Multimarker phenotypic characterization of adult and childhood acute lymphoblastic leukaemia: an Italian multicentre study

Super-Enhancer-Driven IRF2BP2 is Activated by Master Transcription Factors and Sustains T-ALL Cell Growth and Survival

Super enhancers (SEs) are large clusters of transcriptional enhancers driving the expression of genes crucial for defining cell identity. In cancer, tumor-specific SEs activate key oncogenes, leading to tumorigenesis. Identifying SE-driven oncogenes in tumors and understanding their functional mechanisms is of significant importance. In this study, a previously unreported SE region is identified in T-cell acute lymphoblastic leukemia (T-ALL) patient samples and cell lines. This SE activates the expression of interferon regulatory factor 2 binding protein 2 (IRF2BP2) and is regulated by T-ALL master transcription factors (TFs) such as ETS transcription factor ERG (ERG), E74 like ETS transcription factor 1 (ELF1), and ETS proto-oncogene 1, transcription factor (ETS1). Hematopoietic system-specific IRF2BP2 conditional knockout mice is generated and showed that IRF2BP2 has minimal impact on normal T cell development. However, in vitro and in vivo experiments demonstrated that IRF2BP2 is crucial for T-ALL cell growth and survival. Loss of IRF2BP2 affects the MYC and E2F pathways in T-ALL cells. Cleavage under targets and tagmentation (CUT&Tag) assays and immunoprecipitation revealed that IRF2BP2 cooperates with the master TFs of T-ALL cells, targeting the enhancer of the T-ALL susceptibility gene recombination activating 1 (RAG1) and modulating its expression. These findings provide new insights into the regulatory network within T-ALL cells, identifying potential new targets for therapeutic intervention.

Immunophenotypic Characteristics of T-Acute Lymphoblastic Leukemia in Omani Patients: A Correlation with Demographic Factors

Objectives

To study and classify the immunophenotypic characteristics of Omani patients diagnosed with T-cell acute lymphoblastic leukemia (T-ALL) and to correlate the results with age and gender as well as biological factors (peripheral and bone marrow blast cells percentage).

Methods

Fifty cases from both genders and of all ages who fulfilled the inclusion criteria with a diagnosis of T-ALL were included in the study. Correlation of T-ALL subtypes with age, gender, and initial bone marrow and peripheral blood blast cells percentage was assessed using ANOVA.

Results

Among the 50 T-ALL patients analyzed, 44 were male and six were female giving a male-to-female ratio of 7:1 (p = 0.007). The average age of patients was 19.2 years with no significant differences in the three disease subtypes. No significant association was seen between the peripheral or bone marrow blast cell percentage and the differentiation stages of the neoplastic clone of T-ALL. All female patients were found to express an immature T-ALL phenotype.

Conclusions

This study reports the subtypes of T-ALL in Oman for the first time. It is hoped that this will lead to a better understanding of the disease outcomes.

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.

Acute lymphoblastic leukaemia in the elderly

Acute lymphoblastic leukaemia (ALL) is rare in adults over the age of 60 years, with an incidence of 1 per 100,000 per year. We review the current (sparse) literature and our Regional experience of 62 consecutive cases of ALL in this age group collected over a ten year period. The patterns of cytogenetic abnormalities and immunophenotypes differs from those seen in ALL in childhood and young adults, but are similar to those reported in previous studies. B-ALL was found at twice the rate observed in younger adults (9/51 versus 6/99) and T-ALL was rare (2/51). In our patients we had few cytogenetic results but in the literature up to 50% of patients have been found to be Philadelphia positive, supporting the hypothesis that ALL in this group is often a stem cell disorder. In our patients treatment results were disappointing, with only 30% of those given 'curative' treatment achieving a complete remission, and a relapse rate of 92%, mirroring other published series. The overall four year survival was 4%. We conclude that ALL in the elderly is a rare condition with an extremely poor prognosis. Aggressive treatment may prolong life but it seldom cures.

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.

Preferential clustering of chromosomal breakpoints in Burkitt's lymphomas and L3 type acute lymphoblastic leukemias with a t(8;14) translocation

We have analyzed the type of MYC/IG heavy-chain locus (IGH) rearrangement present in 15 patients affected by t(8;14)-positive primary Burkitt's lymphoma or acute lymphoblastic leukemia of the L3 type in an attempt to map in detail the locations of the chromosome 8 and chromosome 14 breakpoints. The almost constant position of the chromosome 8 breakpoint (within or immediately 5' of the MYC gene) together with two distinct clusters of breakpoints on chromosome 14 resulted in two main types of MYC/IGH (present in 12 of 15 cases). In the first type (six cases), the MYC gene or at least its coding portion was joined with the JH region on chromosome 14, whereas in the second, present in another six cases, the MYC gene and the C alpha I region were juxtaposed. Physical linkage between the translocated MYC and a known enhancer element of the IGH locus is the common feature in the two types of rearrangement, suggesting that a high-level constitutive expression plays a prominent role in MYC activation. Interestingly, the chromosome 14 break site within the switch alpha 1 region, which has been only occasionally described in other cases, is present in 40% of our patients, suggesting the existence of preferential breakpoint cluster regions in cases of similar geographic origin.

Acute lymphoblastic leukaemia in adults: immunological subtypes and clinical features at presentation

In 91 of 106 adult patients with acute lymphoblastic leukemia (ALL) enrolled in the treatment protocol ALL HOVON-5 between May 1988 and October 1991, the immunophenotype of the leukemia was determined and correlated with clinical characteristics at presentation. The immunological marker analysis was performed in ten laboratories, all members of the Dutch Study Group on Immunophenotyping of Leukemias and Lymphomas (SI-HON). Undifferentiated blasts were found in four patients, 67 had B-lineage ALL, 18 had T-lineage ALL, and two had biphenotypic ALL. The age of T-lineage ALL patients was lower (mean 29.3) than that of B-lineage ALL patients (mean 35.5). Tumor mass, as expressed by leukocyte count, organomegaly, and LDH, was more pronounced in T-lineage ALL. Hemoglobin and platelet count was similar in all (sub)types. CD34 was expressed in 58% of the leukemias, but most frequently in the common B-ALL (70%). Thirteen percent of the leukemias expressed one or more markers not associated with their lineage. In this prospective study immunological data were not evaluable for 15 patients. On four of them data were not available because of dry tap, for six patients the typing was technically insufficient, and for four patients the results were unclassifiable; with one patient the marker analysis was not performed.

Adult and childhood acute lymphocytic leukemia: are they different diseases?

Age has long been recognized as an important factor in predicting response to treatment for acute lymphocytic leukemia (ALL). Specifically, the results of treatment of childhood ALL have been far superior to the treatment of what appears to be the same disease in adults. However, from an analysis of the clinical and biological prognostic factors known to be predictive in childhood ALL, there is a striking difference in their distribution in adults with ALL. It appears that there is a special form of ALL seen in children of some populations with a peak incidence of three to seven years. This treatment responsive leukemia appears to be different clinically, biologically, and epidemiologically from adult ALL.

Phenotypic and genotypic switch in Philadelphia-positive, BCR-positive blast crisis of chronic myeloid leukemia

We report a case of Ph1-positive, bcr-positive chronic myeloid leukemia blast crisis (CML-BC) which at presentation showed a mixed myeloid/B-lymphoid immunophenotype along with TdT positivity and, at the molecular level, an oligoclonal rearrangement of the immunoglobulin heavy chain (IgH) gene region. After obtaining a successful remission, at the time of relapse the patient underwent a phenotypic and genotypic switch from mixed to myeloid phenotype, characterized by the loss of the lymphoid markers and TdT expression and by a germline configuration of the IgH gene region. The same bcr rearrangement was, however, found in both phases of the disease, supporting the suggestion of a true phenotypic and genotypic conversion. This report confirms that the neoplastic event in CML may take place at an early multipotent stem-cell level, prior to a well-defined phenotypic and genotypic lineage expression. Moreover, it is suggested that different factors (chemotherapy? growth factors?) may have either eradicated the bcr+/IgH+ clone and promoted the growth of bcr+/IgH- leukemic cells or, alternatively, supported the lymphoid differentiation program and induced a myeloid lineage shift.

Co-expression of myeloid antigens in childhood acute lymphoblastic leukaemia: relationship with the stage of differentiation and clinical significance

Co-expression of myeloid antigens on the leukaemic blast cells was evaluated in 532 children with a diagnosis of acute lymphoblastic leukaemia (ALL). Using a panel of monoclonal antibodies belonging to CD11b, CD13, CD14, CD15 and CD33 an overall incidence of 4.3% was found, with values ranging between 1.8% for CD14 and 6.1% for CD15. When the data were further dissected, a significantly higher incidence of co-expression was noted in null-ALL (15/70 cases = 21.4%), compared to cases expressing a more mature immunophenotype, i.e. common-ALL (7/394 cases = 1.7%) and T-ALL (1/68 cases = 1.4%) (P less than 0.001). In null-ALL, 9/15 patients were infants, five of whom with the t(4;11); two further children also had a t(4;11). The clinical outcome of the 23 cases which co-expressed myeloid antigens was unfavourable. Only two of the 15 null-ALL, two of the seven common-ALL and the unique case with T-ALL are in fact in persistent first remission between 19 and 93 months from diagnosis. Though the overall incidence of childhood ALL expressing myeloid antigens is low, the evidence that this co-expression may be related to an unfavourable clinical course and that it more frequently occurs in null-ALL, particularly in the first year of life, suggests that the routine assessment of myeloid antigens may allow to identify a subgroup of childhood ALL with a poor clinical outcome.

Heterogeneity of T cell lymphoblastic leukaemias

Twenty eight out of 170 consecutive cases of acute lymphoblastic leukaemia (ALL) were examined. They were of T cell origin, with the following distribution: seven (28%) cases had pre-T or prothymic features; nine (36%) cases showed early thymocytic features, six (24%) had cortical features; and three (12%) had a "mature" phenotype. The remaining three cases could not be sub-classified. A striking finding was that pre-T ALL differed from intrathymic ALL not only in the absence of both E rosettes and intrathymic differentiation antigens, but also in the expression of two non-lineage specific antigens HLA-DR and CD10. Both antigens appear in the bone marrow from the very first stages of lymphoid differentiation, implying that the origin for pre-T ALL is bone marrow. A comparison of the clinical features of pre-T and thymic ALL showed that pre-T ALL disease showed a pattern more similar to non-T ALL disease: a lower incidence of mediastinal mass, absence of extrahaematopoietic disease, lower white cell counts and haemoglobin concentrations, and a higher incidence of bone pain. No obvious difference in response to treatment was apparent. The results show that T-ALL is not only a heterogeneous immunological group but also suggest that it may have different origins: bone marrow for pre-T ALL and the thymus for thymic ALL.

ABL proteins in Philadelphia-positive acute leukaemias and chronic myelogenous leukaemia blast crises

The Philadelphia chromosome (Ph1) is present in 95% of chronic myelogenous leukaemias (CML) and 15% of acute lymphoblastic leukaemias (ALL). This cytogenetic marker is due to a t(9;22) translocation, which causes a rearrangement of the ABL oncogene. In order to better define the relationship between type of genomic rearrangement, variant ABL protein expressed and haematological phenotype, a series of Ph1-positive acute leukaemias, both myeloblastic (AML) and lymphoblastic, and several CML lymphoid blast crises have been analysed at the DNA and protein level. The results confirm the presence of the ABL protein P210 in all cases of CML, ALL and AML positive for rearrangement in the bcr region of chromosome 22, and, surprisingly, in one AML case apparently negative for bcr rearrangement. The ABL protein P190 was found to be present only in cases of ALL negative for bcr rearrangement. Polymerase chain reaction (PCR) analysis of the types of 9/22 junctions present in the mRNA of CML lymphoid blast crises showed no evidence of 'ALL-type' transcripts.

Interleukin 2 does not promote the in vitro and in vivo proliferation and growth of human acute leukaemia cells of myeloid and lymphoid origin

The effect of recombinant interleukin 2 (IL2) on the in vitro and in vivo proliferation and growth of human acute leukaemia cells of both myeloid and lymphoid origin was investigated. In none of the 25 primary samples tested could a continuously in vitro growing cell line be obtained by adding IL2 to the culture medium. Although IL2 induced a proliferative signal in three of the 31 acute leukaemias analysed, the overall 3H-thymidine uptake of the neoplastic cells was significantly reduced (P less than 0.05) in the presence of IL2. The unlikelihood of an important proliferative signal triggered by IL2 was confirmed in a semisolid clonogenic assay, which failed to document an increased colony growth in the 26 samples studied. Furthermore, using a colorimetric assay as a test for cell proliferation and survival, in seven of the 11 fresh acute leukaemia samples tested a 22-40% reduction in viability was observed in the presence of IL2, while in the remaining four, IL2 was ineffective. In order to investigate the effect of IL2 in an in vivo setting, an experimental model in heavily immunosuppressed nu/nu mice was established. In no case did IL2 promote the in vivo proliferation and growth of human myeloid and lymphoid acute leukaemia cells injected in the mice. On the contrary, with seven of the eight leukaemic cell lines which gave rise spontaneously to leukaemic masses, this could be prevented when the mice received locally 300 U of IL2 three times daily for 90 d. IL2 also blocked the growth in vivo of three fresh acute leukaemia samples (two myeloid and one lymphoid). Co-culture experiments using leukaemic cell lines and increasing numbers of normal lymphocytes suggest that the inhibitory effect of IL2 is probably exerted via an indirect mechanism. These findings, coupled to the well-documented ability of IL2 to generate lymphokine activated killer cells cytolytic against leukaemic blasts, further point to the potential role of immunotherapy with IL2 in the management of patients with haematological malignancies.

Cell kinetics in acute lymphoblastic leukaemia: comparative analysis between adults and children

Cell kinetics were studied in 124 patients with acute lymphoblastic leukaemia (ALL) by flow cytometry, comparing cell cycle characteristics between adults (57 cases) and children (67 cases). S, G2 + M and the low protein content fraction of G1 (LPC fraction) were determined and studied in relation to other clinical and biological features. No difference was found between adults and children in the distribution of these variables. The proliferative rates according to organomegaly, leukocytosis, the FAB cytological groups and the immunological groups did not present any significant differences between the two groups of patients. However, cell cycle did seem to have a very different prognostic value for adults and for children. G2 + M was a strong prognostic indicator for childhood ALL: duration of CR and survival were significantly longer when G2 + M was higher (P less than 0.01). In adults, survival was longer for intermediary (between 3.8 and 5.8%) and high (over 7.2%) G2 + M values (P less than 0.01). The negative correlation between S and G2 + M observed in adults and the absence of correlation in children raise the possibility of differences in duration of the different phases for the two groups and perhaps an accumulation of cells in G2 or tetraploidy in some cases.

Induction of myeloperoxidase in five cases of acute unclassified leukaemia

For further analysis of their lineage affinity the differentiation capacity of five cases of acute unclassified leukaemias were studied in vitro using 5 nM 12-O-tetradecanoyl-phorbol-13-acetate as an inducing agent. After 4 d in vitro a co-expression of both myeloid and early B-lymphoid or myeloid and early T-lymphoid antigens on the same population of cells was found. While ultrastructural analysis of the blasts prior to culture revealed the morphology of undifferentiated blasts without any specific endogenous peroxidase activity, the cultured blasts displayed monoblastic features and myeloperoxidase activity after 4 d in vitro. Since this type of peroxidase is highly specific for the myelomonocytic lineage the data indicate myelomonocytoid differentiation of all five cases studied. The co-expression of lymphoid as well as myeloid antigens and myeloperoxidase by the same blasts after culture could be indicative of bilineage differentiation capacity characterizing the original blasts as bipotential progenitor cells.

Rearrangements of immunoglobulin and T cell receptor beta and gamma genes are associated with terminal deoxynucleotidyl transferase expression in acute myeloid leukemia

The cell origin of the rare terminal deoxynucleotidyl transferase (TdT)-positive acute myeloid leukemias (AML) was investigated at the molecular level, by examining the configuration of the Ig H (Igh) and L (Ig kappa, Ig lambda) chain gene regions, and of the T cell receptor (TCR) beta and T cell rearranging (TRG) gamma loci. In 8 of the 10 TdT+ AML analyzed (classified as myeloid according to morphological and cytochemical criteria, and to the reactivity with one or more antimyeloid mAbs), a rearrangement of the Igh chain gene was found. In TdT- AML, evidence of an Igh gene reorganization was instead observed only in 2 of the 42 patients studied. Furthermore, evidence of TCR-beta and/or TRG-gamma gene rearrangement was observed in four AML, all of which belonged to the Igh-rearranged TdT+ group. In three cases (one TdT+ and two TdT-), the Ig kappa L chain gene was also in a rearranged position. These findings demonstrate a highly significant correlation between TdT expression and DNA rearrangements at the Igh and TCR chain gene regions and support the view that this enzyme plays an important role in the V-(D)-J recombination machinery. Overall, the genomic configuration, i.e., JH gene rearrangement sometimes coupled to a kappa L chain and TCR gene reorganization, similar to that found in non-T-ALL, suggests that in most cases of TdT+ AML, the neoplastic clone, despite the expression of myeloid-related features, is characterized by cells molecularly committed along the B cell lineage.

Rearrangement for the T-cell receptor gene and co-expression of immature T-cell markers and natural killer cell phenotype, in a patient with acute lymphoblastic leukaemia

We describe a patient with acute lymphoblastic leukaemia whose blasts co-expressed immature T-cell markers and nearly the entire phenotypic repertoire of NK cells. The T-cell nature of the proliferating blasts was proven by the demonstration of the rearrangement for the beta-chain of the T-cell antigen receptor. Although an abnormal phenotypic expression related to the neoplastic proliferation cannot be formally excluded, it is possible that the cells in this patient may represent the clonal expansion of a normal subpopulation of T-cell lineage NK-related cells frozen at an early stage of differentiation. These features provide arguments for discussing the controversial issue of the ontogeny of NK cells and their relationship to the T-cell lineage.

Molecular and immunological evidence of B-cell commitment in "null" acute lymphoblastic leukaemia

The DNA configuration of the immunoglobulin (Ig) heavy and light chain genes and the expression of B-cell-related markers were evaluated in 13 cases of non-T, non-B, non-common ("null") acute lymphoblastic leukaemia (ALL). A rearrangement of the Ig heavy-chain gene was found in all cases studied; in 5 of these a structural reorganization of the kappa or lambda light chain gene was also demonstrated. Leukaemic cells from 10 of the 13 cases analysed showed one or more B-cell antigens, the expression of which followed a sequential order of presentation (OKB2, B4, BA-1, B1). The B-cell commitment was confirmed by means of a sensitive immunoperoxidase assay which revealed a weak expression of the common ALL (cALL) antigen in 7/10 cases tested, which were all cALL-negative by conventional immunofluorescence techniques. These findings suggest that in "null" ALL the neoplastic cells show molecular and immunological evidence of B-cell differentiation and that most cases may indeed be characterized by "early" cALL with a very low density expression of the cALL antigen. This was further documented in one case in which the expression of the cALL antigen (and of other B-cell markers) could be induced after exposure to 12-O-tetradecanoylphorbol-13-acetate (TPA). The presence in a few cases of myeloid features, particularly when the cALL antigen could not be demonstrated by the immunoperoxidase assay, suggests that the leukaemic process may sometimes involve a very early progenitor cell capable of both lymphoid and myeloid phenotypic differentiation. The heterogeneity of "null" ALL documented by this study may help to explain the variable clinical course and prognosis of these patients.

Immunological typing of acute lymphoblastic leukemia: concurrent analysis by flow cytofluorometry and immunocytology

For 60 cases of acute lymphoblastic leukemia (ALL) immunological typing was done concurrently by the avidin-biotin-peroxidase method using cytocentrifuged smears and by flow cytofluorometry for the study of surface antigens. The use of a large panel of antibodies detecting differentiation antigens allowed us to sub-classify 57/60 cases as 43 B-lineage ALLs and 14 T-lineage ALLs. The two types of ALL can be accurately distinguished by the expression of the antigens recognized by the antibodies of the clusters of differentiation CD19 (B4) and CD7 (Leu 9). Almost perfect agreement was obtained between the results of the two methods for antigens DR, CD10 (cALLA;J5) and CD7. A number of discordances were observed with other antigens [CD19 (B4), CD20 (B1), CD22 (To15), CD1 (T6), CD2 (T11), CD4 (T4), CD8 (T8), CD3 (T3), T9, T10]. In spite of these discordances, the avidin-biotin-peroxidase method can predict the lineage involved in most ALLs with a high degree of reliability. Nevertheless, for weakly expressed surface antigens (such as B4 and B1) the immunocytological method is less sensitive than flow cytofluorometry and can only approximately determine the stage of differentiation of neoplastic cells. Furthermore, the existence of cases which are at the same time negative with flow cytofluorometry and positive with immunocytology is consistent with the intracytoplasmic expression of certain differentiation antigens. Thus in the course of lymphoid differentiation, intra-cytoplasmic expression of T3, To15 and possibly J5 precedes their expression at the cell surface.