Immunologic Markers in Childhood Acute Lymphoblastic Leukemia

Immunophenotypic Analysis of Hematogones (B-Lymphocyte Precursors) and Neoplastic Lymphoblasts by 4-Color Flow Cytometry

Hematogones are identified by 4-color flow cytometry in most bone marrow specimens. They are more commonly found and are generally present in higher numbers in children. There is a general decline in hematogones with increasing age but a broad range exists at all ages and marrow from some adults contains relatively high numbers. They are often increased (> 5%) in regenerating marrow and in some clinical conditions, particularly various types of cytopenias and neoplastic diseases. Hematogones may morphologically resemble the neoplastic lymphoblasts of precursor B ALL and their immunophenotype also has features in common with neoplastic lymphoblasts. Distinguishing hematogones from neoplastic lymphoblasts may be problematic in post-chemotherapy and post-bone marrow transplant regenerating marrow. With 4-color flow cytometry using optimal antibody combinations the distinction can nearly always be made. Hematogone populations always exhibit a continuous and complete maturation spectrum of antigen expression typical of the normal evolution of B-lineage precursors; they lack aberrant or asynchronous antigen expression. The neoplastic lymphoblasts in precursor B ALL deviate from the normal B-lineage maturation spectrum and exhibit maturation arrest and over-, under-, and asynchronous expression of antigens observed on normal B-cell precursors and they often aberrantly express myeloid-associated antigens.

Adult acute lymphoblastic leukemia

Much progress has been made in understanding the biology of and therapy for acute lymphoblastic leukemia (ALL). This progress has translated into the recognition of several subgroups of ALL and the institution of risk-adapted therapies. New therapies are emerging based on the definition of specific cytogenetic-molecular abnormalities. Changes in the pathologic classification of ALL have led to therapeutic consequences. Adaptation of successful treatment strategies in children with ALL has resulted in similar complete remission rates in adults. Prognosis has Improved especially in mature B-cell ALL and T-cell lineage ALL. However, regardless of ALL subgroup, long-term survival in adults is still inferior to that in children. Development of new drugs and agents tailored to subset-specific cytogenetic-molecular characteristics is vital to the therapeutic success in adult ALL.

THE CD 10 MARKER IN THE INVESTIGATION OF ACUTE LYMPHOBLASTIC LEUKAEMIA

Immunophenotyping of leukaemias is presently well established. It is invaluable for proper case management [1]. The most useful information on the management of cases of Acute Lymphocytic Leukaemia (ALL) is provided by the detection of the CD 10 marker on the leukaemic cell. The CD 10 positive ALL has since long been associated with a favourable prognosis as compared to the CD 10 negative ALL [1, 2]. As immunophenotyping is resource intensive, the monoclonal antibodies (MO ABS), are not in widespread use in our country. The expenses involved make this procedure prohibitive in most institutions. For this reason, a limited panel of MO ABS has been used in this study, with a special emphasis on the CD 10 marker. A total of 25 cases of ALL were studied. 17 cases were found to be positive for the CD 10 marker (68%). These cases were associated with a favourable prognosis as compared to the CD 10 negative group. Although, the diagnosis of ALL and leukaemias in general, is essentially based on the study of Romanowsky stained smears [3, 4], the additional information provided by the cell surface marker study results in better case management [1].

Flow cytometric analysis of cell-surface and intracellular antigens in the diagnosis of acute leukemia

To evaluate the usefulness of flow cytometric detection of intracellular antigens (Ags) in establishing proper lineage affiliation and its contribution to the diagnosis of acute leukemia, we studied 100 consecutive patients in whom acute leukemia was diagnosed between January 1997 and July 1998. Immunological classification was assessed using a three-line panel of monoclonal antibodies for phenotypic characterization of leukemic blast cells as proposed at the First Latin American Consensus Conference for Flow Cytometric Immunophenotyping of Leukemia. We found 74 cases of B-cell lineage acute lymphoblastic leukemia (ALL), seven cases of T-cell ALL, and 19 cases of acute myeloid leukemia (AML). In this study cytoplasmic (cy) CD79a, cyCD22, cyCD3, and cyMPO were highly sensitive, specific B, T, and myeloid markers that were expressed in virtually all cases of B and T cell ALL and in all subtypes of AML. Applied in combination with immunophenotyping this knowledge led to improvement in diagnostic precision and refinement of immunological classification, ensuring the selection of the most appropriate therapy for the patients studied. In conclusion, intracellular Ags detection was of utmost importance in establishing correct lineage affiliation in cases lacking expression of B, T, or myeloid surface Ags or disclosing equivocal or ambiguous immunophenotypic features and in identifying biphenotypic acute leukemia. In combination with FAB morphology and immunophenotyping, we were able to reliably classify all patients with acute leukemia in this study.

Flow cytometry in the diagnosis of acute leukemia

Acute leukemias are a heterogeneous group of malignancies with varying clinical, morphologic, immunologic, and molecular characteristics. Many distinct types are known to carry predictable prognoses and warrant specific therapy. Distinction between lymphoid and myeloid leukemias, most often made by flow cytometry, is crucially important. Several advances in flow cytometry, including availability of new monoclonal antibodies, improved gating strategies, and multiparameter analytic techniques, have all dramatically improved the utility of flow cytometry in the diagnosis and classification of leukemia. Acute leukemias reflect the pattern of antigen acquisition seen in normal hematopoietic differentiation, yet invariably demonstrate distinct aberrant immunophenotypic features. Detailed understanding of these phenotypic patterns of differentiation, particularly in myeloid leukemia, allows for more precise classification of leukemia than does morphology alone. However, morphologic and differentiation-based classifications of leukemia are limited in their prognostic value; cytogenetics and molecular genetics appear to be most important for identifying entities with distinct prognoses and clinical behavior. Increasingly, many of these genetically distinct subgroups of leukemia have been found to be closely associated with distinct immunophenotypes. For example, translocations such as t(8;21), t(15;17), and inv(16) in acute myeloid leukemia (AML), and t(1;19) and t(12;21) in acute lymphoblastic leukemia (ALL) have distinctive immunophenotypic profiles. Thus, in addition to classification into differentiation-based subtypes, detailed flow cytometric studies can define complex antigenic profiles that are associated with specific molecular defects and well-defined biology. In summary, multiparameter flow cytometry is an invaluable tool in the diagnosis, classification, and monitoring of patients with acute leukemia. Semin Hematol 38:124-138.

Cytochemical staining and flow cytometry methods applied to the diagnosis of acute leukemia in the pediatric population: an assessment of relative usefulness

BACKGROUND

Cytochemical staining has been used in the diagnosis of acute leukemia for more than 20 years. The general availability of flow cytometers and an extensive panel of antibody reagents useful for characterizing blood cell lineage question the usefulness of continuing routine use of the cytochemical staining for the diagnosis of acute leukemia.

PATIENTS AND METHODS

Test results were evaluated in 122 (n = 122; 112 with acute lymphocytic leukemia and 10 with acute myeloid leukemia) patients selected from among 320 patients with acute leukemia at Texas Children's Hospital in 1997 and 1998. Results were selected for review if the clinical encounter represented the initial diagnostic work-up and if data were available from cytochemical staining and flow cytometry studies.

RESULTS

Cell lineage classification derived from flow cytometry and cytochemical stains were in agreement in all cases. Definitive diagnoses were feasible using flow cytometry results alone in 120 of 122 patients (98.4%) as compared with only 99 of 122 patients (81.2%) when only cytochemical staining results were considered. In two patients with inconclusive flow cytometry results, cytochemical staining alone provided information sufficient for diagnosis.

CONCLUSIONS

Results from this study indicate that with few exceptions, flow cytometry studies alone provide sufficient information for diagnosis and management of acute leukemia in children. Nevertheless, cytochemical staining should be available for those cases in which flow cytometry results fail to allow a definitive diagnosis. A modified testing protocol is recommended.

Immunophenotyping pediatric leukemias in Kelantan, Malaysia

This study reviewed the immunophenotyping results of children with acute leukemia in Kelantan, Malaysia. In the 3.5-year period (January 1994 to June 1997), 45 cases were identified. All children were under the age of 12 years and the predominant ethnic group was Malay. Thirty-six cases (80%) were acute lymphoblastic leukemia (ALL) and 9 cases (20%) were acute myeloblastic leukemia (AML). Of the ALL cases, 3% were of B-cell and 22% of T-cell origin, and 96% of the B-lineage ALL were CD10 positive. All the AML cases expressed CD33 and 78% were positive for CD13. The incidence of mixed-lineage leukemias was 13.8% for My+ ALL and 11.1% for Ly+ AML.

Prognostic Significance of Fluorescence Intensity of Surface Marker Expression in Childhood B-Precursor Acute Lymphoblastic Leukemia. A Pediatric Oncology Group Study

This report describes the prognostic significance of the intensity of surface membrane antigen expression in a series of 1,231 children older than 1 year with newly diagnosed B-precursor acute lymphoblastic leukemia (ALL) treated on Pediatric Oncology Group (POG) treatment protocols. All patients had dual-color flow cytometric immunophenotyping performed at a central reference laboratory with a standard panel of monoclonal antibodies. The flow cytometers used in the study were calibrated with a standard fluorescence microparticle that permitted conversion of relative fluorescence channels to standard units of mean equivalents of soluble fluorochrome (MESF). In univariate analysis, fluorescence intensity of CD45 and CD20 was significantly associated with event-free survival (EFS), whereas other markers showed no significant correlation with outcome. Patients whose blasts were greater than the 75th percentile of intensity for CD45 (corresponding to 18,000 MESF units with CD45-FITC, or about 8% of the intensity of normal lymphocytes) fared significantly worse than those with lower-density CD45, and those whose blasts were greater than the 25th percentile of intensity for CD20 (corresponding to 17,900 MESF units with CD20-PE) had a poorer EFS. The intensity of both CD45 and CD20 was independently correlated with outcome. There was no significant correlation between intensity of expression of either antigen and traditional clinical risk factors, ploidy, or t(9; 22) or t(1; 19). All patients with t(4; 11) had CD45 intensity greater than the 75th percentile, but CD45 intensity retained its prognostic significance after adjusting for t(4; 11). In multivariate analysis, both CD45 intensity greater than the 75th percentile and CD20 intensity greater than the 25th percentile were significantly correlated with poor outcome independently of previously reported poor prognostic factors including National Cancer Institute (NCI) risk group, ploidy, trisomies of 4 and 10, and adverse translocations including t(1; 19), t(9; 22), and t(4; 11). We conclude that in childhood B-precursor ALL, the intensity of expression of CD20 and CD45 provides prognostic information not available from simple consideration of antigen expression as positive or negative, and adds to that obtained from traditional clinical and biologic risk factors.

Neural network analysis of flow cytometry immunophenotype data

Acute leukemia is one of the leading malignancies in the United States with a mortality rate strongly influenced by the phenotype. This phenotype is based on detection of cell associated antigens normally expressed during leucopoietic differentiation. In this regard, leukemia classified as lymphoid or myeloid by phenotype is also classified as a candidate for the corresponding chemotherapy protocol. Additionally, the subtype of leukemia based on the degree of differentiation and cell maturity influence prognosis, response to treatment, and median survival times. In this paper, we analyze immunophenotype flow cytometry data toward categorization of leukemia into subcategories based on lineage and differentiation antigen expression. Twenty-eight inputs (derived from the mean fluorescence intensity of up to 27 antibodies, and an additional binary input denoting the past diagnosis of leukemia) are used as input to a neural classifier to categorize a total of 170 cases into the lineage and differentiation categories of leukemia. The neural classifier consisted of a feed forward network trained using back propagation. A complexity regulation term (weight decay) was used to improve the generalization performance of the neural classifier. A training error of 0.0% and a generalization error of 10.3% was obtained for categorization based on lineage, while a training error of 0.0% and a generalization error of 10.0% was obtained for categorization based on differentiation. These results indicate that objective classification of multifaceted phenotypes in leukemia can be achieved for analyzing multiparameter data in flow cytometry and further categorization into the prognostic subtypes.

Clinical implications of cytogenetic classification in adult acute lymphoblastic leukaemia patients

Cytogenetic analysis performed on pretreated unstimulated, bone marrow/peripheral blood samples of 46 adult patients with acute lymphoblastic leukaemia (ALL) showed sufficient metaphases in 39 patients and insufficient metaphases in 7 patients. G-banded karyotype analysis of these 39 patients revealed non-random clonal chromosome abnormalities in 31 patients and apparently normal karyotypes in 8 patients. Numerical abnormalities involving chromosome trisomies and structural abnormalities involving different types of chromosomal translocations and deletions were encountered in varying percentages. These patients were grouped into various cytogenetic subsets on the basis of their karyotype pattern and followed-up to evaluate their prognosis. Patients with apparently normal karyotypes showed good prognosis and those with 6q- showed intermediate prognosis. But all other patients with hyperdiploid, pseudodiploid and hypodiploid karyotypes were associated with poor prognosis. Cytogenetic classification of ALL patients is thus of clinical importance, as it helps the early identification of clinically important prognostic groups.

Prognostic variables and survival in pediatric acute lymphoblastic leukemias: cancer institute experience

This presentation is an analysis of front-end prognostic variables in achieving a complete response, a continuous complete remission, and disease-free survival in pediatric acute lymphoblastic leukemia at the Cancer Institute, Madras, India between 1983 and 1988. The clinical characteristics at presentation showed that virtually 100% of patients belong to the poor risk category, age < 3 years of > 6 years 72.2%, WBC > 10,000/mm3 59.8%, blast count > 50% 39.2%, organomegaly 91.8%, and L2 morphology 66.0%. All patients had more than one risk factor. Between 1983 and 1988, 97 children were treated on a pilot protocol designed in collaboration with the Lymphoma Biology Division of the Pediatric Oncology Branch of the National Cancer Institute, Bethesda, Maryland. The protocol was designed for a poor prognostic group. The significance of implicated poor prognostic factors was analyzed using the Cox proportional hazard model. Age at presentation was the only variable that emerged as an independent risk factor, and sex appeared to be a modifier. No other variables attained significance. Survival data were calculated by the Kaplan-Meier method. The relapse-free and event-free survivals up to 10 years were 50.7% and 38.1%, and compare reasonably well with results reported for similar groups elsewhere for the same period.

Characterization of acute lymphoblastic leukemia subtypes in Brazilian patients

The distribution of the acute lymphoblastic leukemia (ALL) subsets in 225 consecutive Brazilian patients was determined by an immunophenotypic study with an extensive panel of monoclonal antibodies. All subsets were detected and their relative frequencies were similar to those described in developed countries, except for the B-mature subset which had a higher frequency, especially in adults. Associated myeloid markers were expressed by 11% of the ALL and CD10 by 15.9% of T-ALL cases. Besides, the incidence rates determined for the region of Ribeirão Preto showed that the overall incidence of ALL was 12.5 cases/10(6) people years (PY) (5 cases/10(6) PY in non-Whites versus 14 cases/10(6) PY in Whites); the incidence of childhood ALL was 25.5 cases/10(6) PY (8.1 versus 29.8 cases/10(6) PY in non-Whites and Whites, respectively) and the incidence of ALL in adults was 6.2 cases/10(6) PY (5.5 versus 6.1 cases/10(6) Py in non-Whites and Whites, respectively). The significantly lower incidence rate of ALL in non-White children was associated with a selective deficit of the common subtype and a lack of the typical age peak of incidence in this group. The ALL features demonstrated here in Brazilian non-White children resemble those described in the American non-Whites before the seventies and those in British and American Whites at the beginning of the century.

[Neonatal acute leukemia: apropos of 7 cases]

BACKGROUND

Acute leukemia in neonates is rare and is more severe than leukemia in childhood.

POPULATION

Seven cases (four girls, three boys) were included in this series. Leukemia was diagnosed at birth in three cases; hepatosplenomegaly was seen in five cases and skin nodules in three. Hyperleukocytosis more than 100,000/mm3 was present in four cases; the WBC and differential counts were normal in two. A meningeal involvement was seen in one case. The leukemia was lymphoblastic (ALL) in three cases and myeloblastic (AML) in four. Intensive chemotherapy induced complete remission in five patients, persisting 5 and 4 years after the diagnosis in two. Classic risk factors such as high white blood counts, central nervous system involvement, myeloblastic lineage, absence of CALLA (common acute lymphoblastic leukemia antigen) expression and abnormal blast cell karyotype interesting the 11q23 area were found again in this series. Risk related to drug toxicities and infectious complications were also noted in this series of very young patients.

CONCLUSIONS

The outcome may depend on progress in pharmacology, search for new drugs and use of bone marrow transplantation.

IMMUNOPHENOTYPING OF ACUTE LEUKAEMIAS : A CRITICAL ANALYSIS OF 35 CASES

Accurate classification of acute leukaemias is essential for proper case management. The utility of monoclonal antibodies in the diagnosis and classification of acute leukaemias is well established. This diagnostic utility relates primarily to two points : firstly the distinction between acute myeloid leukaemia and acute lymphoblastic leukaemia and secondly to subtypes of acute lymphoblastic leukaemia. Leukaemic cells were immunophenotyped using the alkaline phosphatase antialkaline phosphatase techniques. The monoclonal antibodies were very useful in distinguishing cases of acute myeloid leukaemia from acute lymphoblastic leukaemia. Cases of acute lymphoblastic leukaemia with CD10 positivity showed a better prognosis. T-cell acute lymphoblastic leukaemia was uncommon and was associated with unfavourable prognosis. The alkaline phosphatase antialkaline phosphatase technique served as a reliable and convenient method for immunophenotyping of leukaemias.

Detection of intracellular lymphoid differentiation antigens by flow cytometry in acute lymphoblastic leukemia

The value of flow cytometric detection of the intracellular lymphoid differentiation antigens CD3 and CD22 in the differential diagnosis of acute leukemia was assessed in cases of acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and leukemic cell lines. Cells were fixed in 0.25% paraformaldehyde at 4 degrees C for 60 min, permeabilized with 0.2% Tween 20 at 37 degrees C for 15 min, then stained with CD3 or CD22 monoclonal antibodies by indirect immunofluorescence. Cytoplasmic CD22 was detected on greater than 20% (mean 55%; range 20-87%) of blasts from all 20 cases of precursor-B ALL analyzed. The percentage of cells with cytoplasmic CD22 was greater than that with membrane CD22 in all except 2 cases of precursor-B ALL. Cytoplasmic CD22 was not detected in 8 cases of precursor-T ALL, 4 T-leukemia cell lines, or in 7 cases of AML. In contrast, cytoplasmic CD3 was detectable by flow cytometry in all 8 cases of precursor-T ALL, but not in precursor-B ALL, pre-B leukemia cell lines, or in AML. These results confirm that cytoplasmic CD3 and CD22 are excellent markers of the early T and B lineages in ALL and can be reliably detected by flow cytometry. This technique should be a valuable addition to routine immunophenotyping for classification of acute leukemia.

Cytogenetics and immunophenotypes of childhood acute lymphoblastic leukemia in Hong Kong

We present the cytogenetics and immunophenotypes of 55 cases of childhood acute lymphoblastic leukemia in Hong Kong. Although the pattern of immunophenotypes is similar to that of the west, hyperdiploidy is rarely observed locally. Our preliminary analysis also reveals some new translocations.

Relapse of acute lymphoblastic leukemia in the inferior rectus muscle of the eye

BACKGROUND

Extramedullary involvement of acute lymphoblastic leukemia (ALL) in sites outside the central nervous system (CNS) or testes is rare and may signal a refractory form of leukemia.

METHODS

The authors describe a child with ALL who experienced a relapse involving the inferior rectus muscle of the eye. This patient had been treated with a bone marrow transplant for previous bone marrow and ovarian relapse.

RESULTS

The patients had a pre-B ALL with a t(1;19) chromosomal translocation and previously had experienced relapse during therapy. At the time of the muscle relapse, she had pancreatomegaly consistent with leukemic infiltration but no CNS or bone marrow disease.

CONCLUSIONS

Relapse of ALL in unusual sites may indicate disease that is particularly difficult to eradicate. Factors in addition to age and leukocyte count at diagnosis determined risk. Additional research is needed to define these factors and develop more effective therapy.

Clinical relevance of in vitro drug resistance testing in childhood acute lymphoblastic leukemia: the state of the art

Nowadays about two-thirds of children with acute lymphoblastic leukemia (ALL) can be cured with chemotherapy, but one-third die from the disease. The clinical response of leukemic cells to chemotherapy is roughly due to two factors: the effective drug levels reaching the cells and the resistance of these cells to the drugs. The clinical value of cellular drug resistance in children with ALL is not known. We developed an in vitro assay to study drug resistance in these children. In this article, the main results obtained with this MTT assay on samples from 137 children with ALL are summarized: (1) patients whose cells are resistant to several drugs at initial diagnosis have a poor prognosis; (2) relapsed leukemias show a considerable drug resistance which might partly explain the poor prognosis. Relapsed cases differ in their type and degree of resistance; (3) the poor outcome of high risk groups as defined by age and immunophenotype can partly be explained by specific patterns of drug resistance; (4) P-glycoprotein-mediated multidrug resistance is not an important cause of resistance in childhood ALL; and (5) no relation exists between the activities of the purine enzymes HGPRT, 5'NT, ADA, and PNP and drug resistance in childhood ALL. The conclusion is that in vitro drug resistance data have clinical relevance and can be used to develop more effective and less toxic treatment strategies in childhood ALL.

Immunophenotypic features of childhood and adult acute lymphoblastic leukemia (ALL): experience of the German Multicentre Trials ALL-BFM and GMALL

Immunophenotyping prospectively performed in about 2800 children and adults within the framework of the German multicentre ALL trials revealed marked differences in frequency distribution of immunologic subgroups with a higher incidence of immature B-cell precursor and pre-T/T phenotypic features in adults. Detailed immunophenotypic characterization by applying monoclonal antibodies to lymphoid- and myeloid-associated antigens as well as non-lineage-restricted molecules underlined the diagnostic value of pan-B and pan-T antigens that were expressed in virtually all cases of B-cell precursor (CD19, CD24) or T-cell ALL (cytoplasmic CD3, CD7) for lineage affiliation of leukemic blasts. About 10% of children and 20% of adults disclosed simultaneous expression of lymphoid markers and at least one myeloid-lineage-associated antigen. Our data confirm that immunophenotyping in ALL provides a solid basis for a biologically oriented and reliable classification of this heterogeneous disease.

The diagnostic and prognostic value of immunophenotyping in acute leukemia

Immunophenotyping with monoclonal antibodies to leucocyte differentiation antigens has an established diagnostic role in the laboratory investigation of acute leukemia. In the vast majority of cases, a hemopoietic lineage can be confidently assigned; namely, acute myeloid leukemia (AML), or the precursor-B and precursor-T variants of acute lymphoblastic leukemia (ALL). The areas of greatest practical importance are in morphologically difficult or undifferentiated cases, and in distinguishing between the major variants of precursor-B and T-ALL. Cases with aberrant patterns of marker expression (acute mixed lineage leukemia, lineage infidelity) are frequently encountered in both ALL and AML, and can lead to diagnostic confusion. However, correlation with morphology and other clinicopathologic features, and careful consideration of the weight of phenotyping evidence almost always allows the correct lineage to be identified. The prognostic value of phenotypic information in acute leukemia is generally limited. Recognition of the major variants of ALL is still of clinical importance, but the significance of myeloid antigen positivity in ALL is controversial, and may not have prognostic value. Patterns of myeloid antigen expression in AML have limited prognostic significance, while the relationship between lymphoid antigen expression and treatment response in AML remains highly controversial. Careful evaluation of the predictive power of immunophenotype in large controlled clinical trials in acute leukemia is still required.