Clinical impact of leukemic blast heterogeneity at diagnosis in cytogenetic intermediate-risk acute myeloid leukemia

Immunophenotypic characterization of leukemic stem cells in acute myeloid leukemia using single tube 10-colour panel by multiparametric flow cytometry: Deciphering the spectrum, complexity and immunophenotypic heterogeneity

INTRODUCTION

Despite extensive research, comprehensive characterization of leukaemic stem cells (LSC) and information on their immunophenotypic differences from normal haematopoietic stem cells (HSC) is lacking. Herein, we attempted to unravel the immunophenotypic (IPT) characteristics and heterogeneity of LSC using multiparametric flow cytometry (MFC) and single-cell sequencing.

MATERIALS AND METHODS

Bone marrow aspirate samples from patients with acute myeloid leukaemia (AML) were evaluated using MFC at diagnostic and post induction time points using a single tube-10-colour-panel containing LSC-associated antibodies CD123, CD45RA, CD44, CD33 and COMPOSITE (CLL-1, TIM-3, CD25, CD11b, CD22, CD7, CD56) with backbone markers that is, CD45, CD34, CD38, CD117, sCD3. Single-cell sequencing of the whole transcriptome was also done in a bone marrow sample.

RESULTS

LSCs and HSCs were identified in 225/255 (88.2%) and 183/255 (71.6%) samples, respectively. Significantly higher expression was noted for COMPOSITE, CD45RA, CD123, CD33, and CD44 in LSCs than HSCs (p < 0.0001). On comparing the LSC specific antigen expressions between CD34+ (n = 184) and CD34- LSCs (n = 41), no difference was observed between the groups. More than one sub-population of LSC was demonstrated in 4.4% of cases, which further revealed high concordance between MFC and single cell transcriptomic analysis in one of the cases displaying three LSC subpopulations by both methods.

CONCLUSION

A single tube-10-colour MFC panel is proposed as an easy and reproducible tool to identify and discriminate LSCs from HSCs. LSCs display both inter- and intra-sample heterogeneity in terms of antigen expressions, which opens the facets for single cell molecular analysis to elucidate the role of subpopulations of LSCs in AML progression.

Methylation of the Phospholipase A2 Receptor 1 Promoter Region in Childhood B Cell Acute Lymphoblastic Leukaemia

Acute lymphoblastic leukaemia (ALL) is the most common form of paediatric cancer and epigenetic aberrations are determinants of leukaemogenesis. The aim of this study was to investigate the methylation degree of a distinct phospholipase A2 receptor 1 (PLA2R1) promoter region in paediatric ALL patients and to evaluate its relevance as new biomarker for monitoring treatment response and burden of residual disease. The impact of PLA2R1 re-expression on proliferative parameters was assessed in vitro in Jurkat cells with PLA2R1 naturally silenced by DNA methylation. Genomic DNA was isolated from bone marrow (BM) and peripheral blood (PB) of 44 paediatric ALL patients. PLA2R1 methylation was analysed using digital PCR and compared to 20 healthy controls. Transfected Jurkat cells were investigated using cell growth curve analysis and flow cytometry. PLA2R1 was found hypermethylated in BM and PB from pre-B and common ALL patients, and in patients with the disease relapse. PLA2R1 methylation decreased along with leukaemic blast cell reduction during ALL induction treatment. In vitro analysis revealed an anti-proliferative phenotype associated with PLA2R1 re-expression, suggesting a tumour-suppressive function of PLA2R1. Collected data indicates that PLA2R1 promoter methylation quantitation can be used as biomarker for ALL induction treatment control, risk stratification, and early detection of ALL relapse.

Diagnostic work-up of acute myeloid leukemia

Acute myeloid leukemia (AML) is characterized by a clonal expansion of undifferentiated myeloid precursors resulting in impaired hematopoiesis and bone marrow failure. In 2016, the World Health Organization (WHO) published revisions to the classification of myeloid neoplasms and acute leukemias. Similar to the 2008 classification, the updated classification incorporates clinical features, morphology, immunophenotyping, and cytogenetics, with greater emphasis on molecular genetics, to define disease entities. This brief review addresses the various components of pathologic assessment to establish a diagnosis of AML and to help risk stratify patients, with an emphasis on newer techniques used in the detection of mutations with prognostic significance, as well as assays employed in the evaluation of minimal residual disease following treatment.

Assessment of myeloid and monocytic dysplasia by flow cytometry in de novo AML helps define an AML with myelodysplasia-related changes category

AIMS

In recent years, multiparameter flow cytometry has been increasingly recognised as an important tool in diagnosis of myelodysplastic syndrome and acute myeloid leukaemia (AML). Assessment of myeloid and monocytic 'immunophenotypic' dysplasia by flow cytometry in de novo AML has not been evaluated.

METHODS

97 cases of de novo AML cases were identified and reviewed by three hematopathologists. 'Immunophenotypic' dysplasia was assessed on blasts, monocytes and granulocytes by mean fluorescence intensity.

RESULTS

Using the 2008 WHO classification criteria, there were 53 AML-not otherwise specified (NOS) (55%) and 28 AML with myelodysplasia-related changes (AML-MRC) (29%), while 16 cases were ambiguous as to AML-MRC status due to limited maturing cells for morphologic but adequate events number for immunophenotypic evaluation (AML-not evaluable, 16%). Compared with AML-NOS, granulocytic cells in AML-MRC had higher CD33 expression but lower CD45, CD11b and CD15. Monocytes in AML-MRC had lower expression of CD14, CD56 and CD45. Morphologic dysplasia was associated with significantly lower granulocytic forward scatter, side scatter and CD10 but higher CD33 expression.

CONCLUSIONS

Our results suggest that the workup of AML cases should include flow cytometric assessment of granulocytes and monocytes. This analysis can aid a morphologic impression of multilineage dysplasia in distinguishing AML-MRC from AML-NOS, especially in cases with limited maturing myeloid cells.

Leukemia-associated aberrant immunophenotype in patients with acute myeloid leukemia: changes at refractory disease or first relapse and clinicopathological findings

INTRODUCTION

Multiparameter flow cytometry (MFC) is commonly used to detect minimal residual disease (MRD) during the course of chemotherapy or relapse. Only one study addressed the immunophenotypic changes in refractory disease. We studied changes in leukemia-associated aberrant immunophenotype (LAIP) in patients with refractory and relapsed acute myeloid leukemia (AML).

METHOD

We analyzed 47 patients (refractory = 22; relapsed = 25) by MFC, morphology, and cytogenetic studies.

RESULTS

Thirty-five patients (74%) showed variably changed LAIPs. The frequently altered LAIPs were lack of lineage-specific antigen and lineage infidelity. The most frequently changed marker was CD13, followed by CD33, CD56, CD7, CD4, and CD11b. Cytogenetic clonal evolution at persistence/relapse was observed in 15 patients (32%). Morphologically, three patients (6%) showed significant changes at relapse. Patients with refractory AML had a higher association with poor cytogenetic risk and classification of AML with myelodysplasia-related changes. Positive MRD at postinduction was of prognostic significance. Allogeneic stem cell transplant improved overall survival.

CONCLUSIONS

LAIP alterations in refractory/relapsed AMLs are common findings. Presence of persistent disease indicates a poor prognosis, regardless of cytogenetic risk or expression of CD7 or CD56. Discordance between cytogenetic and LAIP changes suggests that gross cytogenetic clonal evolution during disease progression only partly contributes to immunophenotypic instability.

Validation and implementation of a method for microarray gene expression profiling of minor B-cell subpopulations in man

BACKGROUND

This report describes a method for the generation of global gene expression profiles from low frequent B-cell subsets by using fluorescence-activated cell sorting and RNA amplification. However, some of the differentiating compartments involve a low number of cells and therefore it is important to optimize and validate each step in the procedure.

METHODS

Normal lymphoid tissues from blood, tonsils, thymus and bone marrow were immunophenotyped by the 8-colour Euroflow panel using multiparametric flow cytometry. Subsets of B-cells containing cell numbers ranging from 800 to 33,000 and with frequencies varying between 0.1 and 10 percent were sorted, subjected to mRNA purification, amplified by the NuGEN protocol and finally analysed by the Affymetrix platform.

RESULTS

Following a step by step strategy, each step in the workflow was validated and the sorting/storage conditions optimized as described in this report. First, an analysis of four cancer cell lines on Affymetrix arrays, using either 100 ng RNA labelled with the Ambion standard protocol or 1 ng RNA amplified and labelled by the NuGEN protocol, revealed a significant correlation of gene expressions (r ≥ 0.9 for all). Comparison of qPCR data in samples with or without amplification for 8 genes showed that a relative difference between six cell lines was preserved (r ≥ 0.9). Second, a comparison of cells sorted into PrepProtect, RNAlater or directly into lysis/binding buffer showed a higher yield of purified mRNA following storage in lysis/binding buffer (p < 0.001). Third, the identity of the B-cell subsets validated by the cluster of differentiation (CD) membrane profile was highly concordant with the transcriptional gene expression (p-values <0.001). Finally, in normal bone marrow and tonsil samples, eight evaluated genes were expressed in accordance with the biology of lymphopoiesis (p-values < 0.001), which enabled the generation of a gene-specific B-cell atlas.

CONCLUSION

A description of the implementation and validation of commercially available kits in the laboratory has been examined. This included steps for cell sorting, cell lysis/stabilization, RNA isolation, RNA concentration and amplification for microarray analysis. The workflow described in this report will enable the generation of microarray data from minor sorted B-cell subsets.

Blast cell deficiency of CD11a as a marker of acute megakaryoblastic leukemia and transient myeloproliferative disease in children with and without Down syndrome

BACKGROUND

The classification of acute myeloid leukemia (AML) FAB subtype M7 relies on immunophenotypic assessment. CD41 is expressed throughout all stages of maturation of megakaryocytes and has therefore been described as a specific blast cell marker in AML M7 as well as in transient myeloproliferative disease (TMD) of patients with Down syndrome (DS). However, technical difficulties underlie the need for new markers for these entities.

METHODS

We evaluated the expression of human lymphocyte function-associated antigen 1 (CD11a) in a large cohort of pediatric AML and TMD patients (n = 91) of the Austrian AML-BFM 98 and 2004 studies.

RESULTS

We found a consistent deficiency of CD11a as assessed by mean fluorescence intensity in all patients with non-DS AML M7 (n = 8) and M6 (n = 1), all cases of classical DS-AML (n = 12) as well as TMD (n = 15) that was statistically significant in comparison to non-DS AML M0-M5 patients (n = 55; P < 0.001, sensitivity 100%). Only three of 55 Non-DS M0-5 patients were CD11a deficient (specificity 95%). Monocytic leukemias (M4/5) and normal monocytes typically showed a high CD11a expression, FAB types M1/2 and normal neutrophils an intermediate expression level, while all M3 leukemias were rather low in CD11a expression.

CONCLUSIONS

We conclude, that deficiency of CD11a expression should be added to the diagnostic criteria of AML-M7, classical DS-AML and TMD.

Modeling SDF-1-induced mobilization in leukemia cell lines

The stromal cell-derived factor 1 (SDF-1) is essential for circulation, homing, and retention of hematopoietic stem cells in the bone marrow. Present evidence indicates that this factor might play an important role in leukemia cells as well. The aim of this study is to present a model of SDF-1-induced mobilization using leukemia cell lines. CXCR4 expression was compared in Kasumi-1, Jurkat, HL-60, KG-1a, and K562 cells by flow cytometry and Western blot. Migration was analyzed with Transwell assays, and adhesive cell-cell interaction was quantified with a standardized adhesion assay and flow cytometry. CXCR4 was expressed by all leukemic cell lines analyzed, although surface expression of this receptor was found in Kasumi-1 and Jurkat cells only. Correspondingly, SDF-1α effects on migration and cell-cell adhesion were observed in Kasumi-1 and Jurkat cells only, and this could be blocked by AMD3100 in a reversible manner. We have provided evidence that SDF-1α acts as a chemotactic and chemokinetic agent. In addition, surface expression of integrin-β2, activated leukocyte cell adhesion molecule and N-cadherin decreased after stimulation with SDF-1α. SDF-1α affects cell-cell adhesion and migration only in leukemia cells on which the CXCR4 receptor is present on the surface. An SDF-1 gradient is not necessarily required to induce migration, as chemokinesis can also occur. Upon stimulation with SDF-1, CXCR4 promotes modifications on the surface pattern of adhesion molecules, which have an influence on adhesion and migration.