Routine immunophenotyping of acute leukaemias

Computational analysis of high-throughput flow cytometry data

INTRODUCTION

Flow cytometry has been around for over 40 years, but only recently has the opportunity arisen to move into the high-throughput domain. The technology is now available and is highly competitive with imaging tools under the right conditions. Flow cytometry has, however, been a technology that has focused on its unique ability to study single cells and appropriate analytical tools are readily available to handle this traditional role of the technology.

AREAS COVERED

Expansion of flow cytometry to a high-throughput (HT) and high-content technology requires both advances in hardware and analytical tools. The historical perspective of flow cytometry operation as well as how the field has changed and what the key changes have been discussed. The authors provide a background and compelling arguments for moving toward HT flow, where there are many innovative opportunities. With alternative approaches now available for flow cytometry, there will be a considerable number of new applications. These opportunities show strong capability for drug screening and functional studies with cells in suspension.

EXPERT OPINION

There is no doubt that HT flow is a rich technology awaiting acceptance by the pharmaceutical community. It can provide a powerful phenotypic analytical toolset that has the capacity to change many current approaches to HT screening. The previous restrictions on the technology, based on its reduced capacity for sample throughput, are no longer a major issue. Overcoming this barrier has transformed a mature technology into one that can focus on systems biology questions not previously considered possible.

Differential regulation of vitamin D receptor expression in distinct leukemic cell lines upon phorbol ester-induced growth arrest

A close correlation between vitamin D receptor (VDR) abundance and cell proliferation rate has been shown in NIH-3T3 fibroblasts, MCF-7 breast cancer and in HL-60 myeloblastic cells. We have now determined if this association occurs in other leukemic cell lines, U937 and K562, and if VDR content is related to c-myc expression, which is also linked to cell growth state. Upon phorbol myristate acetate (PMA) treatment, cells from the three lineages (HL-60, U937 and K562) differentiated and expressed specific surface antigens. All cell lines analyzed were growth inhibited by PMA and the doubling time was increased, mainly due to an increased fraction of cells in the G0/G1 phase, as determined by flow cytometry measurements of incorporated bromodeoxyuridine and cell DNA content. C-myc mRNA expression was down-regulated and closely correlated to cell growth arrest. However, VDR expression in leukemic cell lines, as determined by immunofluorescence and Northern blot assays, was not consistently changed upon inhibition of cell proliferation since VDR levels were down-regulated only in HL-60 cells. Our data suggest that VDR expression cannot be explained simply as a reflection of the leukemic cell growth state.

Monoclonal antibodies in the management of acute leukemia

This report reviews the diagnostic significance of immune markers, their relationship to patient outcome, and the therapeutic uses of monoclonal antibodies (MoAbs) in acute leukemia. Immunophenotyping allows for rapid and reproducible diagnosis in the majority of cases of acute leukemia. It is of particular importance in recognizing the major immunologic subclasses of acute lymphoblastic leukemia (ALL), and in identifying subtypes of acute myeloblastic leukemia (AML) which cannot be differentiated by morphology and cytochemistry alone, such as FAB M0 or M7. Immune marker analysis has been used to detect minimal residual disease in patients' bone marrow and CSF after treatment. However, the presence of leukemia-associated phenotypes on small numbers of normal cells may reduce the sensitivity of detection in some cases. The prognostic value of immune markers in AML is limited. In ALL, the prognostic significance of the different immunophenotypic subtypes has been lessened by modern treatment protocols. The relationship of mixed-lineage or biphenotypic antigen expression to patient outcome in both AML and ALL is unclear. Therapeutic applications of MoAbs in acute leukemia include immunologic techniques for purging malignant cells from autografts prior to transplantation, T-lymphocyte depletion from allografts as a strategy to reduce graft-versus-host disease, and the use of flow cytometry to monitor the timing and extent of leukapheresis in peripheral stem cell transplantation. MoAbs have also enabled the recent development of transplantation protocols using positively-selected CD34+ stem cells.

Relationship between responsiveness to colony stimulating factors (CSFs) and surface phenotype of leukemic blasts

We examined the responsiveness of leukemic cells to colony stimulating factors (CSFs) as determined by 3H-TdR incorporation and surface phenotypes of leukemic blasts. In acute myeloid leukemia (AML), CD13 and/or CD33 positive and HLA-DR negative M1 and M3 cases tended to show high response to G-CSF, GM-CSFs and IL-3, however, all HLA-DR positive M1, M2, M4 and M5 cases were unresponsive to CSFs but showed high autonomous growth. In acute lymphocytic leukemia (ALL), no response was observed to any CSFs but high autonomous growth was found in mixed leukemia cases. Sole T or B lineage cases showed low autonomous growth. These results suggest the varied nature of the proliferative state in leukemia and the existence of a subgroup in M1.

Modulation of CD13 expression during retinoic acid-induced differentiation of HL60 cells

CD13/aminopeptidase-N, an enzyme expressed by myeloid cells, may be important in the regulation and signalling pathways that control myeloid growth and differentiation. In this study we have used the myeloid leukaemic cell line HL60, and its ability to differentiate when induced by all-trans-retinoic acid (ATRA), to study the regulation of CD13 molecules, and its associated aminopeptidase-N enzyme activity during the myeloid differentiation pathway. In addition, the effect of the growth factor granulocyte-macrophage colony stimulating factor (GM-CSF) on CD13 expression, by undifferentiated and differentiated HL60 cells, has been investigated. Our results show that CD13 expression, and its enzyme activity, is downregulated during differentiation of HL60 induced by ATRA, but not when using GM-CSF.

Clinical relevance of acute mixed-lineage leukemias

Conflicting results have been reported in recent years concerning the incidence and prognostic relevance of acute mixed-lineage leukemias (AMLL). Among the high number of possible hybrid antigen combinations, it is important to discriminate those occurring with sufficient frequency to be of general clinical significance. In this review an approach to a classification based upon the hierarchical import of developmental antigens seen during hemopoietic differentiation is suggested. As far as the clinical relevance of AMLL is concerned, some hybrid patterns have been found to be associated with distinct characteristics in terms of clinical features at the time of presentation and poor response to treatment. For these particular types of leukemia, the time has probably arrived to design more specific therapeutic regimens.

Megakaryocyte markers in myeloproliferative disorders

Identification of megakaryocyte precursors with immunohistochemical methods in bone marrow trephine biopsy specimens (embedded in a plastic resin, Immuno-Bed) was performed from patients with blastic phase of chronic granulocytic leukaemia (five cases), from chronic megakaryocytic-granulocytic myelosis (four cases) and from acute megakaryoblastic leukaemia (11 cases). In megakaryoblasts of bone marrow biopsies immunohistochemical reactions using the ABC method and monoclonal antibodies against von Willebrand antigen and GpIIb/IIIa (CD41) were visible in various percentages depending on the maturation's degree of megakaryocyte precursors. The number of circulating blast cells determined by flow cytophotometry was nearly similar to those of observed in biopsies. The greatest bone marrow reticulin content could be detected in acute megakaryoblastic leukaemia cases. Despite the different clinicopathological entities, the presence of the same phenotype (megakaryoblasts) was associated with a short survival in these haematological malignancies (in CGL MKB phase 4.0, in CMGM MKB phase 4.2, and in AML M7 5.8 months, respectively).

The significance of aminopeptidases and haematopoietic cell differentiation

Aminopeptidases are a group of enzymes found on the cell surface and in the cytoplasmic compartments of many peripheral blood cell types and their progenitors. Their functional roles include the hydrolysis of several biologically active peptides and growth factors and some have proved to be of diagnostic and prognostic value in leukaemia. These enzymes may also be found in serum as a consequence of non-haematopoietic related diseases and so have been used as indicators of liver damage.

Haematopoietic cells in the bone marrow go through a process of growth and differentiation before being released into the peripheral circulation where they fulfill many functional roles. The enzyme activities of some aminopeptidases have been shown to modulate the growth of these cells. In addition, the activities of these enzymes themselves can be regulated by haematopoietic growth factors. However, the mechanisms that regulate their expression and activity are not fully understood. In this report the current literature has been reviewed for evidence of expression, regulation and clinical significance.

Immunophenotype of acute lymphoblastic leukemia cells: the experience of the Italian Cooperative Group (Gimema)

The immunophenotype of 304 adult lymphoblastic leukemias (> 18 years) diagnosed on the basis of the FAB criteria was determined at the time of diagnosis using a panel of monoclonal antibodies. The series comprised cases diagnosed and immunophenotyped in 43 Italian centers (GIMEMA Cooperative Group) between April 1988 and June 1991. The immunophenotypic characterization consisted of two consecutive steps. The initial screening was based on the reactivity for TdT, HLA-Dr, CD7, CD10, CD13, CD19, CD24, CD33 and CD41. According to the results obtained, the second level of investigation assessed the positivity for intra cytoplasmic (Cy) Ig, CD1a, CD2, CD3, CD4, CD5, CD8 and CD20. Based on the hierarchical expression of the different B- and T-cell related antigens, each case was assigned to a given differentiation stage. B-lineage ALL were classified in five subgroups (B0-B4) and T-lineage ALL in four subgroups (T0-T3). Cases in which the blasts were lymphoid according to the FAB criteria, but expressed myeloid antigens in association with B- and T-lymphoid markers were defined as hybrid leukemias. As expected, CD10+ cases (B2-B3) were the most frequent within the B-lineage ALL (83.2% of cases). CyIg+ (B3) accounted for about 20% of CD10+ ALL. Twenty eight cases (13.4%) were at a pre-cALL stage (B0-B1) and of these, 8 (3.8% of the total series) were positive only for TdT and HLA-Dr (B0). Intermediate and mature thymic phenotypes (T2-T3) were predominant within the T-ALL (67.2%) groups. Five cases, were positive only for TdT and CD7 (CD5+), and classified as T0. 9.2% of cases fulfilled the definition of hybrid leukemia, largely in view of the co-expression of B-lymphoid and myeloid markers.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of blast cell immunophenotyping for the diagnosis and prognosis of acute myeloid leukemia

Bone marrow blast cell antigen expression from 86 patients with de novo acute myeloid leukemias (AML) was studied and correlated with FAB classification and clinical outcome. Among a panel of 14 monoclonal antibodies routinely used for the diagnosis of acute leukemias we studied the expression of six antibodies (CD13, CD15, VIM2, CD33, CD14, CD34) of the granulomonocytic lineage and found that some of them were useful for diagnosis and/or prognosis. For FAB subclassification of AML, the CD13 or VIM2 antigen expression was of no benefit. Monocytic leukemias (M4 + M5PD + M5WD) more frequently expressed CD34 antigen (28/31) than granulocytic (M1 + M2 + M3) subtypes (33/53) (P < 0.01). Finally, the most striking differences were found with CD14 antigen expression: CD14 antigen was more frequently expressed in M4 + M5 leukemias (21/31) than in M1 + M2 + M3 subtypes (12/33) (P < 0.01). The mean percentage of CD14 positive blast cells was accordingly higher in monocytic leukemias than in granulocytic leukemias and the difference was highly significant (P < 0.0001). The CD15 antigen was more frequently expressed in differentiated leukemias (M2 + M3 + M4 + M5WD) (35/44) than in poorly differentiated forms (M1 + M5PD) (17/37) (P < 0.001). The statistical difference was higher when the mean percentage of CD15 positive blast cells were compared (P < 0.0003). Moreover these latter percentages were different in M1 and M2 subtypes (P < 0.003). The blast cell expression of CD13, CD14, CD15 or CD33 was not predictive of the length of CR or survival. Moreover, our results support previously published findings suggesting a longer overall survival duration for patients whose leukemic cells do not express the CD34 antigen (P < 0.01). We also confirm that patients with the more differentiated subtypes of AML (CD13-, CD34+) tend to survive longer than patients with the less differentiated subtypes of AML (CD13-, CD34+) (P < 0.001).

Induction of CD13 expression on fresh myeloid leukaemia: correlation of CD13 expression with aminopeptidase-N activity

CD13 has proved to be a useful cell surface marker for depicting haematopoietic cells of the myeloid and monocytic lineages. Sequence data has shown CD13 to bear strong homology to Aminopeptidase-N. Expression of this antigen on myeloid leukaemic cells is, however, variable. We have looked at the effects of a phorbol ester PMA and a haematopoietic growth factor GM-CSF on the expression of CD13 displayed by a selected group of myeloid leukaemias at presentation and by normal peripheral blood granulocytes. We have found that PMA but not GM-CSF was able to stimulate CD13 expression on fresh myeloid leukaemic cells but granulocytes were stimulated by either PMA or GM-CSF. In addition, we have correlated CD13 expression with Aminopeptidase-N enzyme activity on fresh myeloid leukaemic cells. These results suggest that CD13 is functionally active on leukaemic cells and normal granulocytes.

The effect of high-dose methylprednisolone treatment on GM-CSF level in children with acute leukemia: a pilot study

High-dose methylprednisolone therapy (HDMP) induces acceleration of leukocyte recovery in acute lymphoblastic leukemia (ALL) and the differentiation of myeloblasts to mature granulocytes in acute myeloblastic leukemia (AML). These effects of corticosteroids have been shown to be due to the enhanced colony-stimulating activity (CSA) and responses to corticosteroids in some patients with aplastic anemia and myelodysplastic syndromes (MDS) have been related to increased CSA activity. We measured the serum (granulocyte-macrophage colony-stimulating factor (GM-CSF) levels by a sandwich linked immunoabsorbent assay (ELISA) in patients with ALL and AML at presentation and following high-dose methylprednisolone (HDMP) therapy. Serum GM-CSF levels at presentation in the ten cases studied ranged between 160 and 700 pg/ml (mean 418.5 +/- 252.5). One week following HDMP therapy GM-CSF levels increased to between 260 and 950 pg/ml (733.5 +/- 203.2). Four weeks after therapy the GM-CSF levels increased to between 470 and 1350 pg/ml (911 +/- 278.7). GM-CSF levels were markedly elevated one week after HDMP in the patients with ALL, suggesting that in addition to the lymphotoxic effects on leukemic blasts, the acceleration in neutrophil recovery may be due to release of GM-CSF induced by HDMP and its effects on myeloid progenitors.

T-cell receptor γ/δ expressing acute leukemia emerging from sideroblastic anemia: Morphological, immunological, and cytogenetic features

Striking numerical and structural chromosome abnormalities (-Y, +8, i(7q), del (10)(q24), and del (11)(q21)) were detected by cytogenetic analysis in a patient's bone marrow with morphological features of both acute lymphoblastic leukemia and myelodysplastic disorder. Surface marker analysis characterized blast cells to be CD2+ CD7+ CD3+ CD4- CD8- expressing gamma/delta-T-cell receptor antigen and coexpressing CD11b and CD16. Exhibiting an identical phenotype as the leukemic cells, a prominent gamma/delta-TCR+ lymphocyte population was found in the bone marrow as well as in the peripheral blood. Cells of the latter compartment coexpressed CD56 and HLA-DR antigens and exhibited nonspecific cytotoxic activity. In the bone marrow cells NSCA could be induced after stimulation with interleukin 2 in vitro. Morphological, immunological, and cytogenetic findings suggest that gamma/delta-T-ALL emerged from a myelodysplastic disorder after sequential steps of malignant transformation. Leukemic cells with "mixed lineage" character may provide evidence for a common progenitor cell in the bone marrow. Assuming that the leukemic cells represent the malignant counterpart of normal CD3+ gamma/delta-TCR+ cells the results may contribute to our understanding of the origin and differentiation as well as the possible steps of malignant transformation of a gamma/delta-TCR+ lymphocyte population.

Use of quality control standards in clinical flow cytometry

Flow cytometry is important in the clinical laboratory, especially in hematology and cancer diagnosis. With newer applications being continuously developed clinicians who will use the results and laboratory staff who produce them should be aware of the instrumental quality control procedures required. This will allow evaluation of the reliability as well as the comparison of results between different laboratories. While information about sample preparation as well as staining procedures is easily available, information about instrumental quality control procedures is less so. Various standards and controls are available commercially and their correct choice and usage requires an understanding of the methodology of instrumental quality control. Methods to evaluate the precision, sensitivity and accuracy of measurements are discussed. Most laboratories report immunophenotyping data as the percentage of antibody positive cells and make no attempt to quantitate the amount of antibody binding per cell. Methods for quantitating the number of bound antibody molecules per cell along with a simple technique to compare results between laboratories are discussed. These techniques should encourage laboratory staff and clinicians to standardise methodology and to exchange patient data between laboratories.

Regeneration of CALLA (CD10+), TdT+ and double-positive cells in the bone marrow and blood after autologous bone marrow transplantation

In this prospective study we investigated the frequency of CD10+, TdT+ and CD10+TdT+ mononuclear cells in the bone marrow (BM) and peripheral blood (PB) before and after autologous bone marrow transplantation (ABMT). 49 patients treated for acute lymphoblastic or myeloblastic leukaemia, malignant lymphoma or multiple myeloma were included. A significant increase in CD10+ cells occurred in BM in both children and adults after ABMT. In children, we also found a significant increase in CD10+ cells in PB. In individual patients remaining in remission, up to 34% CD10+ cells having a normal Ig kappa/lambda light chain ratio were recorded after ABMT. In children, the percentage of TdT+ and CD10+ TdT+ cells increased significantly in BM. In most cases the CD10/TdT-ratio was greater than 1.0, but during early regeneration after ABMT this ratio was less than 1.0 in several patients remaining in complete remission. In patients remaining in remission, CD10+TdT+ cells were detected in the blood in only 2 out of 140 samples tested, and the proportion of these cells never exceeded 0.03%. We conclude that quantitation of CD10+TdT+ cells in peripheral blood is helpful in the evaluation of complete remission in patients treated for pre-B-ALL.

Monocyte-specific esterase isoenzyme demonstrated by isoelectric focusing

Using horizontal thin-layer isoelectric focusing in polyacrylamide gels, we separated the isoenzymes of carboxylic esterase (EC 3.1.1.1) of cell extracts prepared from human hematopoietic cells. Isoenzyme bands were visualized by staining with naphthol ester as substrate and coupling to an azo dye. Staining intensities of isoenzymes were quantified by densitometric scanning. On isoelectric focusing in a pH 2-11 gradient, distinct esterase isoenzyme profiles could be discerned and correlated to various types of normal hematopoietic cells and their leukemic counterparts. One unique isoenzyme, termed monoband, could be clearly identified on the basis of its isoelectric point (pI 6.0), its strong expression by normal and malignant monocytes and its complete and selective inhibition by sodium fluoride. This band was only found in monocytes of either normal or leukemic origin, but not in lymphoid or myeloid cells. The monocyte esterase could be inhibited by sodium fluoride whereas other isoenzyme bands were resistant to this inhibition. However, the specificity of this inhibitory reaction was relative, depending on the concentration of sodium fluoride. Compared with normal monocytes, leukemic monocytes often showed an overexpression of the mono-bands. Dilution experiments established the distinct prominence of the mono-band which could be detected among the other isoenzymes even when only 1% of the total cell population consisted of monocytes. Immature myeloid, but mono-band negative leukemic cells whose arrest of differentiation can be overcome by in vitro 12-O-tetradecanoylphorbol 13-acetate-promoted differentiation to more mature cells, could be induced to express the mono-band which paralleled their maturation to monocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Electron microscopy: a contribution to further classification of acute unclassifiable childhood leukemia

The ultrastructural, light microscopical and immunological features of twelve cases of acute childhood leukemia are described. Nine cases were unclassifiable by light microscopy, morphology and cytochemistry, and three were difficult to classify because of a low percentage of Sudan-Black B positive blasts. By means of electron microscopy (including peroxidase cytochemistry), two main groups were seen: 1. Acute myeloid leukemia, in which could be distinguished a) a more differentiated myeloid leukemia, b) a leukemia with megakaryoblastic involvement and c) a minimally differentiated acute myeloid leukemia with granules present and 2. lymphoblastic leukemia. One case could not be classified. The first group included two possible cases of a hybrid leukemia with CD19 or CD10 positivity as well as ultrastructural peroxidase activity. We conclude that electron microscopy aids to further classification of minimally differentiated and hybrid acute leukemias.

Analysis of 135 autopsy eyes for ocular involvement in leukemia

To explain the marked variation in the reported incidence of how often leukemic cells infiltrate the eye in fatal cases of leukemia, we tested the hypothesis that ocular leukemic infiltration is related to the peripheral leukocyte count during the final hours of life. We reviewed tissue sections, as well as autopsy and clinical records, from 135 patients who had fatal leukemia and had their eyes examined after death at Duke University Medical Center. Infiltrates of leukemic cells were found in the eyes of 42 of 135 patients (31.1%), with the choroid being the most frequently involved site. We detected a significant positive correlation between the ocular leukemic infiltration and an agonal leukocyte count as well as the severity of systemic disease. Differences in the agonal circulating leukocyte count may partly explain variations in the incidence of leukemic infiltrates in different postmortem studies.

Monoclonal antibodies for diagnosis of immunodeficiencies

Progress in immunophenotyping is characterized by the availability of monoclonal antibodies and an increased number of clusters of differentiation consisting of reagents with known specificity and defined reactivity patterns. Technical improvements have lead to standardization of immunofluorescence staining procedures and broad application of flow cytometry. These developments have contributed to better diagnosis of immunodeficiencies characterized by the lack of certain lymphocyte subsets or more broadly expressed, functionally important cell-surface molecules. Antibodies valuable for routine immunophenotyping of immunodeficiencies as well as examples of the different antibody groups desirable for immunofluorescence studies are presented. When used in concert with clinical and other laboratory tests, immunophenotyping provides a valuable instrument for differential diagnosis of defects in the immune system. As a consequence, detection of new defects of cell surface antigens and respective cell subpopulations is facilitated and a basis is provided for further study of the genetic and molecular regulatory aspects of immunologic disorders.