentiation, indicating that MRD detection will not be hampered by aberrant immunophenotypes of regenerating BCPs. Importantly, no enhanced proliferation is observed in BCP subsets in BM and mature B-cells subsets in PB of patients during and after therapy. The lack of compensatory proliferation suggests that B-cell regeneration is due to a larger influx of non-committed stem cells into the B-cell lineage and indicates that a diverse immune repertoire will most likely be restored during recovery of the B-cell compartment. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Background CXCR4 (CD184) is a receptor specific to the Stromal Derived Factor 1 (SDF-1), a ligand also known as CXCL12. The ligand-receptor interaction has a pleiotropic effect on hematopoietic cell proliferation, migration and activation through several signaling pathways. CXCR4 expression on neoplastic cells might be responsible for their dissemination to particular organs with cells expressing CXCL12 (e.g. lymph nodes, bones, and within bone marrow). In B-cell precursor acute lymphoblastic leukemia (BCP-ALL), expression of CXCR4 was associated with higher capacity of leukemic blasts to seed into bone marrow niches. Aim of the study The study aimed at thorough analysis of CXCR4 expression on BCP-ALL blasts and correlation of CXCR4 expression with the expression of other antigens such as CD66c, CD34, CD10, CD38, CD20 and CD45 as well as with the levels of minimal residual disease on day 15. Patients and Methods The study group consisted of 198 consecutive children aged 0-18 years (median 4.4 years) treated for BCP-ALL in the centers of the Polish Pediatric Leukemia/Lymphoma Study Group. Bone marrow samples obtained at initial diagnosis were stained with monoclonal antibodies (CD58, CD66c, CD34, CD19, CD10, CD38, CD20, CD45, CXCR4) in two 8-color tubes and analyzed with multiparameter flow cytometry (BD FACSCanto II, Becton Dickinson, San Jose, CA, USA) according to the EuroFlow standard protocols. The expression of particular antigens on BCP-ALL blasts was defined by median fluorescence. In 177 patients the samples from day 15 were available and analyzed for the presence of minimal residual disease (MRD) with multicolor flow cytometry. Infinicyt software (Cytognos, Salamanca, Spain) was used for more detailed analyses of the flow cytometric data. Results The expression of CXCR4 in BCP-ALL was highly variable with median fluorescence ranging from 252 to 24 388 (median 4011). There was no obvious correlation of CXCR4 expression with immunophenotype and with the expression of other analyzed markers (CD66, CD34, CD10, CD38 i CD45). The only borderline significant correlation found was between CXCR4 and CD20 expression. On day 15, 70 children (39%) demonstrated MRD levels below 0.1%, which is consistent with MRD-based low-risk group. Among these patients, 41 children had undetectable MRD already at this time point. In contrary, MRD levels > 10% were recorded in 21 patients (12%), who were stratified to high-risk group, accordingly. Maximal MRD levels recorded at day 15 were 85.6%. In remaining 86 children (49%), MRD levels at day 15 were in-between 0.1% and 10%, which reflects intermediate response to the treatment. There was no correlation between CXCR4 expression and MRD levels at day 15. Conclusion CXCR4 expression on BCP-ALL blasts is highly heterogeneous and is not associated with particular leukemia immunophenotype. Further analyses should characterize clinical features of leukemia and treatment response with regard to CXCR4 expression. The study was supported by Polish National Center of Science grant N N407 687040. Disclosures: No relevant conflicts of interest to declare.

Abstract 2506 Comprehensive identification of leukemia-associated cell surface molecules is required to improve the specificity and sensitivity of flow cytometric analysis of minimal residual disease. A more comprehensive map of leukemia-associated cell surface features could facilitate the selection and subsequent evaluation of new minimal residual disease (MRD) markers as a resource and provide direct cues for new therapeutic targets. Here, we used the chemoproteomic Cell Surface Capturing technology (CSC) to establish a surfaceome map consisting of 807 cell surface detectable proteins detected in an xenograft model derived from diagnostic samples from 19 pediatric patients with acute lymphoblastic leukemia (ALL). Because CSC is based on direct chemical tagging of protein and glycoprotein residues on the surface of living cells, highly viable samples are required to avoid intracellular contaminants. Direct processing of xenograft samples provided optimal conditions for CSC. We included 8 cases with resistant disease based on persistence of minimal residual disease (MRD) during chemotherapy, which represents a group of patients at need for innovative approaches. Comparative analysis of this proteomic dataset showed that CSC recapitulated and expanded the diagnostic immunophenotype of each patient. To select and test for new proteins with potential value for MRD detection within the large set of identified leukemia proteins, the dataset was filtered against gene expression data from sorted populations of the normal human hematopoietic tree according to their relative RNA expression levels in normal hematopoiesis (DMAP, Novershtern et al, 2011, Cell, 144, 296–309). Based on expected low levels of mRNA expression in normal early and late B-cell precursors in the bone marrow, a subset of markers was identified. These included cell surface features that were previously implicated in leukemogenesis, such as IL7R or FLT3, or shown to serve as diagnostic markers for flow cytometry such as CD58, CD99 and CD300A. For a first clinical validation phase, we selected 38 markers based on their frequency in the CSC dataset to evaluate whether they could contribute to a better distinction of leukemic blasts from their normal counterparts. We tested monoclonal antibodies that were available for 15 candidate markers on diagnostic and remission samples from ALL patients for relevant expression on leukemia cells. Data is currently available for 9 markers that were evaluated prospectively on 51 patients enrolled in current clinical treatment protocols. All markers detected leukemia-associated features in at least a subset of the patients. As anticipated, differences in antigen abundance and antigenic shifts under treatment varied from case to case, underscoring the advantage of increasing the number of available markers for MRD detection. Taken together, our surfaceome data provides an unprecedented view at the cell surface landscape of ALL cells including new prequalified candidate MRD markers, which will accelerate the introduction and subsequent evaluation of multiple parameters for leukemia diagnostics. This also constitutes a valuable resource for functional studies and evaluation of new options for therapeutic targeting. Disclosures: No relevant conflicts of interest to declare.