An abnormal CD34+ myeloid/CD34+ lymphoid ratio at the end of chemotherapy predicts relapse in patients with acute myeloid leukemia

The changing pattern of "smart" flow cytometry (S-FC) to assist the cost-effective diagnosis of HIV, tuberculosis, and leukemias in resource-restricted conditions

There is a need to introduce cytometry into areas of the globe that have remained virtually untouched by modern laboratory medicine. With the demand to carry out tests on 100,000 s of individuals requiring antiretroviral therapy (ART), flow cytometry must remain simple and cost-effective - while being sustainable and industry supported as well as proven by quality assessment (QA). This outlook is referred to as "smart flow cytometry" (S-FC). There are five main areas where the power of S-FC is demonstrated. These are: (i) the use of CD45 to assist precise cell counting in blood and tissue samples; (ii) the primary CD4 gating to count CD4+ T cells in patients waiting for ART, including the combination (i) and (ii) in the panleucogating (PLG) protocol; (iii) monitoring of human immunodeficiency virus (HIV+) patients during ART by the decreasing levels of lymphocyte activation in a CD8/CD38 test - leading to economies of viral-load assays; (iv) in tuberculosis and HIV-TB coinfections the use of TB-antigen-stimulated cytokine-synthetic CD4+ T cells to identify active disease; and (v) the utilization of "minimal residual disease (MRD)-Lite" technology in patients 19 days after the start of antileukemic therapy to detect MRD. These methods of S-FC have been successfully introduced in "resource-restricted" countries with international and local QA.

Adverse prognostic impact of CD36 and CD2 expression in adult de novo acute myeloid leukemia patients

BACKGROUND AND OBJECTIVES

A consecutive series of acute myeloid leukemias (AML) patients was analyzed in conditions which reduce the inter-assay variations (the same flow cytometer, the same observers and the same panel of monoclonal antibodies) in order to investigate the prognostic information provided by flow cytometry.

DESIGN AND METHODS

Two hundred and sixty-six bone marrow (BM) samples from 326 patients enrolled in the LMA-99 protocol from the CETLAM group were studied by multiparametric flow cytometry. Immunophenotyping studies were performed on erythrocyte-lysed BM samples. Antigen expression of leukemic cells was analyzed using triple stainings with fluorochrome-conjugated combinations of monoclonal antibodies.

RESULTS

CD2 was positive in 21 cases (8%); an associated inv(16) was detected in eight CD2+ cases (38%). Two-year overall survival (OS) rate for CD2+/inv(16)+ patients was 75%, whereas it was 0% for CD2+/inv(16)- patients and 47% for CD2- patients (p=0.0001). CD36 was expressed in 37% of patients (n=98). Two-year leukemia-free survival (LFS) rate was 34% for CD36+ patients and 55% for CD36- patients (p=0.001). In the multivariate analysis, CD2+ (RR=8.4; p=0.0001) and adverse karyotype (RR=10.2; p=0.0001) were associated with a lower CR rate, CD36+ (RR=1.5; p=0.03), CD2+ (RR=2; p=0.04) and adverse karyotype (RR=4; p=0.0001) were associated with a lower OS and CD36+ (RR=2; p=0.002) and adverse karyotype (RR=3.5; p=0.005) predicted a lower LFS.

CONCLUSIONS

CD2+ patients had a very poor OS when CD2/inv(16)+ cases were excluded. CD36 and CD2 expression at diagnosis can provide prognostically important information in adult de novo AML.

Minimal residual disease monitoring by flow cytometry

In patients with acute leukaemia, studies of minimal residual disease (MRD) provide powerful and independent prognostic information. Multiparameter flow cytometry is a widely applicable and reliable approach for monitoring MRD. Using triple or quadruple marker combinations, aberrant or uncommon phenotypic profiles can be identified in about 80% of patients with acute myeloid leukaemia (AML) and 95% of patients with acute lymphoblastic leukaemia (ALL). These profiles can reveal leukaemic cells even when these are not evident by morphological analysis. Thus, one leukaemic cell among 1000-10000 normal bone marrow or peripheral blood cells can be routinely detected. In this chapter we discuss technical aspects of MRD detection by flow cytometry and summarize results of correlative studies between MRD, clinical and biological features of leukaemia and treatment outcome. Current knowledge indicates that MRD studies using well-tested methodologies are clinically useful and should be incorporated into the clinical management of patients with acute leukaemia.

Acute myeloid leukemia with MLL rearrangements: clinicobiological features, prognostic impact and value of flow cytometry in the detection of residual leukemic cells

The MLL gene, located at 11q23 band, is frequently disrupted by different chromosomal rearrangements that occur in a variety of hematological malignancies. MLL rearrangements are associated with distinct clinical features and a poor prognosis. The aim of this study was to analyze the incidence and the prognostic significance of MLL rearrangements in a consecutive series of adult AML patients and to determine the immunophenotypic features of these cases. The identification of abnormal immunophenotypes could be used for the detection of minimal residual disease (MRD). Ninety-three adult patients with de novo acute myeloid leukemia (AML) were analyzed by Southern blot in order to detect MLL rearrangements (MLL+). RT-PCR and genomic long-range PCR were performed to further characterize MLL partial tandem duplication (PTD) in those patients in whom conventional karyotype did not show 11q23 chromosomal translocations. All the patients were homogeneously immunophenotyped at diagnosis. MLL rearrangements were detected in 13 (14%) patients. Four patients (5%) showed 11q23 translocations by karyotypic conventional analysis. Nine patients (10%) revealed PTD of MLL and one patient showed a MLL cleavage pattern. The MLL+ patients usually expressed myeloid and monocytic antigens CD33 (12/13 cases), CD13 (9/13), CD117 (9/13), CD64 (11/13) and in some cases CD14 (4/11). HLA-DR was also positive in (12/13). Eight out of 13 cases expressed the stem cell marker CD34. Only one patient revealed lymphoid marker reactivity (CD7) and CD56 was expressed in 5/13 cases. All the MLL+ patients showed at least one aberrant phenotype at diagnosis, which allowed us to set out a simple panel for the MRD studies. Twenty-seven samples from eight patients in morphologic complete remission (CR) were analyzed using the aberrant immunologic combinations detected at diagnosis. Phenotypically abnormal cells were detected in all the patients who subsequently relapsed, whereas only one patient with MRD+ remained in CR. Owing to the high level of residual leukemic cells, the MLL+ patients showed a short CR duration and a poor survival. In conclusion, immunophenotyping may be a suitable approach to investigating MRD status in AML patients with PTD of the MLL gene.

CD34 and CD117 are overexpressed in AML and may be valuable to detect minimal residual disease

We estimated by quantitative flow cytometry (FC) the expression of CD13, CD33, CD34 and CD117 antigens in cells from 64 patients with acute myeloid leukaemia (AML) and 22 normal bone marrows (BMs). The method converts fluorescence intensity into number of antigen molecules per cell, measured by antibody binding capacity (ABC). The number of molecules per cell in normal BM was 9.5+/-5.7 for CD13, 7+/-2.3 for CD33, 6+/-0.7 for CD34, and 6.3+/-1.5x10(3) for CD117. AML blasts expressed 11.4+/-12.4 molecules per cell for CD13, 9.5+/-9.7 for CD33, 74+/-2328.5 for CD34 and 12.5+/-33 x 10(3) for CD117. The number of CD34 and CD117 molecules were significantly higher in AML than in normals (P<0.0001 and P<0.05, respectively) while only in a few cases, CD13 and CD33 were abnormally expressed in myeloblasts. Our results indicate that quantitative analysis of CD34 and CD117 may be useful to detect minimal residual disease (MRD) and could be tested in a future to monitor therapy in AML.

Immunological evaluation of minimal residual disease (MRD) in acute myeloid leukaemia (AML)

Immunophenotypic analysis of leukaemic cells using multiparametric flow cytometry has proved to be an attractive approach for MRD investigation in acute lymphoblastic leukaemia (ALL); by contrast, information on acute myeloid leukaemia (AML) is still scanty. Here, we first review the methodological strategies for these studies. Triple or quadruple antigenic combinations, analysed by multiparametric flow cytometry, have shown that in 80% of AML patients it is possible to identify aberrant or uncommon phenotypic profiles on blast cells, thereby allowing their distinction from normal cells and their use as leukaemia-associated phenotypes (LAP). We also focus on technical aspects that are important in the definition of LAP. We then review pitfalls that could potentially affect results using this approach. Finally, we review available information concerning the clinical value of these studies. Although reported data in the literature are still scanty, several authors have shown that this technique could be used for the prognostic evaluation of AML patients, when immunophenotypic evaluation is applied after induction therapy.