Myeloid Malignancies: Myelodysplastic Syndromes, Myeloproliferative Disorders, and Acute Myeloid Leukemia

Flow Cytometric Assessment of Myelodysplastic Syndromes/Neoplasms

Myelodysplastic syndromes/neoplasms (MDS) are a heterogeneous class of hematopoietic stem cell neoplasms characterized by ineffective hematopoiesis leading to peripheral cytopenias. This group of diseases is typically diagnosed using a combination of clinical, morphologic, and genetic criteria. Many studies have described the value of multiparametric flow cytometry (MFC) in the diagnosis, classification, and prognostication of MDS. This review summarizes the approach to MDS diagnosis and immunophenotypic characterization using MFC and describes the current state while highlighting future opportunities and potential pitfalls.

Association of Minimal Residual Disease by a Single-Tube 8-Color Flow Cytometric Analysis With Clinical Outcome in Adult B-Cell Acute Lymphoblastic Leukemia: A Real-World Study Based on 486 Patients

CONTEXT.—

Minimal/measurable residual disease (MRD) measured by molecular and multiparametric flow cytometry (MFC) has been proven to be predictive of relapse and survival in patients with B-cell acute lymphoblastic leukemia (B-ALL). A universally applicable antibody panel at a low cost but without compromising sensitivity and power of prognosis prediction in adult B-ALL remains unestablished.

OBJECTIVE.—

To report our experience of using a single-tube 8-color MFC panel to measure the MRD status as a prognostic indicator in adult B-ALL patients.

DESIGN.—

We retrospectively analyzed the characteristics, MRD status, and prognosis of adult B-ALL based on a large real-world cohort of 486 patients during a 10-year period.

RESULTS.—

MRD assessed by MFC and polymerase chain reaction (PCR) assays for BCR-ABL+ patients showed concordant results in 74.2% of cases. MRD- status by our MFC panel could clearly predict a favorable relapse-free survival (RFS) and overall survival (OS) both at the end of induction and at the end of 1 consolidation course. Patients with continuous MRD- and with at least 1 MRD- result showed a favorable RFS and OS compared with those with at least 1 MRD+ result and continuous MRD+, respectively.

CONCLUSIONS.—

The single-tube 8-color MFC panel demonstrated a low cost, decent sensitivity, and comparability with polymerase chain reaction-MRD but an excellent performance in predicting RFS and OS, and thus could potentially be taken as a routine indicator in the evaluation of the treatment response for adult patients with B-ALL.

Acute Myeloid Leukemia Minimal Residual Disease Detection: The Difference from Normal Approach

The identification of residual leukemia following therapy, termed minimal or measurable residual disease (MRD), has emerged as one of the most important prognostic factors for patients with acute leukemia, including acute myeloid leukemia (AML). Flow cytometry is a preferred method for MRD detection due to its general applicability and the rapid results that it makes available. In this article, the basic protocol outlines a simple and efficient method for the labeling of hematopoietic cells from bone marrow or peripheral blood with a panel of monoclonal antibodies designed both to highlight patterns of normal maturation and allow identification of neoplastic hematopoietic progenitor populations with a high degree of sensitivity and specificity. The method was developed in a clinical laboratory setting for the diagnosis of myeloid stem cell disorders and neoplasms, and has been extensively validated both technically and clinically for the detection of MRD in AML. © 2020 The Authors. Basic Protocol: Staining and flow cytometry for AML minimal residual disease detection Support Protocol: Analysis and interpretation of data for AML minimal residual disease detection.

Pediatric Myelodysplastic Syndromes

Pediatric myelodysplastic syndromes (MDS) comprise less than 5% of childhood malignancies. Approximately 30% to 45% of pediatric MDS cases are associated with an underlying genetic predisposition syndrome. A subset of patients present with MDS/acute myeloid leukemia (AML) following intensive chemotherapy for an unrelated malignancy. A definitive diagnosis of MDS can often only be rendered pending a comprehensive clinical and laboratory-based evaluation, which frequently includes ancillary testing in a reference laboratory. Clinical subtypes, the current diagnostic schema, and the results of more recently performed next-generation sequencing studies in pediatric MDS are discussed here.

Leukocyte immunoglobulin-like receptor B1 and B4 (LILRB1 and LILRB4): Highly sensitive and specific markers of acute myeloid leukemia with monocytic differentiation

BACKGROUND

Acute myeloid leukemia (AML) with monocytic differentiation (M-AML) remains a diagnostic challenge largely due to lack of sensitive and specific markers for immature monocytes. The immunoglobulin-like inhibitory receptors, LILRB1 and LILRB4, are expressed on monocytes but have not yet been systematically evaluated in the clinical setting.

METHODS

We evaluated the diagnostic performance of LILRB1 and LILRB4 as monocytic markers for both immature and mature monocytes in comparison to other myelomonocytic markers including CD14, CD15, CD33, CD36, and CD64 in eight cases of control bone marrow (BM, 5) and peripheral blood (PB, 3), 64 cases of (M-AML), and 57 cases of AML without monocytic differentiation (NM-AML) by flow cytometric immunophenotyping.

RESULTS

In control BM, LILRB1 and LILRB4 were consistently expressed on monocytes at all stages of maturation, from CD34⁺ /CD14^- monocytic precursors to CD14^-/dim+ maturing and CD14⁺ mature monocytes. In M-AML, LILRB1 and LILRB4 were consistently expressed on monocytes, regardless of the degree of maturity, from CD14^-/dim+ monoblasts/promonocytes to CD14⁺ mature monocytes but were not expressed on myeloblasts. The diagnostic performances as a monocytic marker assessed by sensitivity/specificity were 100%/100% for LILRB1/LILRB4, 100%/82% for CD11b, 80%/100% for CD14, 100%/81% for CD64, 100%/58% for CD15/CD33, and 89%/97% for CD36/CD64.

CONCLUSION

The co-expression of LILRB1/LILRB4 outperformed other myelomonocytic markers as a highly sensitive and specific marker for monocytes at all stages of maturation and could reliably distinguish M-AML from NM-AML. LILRB4 additionally represents a novel therapeutic target for treating M-AML.

Mutation topography and risk stratification for de novo acute myeloid leukaemia with normal cytogenetics and no nucleophosmin 1 (NPM1) mutation or Fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD)

About 25% of patients with newly diagnosed acute myeloid leukaemia (AML) have normal cytogenetics and no nucleophosmin 1 (NPM1) mutation or Fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD). The prognosis and best therapy for these patients is controversial. We evaluated 158 newly diagnosed adults with this genotype who achieved histological complete remission within two cycles of induction therapy and were assigned to two post-remission strategies with and without an allotransplant. Targeted regional sequencing at diagnosis was performed and data were used to estimate their prognosis, including relapse and survival. In multivariable analyses, having wild-type or mono-allelic mutated CCAAT/enhancer-binding protein alpha (CEBPA) [hazard ratio (HR) 2·39, 95% confidence interval (CI) 1·08-5·30; P = 0·032), mutated NRAS (HR 2·67, 95% CI 1·36-5·25; P = 0·004), mutated colony-stimulating factor 3 receptor (CSF3R) (HR 2·85, 95% CI 1·12-7·27; P = 0·028) and a positive measurable residual disease (MRD)-test after the second consolidation cycle (HR 2·88, 95% CI 1·32-6·30; P = 0·008) were independently correlated with higher cumulative incidence of relapse (CIR). These variables were also significantly associated with worse survival (HR 3·02, 95% CI 1·17-7·78, P = 0·022; HR 3·62, 95% CI 1·51-8·68, P = 0·004; HR 3·14, 95% CI 1·06-9·31, P = 0·039; HR 4·03, 95% CI 1·64-9·89, P = 0·002; respectively). Patients with ≥1 of these adverse-risk variables benefitted from a transplant, whereas the others did not. In conclusion, we identified variables associated with CIR and survival in patients with AML and normal cytogenetics without a NPM1 mutation or FLT3-ITD.

Minimal residual disease status determined by multiparametric flow cytometry pretransplantation predicts the outcome of patients with ALL receiving unmanipulated haploidentical allografts

This study evaluated the effects of pretransplantation minimal residual disease (pre-MRD) on outcomes of patients with acute lymphoblastic leukemia (ALL) who underwent unmanipulated haploidentical stem cell transplantation (haplo-SCT). A retrospective study including 543 patients with ALL was performed. MRD was determined using multiparametric flow cytometry. Both in the entire cohort of patients and in subgroup cases with T-ALL or B-ALL, patients with positive pre-MRD had a higher incidence of relapse (CIR) than those with negative pre-MRD in MSDT settings (P < 0.01 for all). Landmark analysis at 6 months showed that MRD positivity was significantly and independently associated with inferior rates of relapse (HR, 1.908; P = 0.007), leukemia-free survival (LFS) (HR, 1.559; P = 0.038), and OS (HR, 1.545; P = 0.049). The levels of pre-MRD according to a logarithmic scale were also associated with leukemia relapse, LFS, and OS, except that cases with MRD <0.01% experienced comparable CIR and LFS to those with negative pre-MRD. A risk score for CIR was developed using the variables pre-MRD, disease status, and immunophenotype of ALL. The CIR was 14%, 26%, and 59% for subjects with scores of 0, 1, and 2-3, respectively (P < 0.001). Three-year LFS was 75%, 64%, and 42%, respectively (P < 0.001). Multivariate analysis confirmed the association of the risk score with CIR and LFS. The results indicate that positive pre-MRD, except for low level one (MRD < 0.01%), is associated with poor outcomes in patients with ALL who underwent unmanipulated haplo-SCT.

Immunophenotyping of Acute Myeloid Leukemia

Immunophenotyping by multiparameter flow cytometry is a rapid and efficient technique to simultaneously assess and correlate multiple individual cell properties like size and internal complexity along with antigen expression in a population of cells. This method is utilized for rapid characterization of the blasts and classification of acute myeloid leukemia (AML), in both the peripheral blood (PB) and bone marrow (BM). This technique is not only useful in the initial diagnosis but also in monitoring and determining prognosis of the disease through minimal residual disease (MRD) testing. This chapter provides an overview of procedures for specimen processing, staining, and immunophenotyping of AML and describes the principles of data analysis for AML classification and MRD testing.

Idarubicin-Intensified Hematopoietic Cell Transplantation Improves Relapse and Survival of High-Risk Acute Leukemia Patients with Minimal Residual Disease

The optimal conditioning regimen of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for high-risk patients with minimal residual disease (MRD) remains controversial. We studied the results in 98 high-risk acute leukemia patients transplanted with idarubicin (IDA)-intensified conditioning regimens between 2012 January and 2017 January. Among these patients, 31 (31.6%) had more than 5% marrow blasts at time of transplantation and 67 patients were in morphologic remission: MRD negative status at time of conditioning was achieved in 39 patients (39.8%), whereas 28 (28.6%) remained carriers of any other positive MRD level in the bone marrow. Three-year relapse estimates of patients with MRD-positive remission was 22.0%, which was remarkably lower than patients with active disease (45.4%, P = .027) but approximate to that of patients in MRD-negative remission (15.5%, P = .522). There were no significant differences in terms of 3-year estimated overall survival (OS) and disease-free survival (DFS) between MRD-positive remission and MRD-negative remission groups (71.4% versus 79.1% [P = .562] and 67.9% versus 76.9% [P = .634], respectively). Moreover, the estimated rates of 3-year OS and DFS of patients in MRD-positive remission were significantly better than those in patients with active disease (71.4% versus 41.9% [P = .033] and 67.9% versus 38.7% [P = .037], respectively). These data indicate that IDA-intensified conditioning allo-HSCT could overcome the negative prognostic impact of MRD.

Evaluation of the Utility of Bone Marrow Morphology and Ancillary Studies in Pediatric Patients Under Surveillance for Myelodysplastic Syndrome

OBJECTIVES

To evaluate the utility of flow cytometry, karyotype, and a fluorescence in situ hybridization (FISH) panel in screening children for myelodysplastic syndrome (MDS).

METHODS

Bone marrow morphology, flow cytometry, karyotype, and FISH reports from 595 bone marrow specimens (246 patients) were analyzed.

RESULTS

By morphology, 8.7% of cases demonstrated at least unilineage dysplasia and/or increased blasts. Flow cytometry identified definitive abnormalities in 2.8% of cases, all of which had abnormal morphology. Of the 42 cases (7.2%) with acquired karyotypic abnormalities, 26 had no morphologic dysplasia. With a 98.2% concordance between karyotype and MDS FISH, FISH only identified two additional cases, both with low-level (<4%) abnormalities. Peripheral blood count evaluation only identified the absence of thrombocytopenia to correlate with an absence of abnormal ancillary tests.

CONCLUSIONS

The combination of morphologic evaluation and karyotype with judicious use of flow cytometry and MDS FISH is sufficient to detect abnormalities for these indications.

The Use of Flow Cytometry in Myelodysplastic Syndromes: A Review

Myelodysplastic syndromes (MDSs) are a heterogeneous group of hematopoietic stem cell diseases categorized by dysplasia in one or more hematopoietic cell lineages, as well as cytopenia and functional abnormalities in bone marrow cells. Several MDS classification methods have been proposed to categorize the disease and help professionals better plan in patients’ treatment. The World Health Organization classification, released in 2008 and revised in 2016, is the currently and the most used classification method worldwide. Recent advances in MDS molecular biology and innovations in flow cytometry have enabled the development of new parameters for MDS diagnosis and classification. Several groups have published flow cytometry scores and guidelines useful for the diagnosis and/or prognosis of MDS, which are mostly based on detecting immunophenotypic abnormalities in granulocyte, monocyte, and lymphoid lineages. Here, we review the current literature and discuss the main parameters that should be analyzed by flow cytometry with the aim of refining MDS diagnosis and prognosis. Furthermore, we discuss the critical role of flow cytometry and molecular biology in MDS diagnosis and prognosis, as well as the current challenges and future perspectives involving these techniques.

Haploidentical allograft is superior to matched sibling donor allograft in eradicating pre-transplantation minimal residual disease of AML patients as determined by multiparameter flow cytometry: a retrospective and prospective analysis

BACKGROUND

This study compared the effects of pre-transplantation minimal residual disease (pre-MRD) on outcomes in AML patients who underwent human leukocyte antigen-matched sibling donor transplantation (MSDT) or who received unmanipulated haploidentical allografts.

METHODS

A retrospective study (n = 339) and a prospective study (n = 340) were performed. MRD was determined using multiparameter flow cytometry.

RESULTS

Either after retrospective or prospective analysis, patients with negative pre-MRD (pre-MRDneg) had a lower incidence of relapse than those with positive pre-MRD (pre-MRDpos) in MSDT settings (P < 0.001 for all), but relapse was comparable in Haplo-SCT settings for patients with pre-MRDneg versus pre-MRDpos (P = 0.866 and 0.161, respectively). In either the retrospective (n = 65) or the prospective study (n = 76), pre-MRDpos subjects receiving Haplo-SCT experienced a lower incidence of relapse than those who underwent MSDT (P < 0.001 and p = 0.017, respectively). Of the patients with pre-MRDpos in either the total (n = 141) or the subgroup excluding cases which received donor lymphocyte infusion (DLI; n = 105), those who underwent MSDT had a higher incidence of relapse than those receiving haplo-SCT (P < 0.01 for all). Multivariate analysis showed that, for pre-MRDpos cases, haplo-SCT was associated with a low incidence of relapse and with better LFS and OS in either retrospective group, prospective group, combination groups, or subgroup not including cases which received DLI.

CONCLUSIONS

The results indicated that, for pre-MRD-positive AML patients, haplo-SCT was associated with lower incidence of relapse and better survival, suggesting a stronger anti-leukemia effect.

Prognostic significance of flow-cytometry evaluation of minimal residual disease in children with acute myeloid leukaemia treated according to the AIEOP-AML 2002/01 study protocol

In children with acute myeloid leukaemia (AML), assessment of initial treatment response is an essential prognostic factor; methods more sensitive than morphology are still under evaluation. We report on the measurement of minimal residual disease (MRD), by multicolour flow-cytometry in one centralized laboratory, in 142 children with newly diagnosed AML enrolled in the Associazione Italiana di EmatoOncologia Pediatrica-AML 2002/01 trial. At the end of the first induction course, MRD was <0·1% in 69, 0·1-1% in 16 and >1% in 51 patients. The 8-year disease-free survival (DFS) of 125 children in morphological complete remission and with MRD <0·1%, 0·1-1% and ≥1% was 73·1 ± 5·6%, 37·8 ± 12·1% and 34·1 ± 8·8%, respectively (P < 0·01). MRD was also available after the second induction course in 92/142 patients. MRD was ≥0·1% at the end of the first induction course in 36 patients; 13 reached an MRD <0·1% after the second one and their DFS was 45·4 ± 16·7% vs. 22·8 ± 8·9% in patients with persisting MRD ≥0·1% (P = 0·037). Multivariate analysis demonstrated that MRD ≥0·1% after first induction course was, together with a monosomal karyotype, an independent adverse prognostic factor for DFS. Our results show that MRD detected by flow-cytometry after induction therapy predicts outcome in patients with childhood AML and can help stratifying post-remission treatment.

Immunophenotyping by Multiparameter Flow Cytometry

Multiparameter flow cytometry has become an indispensable tool for the diagnosis and classification of acute myeloid leukemia (AML). The basic method relies on the unique ability to detect immunophenotypic abnormalities on discrete subpopulations. The primary roles in the initial assessment of AML are to determine the immaturity of the leukemic population, define the lineage and the immunophenotypic aberrancies in blasts, and identify characteristic immunophenotypic features to predict important recurrent cytogenetic and genetic abnormalities and prognosis. The established immunophenotypic profile, a baseline "fingerprint," is used for follow-up assessment of residual disease. This chapter provides an overview of procedures for specimen processing, staining, and immunophenotyping of AML and describes our strategy for data analysis supplemented with illustrative case examples.

Immunophenotypes of Chronic Myelomonocytic Leukemia (CMML) Subtypes by Flow Cytometry: A Comparison of CMML-1 vs CMML-2, Myeloproliferative vs Dysplastic, De Novo vs Therapy-Related, and CMML-Specific Cytogenetic Risk Subtypes

OBJECTIVES

We sought to immunophenotype blasts, monocytes, and granulocytes in chronic myelomonocytic leukemias (CMMLs) and compare CMML subtypes, to identify if significant antigen expression differences existed.

METHODS

Bone marrow blasts, monocytes, and granulocytes from CMML subgroups (n = 30; World Health Organization types 1/2, proliferative/dysplastic, therapy related/de novo, and low/intermediate/high cytogenetic risk) were immunophenotypically compared by flow cytometry with 10 nonneoplastic control marrows.

RESULTS

Aberrancies were present in blasts of 26 (87%) of 30 CMMLs (26 diagnostic; four follow-up) and six (60%) of 10 controls (P = .089), monocytes of 28 (93%) of 30 CMMLs and six (60%) of 10 controls (P = .026), and granulocytes of eight (28%) of 29 CMMLs and zero of 10 controls (P = .166). Underexpression of CD14 and CD15 on monocytes was more common in CMMLs compared with controls (P = .008 and P = .043). Statistical analysis showed no significant difference in antigen expression between the CMML subgroups on blasts or monocytes; granulocytes demonstrated more common HLA-DR expression in CMML-2 vs CMML-1.

CONCLUSIONS

These findings confirm heterogeneity within CMML subgroups and find no specific qualitative or quantitative findings characteristic of a subgroup.

Minimal Identifiable Disease and the Role of Conditioning Intensity in Hematopoietic Cell Transplantation for Myelodysplastic Syndrome and Acute Myelogenous Leukemia Evolving from Myelodysplastic Syndrome

Allogeneic hematopoietic cell transplantation (HCT) is the only known treatment with curative potential for myelodysplastic syndrome, but relapse is a major cause of failure. We studied results in 289 patients transplanted between June 2004 and December 2013. Minimal identifiable disease (MID) markers pre-HCT were determined by multiparameter flow cytometry (MFC) and cytogenetics on marrow aspirates. The impact of MID on outcome after low- and high-intensity conditioning HCT was determined. Among 287 assessable patients, 68 (23.7%) had more than 5% marrow blasts at HCT; 219 patients were in morphologic remission but 154 (53.7%) were MID positive, whereas 65 (22.6%) were MID negative. The impact of MID on outcome was significantly different between patients who received low-intensity conditioning and patients who received a high-intensity regimen. The impact of conditioning intensity differed across the various MID categories. In particular, the risk of overall mortality was higher with low-intensity than with high-intensity regimens for patients who were positive for MID by cytogenetics regardless of positivity by MFC (HR, 1.67 if MFC positive/cytogenetics positive, HR, 7.23 if MFC negative/cytogenetics positive). On the other hand, patients who were MID negative by both MFC and cytogenetics had similar risks of mortality with low- and high-intensity regimens (HR, .99). The main factor responsible for mortality after low-intensity conditioning in MID-positive patients was relapse. The presence of MID should be considered when deciding on conditioning intensity because it identifies subgroups of patients who may benefit from high- or low-intensity conditioning.

Relation of Clinical Response and Minimal Residual Disease and Their Prognostic Impact on Outcome in Acute Myeloid Leukemia

Purpose

Both presence of minimal residual disease (MRD) and achievement of complete remission (CR) with incomplete platelet recovery (CRp) rather than CR after induction therapy predict relapse in acute myeloid leukemia (AML). These results suggest a correlation between response (peripheral count recovery) and MRD at the time of morphologic remission. Here we examine this hypothesis and whether MRD and response provide independent prognostic information after accounting for other relevant covariates.

Patients and Methods

We retrospectively analyzed data from 245 adults with AML who achieved CR, CRp, or CR with incomplete blood count recovery (CRi) after induction therapy. Bone marrow samples were collected on or closest to the first date of blood count recovery, and MRD was determined by 10-color multiparameter flow cytometry.

Results

The 71.0% of patients who achieved CR had MRD less frequently and had lower levels of MRD than the 19.6% of patients achieving CRp and 9.4% achieving CRi. Although pretreatment covariates such as cytogenetics, monosomal karyotype, relapsed or refractory rather than newly diagnosed AML, and FLT3 internal tandem duplication were associated with relapse, their prognostic effect was much lower once MRD and response were taken into account, the univariable statistical effect of which was not materially affected by inclusion of pretreatment covariates.

Conclusion

Our data indicate that post-therapy parameters including MRD status and response are important independent prognostic factors for outcome in patients with AML achieving remission. MRD status and type of response (CR v CRp or CRi) should play important, and perhaps dominant, roles in planning postinduction therapy.

Minimal residual disease testing in acute leukemia

SUMMARY Predictive/prognostic factors in acute leukemia continue to be sought, in order to refine treatment strategies. Minimal residual disease (MRD) testing has been shown to be a statistically significant factor by multivariate analysis in both acute lymphoblastic leukemia (ALL) and acute myeloid leukemia. Its utility in guiding therapy has been more extensively studied in pediatric ALL, with some protocols having instituted MRD testing into therapeutic algorithms. The clinical impact of MRD testing in ALL and acute myeloid leukemia will be presented, including both molecular and flow cytometric methodologies, with a more focused discussion of the strategy, methodology and interpretation of MRD testing by multiparametric flow cytometry.

Chronic myelomonocytic leukemia monocytes uniformly display a population of monocytes with CD11c underexpression

OBJECTIVES

To examine the utility of CD11c expression on monocytes in normal controls and patients with chronic myelomonocytic leukemia (CMML) (n = 23) with flow cytometric immunophenotyping.

METHODS

Twenty-three CMML samples and 10 control bone marrows submitted for lymphoma staging without evidence of disease were examined.

RESULTS

Monocytes in CMML samples ranged from 4% to 35%. Expression of at least one aberrant monocytic marker was found on the monocytes in 18 (82%) of 22 evaluable cases. The most common aberrancy was underexpression of CD11c (n = 15), while none of the bone marrow controls showed underexpression of CD11c.

CONCLUSIONS

A distinct heterogeneous population of monocytic cells with underexpression of CD11c was identified in all these cases. CD11c underexpression was independent of other aberrancies, including HLA-DR underexpression (n = 14), aberrant CD56 expression (n = 11), and underexpression of CD33, CD38, and CD14 (n = 6, 5, and 5, respectively), supporting the utility of CD11c expression status on monocytes in establishing a CMML diagnosis.

Update on Myelodysplastic Syndromes Classification and Prognosis

Myelodysplastic syndromes (MDS) are a collection of cytogenetically heterogeneous clonal bone marrow (BM) failure disorders derived from aberrant hematopoietic stem cells in the setting of an aberrant hematopoietic stem cell niche. Patients suffer from variably progressive and symptomatic bone marrow failure with a risk of leukemic transformation. Diagnosis of MDS has long been based on morphologic assessment and blast percentage as in the original French-American-British classification. The recently developed Revised International Prognostic Scoring System provides improved prognostication using more refined cytogenetic, marrow blast, and cytopenia parameters. With the advent of deep sequencing technologies, dozens of molecular abnormalities have been identified in MDS.

Significance of CD71 expression by flow cytometry in diagnosis of acute leukemia

In this study we investigated the significance of CD71 (transferrin receptor 1, TfR-1) as a flow cytometric marker in the diagnosis of acute leukemia (AL). A total of 105 patients with AL were enrolled. Poorly differentiated acute myeloid leukemias (AMLs) (including minimally differentiated AML, AML without maturation, AML with maturation, acute myelomonocytic leukemia) tended to express high levels of CD71 on leukemic cells, while partially differentiated AML (including acute promyelocytic leukemia and acute monocytic leukemia) often expressed low levels of CD71 on leukemic cells (p < 0.05, compared to poorly differentiated AML). B-cell acute lymphoblastic leukemia (B-ALL) expressed low levels of CD71 on leukemic cells, significantly lower than AML, mixed phenotype acute leukemia (MPAL) and normal bone marrow blasts (p < 0.05). In the seven cases of acute erythroid leukemia (AEL), leukemic cells rarely expressed CD71, with the mean CD71 expression level significantly lower than that of acute megakaryocytic leukemia (p < 0.05), and also lower than that of poorly differentiated AML and normal blasts but without statistical significance. CD71 may not be a specific marker for AEL leukemic cells. During the process from myeloid dysplasia to apparent leukemic cells, both CD71 and CD34 gradually increased. Consequently, the presence of leukemic cell subsets with variable levels of CD71 and CD34 may be useful for understanding the dynamic processes involved in the clonal development seen in leukemias.

Role of flow cytometry in myelodysplastic syndromes: diagnosis, classification, prognosis and response assessment

Myelodysplastic syndromes (MDS) are a heterogeneous group of myeloid neoplasms. With the emergence of therapeutic options, attempts to standardize diagnostic, prognostic and response criteria to guide treatment decisions are increasingly important. This has been achieved in part by the revised 2008 World Health Organization classification and consensus guidelines outlining refined definitions and standards. Conventional criteria have limitations in terms of sensitivity and specificity. Multiparameter flow cytometry (FC) can be used real-time, and is a highly reproducible and objective way of assessing the pattern of expression of multiple antigens on a single hematopoietic cell and defined subpopulations. By comparing antigen expression within maturing myelomonocytic populations with that identified on the equivalent normal cells, abnormalities identified may provide a diagnostic indication of stem cell dysmaturation. There are now increasingly robust data demonstrating the capacity of FC to discriminate MDS from non-clonal cytopenias and dysplasia, as well as further refine disease classification and prognostication, which will be reviewed here.

Minimal residual disease in acute myeloid leukaemia

Technological advances in the laboratory have led to substantial improvements in clinical decision making through the introduction of pretreatment prognostic risk stratification factors in acute myeloid leukaemia (AML). Unfortunately, similar progress has not been made in treatment response criteria, with the definition of 'complete remission' in AML largely unchanged for over half a century. Several clinical trials have demonstrated that high-sensitivity measurements of residual disease burden during or after treatment can be performed, that results are predictive for clinical outcome and can be used to improve outcomes by guiding additional therapeutic intervention to patients in clinical complete remission, but at increased relapse risk. We review these recent trials, the characteristics and challenges of the modalities currently used to detect minimal residual disease (MRD), and outline opportunities to both refine detection and improve clinical use of MRD measurements. MRD measurement is already the standard of care in other myeloid malignancies, such as chronic myelogenous leukaemia and acute promyelocytic leukaemia (APL). It is our belief that response criteria for non-APL AML should be updated to include assessment for molecular complete remission and recommendations for post-consolidation surveillance should include regular monitoring for molecular relapse as standard of care.

Expression of immune inhibitory receptor ILT3 in acute myeloid leukemia with monocytic differentiation

BACKGROUND

The diagnosis of AML with monocytic differentiation is limited by the lack of highly sensitive and specific monocytic markers. Immunoglobulin-like transcript 3 (ILT3) is an immune inhibitory receptor expressed by myelomonocytic cells and at high levels by tolerogenic dendritic cells.

METHODS

Using flow cytometry, we analyzed the expression of ILT3 in 37 patients with AML and 20 patients with no detectable disease.

RESULTS

We showed that ILT3 was expressed in all cases of AML displaying monocytic differentiation (FAB M4/M5; N = 18), but not in AML M1/M2 and M3 (N = 19; P < 0.0001). Co-expression of ILT3 and immature cell markers, such as CD34 and CD117, was observed in monoblastic leukemia. ILT3 expression was preserved after treatment in M4/M5 patients with refractory or relapsed disease. ILT3 expression was associated with the presence of cytogenetic abnormalities linked to an intermediate prognosis (P = 0.001). Rare CD45dimCD34+CD117+ILT3+ cells were identified in noninvolved bone marrow, suggesting that ILT3 expression is acquired at an early stage by normal myelomonocytic precursors.

CONCLUSIONS

ILT3 is a highly sensitive and specific marker which distinguishes AML with monocytic differentiation from other types of AML. Testing of ILT3 expression should be incorporated into the initial diagnostic work-up and monitoring of patients with AML.

The expression of CD56 antigen is associated with poor prognosis in patients with acute myeloid leukemia

BACKGROUND

The expression of CD56 is considered a bad prognostic factor for overall survival, lower rates or short complete remission and extramedullary invasion but the results are controversial. The importance of validating new prognostic parameters in acute leukemias was the reason to investigate the CD56 expression in blast cells of patients with acute myeloid leukemia.

METHODS

A cohort of 48 patients treated at Hospital de Clinicas de Porto Alegre and diagnosed with acute myeloid leukemia as classified by the French-American-British group (FAB) criteria using cell morphology, cytochemistry and flow cytometry were evaluated.

RESULTS

Eight cases (16.7%) were CD56 positive without correlation to age or gender. The highest incidence of CD56 positivity was in FAB subtypes M4 and M5. The death rate during induction was not significantly different between patients with and without CD56 expression (62.5% vs. 27.5%; p-value = 0.097). However, patients that expressed CD56 had significantly lower overall survival than those who did not (mean 4.0 months vs. 14.5 months; p-value = 0.03).

CONCLUSIONS

The data suggest that expression of CD56 in acute myeloid leukemia may be indicative of poor prognosis because it is associated with a shorter overall survival. The death rate during induction was not significantly different despite an apparent difference in proportions between groups.

Minimal residual disease as a predictive factor for relapse after allogeneic hematopoietic stem cell transplant in adult patients with acute myeloid leukemia in first and second complete remission

Allogeneic hematopoietic stem cell transplantation (allo-SCT) is potentially curative for patients with high-risk leukemia, but disease recurrence remains the leading cause of treatment failure. Our objective was to determine the impact of minimal residual disease (MRD) by any technique in adult patients with acute myeloid leukemia (AML) in morphologic first and second complete remission undergoing allo-SCT. Fifty nine patients were eligible for the study of 160 patients transplanted over ten years. For the MRD assessment we used multiparametric flow cytometry, cytogenetics and fluorescent in situ hybridization; 19 patients (32.2%) were identified as MRD positive. Patients with MRD had a consistently worse outcome over those without MRD, with 3-years leukemia-free survival (LFS) of 15.8% vs. 62.4% and overall survival (OS) of 17.5% vs. 62.3%. Relapse rate was significantly higher in MRD-positive patients; 3 years relapse rate in MRD-positive patients was 57.9% vs. 15.1% in MRD-negative patients. Detection of MRD in complete remission was associated with increased overall mortality (HR = 3.3; 95% CI: 1.45–7.57; p = 0.0044) and relapse (HR = 5.26; 95% CI: 2.0–14.0; p = 0.001), even after controlling for other risk factors. Our study showed that for patients in morphologic complete remission the presence of MRD predicts for significantly increased risk of relapse and reduced LFS and OS.

Standardization of flow cytometry in myelodysplastic syndromes: a report from an international consortium and the European LeukemiaNet Working Group

Flow cytometry (FC) is increasingly recognized as an important tool in the diagnosis and prognosis of myelodysplastic syndromes (MDS). However, validation of current assays and agreement upon the techniques are prerequisites for its widespread acceptance and application in clinical practice. Therefore, a working group was initiated (Amsterdam, 2008) to discuss and propose standards for FC in MDS. In 2009 and 2010, representatives from 23, mainly European, institutes participated in the second and third European LeukemiaNet (ELN) MDS workshops. In the present report, minimal requirements to analyze dysplasia are refined. The proposed core markers should enable a categorization of FC results in cytopenic patients as 'normal', 'suggestive of', or 'diagnostic of' MDS. An FC report should include a description of validated FC abnormalities such as aberrant marker expression on myeloid progenitors and, furthermore, dysgranulopoiesis and/or dysmonocytopoiesis, if at least two abnormalities are evidenced. The working group is dedicated to initiate further studies to establish robust diagnostic and prognostic FC panels in MDS. An ultimate goal is to refine and improve diagnosis and prognostic scoring systems. Finally, the working group stresses that FC should be part of an integrated diagnosis rather than a separate technique.

Methods for the identification, characterization and banking of human DPSCs: current strategies and perspectives

Dental pulp stem cells (DPSCs), originating from neural crests, can be found within dental pulp. Up to now, it has been demonstrated that these cells are capable of producing bone tissue, both in vitro and in vivo and differentiate into adipocytes, endotheliocytes, melanocytes, neurons, glial cells, and can be easily cryopreserved and stored. Moreover, recent attention has been focused on tissue engineering and on the properties of these cells. In addition, adult bone tissue with good vascularisation has been obtained in grafts. The latest use in clinical trials for bone repair enforces the notion that DPSCs can be used successfully in patients. Therefore, their isolation, selection, differentiation and banking is of great importance. The isolation and detection techniques used in most laboratories are based on the use of antibodies revealed by flow-cytometers with cell sorter termed FACS (fluorescent activated cell sorter). In this report, we focus our attention on the main procedures used in the selection of DPSCs by flow cytometry, cell culture, freezing/thawing, cell cycle evaluation, histochemistry/immunofluorescence and differentiation of DPSCs. In addition, new methods/protocols to select and isolate stem cells without staining by fluorescent markers for implementation in biomedical/clinical laboratories are discuss. We emphasize that the new methods must address simplicity and short times of preparation and use of samples, complete sterility of cells, the potential disposable, low cost and complete maintenance of the viability and integrity of the cells with real-time response for subsequent applications in the biomedical/clinical/surgical fields.

Prognostic impact of discordant results from cytogenetics and flow cytometry in patients with acute myeloid leukemia undergoing hematopoietic cell transplantation

BACKGROUND

Cytogenetics and multicolor flow cytometry (MFC) are useful tools for monitoring outcome of treatment in acute myeloid leukemia (AML). However, no data are available regarding the meaning of results when the 2 tests do not agree.

METHODS

The authors of this report analyzed 1464 pairs of concurrent cytogenetics and flow results from 424 patients, before and after hematopoietic cell transplantation, and compared the prognostic impact of discordant and concordant results.

RESULTS

Informative discordant results were observed in 22% of patients. Compared with patients who had double-negative test results, either positive result had a significant impact on overall survival and relapse-free survival. The hazard ratios with either positive cytogenetic results or positive MFC results pretransplantation were 3.1 (P = .009) and 2.5 (P = .0008), respectively, for reduced overall survival and 2.7 (P = .01) and 4.1 (P < .0001), respectively, for decreased recurrence-free survival. Similar findings were obtained post-transplantation. Molecular cytogenetics, ie, fluorescence in situ hybridization (FISH), added value to the evaluation of discordant cases.

CONCLUSIONS

The detection of residual AML by either cytogenetics or flow cytometry in patients who underwent hematopoietic cell transplantation predicted early relapse and shortened survival.

Impact of pretransplantation minimal residual disease, as detected by multiparametric flow cytometry, on outcome of myeloablative hematopoietic cell transplantation for acute myeloid leukemia

PURPOSE

Allogeneic hematopoietic cell transplantation (HCT) benefits many patients with acute myeloid leukemia (AML) in first remission. Hitherto, little attention has been given to the prognostic impact of pretransplantation minimal residual disease (MRD).

PATIENTS AND METHODS

We retrospectively studied 99 consecutive patients receiving myeloablative HCT for AML in first morphologic remission. Ten-color multiparametric flow cytometry (MFC) was performed on bone marrow aspirates before HCT. MRD was identified as a cell population showing deviation from normal antigen expression patterns compared with normal or regenerating marrow. Any level of residual disease was considered MRD positive.

RESULTS

Before HCT, 88 patients met morphologic criteria for complete remission (CR), whereas 11 had CR with incomplete blood count recovery (CRi). Twenty-four had MRD before HCT as determined by MFC. Two-year estimates of overall survival were 30.2% (range, 13.1% to 49.3%) and 76.6% (range, 64.4% to 85.1%) for MRD-positive and MRD-negative patients; 2-year estimates of relapse were 64.9% (range, 42.0% to 80.6%) and 17.6% (range, 9.5% to 27.9%). After adjustment for all or a subset of cytogenetic risk, secondary disease, incomplete blood count recovery, and abnormal karyotype pre-HCT, MRD-positive HCT was associated with increased overall mortality (hazard ratio [HR], 4.05; 95% CI, 1.90 to 8.62; P < .001) and relapse (HR, 8.49; 95% CI, 3.67 to 19.65; P < .001) relative to MRD-negative HCT.

CONCLUSION

These data suggest that pre-HCT MRD is associated with increased risk of relapse and death after myeloablative HCT for AML in first morphologic CR, even after controlling for other risk factors.

The specificity of immunophenotypic alterations in blasts in nonacute myeloid disorders

Data regarding flow cytometry (FC) in nonacute myeloid disorders is confounded by variable gating strategies and controls limited to normal bone marrow (BM) samples. Blasts in diagnostic BM samples of myelodysplastic syndromes (MDSs), myeloproliferative neoplasms (MPNs), and chronic myelomonocytic leukemias (CMMLs) were compared with 20 nonneoplastic cytopenias/cytoses (CCs) and negative staging BM samples using 4-color FC. Blasts in 10 of 20 CCs showed immunophenotypic differences vs control samples. Immunophenotypic alterations were identified in 18 of 21 MDSs, 11 of 14 MPNs, and 7 of 7 CMMLs vs control samples and 13 (62%) of 21 MDSs, 7 (50%) of 14 MPNs, and 3 (43%) of 7 CMMLs vs CCs. Neoplastic-specific blast immunophenotypic changes included expression of CD7, CD11b, CD15, CD36, and CD56; CD34 overexpression; HLA-DR variability; lack of CD13 and CD33; underexpression of CD13, CD33, CD45, and HLA-DR; and partial loss of CD13, CD33, CD38, and CD117. In all cases, blasts were CD34+. Several blast immunophenotypic alterations are shared in neoplastic and nonneoplastic BM samples. Approximately 40% to 60% of neoplastic BM samples exhibited aberrancies not seen in reactive BM samples.

Flow cytometric analysis of CD123 is useful for immunophenotyping classical Hodgkin lymphoma

Although the diagnosis of classical Hodgkin lymphoma (CHL) is traditionally made morphologically in tissue sections, it is now possible to diagnose CHL by flow cytometry (FC). In an effort to identify additional antigens on Hodgkin and Reed-Sternberg (HRS) cells that might be useful for immunophenotyping this lymphoma by FC, we examined the expression of CD123 (α chain of the IL-3R) on HRS cells and compared this with the expression of CD123 in other lymph node samples (372 tissue specimens, including 98 reactive and 274 neoplastic cases), using a nine-color FC reagent combination including anti-CD123. CD123 was found to be expressed on the majority of HRS cell populations (59% of 59 CHL lymph nodes examined), rarely on B-cell non-Hodgkin lymphomas (NHLs) (3 of 3 hairy cell leukemia cases, 3 of 29 chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) cases, 1 of 55 large B-cell lymphoma cases, but not on 95 other B-cell NHL examined), and in none of the 16 T-cell NHL cases examined. In reactive lymph nodes, CD123 expression was largely limited to plasmacytoid dendritic cells and rare histiocyte populations that can readily be distinguished from HRS populations. As the expression of this antigen is shown to be relatively limited in B- and T-NHL and in reactive lymph node populations, assessment of CD123 expression is useful for supporting the FC diagnosis of CHL.

Highly multiparametric analysis by mass cytometry

This review paper describes a new technology, mass cytometry, that addresses applications typically run by flow cytometer analyzers, but extends the capability to highly multiparametric analysis. The detection technology is based on atomic mass spectrometry. It offers quantitation, specificity and dynamic range of mass spectrometry in a format that is familiar to flow cytometry practitioners. The mass cytometer does not require compensation, allowing the application of statistical techniques; this has been impossible given the constraints of fluorescence noise with traditional cytometry instruments. Instead of "colors" the mass cytometer "reads" the stable isotope tags attached to antibodies using metal-chelating labeling reagents. Because there are many available stable isotopes, and the mass spectrometer provides exquisite resolution between detection channels, many parameters can be measured as easily as one. For example, in a single tube the technique allows for the ready detection and characterization of the major cell subsets in blood or bone marrow. Here we describe mass cytometric immunophenotyping of human leukemia cell lines and leukemia patient samples, differential cell analysis of normal peripheral and umbilical cord blood; intracellular protein identification and metal-encoded bead arrays.

Four- and five-color flow cytometry analysis of leukocyte differentiation pathways in normal bone marrow: a reference document based on a systematic approach by the GTLLF and GEIL

BACKGROUND

The development of multiparameter flow cytometry (FCM) and increasingly sophisticated analysis software has considerably improved the exploration of hematological disorders. These tools have been widely applied in leukaemias, lymphomas, and myelodysplasias, yet with very heterogeneous approaches. Consequently, there is no extensive reference document reporting on the characteristics of normal human bone marrow (BM) in multiparameter FCM. Here, we report a reference analysis procedure using relevant antibody combinations in normal human BM.

METHODS

A first panel of 23 antibodies, constructed after literature review, was tested in four-color combinations (including CD45 in each) on 30 samples of BM. After evaluation of the data, a second set of 22 antibodies was further applied to another 35 BM samples. All list-modes from the 65 bone marrow samples were reviewed collectively. A systematised protocol for data analysis was established including biparametric representations and color codes for the three major lineages and undifferentiated cells.

RESULTS

This strategy has allowed to obtain a reference atlas of relevant patterns of differentiation antigens expression in normal human BM that is available within the European LeukemiaNet. This manuscript describes how this atlas was constructed.

CONCLUSIONS

Both the strategy and atlas could prove very useful as a reference of normality, for the determination of leukemia-associated immunophenotypic patterns, analysis of myelodysplasia and, ultimately, investigation of minimal residual disease in the BM.

Standardization of flow cytometry in myelodysplastic syndromes: report from the first European LeukemiaNet working conference on flow cytometry in myelodysplastic syndromes

The myelodysplastic syndromes are a group of clonal hematopoietic stem cell diseases characterized by cytopenia(s), dysplasia in one or more cell lineages and increased risk of evolution to acute myeloid leukemia (AML). Recent advances in immunophenotyping of hematopoietic progenitor and maturing cells in dysplastic bone marrow point to a useful role for multiparameter flow cytometry (FCM) in the diagnosis and prognostication of myelodysplastic syndromes. In March 2008, representatives from 18 European institutes participated in a European LeukemiaNet (ELN) workshop held in Amsterdam as a first step towards standardization of FCM in myelodysplastic syndromes. Consensus was reached regarding standard methods for cell sampling, handling and processing. The group also defined minimal combinations of antibodies to analyze aberrant immunophenotypes and thus dysplasia. Examples are altered numbers of CD34(+) precursors, aberrant expression of markers on myeloblasts, maturing myeloid cells, monocytes or erythroid precursors and the expression of lineage infidelity markers. When applied in practice, aberrant FCM patterns correlate well with morphology, the subclassification of myelodysplastic syndromes, and prognostic scoring systems. However, the group also concluded that despite strong evidence for an impact of FCM in myelodysplastic syndromes, further (prospective) validation of markers and immunophenotypic patterns are required against control patient groups as well as further standardization in multi-center studies. Standardization of FCM in myelodysplastic syndromes may thus contribute to improved diagnosis and prognostication of myelodysplastic syndromes in the future.

A chromatic explosion: the development and future of multiparameter flow cytometry

Multiparameter flow cytometry has matured tremendously since the 1990s, giving rise to a technology that allows us to study the immune system in unprecedented detail. In this article, we review the development of hardware, reagents, and data analysis tools for multiparameter flow cytometry and discuss future advances in the field. Finally, we highlight new applications that use this technology to reveal previously unappreciated aspects of cell biology and immunity.

NDRG1 contributes to retinoic acid-induced differentiation of leukemic cells

N-Myc downstream-regulated gene 1 (NDRG1) protein has been shown to be up-regulated during leukemic cell differentiation induced by some differentiation-inducing agents such as all-trans retinoic acid (ATRA). However, the potential role of up-regulated NDRG1 in the event is greatly unknown. In this work, we show that inducible NDRG1 expression can drive leukemic U937 cells to undergo differentiation, while the knock-down of NDRG1 expression by specific small interfering RNA significantly antagonizes ATRA-induced differentiation of leukemic cells, proposing the role of NDRG1 in leukemic cell differentiation. Furthermore, our work shows that CCAAT/enhancer-binding protein beta (C/EBPbeta) and PU.1, which are important hematopoiesis-related transcription factors, may act as downstream effectors of NDRG1 in leukemic cell differentiation. Taking together, this study provides direct evidence for the role of NDRG1 protein in myeloid leukemic cell differentiation.

Flow cytometric immunophenotyping for hematologic neoplasms

Flow cytometric immunophenotyping remains an indispensable tool for the diagnosis, classification, staging, and monitoring of hematologic neoplasms. The last 10 years have seen advances in flow cytometry instrumentation and availability of an expanded range of antibodies and fluorochromes that have improved our ability to identify different normal cell populations and recognize phenotypic aberrancies, even when present in a small proportion of the cells analyzed. Phenotypically abnormal populations have been documented in many hematologic neoplasms, including lymphoma, chronic lymphoid leukemias, plasma cell neoplasms, acute leukemia, paroxysmal nocturnal hemoglobinuria, mast cell disease, myelodysplastic syndromes, and myeloproliferative disorders. The past decade has also seen refinement of the criteria used to identify distinct disease entities with widespread adoption of the 2001 World Health Organization (WHO) classification. This classification endorses a multiparametric approach to diagnosis and outlines the morphologic, immunophenotypic, and genotypic features characteristic of each disease entity. When should flow cytometric immunophenotyping be applied? The recent Bethesda International Consensus Conference on flow cytometric immunophenotypic analysis of hematolymphoid neoplasms made recommendations on the medical indications for flow cytometric testing. This review discusses how flow cytometric testing is currently applied in these clinical situations and how the information obtained can be used to direct other testing.