The use of enzyme marker analysis for subclassification of acute lymphocytic leukemia in childhood

Acute lymphocytic leukemia: correlation of clinical features with immunocytochemical classification

Many immunologic studies of acute lymphocytic leukemia (ALL) during the past decade have demonstrated the close correlation of immunologic phenotypes of ALL subclasses with the clinical presenting features and prognosis. However, the clinical application of conventional immunologic techniques had been very limited because of the requirement of a fresh sample to prepare the mononuclear cell suspensions for study. We studied 81 cases of ALL using immunoperoxidase stain for nuclear terminal deoxynucleotidyl transferase (TdT) and immunoalkaline phosphatase stain for surface markers (using monoclonal antibody J5 for common ALL antigen [CALLA], Leu-1 for pan-T antigen, and B1 for pan-B antigen) on air-dried smears. The cases were classified as common ALL (TdT+, CALLA+, pan-T-, and pan-B-) (41 cases), null-ALL (TdT+, CALLA-, pan-T-, and pan-B-) (19 cases), T-ALL (TdT+, CALLA-, pan-T+, and pan-B-) (nine cases), B-ALL (TdT-, CALLA-, pan-T-, and pan-B+) (six cases), pre-B-ALL (TdT+/-, CALLA+, pan-T-, and pan-B+) (four cases), or pre-T-ALL (TdT+, CALLA+, pan-T+, and pan-B-) (two cases). This subtyping of ALL correlated well with known clinical presenting features, prognosis, chromosome analysis in 35 cases with an abnormal clone, and conventional immunologic typing in 38 cases. The data suggest that these simple and practical immunocytochemical stains can be used for immunologic subclassification of ALL.

Expression of a monocyte-specific esterase isoenzyme in cases of acute myeloid leukemias

The carboxylic esterase (E.C. 3.1.1.1) isoenzymes from cases of acute myeloid leukemias were separated by analytical isoelectric focusing on horizontal thin-layer gels. One isoenzyme consisting of one or two components (bands) could be completely and selectively inhibited by addition of 40 mM sodium fluoride (NaF) to the staining bath. The 105 cases were classified into the groups M1-M6 according to the FAB proposals. The NaF-sensitive isoenzyme was not detected in cases of FAB groups M1/2 (acute myeloblastic leukemia without or with maturation), group M3 (acute promyelocytic leukemia) or group M6 (erythroleukemia). Thirty-one out of 33 cases in the FAB group M4 (acute myelomonocytic leukemia) and 9/9 cases in FAB group M5 (acute monocytic leukemia) expressed the NaF-sensitive isoenzyme. The NaF-sensitive isoenzyme was found at different staining intensities; all M5 cases showed the isoenzyme at strong or very strong intensity, whereas most of the M4 cases displayed the isoenzyme at weak, medium or strong staining intensity. The data presented are further evidence that the presence of the NaF-sensitive esterase isoenzyme indicates monocytic involvement or differentiation in cases of myeloid leukemias. The easy and fast to perform method of isoelectric focusing can be used to distinguish the monocytic variants among the acute myeloid leukemias and can supplement the morphological analysis of these cases.

Isoenzyme studies in human leukemia-lymphoma cell lines--IV. Lactate dehydrogenase

Isoelectric focusing (IEF) in horizontal polyacrylamide gels has been used to separate lactate dehydrogenase (LDH) isoenzymes in 97 human permanent hematopoietic cell lines (85 leukemia-lymphoma cell lines and 12 'normal' B-lymphoblastoid cell lines). Maximally 8 LDH bands were seen; the electrophoretically detectable bands 4 and 5 could be separated by IEF into 2 and 3 isoenzymes, respectively. The LDH patterns have been found to vary both in number of isoenzymes and in relative intensity in different cell lines depending upon the stage at which arrest of differentiation occurred. These differences can be used to analyse and distinguish different cell lines. The method should provide a valuable supplement to the enzymatic phenotyping and complete characterization of fresh and cultured leukemias and for the monitoring of phenotypic changes occurring during induction of differentiation.

Lysosomal isoenzyme profiles used to classify a case of acute undifferentiated leukaemia

Lysosomal enzyme activities and isoenzyme profiles were measured in lymphoid and non-lymphoid leukaemic cells from childhood patients. High activities, especially of beta-hexosaminidase and alpha-mannosidase, were associated with leukaemic cells of myeloid or monocytic origin. Leukaemic cells from two children with acute myeloid leukaemia had a relative reduction in the B isoenzyme of beta-hexosaminidase activity, whereas in patients with non T, non B cell acute lymphoblastic leukaemia, intermediate beta-hexosaminidase isoenzymes were expressed. A patient is described on whom conventional marker studies were either negative or equivocal, but lysosomal enzyme markers were consistent with a myeloid leukaemia. This observation was supported by the clinical course of this patient.

Isoenzyme studies in human leukemia-lymphoma cell lines--1. Carboxylic esterase

The isoenzyme patterns of carboxylic esterase (E.C. 3.1.1.1) were studied in 74 proven human leukemia-lymphoma and 12 normal B-lymphoblastoid cell lines. These cell lines have been extensively phenotyped using poly- and monoclonal antibodies. Esterase isoenzymes were separated by isoelectric focusing and visualized by histo-cytochemical techniques. No leukemia-specific or (except for monocytes) blood cell type-specific isoenzyme or isoenzyme pattern could be detected. The monocytic element in some cell lines was characterized by a strong isoenzyme band which could be selectively and completely inhibited by sodium fluoride. The enzyme phenotypes were stably expressed in all subcultures of a given cell line and did not appear to have any cell cycle dependency. The leukemia-lymphoma cell lines have been subclassified into four major groups according to immunological parameters: T-cell, B-cell, myelomonocytic and non-T, non-B-cell. On the basis of immunological data the T-cell lines were assigned to five stages of differentiation. The number and staining intensity of the isoenzymes increased with differentiation of the T-cells paralleling the expression of immunological markers. The B-cell leukemia-lymphoma cell lines were divided into pre B-, B-, Burkitt lymphoma, multiple myeloma and hairy cell leukemia cell lines. Substantial variability among the isoenzyme patterns was detected ranging from immature profiles of pre B-cell lines to complete isoenzyme repertoires of multiple myeloma cell lines. No significant difference was seen between the isoenzymes of mature B-cell lines and normal B-lymphoblastoid cell lines. The most prominent feature seen in myelomonocytic cell lines was the monocytic band indicating a monocytic origin and separating the 'monocytoid' from the 'pure myeloid' cell lines. Considerable heterogeneity in the isoenzyme patterns was observed in the non-T, non-B cell groups which comprised erythroleukemia cell lines and cell lines arrested at a very early stage of lymphoid differentiation. These latter cell lines together with some T- and B-cell lines shared the common characteristics of positivity for cALLA, TdT and Ia antigens and an immature, incomplete isoenzyme profile. The results support the notions of maturation arrest and normal gene expression in leukemic cell populations. Furthermore, the importance of biochemical studies as part of the multiple marker analysis could be demonstrated.

Isoenzyme studies in human leukemia-lymphoma cells lines--II. Acid phosphatase

This report describes the qualitative acid phosphatase (acP) isoenzyme profiles detected in permanent human hematopoietic cell lines. The acP activity was separated into its isoenzymes by isoelectric focusing on horizontal thin-layer polyacrylamide gels. The pattern of acP isoenzyme was investigated in a total of 86 cell lines. These cell lines were classified into five groups on the basis of their phenotypes characterized in the multiple marker analysis: 74 leukemia-lymphoma cell lines (26 T-, 34 B-, 6 myelomonocytic, 8 Non-T, Non-B cell lines) and 12 so-called 'normal' Epstein-Barr virus transformed B-lymphoblastoid cell lines. Their immunological features had been analysed in detail by use of a large panel of poly- and monoclonal antibodies which led to a further subclassification into stages of differentiation. A progressive increase in number and staining intensity of the isoenzymes which paralleled the expression of surface markers at different stages of differentiation along their developmental pathway was seen in the T- and B-leukemia-lymphoma cell lines. Some cell lines whose isoenzyme profiles did not correspond to the stage of differentiation as evidenced by surface antigen analysis might represent good examples of deranged gene expression in otherwise normally programmed malignant cells, i.e. in our study a mismatch between the isoenzymatic and immunological phenotypes. The tartrate-resistant isoenzyme was detected in 9 out of 74 leukemia-lymphoma cell lines (4 T-, 2 B-, 1 myelomonocytic, 2 Non-T, Non-B cell lines) and in 10 out of 12 normal B-lymphoblastoid cell lines; the only one studied hairy cell leukemia cell line did not express this isoenzyme. The relative specificity of the tartrate-resistant acP is discussed in detail. No leukemia-lymphoma specific isoenzyme or an additional isoenzyme which was not seen in normal hematopoietic cells could be observed. Nor did we find an isoenzyme or isoenzyme pattern characteristic for a certain cell lineage. This underlines the necessity of a combined analysis using markers from different disciplines in the 'multiple marker analysis' in order to accurately characterize normal and malignant blood cells. Furthermore, our results support the concept of maturation arrest at particular stages of differentiation together with the theory of normal gene expression in leukemic cells equivalent to that in their normal counterparts.

Leukemic cell differentiation in childhood leukemias. Analysis by enzyme markers

Enzyme marker analysis has become a valuable tool in leukemia research, especially as a part of the so-called multiple marker analysis which combines several disciplines for characterization of leukemia cells. In this study the qualitative activities of three enzyme markers were determined in leukemic cells from pediatric patients with acute leukemias: acid phosphatase (E.C. 3.1.3.2), carboxylic esterase (E.C. 3.1.1.1) and hexosaminidase (E.C. 3.2.1.30). The leukemia subtypes displayed different types of isoenzyme patterns. No additional isoenzyme was found that was not observed in normal blood cells, nor a single isoenzyme specific for a leukemia subtype. The biochemical profiles illustrated the existence of subsets in cALL, T-ALL and AML. The enzymologic polymorphism and the immunologic heterogeneity seen in leukemia subclasses have led together to an extended classification scheme of leukemias as well as to model schemes of normal hematopoietic cell differentiation. Despite former and constantly published assumptions there are still no specific markers of leukemia cells.

Development and properties of a monoclonal antibody specific for human ecto-5'-nucleotidase

After immunization with purified human placental ecto-5'-nucleotidase and fusion, 18 different hybrids were obtained which produce an antibody inhibitory for enzyme activity. These antibodies show complete cross-reactivity with the enzyme in a membrane-bound form or on the surface of intact cells. After cloning and ascites production, the antibody of one clone ( IFH - 5N1 ) was studied in greater detail. The IFH - 5N1 antibody is of the IgG 1 subclass. Optimal enzyme inhibition is 90% for purified 5'-nucleotidase and 80% for the enzyme on lymphoblasts. The specificity of this antibody is further demonstrated by enzyme inhibition assays and fluorescence labeling using various 5'-nucleotidase-positive and -negative human cells such as peripheral blood lymphocytes, leukemic cells, lymphoblastoid B- and T-cell-lines and fibroblasts. The antibody should provide a useful tool for the diagnosis of certain forms of acute leukemias and for the study of normal human lymphocyte subpopulations.

Analysis of isoenzyme patterns of acid phosphatase in acute leukemias

The status of acid phosphatase isoenzymes was evaluated in cells of patients with acute lymphocytic leukemias or lymphomas by analytical isoelectric focusing in polyacrylamide gels (IEF) on horizontal thin-layer slabs. The isoenzyme patterns were correlated with routine immunological cell surface markers and the relationship of enzyme activity to specific immunological subclasses of ALL is discussed. By isoelectric focusing up to five isoenzyme groups (I-V) containing several isoenzyme were observed. No leukemia specific or additional isoenzyme could be demonstrated. This biochemical characterization showed a marked heterogeneity within two major immunologic subgroups indicating that various differentiation stages of cell maturation could be involved in cALL and T-ALL. According to their degree of maturation along T-cell differentiation axis the leukemic cells displayed no enzyme activity, weak isoenzyme bands or the incomplete or complete isoenzyme pattern seen with normal lymphocytes from human tonsils which were used as controls. The investigation of specific enzymatic patterns can lead to a further definition of subsets of acute leukemias and give insight into lymphopoietic differentiation.

Isoenzyme studies in human leukemia -- III. beta-Hexosaminidase (E.C. 3.2.1.30)

Enzymologic profiles of beta-hexosaminidase (N-acetyl-beta-D-glucosaminidase, E.C.3.2.1.30) were studied in cells from childhood acute leukemias and lymphomas. By analytical isoelectric focusing or disc electrophoresis the beta-hexosaminidase activity was separated into its components A, B, I and C. The isoenzyme patterns were correlated with immunologic cell surface marker characteristics found on the investigated leukemic cells. In all cases of T-ALL the beta-hexosaminidase forms A and B were observed, an enzyme pattern similar to that found in normal lymphocytes. Seven out of 11 cases with cALL, three of six cases with AML and one case of AUL displayed the intermediate component (Hex I). Marked heterogeneity within the immunologically classified subgroup cALL was reflected in different enzyme patterns of the cALL samples. These biochemical phenotypes may indicate the different maturation and differentiation status of cells expressing the same immunologic surface markers.

Isoenzyme studies in human leukemia -- II. Carboxylic esterase (E.C. 3.1.1.1.)

Isoelectric focusing analysis of esterase activity (E.C. 3.1.1.1.) has been carried out on polyacrylamide gel slabs of a variety of immunologically defined acute leukemia subtypes. Distinct isoenzyme bands and isoenzyme groups have been identified and characterized biochemically with regard to their features for substrate specificity, pH optimum and inhibition experiments. The esterase isoenzyme patterns permitted the distinction between acute myeloid and non-myeloid leukemias. Acute lymphocytic leukemias localized by their immunological profile along the T-cell axis exhibited a readily recognizable isoenzyme group (T group). Reproducible differences in isoenzyme patterns were observed in childhood common ALL which indicate that the immunologically determined entity cALL displays a clear heterogeneity with respect to biochemical profiles of enzyme markers. These results suggest that further combined biochemical and immunological characterization may significantly contribute to a better understanding of lymphopoietic and leukemic cell differentiation.