Principal component analysis yields results comparable to those of an elaborate Boolean strategy: simplifying the assessment of measurable residual disease in chronic lymphocytic leukemia patients

INTRODUCTION

Measurable residual disease (MRD) is becoming increasingly important in the chronic lymphocytic leukemia (CLL) context. It is of independent prognostic significance in terms of favorable progression-free and overall survival. The standardized methods used to assess CLL MRD are based on flow cytometry and real-time quantitative PCR. We here present a nine-color assay for CLL MRD with the ROR-1 marker antigen as recommended by the European Research Initiative (ERIC) on CLL; the sensitivity is at least 10-5.

MATERIALS AND METHODS

We used 54 samples to develop a new principal component analysis (PCA) method based on the Kaluza© "radar" presentation mode. We used a Navios flow cytometer (Beckman Coulter©).

RESULTS

We confirmed the linearity of our method over more than five dilutions. The specificity limit was 1.3×10-6 and the lower limit of detection was 3.6×10-6. Compared to the Boolean method, the sensitivity, specificity, and positive and negative predictive values of our PCA method were 100%. When MRD was detectable, PCA and Boolean assays were in agreement (linear regression, R2 = 0.99).

CONCLUSION

We developed a new PCA-based method for detection of CLL MRD. Our method is comparable to that of the consensus method in terms of sensitivity, and it is also much easier and faster.

A fixed-duration immunochemotherapy approach in CLL: 5.5-year results from the phase 2 ICLL-07 FILO trial

In previously untreated, medically fit patients with chronic lymphocytic leukemia (CLL), research is focused on developing fixed-duration strategies to improve long-term outcomes while sparing patients from serious toxicities. The ICLL-07 trial evaluated a fixed-duration (15-month) immunochemotherapy approach in which after obinutuzumab-ibrutinib induction for 9 months, patients (n = 10) in complete remission (CR) with bone marrow (BM) measurable residual disease (MRD) <0.01% continued only ibrutinib 420 mg/day for 6 additional months (I arm), whereas the majority (n = 115) received up to 4 cycles of fludarabine/cyclophosphamide-obinutuzumab 1000 mg alongside the ibrutinib (I-FCG arm). Primary analysis at month 16 showed that 84 of 135 (62.2%) patients enrolled achieved CR with a BM MRD <0.01%. Here, we report follow-up at median 63 months. Peripheral blood (PB) MRD was assessed 6 monthly beyond the end of treatment using a highly sensitive (10-6) flow cytometry technique. In the I-FCG arm, the PB MRD <0.01% rate (low-level positive <0.01% or undetectable with limit of detection ≤10-4) in evaluable patients was still 92.5% (74/80) at month 40 and 80.6% (50/62) at month 64. No differences in the PB MRD status were apparent per to the IGHV mutational status. In the overall population, 4-year progression-free and overall survival rates were 95.5% and 96.2%, respectively. Twelve deaths occurred overall. Fourteen serious adverse events occurred beyond the end of treatment. Thus, our fixed-duration immunochemotherapy approach produced deep and sustained PB MRD responses, high survival rates, and low long-term toxicity. A randomized trial is needed to compare our immunochemotherapy approach with a chemotherapy-free strategy. This trial was registered at www.clinicaltrials.gov as #NCT02666898.

Immuno-regulatory malignant B cells contribute to Chronic Lymphocytic Leukemia progression

Chronic Lymphocytic Leukemia (CLL) is a heterogeneous B cell neoplasm ranging from indolent to rapidly progressive disease. Leukemic cell subsets with regulatory properties evade immune clearance; however, the contribution of such subsets during CLL progression is not completely elucidated. Here, we report that CLL B cells crosstalk with their immune counterparts, notably by promoting the regulatory T (Treg) cell compartment and shaping several helper T (Th) subsets. Among various constitutively- and BCR/CD40-mediated factors secreted, tumour subsets co-express two important immunoregulatory cytokines, IL10 and TGFβ1, both associated with a memory B cell phenotype. Neutralizing secreted IL10 or inhibiting the TGFβ signalling pathway demonstrated that these cytokines are mainly involved in Th- and Treg differentiation/maintenance. In line with the regulatory subsets, we also demonstrated that a CLL B cell population expresses FOXP3, a marker of regulatory T cells. Analysis of IL10, TGFβ1 and FOXP3 positive subpopulations frequencies in CLL samples discriminated 2 clusters of untreated CLL patients that were significantly different in Tregs frequency and time-to-treatment. Since this distinction was pertinent to disease progression, the regulatory profiling provides a new rationale for patient stratification and sheds light on immune dysfunction in CLL.

miRNA profile at diagnosis predicts treatment outcome in patients with B-chronic lymphocytic leukemia: A FILO study

During many years, chemo-immunotherapy fludarabine-cyclophosphamide-rituximab (FCR) was the gold standard for first line treatment of medically fit patients with symptomatic B-chronic lymphocytic leukemia (CLL). Over the last decade, targeted biotherapies have revolutionized the treatment of B-CLL patients and almost entirely supplanted FCR. However, no biomarker still exists to predict the complete remission (CR) with undetectable minimal residual disease (uMRD) in bone marrow (BM), which remains the best predictive factor for survival. MicroRNAs represent a class of molecular biomarkers which expression is altered in B-CLL. Our study aimed at identifying before treatment blood miRNAs that predict treatment outcome in previously untreated B-CLL patients (NCT 01370772, https://clinicaltrials.gov/ct2/show/NCT01370772). Using hierarchical clustering of miRNA expression profiles discriminating 8 patients who achieved CR with BM uMRD from 8 patients who did not achieve CR and displayed detectable BM MRD, we identified 25 miRNAs differentially expressed before treatment. The expression of 11 miRNAs was further validated on a larger cohort (n=123). Based on the dosage of 5 miRNAs at diagnosis, a decision tree was constructed to predict treatment outcome. We identified 6 groups of patients with a distinct probability of being CR with BM uMRD to FCR treatment, ranging from 72% (miR-125b, miR-15b and miR-181c high) to 4% (miR-125b and miR-193b low). None of the patients displaying high expression levels of miR-125b, miR-15b and miR-181c relapsed during study follow-up. In contrast, patients with low miR-15b and high miR-412, or with low miR-125b and miR-193b, demonstrated significant low PFS. RNA sequencing of blood at diagnosis identified that patients relapsing after treatment are characterized by significant enrichment of gene signatures related to cell cycle, MYC target genes, metabolism and translation regulation. Conversely, patients achieving CR with BM uMRD displayed significant enrichment in genes related to communication between CLL cells and the microenvironment, immune system activation and upregulation of polycomb PRC2 complex target genes. Our results suggest that blood miRNAs are potent predictive biomarkers for FCR treatment efficacy and might be implicated in the FCR efficacy in B-CLL patients, providing new insight into unmet need for the treatment of B-CLL patients and identifying pathways predictive of patients’ remission.

Angiogenic factors could help us to define patients obtaining complete response with undetectable minimal residual disease in untreated CLL patients treated by FCR: results from the CLL2010FMP, a FILO study

Angiogenesis is in a constant balance between pro and anti-angiogenic factors. Neoangiogenesis, implicated in metastatic spreading is characterized in solid cancers, but fairly new in chronic lymphocytic leukemia (CLL). We hypothesize that secretion of angiogenic factors could be correlated to the pathogenesis of CLL, and therefore predict the outcome of patients. We investigated concentrations of 22 cytokines and chemokines in 137 non-del 17p B-CLL patients, treated with a fludarabine-cyclophosphamide-rituximab (FCR)-based regimen. We constructed a biomarker index defining different risk groups based on lymphocyte count, the intensity of CD20 antigen on CD19⁺ cells, Ang-2, and PDGF-BB plasma concentrations at diagnosis. Four groups were defined, exhibiting specific molecular signatures and correlated with progression-free survival of patients. Our results suggest that we can determine at diagnosis of non-del 17p B-CLL patients, those with a very high probability of progression-free survival, independently of IGVH mutational status and residual disease at the end of treatment.

Obinutuzumab and ibrutinib induction therapy followed by a minimal residual disease-driven strategy in patients with chronic lymphocytic leukaemia (ICLL07 FILO): a single-arm, multicentre, phase 2 trial

BACKGROUND

In patients with chronic lymphocytic leukaemia, achievement of a complete response with minimal residual disease of less than 0·01% (ie, <1 chronic lymphocytic leukaemia cell per 10 000 leukocytes) in bone marrow has been associated with improved progression-free survival. We aimed to explore the activity of induction therapy for 9 months with obinutuzumab and ibrutinib, followed up with a minimal residual disease-driven therapeutic strategy for 6 additional months, in previously untreated patients.

METHODS

We did a single-arm, phase 2 trial in 27 university hospitals, general hospitals, and specialist cancer centres in France. Eligible patients were at least 18 years old and previously untreated, and had immunophenotypically confirmed B-cell chronic lymphocytic leukaemia; an Eastern Cooperative Oncology Group (ECOG) performance status score of less than 2; a Binet stage C according to IWCLL 2008 criteria or Binet stage A and B with active disease; no 17p deletion or absence of p53 mutation; and were considered medically fit. In the first part of the study (induction phase), all participants received eight intravenous infusions of obinutuzumab 1000 mg over six 4-weekly cycles and oral ibrutinib 420 mg once per day for 9 months. In part 2, after assessment on day 1 of month 9, patients with a complete response and bone marrow minimal residual disease of less than 0·01% received only oral ibrutinib 420 mg once per day for 6 additional months. Patients with a partial response, or with a complete response and bone marrow minimal residual disease of 0·01% or more, received 6 months of four 4-weekly cycles of intravenous fludarabine, cyclophosphamide, and obinutuzumab 1000 mg, alongside continuing ibrutinib 420 mg once per day. The primary endpoint was the proportion of patients achieving a complete response with bone marrow minimal residual disease less than 0·01% on day 1 of month 16 assessed by intention to treat (ITT). This trial is registered with ClinicalTrials.gov (number NCT02666898) and is still open for follow-up.

FINDINGS

Between Oct 27, 2015, and May 16, 2017, 135 patients were enrolled. After induction treatment (day 1 of month 9), 130 patients were evaluable, of which ten (8%) achieved a complete response with bone marrow minimal residual disease of less than 0·01% and were assigned to ibrutinib, and 120 (92%) were assigned to ibrutinib plus fludarabine, cyclophosphamide, and obinutuzumab. After minimal residual disease-guided treatment (day 1 of month 16), 84 (62%, 90% CI 55-69) of 135 patients (ITT population) achieved a complete response with bone marrow minimal residual disease of less than 0·01%. The most common haematological adverse event was thrombocytopenia (in 45 [34%] of 133 patients at grade 1-2 in months 1-9 and in 43 [33%] of 130 patients at grade 1-2 in months 9-15). The most common non-haematological adverse events were infusion-related reactions (in 83 [62%] patients at grade 1-2 in months 1-9) and gastrointestinal disorders (in 62 [48%] patients at grades 1 and 2 in months 9-15). 49 serious adverse events occurred, most frequently infections (ten), cardiac events (eight), and haematological events (eight). No treatment-related deaths occurred.

INTERPRETATION

Obinutuzumab and ibrutinib induction therapy followed by a minimal residual disease driven strategy is safe and active in patients with previously untreated chronic lymphocytic leukaemia. With longer follow-up, including assessing the evolution of minimal residual disease, if response is maintained, this strategy could be an option in the first-line setting in patients with chronic lymphocytic leukaemia, although randomised evidence is needed.

FUNDING

Roche, Janssen.

Rituximab maintenance versus observation following abbreviated induction with chemoimmunotherapy in elderly patients with previously untreated chronic lymphocytic leukaemia (CLL 2007 SA): an open-label, randomised phase 3 study

BACKGROUND

Most patients with chronic lymphocytic leukaemia relapse after initial therapy combining chemotherapy with rituximab. We assessed the efficacy and safety of rituximab maintenance treatment versus observation for elderly patients in remission after front-line abbreviated induction by fludarabine, cyclophosphamide, and rituximab (FCR).

METHODS

This randomised, open-label, multicentre phase 3 trial at 89 centres in France enrolled treatment-naive and fit patients aged 65 years or older with chronic lymphocytic leukaemia without del(17p). Eligible patients had an Eastern Cooperative Oncology Group performance status of 0-1 and adequate renal and hepatic function. Patients in response to complete induction treatment with four monthly courses of full-dose FCR with two interim rituximab doses on day 14 of cycles 1 and 2 (oral fludarabine [40 mg/m² per day] and oral cyclophosphamide [250 mg/m² per day] for the first 3 days of each cycle, rituximab at 375 mg/m² intravenously on day 0 of cycle 1 and subsequently at 500 mg/m² on day 14 of cycle 1, days 1 and 14 of cycle 2, and day 1 of cycles 3 and 4) were eligible for randomisation. Recovery from FCR toxicity and patient willingness to continue the trial were mandatory. We randomly assigned (1:1) patients to either receive intravenous rituximab (500 mg/m²) every 8 weeks for up to 2 years or undergo observation, with a central computer-generated randomisation list using randomly permuted blocks of variable sizes. Randomisation was stratified by IGHV mutational status, the presence or absence of del(11q), and response level to induction treatment. The primary endpoint was progression-free survival, with the objective to assess the superiority of rituximab maintenance relative to observation. The final analysis was done in the intention-to-treat population. Safety was analysed in all patients who received at least one dose of study drug in the rituximab group and in all patients in the observation group. This trial is closed to accrual whilst continuing patient follow-up. The study is registered with ClinicalTrials.gov, number NCT00645606.

FINDINGS

Between Dec 14, 2007, and Feb 18, 2014, 542 patients were enrolled, of whom 525 started FCR induction. Between June 10, 2008, and Aug 14, 2014, 409 (78%) patients were randomly assigned to rituximab maintenance (n=202) or observation (n=207). Four (2%) patients in the rituximab group did not receive the allocated treatment (progressive disease [n=1], adverse events [n=3]). After a median follow-up of 47·7 months (IQR 30·4-65·8), median progression-free survival in the rituximab group (59·3 months, 95% CI 49·6-not estimable) was improved compared with the observation group (49·0 months, 39·9-60·5; hazard ratio 0·55, 95% CI 0·40-0·75; p=0·0002). Neutropenia and grade 3-4 infections were more common with rituximab maintenance (105 [53%] of 198 patients vs 74 [36%] of 207 patients and 38 [19%] vs 21 [10%], respectively) during the study. The most common grade 3-4 infection was lower respiratory tract infection (24 [12%] vs eight [4%]). The incidence of second cancers, except basal cell carcinoma, was similar in both groups (29 [15%] vs 23 [11%]). Deaths were related to adverse events for 23 (11%) patients in the rituximab group and 16 (8%) in the observation group.

INTERPRETATION

2-year maintenance rituximab in selected elderly patients improves progression-free survival and shows an acceptable safety profile. Immunotherapy maintenance strategy is a relevant option in front-line treatment of chronic lymphocytic leukaemia, even in the age of targeted therapy.

FUNDING

French National Cancer Institute (INCa), Roche, Chugai.

Thromboxane Synthase Has the Same Pattern of Expression as Platelet Specific Glycoproteins during Human Megakaryocyte Differentiation

Regulation of the platelet formation process is poorly understood. It has been shown that p45NF-E2 deficient mice have a profound defect in platelet formation and recently the first platelet/megakaryocytic gene regulated by NF-E2, thromboxane synthase (TXS), has been identified. In this study, we investigated TXS expression as a model of a gene regulated by NF-E2 during MK differentiation. Megakaryocytic cells derived from blood CD34+ cells were purified according to their stage of maturation on the basis of expression of CD34, CD41a and CD42a, permitting to define different stages in MK differentiation. By means of real-time quantitative RT-PCR, we could determine that the level of TXS increased during differentiation in parallel with the expression of c-mpl and GPIIb (CD41). However, amounts of TXS transcripts increased about 1.6-fold more than that of GPIIb or c-mpl transcripts during maturation. Expression of TXS and MK specific proteins such as CD41a, CD42a and vWF was also correlated in maturing MKs. In addition, staining by anti-TXS antibody of proplatelet bearing MKs was not increased in comparison to that observed in mature MK, suggesting that TXS is not upregulated during platelet formation. In addition, we investigated whether TXS and cyclooxygenase could be involved in platelet formation by adding aspirin into the cultures. No significant decrease of platelet production was observed.

In conclusion, this study shows that TXS is coordinately expressed with the other platelet proteins during MK differentiation but is not directly involved in platelet formation.

miR-125b and miR-532-3p predict the efficiency of rituximab-mediated lymphodepletion in chronic lymphocytic leukemia patients. A French Innovative Leukemia Organization study

The underlying in vivo mechanisms of rituximab action remain incompletely understood in chronic lymphocytic leukemia. Recent data suggest that circulating micro-ribonucleic acids correlate with chronic lymphocytic leukemia progression and response to rituximab. Our study aimed at identifying circulating micro-ribonucleic acids that predict response to rituximab monotherapy in chronic lymphocytic leukemia patients. Using a hierarchical clustering of micro-ribonucleic acid expression profiles discriminating 10 untreated patients with low or high lymphocyte counts, we found 26 micro-ribonucleic acids significantly deregulated. Using individual real-time reverse transcription polymerase chain reaction, the expression levels of micro-ribonucleic acids representative of these two clusters were further validated in a larger cohort (n=61). MiR-125b and miR-532-3p were inversely correlated with rituximab-induced lymphodepletion (P=0.020 and P=0.001, respectively) and with the CD20 expression on CD19⁺ cells (P=0.0007 and P<0.0001, respectively). In silico analyses of genes putatively targeted by both micro-ribonucleic acids revealed a central role of the interleukin-10 pathway and CD20 (MS4A1) family members. Interestingly, both micro-ribonucleic acids were negatively correlated with MS4A1 expression, while they were positively correlated with MS4A3 and MSA47 Our results identify novel circulating predictive biomarkers for rituximab-mediated lymphodepletion efficacy in chronic lymphocytic leukemia, and suggest a novel molecular mechanism responsible for the rituximab mode of action that bridges miR-125b and miR-532-3p and CD20 family members. (clinicaltrials.gov Identifier: 01370772).

HBME-1 is expressed by erythroid precursors in early maturation stage and can be a valuable tool for evaluation of dyserythropoiesis in bone marrow core biopsy specimens

The reaction of Hector Battifora mesothelial epitope-1 (HBME-1) antibody with scattered pronormoblasts in normal bone marrow core biopsy specimens has been reported. This study evaluated the immunohistochemical profile of HBME-1 in a panel of 52 normal, dyserythropoietic and neoplastic marrow samples. We compared the staining property of HBME-1 with that of the commonly used erythroid marker, glycophorin A (CD235a) and in each case, we semi-quantitatively evaluated the HBME-1/CD235a-positive cells ratio. In normal samples, HBME-1 labelled scattered immature erythroid precursors. In dyserythropoietic specimens, HBME-1 stained nucleated erythroid precursors in varying degrees, from pronormoblast through normoblast stages, with the highest intensity in immature forms. Overall, the cellular background of non-erythroid progenitors, erythrocytes and neoplastic cells did not react with HBME-1, except in leukaemia cases with myelodysplasia-related changes. Our study shows that HBME-1 is a useful marker to identify immature erythroid precursors and that an HBME-1/CD235a-positive cells ratio ≥10% is associated with dyserythropoiesis.

Evaluation of Fluorescently Labeled Aerolysin as a New Kind of Reagent for Flow Cytometry Tests: Optimization of Use of FLAER, Hints, and Limits

OBJECTIVES

Diagnostic tests for paroxysmal nocturnal hemoglobinuria (PNH) are currently based on flow cytometry techniques. Typically, these tests use antibodies against glycosylphosphatidylinositol (GPI)-anchored proteins, but a new approach has been described recently, using a novel reagent named FLAER (fluorescently labeled aerolysin). In this work, we evaluate the performance and highlight the peculiarities of using this new reagent.

RESULTS

We investigated the general conditions of staining and explored optimal labeling settings. We found that the kinetics of the FLAER labeling is slightly different from that of antibodies. Our results led us to select a 30-minute incubation period at room temperature using 50 nmol/L as a final concentration of FLAER. As the nonspecific binding was dependent on the balance between FLAER and its ligand, the number of target cells was also found critical. In addition, sample preparation affected FLAER staining, and the lyse-before-stain preparation was preferred. Interestingly, FLAER affinity seems restricted to certain types of GPI anchors, making it unsuitable for exploration of RBCs. Finally, we aimed to evaluate FLAER as a possible single diagnostic tool; we studied cellular background in non-PNH samples and found a limit of detection close to 0.01% in optimal conditions.

CONCLUSIONS

The performance of the FLAER labeling on leukocytes proves that this reagent is a valuable tool for PNH diagnosis and particularly appropriate for high-sensitivity tests in laboratories aiming to detect minor PNH clones.

Evaluation of paroxysmal nocturnal hemoglobinuria screening by flow cytometry through multicentric interlaboratory comparison in four countries

OBJECTIVES

Paroxysmal nocturnal hemoglobinuria (PNH) is currently diagnosed by flow cytometry; although highly sensitive, its interpretation and reporting appear as critical as its technique. Thus, we developed a quality control scheme for the French-speaking region based on the international recommendations for PNH screening.

METHODS

After a topical workshop, we proposed a 1-year, two-step survey program to any volunteering French-speaking clinical laboratory. The first survey consisted of sending raw data files to evaluate gating and the interpretation strategy of each center. The second stipulated sending fresh whole-blood samples to evaluate the whole process and its practice.

RESULTS

Forty-nine participants from voluntary centers returned results for each of the two successive surveys. On virtual survey, 27% reported false-positive PNH created by immature granulocytes, whereas the minor PNH clone was not detected by 9%. On fresh survey, 63% of centers used at least the same six-color combination (CD24, CD14, CD33, CD15, CD45, and fluorescent aerolysin), and nearly 70% of participants were able to perform a sensitivity test less than 0.1% on neutrophils. All participants detected the major PNH clone, yet 16% returned false-positive results for the non-PNH clone case.

CONCLUSIONS

We succeeded in rallying numerous French-speaking clinical laboratories for both surveys and in harmonizing the technical practice by highlighting common pitfalls.

Evaluating abbreviated induction with fludarabine, cyclophosphamide, and dose-dense rituximab in elderly patients with chronic lymphocytic leukemia

Elderly patients with chronic lymphocytic leukemia (CLL) are underrepresented in trials evaluating fludarabine, cyclophosphamide, and rituximab (FCR). We assessed four cycles of FCR with two additional rituximab doses on day 14 of cycles 1 and 2 in 194 untreated CLL patients > 65 years (median age 71.2) without del17p. Four FCR cycles were administered to 90.7% (176/194), with (n = 74) or without (n = 102) dose-delay and/or dose-reduction. A total of 50% grade 3/4 neutropenia occurred after each cycle. Only 6.2% cycles were associated with severe infection. Complete remission (CR) was achieved in 19.7%, and partial remission (PR) in 73.9% of patients. Minimal residual disease (MRD) was negative in 36.7%. Overall survival at 36 months was estimated at 87.4%. Oral FC and dose-dense rituximab is feasible and active in fit elderly CLL patients. However, myelosuppression is significant and frequent dose adaptations are required implying that these results cannot be generalized to unfit or frail elderly CLL.

Post-remission intervention with alemtuzumab or rituximab to eradicate minimal residual disease in chronic lymphocytic leukemia: where do we stand?

The introduction of purine nucleoside analogs, later in combination with alkylating moieties and anti-CD20 immunotherapy, has profoundly improved the response rate and response duration in patients with chronic lymphocytic leukemia (CLL). The quality of clinical response following treatment may be improved to a level where residual leukemic cells become undetectable. As patients with this type of response appear to have extended survival rates, minimal residual disease (MRD) eradication is considered a new objective in CLL treatment with the aim of improving progression-free survival (PFS) and potentially overall survival (OS). This review therefore aims to overview the prognostic value of MRD eradication in CLL, the role of post-remission intervention with "passive" immunotherapy (alemtuzumab or rituximab) so as to eliminate persistent MRD or prevent MRD relapse, the impact of these strategies on disease-free survival and their possible adverse consequences. The data indicate a potential for post-remission alemtuzumab or rituximab to prolong PFS in CLL, although more investigations and longer follow-up are required before MRD-guided strategies can be recommended outside of clinical trials.

Routine diagnostic procedures of myelodysplastic syndromes: value of a structural blood cell parameter (NEUT-X) determined by the Sysmex XE-2100™

INTRODUCTION

Diagnostic features of myelodysplastic syndromes (MDS) are often polymorphic and nonspecific including anemia in most cases. Standard parameters provided by an automated analyzer seldom bring any argument for this diagnosis. The aim of this study was to investigate whether some structural parameters, not routinely provided by Sysmex™ XE 2100 analyzer, could help diagnose MDS in a simple way, adapted to routine practice.

METHODS

Blood samples from 184 MDS fully annotated cases and 3545 normal blood count controls were performed with XE 2100 Sysmex™ analyzer. Quantitative and structural parameters were considered.

RESULTS

We found that the structural neutrophil parameter, NEUT-X, converted into a semi-quantitative parameter, the granularity index (GI), could be used as a flag for MDS in front of anemia. Negative GI and anemia were able to make otherwise unrecognized MDS stand out in routine practice, increasing the number of slides addressed to review from 67% to 96%, without leading to a large excess of unfounded slide review among non-MDS.

CONCLUSION

Including the GI index in the routine parameters provided by the Sysmex analyzer could be of major help for nonspecialized routine laboratories in detecting MDS.

Flow cytometry APC-tandem dyes are degraded through a cell-dependent mechanism

Technological developments of multiparametric flow cytometry come along with the generation of new dyes. The APC-tandem dyes, which combine the fluorophores APC and Cy7/H7, allow the detection of a specific signal in the APC-Cy7/H7 channel along with an unexpected nonspecific signal in the APC channel. Depending on the magnitude of the latter, it may be a handicap for interpreting the data of multicolor labeling experiments. We investigated the alteration of the APC-tandem dyes by labeling peripheral blood cells with antibodies directed toward leukocyte surface proteins and by analyzing cells by flow cytometry. Our results show that the APC-Cy7/H7 tandem fluorochromes degraded over time. Nonspecific APC signal was observed with the various antibodies tested only upon cell attachment but not under bead linkage. Moreover, the percentage of degradation of the APC-Cy7/H7 dyes was dependent on the cell type analyzed. Interestingly, nonspecific APC signal strongly decreased when the metabolic activity of immunolabeled cells was inhibited or when cells were incubated with vitamin C. This study demonstrates that the APC-tandem dyes are the target of cell-dependent degradation, which may be antagonized. These findings will allow cytometer users to optimize their multicolor panels.

Down-regulation of CXCR4 and CD62L in chronic lymphocytic leukemia cells is triggered by B-cell receptor ligation and associated with progressive disease

Progressive cases of B-cell chronic lymphocytic leukemia (CLL) are frequently associated with lymphadenopathy, highlighting a critical role for signals emanating from the tumor environment in the accumulation of malignant B cells. We investigated on CLL cells from 30 untreated patients the consequence of B-cell receptor (BCR) triggering on the membrane expression of CXCR4 and CD62L, two surface molecules involved in trafficking and exit of B-lymphocytes from lymph nodes. BCR stimulation promoted a strictly simultaneous down-regulation of CXCR4 and CD62L membrane expression to a variable extent. The variable BCR-dependent decrease of the two proteins was strikingly representative of the heterogeneous capacity of the CLL cells to respond to BCR engagement in a given patient. Functionally, cells down-regulating CXCR4 and CD62L in response to BCR engagement displayed a reduction in both migration toward CXCL12 and adhesion to lymphatic endothelial cells. Remarkably, the ability of CLL cells to respond to BCR ligation was correlated with unfavorable prognostic markers and short progression-free survival. In conclusion, BCR signaling promotes decrease of CXCR4 and CD62L membrane expression in progressive cases only. These results are consistent with the hypothesis that BCR-mediated signaling pathways favor accumulation of a proliferative pool within the lymph nodes of progressive CLL cases.

Use of hematopoietic progenitor cell count on the Sysmex XE-2100 for peripheral blood stem cell harvest monitoring

Successful peripheral blood stem cell (PBSC) collection depends on the timing of apheresis based on CD34+ cell enumeration. Because this analysis is expensive and induces organization difficulties, we evaluated hematopoietic progenitor cell (HPC) quantification on the Sysmex XE-2100 as a surrogate analysis. We tested 157 blood samples for CD34+ cells and HPC counts. We found a good linear correlation between HPC and CD34+ and determined simple rules allowing to use HPC count in daily practice. We set a positive cut-off >30 HPC/mm(3) for allowing PBSC harvest and a negative cut-off at 0 HPC/mm(3) for which collection should be delayed. These two situations accounted for 62% of cases and CD34+ cell count by flow cytometry confirmed HPC result in 95% of cases. Between 0 and 30 HPC/mm3, CD34+ enumeration is required for decision-making. We conclude that HPC count may be a useful surrogate for CD34+ enumeration in PBSC harvest monitoring.

Deciphering leukemic B-cell chronic lymphoproliferative disorders

Diagnosis of leukemic B-cell chronic lymphoproliferative disorders (B-CLPD) is a frequent challenge in hematology. In this multicentric study, we prospectively studied 165 new consecutive leukemic patients with B-CLPD selected on the basis of Royal Marsden Hospital scoring system < or =3. The primary aim of the study was to try to decipher the atypical cases and identify homogenous subgroups. Overall, morphological examination contributed to diagnosis in only 20% cases, all of them CD5 negative. Thirty additional cases were CD5 negative suggestive of leukemic marginal zone lymphoma in most cases. The significantly poorer survival of the 26 cyclin D1 positive cases justifies recommending its systematic determination among atypical B-CLPD. CD20 expression segregated clearly two subgroups among CD5 positive cyclin D1 negative B-CLPD. The 17 patients with the CD20 dim profile represent a homogeneous subgroup very close to typical B-cell chronic lymphocytic leukemia (B-CLL) on morphological, phenotypical and cytogenetical criteria. In contrast, the subgroup of 51 patients with a CD20 bright profile is heterogeneous. Their significantly lower p27 expression level suggest the presence of a proliferative component, underlying a more aggressive disease. Further genomic studies are warranted to establish their precise nature. These cases should not be included in the same therapeutic trials as B-CLL.

Evaluation of an algorithm based on peripheral blood hematopoietic progenitor cell and CD34+ cell concentrations to optimize peripheral blood progenitor cell collection by apheresis

BACKGROUND

Quantification of peripheral blood (PB) CD34+ cells is commonly used to plan peripheral blood progenitor cell (PBPC) collection but is time-consuming. Sysmex has developed a hematology analyzer that can quickly identify a population of immature hematopoietic cells (HPCs) according to cell size, cell density, and differential lysis resistance, which may indicate the presence of PBPCs in PB. This prospective study has evaluated the potential of such method to predict the PBPC mobilization.

STUDY DESIGN AND METHODS

A total of 141 patients underwent PBPC mobilization. PB HPCs and PB CD34+ cells were simultaneously quantified with a hematology analyzer (SE2100, Sysmex) and flow cytometry, respectively. The number of blood volumes processed was then based on PB CD34+ cell concentration.

RESULTS

The optimal PB HPC level able to predict a minimal level of 10 x 10(6) PB CD34+ cells per L was 5 x 10(6) per L with positive and negative predictive values of 0.93 and 0.36 percent, respectively. For this cutoff point, sensitivity and specificity were 0.81 and 0.65, respectively. The median number of blood volumes processed according to the PB CD34+ cell count allowed us to perform only one apheresis procedure for a majority of patients.

CONCLUSION

PB HPC quantification is very useful to quickly determine the initiation of PBPC apheresis especially for patients with higher concentrations. For patients exhibiting a lower HPC count (<5 x 10(6)/L), other parameters such as a CD34 test may be needed. Such a policy associated with a length of apheresis adapted to the richness in the PB CD34+ cells allows for optimizing the organization of centers with an improvement in patient comfort and economical savings.

National standardization of ZAP-70 determination by flow cytometry: the French experience

BACKGROUND

ZAP-70, after being considered as a potential surrogate for VH mutational status, has seen its own prognostic value emerge. We aimed at standardizing a simple, fast, and reproducible flow cytometry method.

METHODS

AntiZAP-70 antibody 2F3.2 was used with indirect labeling and secondary anti-IgG2a antibody. The reference values for the expression of the results were determined on 45 normal blood samples. ZAP-70 protein expression was investigated in 192 CLL samples. The indirect technique was compared with FITC-conjugated 2F3.2 clone, and with clone 1E7.2-FITC, -PE or -AlexaFluor 488.

RESULTS

Using FITC or PE-conjugated antibodies, 2F3.2 and 1E7.2 clones allowed a much less adequate discrimination between positive and negative cells and discordant cases were most likely true negative cases. Using the AlexaFluor 488 conjugated 1E7.2 clone, the discordant cases were mostly negative with the conjugated antibody and positive with the 2F3.2 clone but Western blotting or RNA microarray confirmed discordant cases were false negative with the conjugated antibody. Subsequently, recommendations were used by 13 centers participating in an interlaboratory quality control protocol. The use of MFI ratio appeared to be more reliable.

CONCLUSIONS

Results suggested that slight differences in the procedure had little impact on the interpretation in characteristic cases; however, careful interpretation was required for values close to threshold.

Survival response to B-cell receptor ligation is restricted to progressive chronic lymphocytic leukemia cells irrespective of Zap70 expression

Despite very similar gene expression profiles, the clinical course of B-cell chronic lymphocytic leukemia (B-CLL) is heterogeneous. Immunoglobulin VH (IgVH) mutational status and expression of B-cell receptor (BCR) signaling mediators have been associated with disease progression. However, the consequences of BCR engagement on cell survival and evolution of the disease remain unclear. We show here that B-CLL cell survival is dependent on the threshold of BCR stimulation induced by immobilized antibody, in contrast to soluble anti-mu F(ab)'2 antibody, which leads to apoptosis. Measurement of metabolic activity and apoptotic response discriminated two subgroups. "Nonresponders" showed low metabolic activity and unmodified apoptotic response upon BCR stimulation. In contrast, "responders" exhibited increased metabolic activity and inhibition of spontaneous apoptosis. This survival advantage was associated to a BCR-dependent activation profile leading to induction of cyclin D2/cyclin-dependent kinase 4 (cdk4) expression and G1 cell cycle progression. The ability to respond to BCR ligation correlated with an unfavorable clinical course and allowed to define an additional group of patients among IgVH-mutated cases exhibiting a risk of progression. Remarkably, we show that Zap70 expression was neither mandatory nor sufficient to generate downstream survival signals and cyclin D2/cdk4 up-regulation. In conclusion, BCR engagement has a significant effect on B-CLL cell survival, activation, and G1 progression. Furthermore, our results provide new insights in the physiopathology of progressive IgVH-mutated cases.

[Expression of proliferation marker Ki 67 in chronic lymphocytic leukemia]

Chronic lymphocytic leukemia (CLL) is characterized by a clonal expansion of low proliferating mature B and T lymphocytes in the bone marrow and peripheral blood. The nuclear antigen Ki 67 is a protein detected in G1, S, G2 and M phases of the cell cycle, but not in G0, and thus, is a widely accepted proliferation marker of Human tumors. The aim of this study was to evaluate Ki 67 monoclonal antibody in CLL. We studied 48 patients diagnosed as CLL on the presence of clinical signs, over 4.109/l circulating lymphoid cells and immunophenotyping by flow cytometry using CD19, CD5, CD22, CD23, FMC7 and immunoglobulin light chains monoclonal antibodies. Ki 67 immunostaining was determined by Avidin Biotin Complex method. Our results allows to characterize between CLL: one group which proliferation rate (percentage of Ki 67 positive cells) was equal or less than 2%, represented by 14 cases (29,2%) with morphological aspect of typical CLL, one group which proliferation rate was between 3% and 9% represented by 32 cases (66,6%) with morphological aspect of polymorph CLL or prolymphocytic leukemia, and a last group with proliferation rate equal or up to 10% and corresponding to two cases (4,2%) of transformation of CLL to high grade Non Hodgkin lymphoma. There were no correlation between Matutes immunological score and proliferation rate, as this rate was 2.9% in score < 3 and 2.7% in score > 3. This study confirm the Ki 67 usefulness in studying cellular proliferation, and underline that CLL with polymorphic cytology are more proliferate than typical CLL. These data reinforce the notion that CLL is a disease with heterogeneity in clinical behavior, immunophenotype, cytogenetic, molecular aspects, and thus, prognostic.

Prognostic impact of p27KIP1 expression in cyclin D1 positive lymphoproliferative disorders

Nodal mantle cell lymphoma (MCL) is a well-defined entity, but non-nodal leukemic cyclin D1 positive lymphoproliferative disorders have been reported and their relationship with MCL remains controversial and their prognosis heterogeneous. We prospectively studied the expression of cyclin D1 in CD5 positive leukemic B lymphoproliferative disorders at diagnosis and identified 65 cases overexpressing cyclin D1. We did not distinguish any clinical or biological criteria allowing one to identify a non-MCL group. Multivariate analysis identified age, anemia and p27kip1 expression as independent prognostic factors of survival. By univariate analysis, p27kip1 high expression proved to be the strongest predictor of prolonged survival. The median survival of p27 low expressors was 30 months, while it was not reached for p27 high expressors. A high level of p27 expression was often found associated with the absence of nodal involvement and the presence of somatic mutations, but neither of them was restricted to the p27 high expression group. In conclusion, we hypothesize that MCL and these cyclin D1 positive leukemic lymphoproliferative disorders represent a continuous spectrum of diseases. Determination of p27 expression level appears as a routine applicable test allowing identification of a subset of patients who could be considered for different therapeutic approaches.

[Bone marrow aspiration for diagnostic purposes]

Examination of bone marrow aspiration is an important tool in the diagnosis of haematological diseases. First attempts of bone marrow sampling took place at the beginning of the twentieth century. Thereafter, numerous methods were proposed and different materials were described. The commonly accepted sites for sampling are sternum and the iliac crest. We describe here a sampling procedure for each site. Bone marrow aspiration is a safely investigation, but not recommended for patients with impaired haemostasis. The physician must be aware of its side effects and complications which could occur. The consequence of the complications varies according to the type of iatrogenic injury. Prevention and rapid diagnosis are a crucial point in the management of bone marrow aspiration accidents. To avoid malpractice, the procedure should be taught by senior physicians including theoretical as well as practical learning. The purpose of the learning is a high quality of care to ensure patients the best comfort in subsequent bone marrow examinations, this point being particularly important in paediatrics.

Absence of mutations in the HoxA10, HoxA11 and HoxD11 nucleotide coding sequences in thrombocytopenia with absent radius syndrome

Recent studies have suggested the HoxA10, HoxA11 and HoxD11 homeobox genes as candidate loci for the thrombocytopenia with absent radius (TAR) syndrome. For example, targeted disruptions of these Hox genes result in abnormal development of the mouse radius, while overexpression of HoxA10 stimulates mouse megakaryocyte (MK) development in vitro. To examine the expression of Hox genes in human MK cells, we utilized reverse transcription polymerase chain reaction with degenerate oligonucleotides to study megakaryocytic cell lines (MEG-01, DAMI), and primary human MK purified from adult and cord blood. Using this approach, 13 out of 40 clones isolated from cell lines, 10 out of 21 from cord MK, and 11 out of 21 from adult MK were identified as HoxA10, while HoxA11 and HoxD11 sequences were not detected. The normal genomic sequences for the human HoxA10, -A11, and -D11 genes were then determined and sequenced in 10 unrelated individuals with TAR syndrome. In all patients the derived amino acid sequence for the three Hox genes was identical to normal controls. Southern blotting did not reveal genomic rearrangements or deletions at these loci, and in two patients intact HoxA10 transcripts were detected by amplification in myeloid cells. Although these studies cannot completely exclude the possibility that the TAR syndrome results from non-coding mutations that affect the level of Hox gene expression in megakaryocytes, mutations in the coding sequence of the Hox genes known to affect radial development are not a common cause of TAR syndrome.

Different expression of CD41 on human lymphoid and myeloid progenitors from adults and neonates

The glycoprotein (Gp) IIb/IIIa integrin, also called CD41, is the platelet receptor for fibrinogen and several other extracellular matrix molecules. Recent evidence suggests that its expression is much wider in the hematopoietic system than was previously thought. To investigate the precise expression of the CD41 antigen during megakaryocyte (MK) differentiation, CD34(+) cells from cord blood and mobilized blood cells from adults were grown for 6 days in the presence of stem cell factor and thrombopoietin. Two different pathways of differentiation were observed: one in the adult and one in the neonate cells. In the neonate samples, early MK differentiation proceeded from CD34(+)CD41(-) through a CD34(-)CD41(+)CD42(-) stage of differentiation to more mature cells. In contrast, in the adult samples, CD41 and CD42 were co-expressed on a CD34(+) cell. The rare CD34(+)CD41(+)CD42(-) cell subset in neonates was not committed to MK differentiation but contained cells with all myeloid and lymphoid potentialities along with long-term culture initiating cells (LTC-ICs) and nonobese diabetic/severe combined immune-deficient repopulating cells. In the adult samples, the CD34(+)CD41(+)CD42(-) subset was enriched in MK progenitors, but also contained erythroid progenitors, rare myeloid progenitors, and some LTC-ICs. All together, these results demonstrate that the CD41 antigen is expressed at a low level on primitive hematopoietic cells with a myeloid and lymphoid potential and that its expression is ontogenically regulated, leading to marked differences in the surface antigenic properties of differentiating megakaryocytic cells from neonates and adults. (Blood. 2001;97:2023-2030)

Thromboxane synthase has the same pattern of expression as platelet specific glycoproteins during human megakaryocyte differentiation

Regulation of the platelet formation process is poorly understood. It has been shown that p45NF-E2 deficient mice have a profound defect in platelet formation and recently the first platelet/megakaryocytic gene regulated by NF-E2, thromboxane synthase (TXS), has been identified. In this study, we investigated TXS expression as a model of a gene regulated by NF-E2 during MK differentiation. Megakaryocytic cells derived from blood CD34+ cells were purified according to their stage of maturation on the basis of expression of CD34, CD41a and CD42a, permitting to define different stages in MK differentiation. By means of real-time quantitative RT-PCR, we could determine that the level of TXS increased during differentiation in parallel with the expression of c-mpl and GPIIb (CD41). However, amounts of TXS transcripts increased about 1.6-fold more than that of GPIIb or c-mpl transcripts during maturation. Expression of TXS and MK specific proteins such as CD41a, CD42a and vWF was also correlated in maturing MKs. In addition, staining by anti-TXS antibody of proplatelet bearing MKs was not increased in comparison to that observed in mature MK, suggesting that TXS is not upregulated during platelet formation. In addition, we investigated whether TXS and cyclooxygenase could be involved in platelet formation by adding aspirin into the cultures. No significant decrease of platelet production was observed. In conclusion, this study shows that TXS is coordinately expressed with the other platelet proteins during MK differentiation but is not directly involved in platelet formation.

Existence of a differentiation blockage at the stage of a megakaryocyte precursor in the thrombocytopenia and absent radii (TAR) syndrome

The thrombocytopenia and absent radii (TAR) syndrome is a rare disease associating bilateral radial agenesis and congenital thrombocytopenia. Here, we investigated in vitro megakaryocyte (MK) differentiation and expression of c-mpl in 6 patients. Using blood or marrow CD34(+) cells, the colony-forming unit (CFU)-MK number was markedly reduced. CD34(+) cells were also cultured in liquid medium in the presence of a combination of 3 cytokines (stem cell factor, interleukin-3, and interleukin-6) or megakaryocyte growth and development factor (PEG-rHuMGDF) with or without SCF. In the presence of PEG-rHuMGDF, the majority of mature megakaryocytes (CD41 high, CD42 high) underwent apoptosis. This phenomenon was also observed in cultures stimulated by three cytokines. However, this last combination of cytokines allowed a more complete terminal MK differentiation. Surprisingly, a homogeneous population of CD34(-)CD41(+)CD42(-) cells accumulated during the cultures. This population was unable to differentiate along the myeloid pathways. This result suggests that a fraction of MK cells is unable to differentiate in the TAR syndrome. We subsequently investigated whether this could be related to an abnormality in c-mpl. No mutation or rearrangement in the c-mpl gene was found by Southern blots or by sequencing of the c-mpl coding region and its promoter in any of the patients. Using Western blot analysis, a decreased level of Mpl was found in patient platelets. A decreased level of c-mpl messenger RNA in TAR platelets was also detected with a lower c-mpl-P to c-mpl-K ratio in comparison to adult platelets. Altogether, these results demonstrate that the thrombocytopenia of the TAR syndrome is associated with a dysmegakaryocytopoiesis characterized by cells blocked at an early stage of differentiation. (Blood. 2000;95:1633-1641)

Intracellular trafficking of the alphaIIbbeta3 receptor antagonist, abciximab, in normal and Glanzmann's disease megakaryocytes

The alphaIIbbeta3 platelet receptor antagonist abciximab (c7E3Fab, ReoPro(R)) has proved to be effective in preventing arterial thrombosis. However, its binding capacity to the platelet precursors, megakaryocytes (MKs), which also express alphaIIbbeta3, is not known. The purpose of this study was to establish whether abciximab is able to react with alphaIIbbeta3 located on human MKs, and to follow its subsequent intracellular trafficking. MKs were grown from CD34+ progenitors from normal subjects and from a patient with type I Glanzmann's thrombasthenia, and abciximab was added at day 10 of culture (4 microgram/ml). Cells were fixed at day 12, cryosectioned, and immunolabelled for abciximab. Labelling was prominent on the MK plasma membrane; it also lined the demarcation membration system. Interestingly, alpha-granule membranes were labelled showing that the antibody was internalized and further stored into MK secretory granules. Abciximab was also strongly detected on and in newly-formed platelets. Glanzmann's disease MKs (which completely lacked alphaIIbbeta3) were consistently negative, confirming that the antibody fragment was specifically interacting with alphaIIbbeta3. In conclusion, this study demonstrated that abciximab: (i) binds MK plasma membrane and demarcation membranes, (ii) trafficks into alpha-granules, and (iii) is expressed on and in nascent platelets. These findings could be taken in account when monitoring anti-alphaIIbbeta3 receptor therapy.

Phenotypic and functional evidence for the expression of CXCR4 receptor during megakaryocytopoiesis

The identification of stromal cell-derived factor (SDF)-1alpha as a chemoattractant for human progenitor cells suggests that this chemokine and its receptor might represent critical determinants for the homing, retention, and exit of precursor cells from hematopoietic organs. In this study, we investigated the expression profile of CXCR4 receptor and the biological activity of SDF-1alpha during megakaryocytopoiesis. CD34(+) cells from bone marrow and cord blood were purified and induced to differentiate toward the megakaryocyte lineage by a combination of stem-cell factor (SCF) and recombinant human pegylated megakaryocyte growth and development factor (PEG-rhuMGDF). After 6 days of culture, a time where mature and immature megakaryocytes were present, CD41(+) cells were immunopurified and CXCR4mRNA expression was studied. High transcript levels were detected by a RNase protection assay in cultured megakaryocytes derived from cord blood CD34(+) cells as well as in peripheral blood platelets. The transcript levels were about equivalent to that found in activated T cells. By flow cytometry, a large fraction (ranging from 30% to 100%) of CD41(+) cells showed high levels of CXCR4 antigen on their surface, its expression increasing in parallel with the CD41 antigen during megakaryocytic differentiation. CXCR4 protein was also detected on peripheral blood platelets. SDF-1alpha acts on megakaryocytes by inducing intracellular calcium mobilization and actin polymerization. In addition, in in vitro transmigration experiments, a significant proportion of megakaryocytes was observed to respond to this chemokine. This cell migration was inhibited by pertussis toxin, indicating coupling of this signal to heterotrimeric guanine nucleotide binding proteins. Although a close correlation between CD41a and CXCR4 expession was observed, cell surface markers as well as morphological criteria indicate a preferential attraction of immature megakaryocytes (low level of CD41a and CD42a), suggesting that SDF-1alpha is a potent attractant for immature megakaryocytic cells but is less active on fully mature megakaryocytes. This hypothesis was further supported by the observation that SDF-1alpha induced the migration of colony forming unit-megakaryocyte progenitors (CFU-MK) and the expression of activation-dependent P-selectin (CD62P) surface antigen on early megakaryocytes, although no effect was observed on mature megakaryocytes and platelets. These results indicate that CXCR4 is expressed by human megakaryocytes and platelets. Furthermore, based on the lower responses of mature megakaryocytes and platelets to SDF-1alpha as compared with early precursors, these data suggest a role for this chemokine in the maintenance and homing during early stages of megakaryocyte development. Moreover, because megakaryocytes are also reported to express CD4, it becomes important to reevaluate the role of direct infection of these cells by the human immunodeficiency virus (HIV)-1 in HIV-1-related thrombocytopenia.