Comprehensive flow cytometry phenotype in acute leukemia at diagnosis and at relapse

Dissecting the Genetic and Non-Genetic Heterogeneity of Acute Myeloid Leukemia Using Next-Generation Sequencing and In Vivo Models

Simple Summary

Acute myeloid leukemia (AML) is an extremely aggressive form of blood cancer with high rates of treatment failure. AML arises from the stepwise acquisition of genetic aberrations and is a highly heterogeneous disorder. Recent research has shown that individual AML samples often contain several clones that are defined by a distinct combination of genetic lesions, epigenetic patterns and cell surface marker expression profiles. A better understanding of the clonal dynamics of AML is required to develop novel treatment strategies against this disease. In this review, we discuss the recent developments that have further deepened our understanding of clonal evolution and heterogeneity in AML.

Abstract

Acute myeloid leukemia (AML) is an extremely aggressive and heterogeneous disorder that results from the transformation of hematopoietic stem cells. Although our understanding of the molecular pathology of AML has greatly improved in the last few decades, the overall and relapse free survival rates among AML patients remain quite poor. This is largely due to evolution of the disease and selection of the fittest, treatment-resistant leukemic clones. There is increasing evidence that most AMLs possess a highly complex clonal architecture and individual leukemias are comprised of genetically, phenotypically and epigenetically distinct clones, which are continually evolving. Advances in sequencing technologies as well as studies using murine AML models have provided further insights into the heterogeneity of leukemias. We will review recent advances in the field of genetic and non-genetic heterogeneity in AML.

Identifying Leukemia-associated Immunophenotypes in Acute Myeloid Leukemia Patients Using Multiparameter Flow Cytometry

Objectives

We sought to identify leukemia-associated immunophenotypes (LAIPs) in 50 acute myeloid leukemia (AML) patients at diagnosis using an eight-color multiparameter flow cytometry (MFC) panel and to detect if they showed any alteration in relapsed/refractory cases.

Methods

We used the eight-color MFC panel with CD45/side scatter log gating strategy to analyze LAIPs in 50 AML patients presenting to Alexandria University Hospitals, Egypt at diagnosis and relapse and refractory cases. Twenty age and sex matched bone marrow samples from patients performing bone marrow aspirate for non-malignant hematological indications were included as controls.

Results

LAIPs were observed in 43 (86.0%) cases. Only one aberrant immunophenotype was identified in four cases (9.3%), while two to 12 aberrant immunophenotypes were found in the other 39 (90.7%) cases. Strong LAIPs were obtained by combining CD2, CD4, CD56, with either CD34 or CD117, in contrast to CD19, which has to be combined with CD117. Refractory cases showed the presence of the same LAIPs at both initial diagnosis and persistent disease. One case showed the acquisition of new LAIPs after relapse.

Conclusions

The good choice of LAIPs depends on their specificity rather than their frequency. The results of this study can help in increasing the sensitivity of LAIPs strategy in minimal residual disease using MFC in AML patients, which is considered an important post-diagnosis parameter associated with prognosis and clinical outcome.

The prognostic impact of Wilms tumor-1 polymorphism (rs16754) and human myeloid inhibitory C-type lectin-like receptor expression in cytogenetically normal-acute myeloid leukemia

Background

There are several genetic mutations that carry prognostic and predictive values in acute myeloid leukemia (AML). They are also implicated in disease pathogenesis and patient outcome. They can be a target of novel therapies for AML. The aim of the current study was to investigate prognostic value of Wilms’ tumor-1 (WT1) genotypes and human myeloid inhibitory C-type lectin-like (hMICL) receptor expression in normal-cytogenetic group of patients with AML. Genotyping of WT1 mutations was done by Rotor Gene real-time polymerase chain reaction (PCR) while hMICL expression was detected using phycoerythrin (PE)-conjugated mouse monoclonal anti-human (MoAbs) by flow cytometry.

Results

Sixty-three patients with cytogenetically normal AML (CN-AML) were included in the study. The alternate allele of WT1 single nucleotide polymorphism (SNP) rs16754 was found in 26.89%. At day 28 of therapy, complete remission was achieved in 100% of cases harboring mutant AG plus GG genotypes but only in 6.38% of cases harboring wild genotype (AA). After 6 months, 88.23% of patients harboring WT1 mutant genotype maintained complete remission, while only 23.40% of patients with wild type showed complete remission. The overall survival in patients harboring mutant WT1 genotypes was significantly longer than in those who carried the wild type gene (P-value, 0.001). Additionally, hMICL was overexpressed in approximately 87.3% of AML cases and inversely related to complete response. Similarly, overall survival was significantly shorter in patients with positive hMICL (P-value, 0.001).

Conclusion

Mutant WT1 genotypes (SNP rs16754) were conversely, associated with complete response, and hMICL overexpression had poor prognostic value in AML.

Human myeloid inhibitory C-lectin: a highly specific and stable acute myeloid leukemia marker

The prognosis of acute myeloid leukemia (AML) is poor because of relapses occurring on conventional chemotherapy. The distinction between leukemic and normal stem cells relies on the expression of antigen combinations defining leukemia-associated immunophenotypes (LAIPs), which are absent or extremely infrequent in normal bone marrow. However, LAIPs are very different from patient to patient and are not necessarily stable over the course of the disease. Accordingly, we addressed the applicability of human myeloid inhibitory C-lectin (hMICL) by flow cytometry as a specific leukemic myeloid stem cell marker for the diagnosis of AML in CD34⁺ and CD34^- cases and evaluated the stability of hMICL during the course of the disease. hMICL expression was assessed in 78 bone marrow aspirate specimens obtained from AML patients at diagnosis (n = 40), complete remission (CR) (n = 28), and relapse (n = 10). AML patients at diagnosis were compared to 20 newly diagnosed acute lymphoblastic leukemia (ALL) patients and 20 healthy controls. hMICL was reevaluated in CR and relapse specimens. hMICL was expressed in 100% AML patients at diagnosis (mean ± standard deviation [SD], 60.3 ± 19.9%), both CD34⁺ and CD34^- , but not in ALL (mean ± SD, 3.3 ± 1.9%) or healthy controls (mean ± SD, 3.4 ± 2.6%) (P < .001). hMICL median fluorescence intensity ratio was higher in AML (mean ± SD, 15.9 ± 11.7) compared to ALL (mean ± SD, 4.5 ± 1.4) and healthy controls (mean ± SD, 4.4 ± 1.6) (P < .001). hMICL was expressed in all studied AML morphologic subtypes. Preserved stable expression of hMICL was found in CR and relapse specimens with no antigen loss. hMICL is a robust pan-AML-associated antigen with excellent diagnostic impact, extreme specificity to AML blasts, and stability throughout the course of the disease. hMICL could be incorporated into the routine flow cytometry setting within the initial diagnostic work-up and follow-up of AML.

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.

Immunophenotypic shift of CD4 and CD8 antigen expression in primary cutaneous T-cell lymphomas: a clinicopathologic study of three cases

Primary cutaneous T-cell lymphomas (CTCL) comprise a heterogeneous group of neoplasms with diverse clinical behavior. Mycosis fungoides (MF) is the most common type of CTCL. Immunophenotypical shift during progression of the disease is a rare event and its significance is unknown. We present three primary CTCL cases that showed an immunophenotypical shift and poor prognosis. Conventional hematoxylin/eosin and immunohistochemical-stained sections were examined in all the cases. Molecular analysis for rearrangement of the T-cell receptor (TCR) gene was performed in two cases. One case was classified as MF, while the other two lacked epidermotropism, and were considered primary cutaneous peripheral T-cell lymphoma (PTCL), NOS. Two cases were CD3+/CD4+ and one case was CD3+/CD8+ at diagnosis. The first two patients suffered many relapses and eventually, new CTCL lesions with a CD3+/CD8+ phenotype were observed. Both cases revealed identical clonal TCR rearrangements on the initial and late lesions, supporting the interpretation of a single clonal proliferation with different phenotypes. The third case progressed with skin recurrences and pulmonary lesions with a predominant CD3+/CD4+/CD8- phenotype. All cases manifested poor prognosis and two patients died of lymphoma. Immunophenotypical shift between CD4 and CD8 in CTCL seems to be a rare phenomenon that may be associated with disease progression.

Tumor heterogeneity makes AML a "moving target" for detection of residual disease

Detection of minimal residual disease is recognized as an important post-therapy risk factor in acute myeloid leukemia patients. Two most commonly used methods for residual disease monitoring are real-time quantitative polymerase chain reaction and multiparameter flow cytometry. The results so far are very promising, whereby it is likely that minimal residual disease results will enable to guide future post-remission treatment strategies. However, the leukemic clone may change between diagnosis and relapse due to the instability of the tumor cells. This instability may already be evident at diagnosis if different subpopulations of tumor cells coexist. Such tumor heterogeneity, which may be reflected by immunophenotypic, molecular, and/or cytogenetic changes, can have important consequences for minimal residual disease detection, since false-negative results can be expected to be the result of losses of aberrancies used as minimal residual disease markers. In this review the role of such changes in minimal residual disease monitoring is explored. Furthermore, possible causes of tumor instability are discussed, whereby the concept of clonal selection and expansion of a chemotherapy-resistant subpopulation is highlighted. Accordingly, detailed knowledge of the process of clonal evolution is required to improve both minimal residual disease risk stratification and patient outcome.

A comprehensive cytogenetic classification of 1466 Chinese patients with de novo acute lymphoblastic leukemia

Cytogenetics and molecular cytogenetics of 1466 Chinese patients with de novo acute lymphoblastic leukemia (ALL) were studied. Cytogenetic results were available in 1175 patients. Cross-correlations of 23 subclasses of cytogenetic abnormalities were described. Childhood cases had higher incidences of normal karyotype, t(1;19), +8, 12q-, +21, +22 and high hyperdiploidy with 51-65 chromosomes, and lower incidences of t(9;22) and -5/5q- than adult ones (all p<0.05). Relationships of cytogenetic subclasses with immunophenotyping subgroups of ALL were studied. Our study presents the cytogenetic characteristics of a large series of Chinese ALL patients.

Expression of the hMICL in acute myeloid leukemia-a highly reliable disease marker at diagnosis and during follow-up

BACKGROUND

Stable flow cytometric markers for malignant myeloid cells are highly warranted. Based on data from stem cell research, we hypothesized that the human inhibitory C-type lectin like receptor (hMICL) might represent a novel diagnostic and prognostic vehicle in a standard flow cytometry (FCM) setting.

METHODS

Standard four-color FCM was employed to uncover the expression patterns of hMICL in bone marrow in a test set of 55 retrospectively collected diagnostic acute myeloid leukemia (AML) samples and in a set of 36 prospectively collected diagnostic AML samples.

RESULTS

Ninety-two percent of the AML patients stained positive for hMICL and in the otherwise poorly characterized CD34 negative patient group hMICL staining revealed a very homogenous expression profile in the blast cell compartment with a mean of 88% hMICL positive cells. Moreover, hMICL displayed significantly higher expression in AML as compared with normal donors as measured by median fluorescence intensity (MFI) ratios (P = 0.01). There was no difference in hMICL MFI ratios between the CD34 positive and the CD34 negative subgroups (P = 0.89). Importantly, there was no difference in MFI ratios between paired diagnostic and relapse samples (P = 0.76) in 23 cases studied, indicating stable expression of hMICL during the course of the disease. In contrast to the other stem cell associated antigens analyzed (CD34, CD96, CD117, and CD133), hMICL was expressed on myeloid blast cells only, revealing hMICL as a diagnostic marker in AML.

CONCLUSION

These data identify hMICL as a myeloid leukemia-associated antigen and establishes its applicability for diagnosis and follow-up of AML patients in a standard FCM setting.