Rearrangement of the T cell receptor gamma-chain gene in childhood acute lymphoblastic leukemia

We analyzed rearrangements of the T cell receptor gamma-chain (T gamma) gene as well as rearrangements of the T cell receptor beta-chain (T beta) gene and immunoglobulin heavy-chain (IgH) gene in 68 children with acute lymphoblastic leukemia (ALL). All 15 patients with T cell ALL showed rearrangements of both T beta and T gamma genes. Twenty-four of 53 non-T, non-B ALL patients (45%) showed T gamma gene rearrangements and only 14 of these also showed T beta gene rearrangements. Only a single patient rearranged the T beta gene in the absence of T gamma gene rearrangement. The rearrangement patterns of the T gamma gene in non-T, non-B ALL were quite different from those observed in T cell ALL, as 20 of 23 patients retained at least one germline band of the T gamma gene. In contrast, all T cell ALL patients showed no retention of germline bands. These data indicate that rearrangement of the T gamma gene is not specific for T cell ALL. Further, the results also suggest that T gamma gene rearrangement precedes T beta gene rearrangement. The combined analysis of rearrangement patterns of IgH, T beta, and T gamma genes provides new criteria for defining the cellular origin of leukemic cells and for further delineation of leukemia cell heterogeneity.     

Immunoglobulin and T cell receptor gene configuration in acute lymphoblastic leukemia of infancy

We examined immunoglobulin (Ig) heavy chain, K light chain, and T cell receptor (TCR) gamma and beta gene configuration in the leukemic cells from a series of infants aged less than 1 year with acute lymphoblastic leukemia (ALL). Each of these 11 cases demonstrated leukemic cell surface antigens that have been correlated with a B cell precursor phenotype. Of the 11, lymphoblasts of 4 retained the germline configuration of both Ig and TCR loci, whereas 7 had rearranged the Ig heavy chain gene. Two of these seven showed light chain gene rearrangement. TCB beta chain rearrangement had occurred in only one of the 11 patients' tumors. No TCR gamma chain rearrangements were identified. These results are in contrast to earlier studies of B cell precursor ALL in children in which Ig heavy chain gene rearrangements were evident in every case and approximately 40% showed Ig light chain rearrangement as well. In addition, 45% of cases of B cell precursor ALL of children had rearranged their gamma TCR genes, and 20% had rearranged beta. These data suggest that ALL in infancy represents an earlier stage of B cell development than is found in B cell precursor ALL of children. ALL in the infant age group has been associated with the worst prognosis of all patients with ALL. This study suggests that the disease in infants differs not only clinically, but also at the molecular genetic level, from the disease in children.     

Lineage specific classification of leukaemia: results of the analysis of sixty cases of childhood leukaemia

In addition to conventional morphological, histochemical and immunological marker studies, cells from 60 children with leukaemia were further analysed using the Southern blot hybridization technique to look at differences in the organization of immunoglobulin (Ig) genes. Of the 60 patients studied by conventional means, 47 were diagnosed as acute lymphocytic leukaemia (ALL) and 13 as non-lymphocytic leukaemia. Seven patients were initially classified as T ALL and 40 as non-T, non-B ALL. Further subclassification of the 40 patients with non-T, non-B ALL indicated three pre-B ALL and 29 patients diagnosed as common ALL, expressing Ia and CALLA antigens. All 29 patients with common ALL demonstrated C mu gene rearrangements with or without light chain (kappa and lambda) genes rearrangement. Based on the developmental hierarchy of Ig gene rearrangement, it was possible to further subclassify the patients with common ALL into different stages of B cell development. Eight (of the 40) patients with non-T, non-B ALL were identified as CALLA- but further analysis indicated T-lineage origin in two patients and three patients were reclassified as acute undifferentiated leukaemia (AUL). C mu gene rearrangements were detected in two patients with T ALL, two patients with AUL and one patient with acute myelogenous leukaemia (AML). In contrast to the patients with common ALL, Ig gene rearrangement observed in these non-B-lineage cells was restricted to a single C mu gene while retaining germ-line configuration of the other allele of the C mu gene and both light chain genes.     

Distinct ongoing Ig heavy chain rearrangement processes in childhood B- precursor acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is thought to arise from the clonal expansion of a single transformed precursor cell. However, an oligoclonal Ig heavy chain (IgH) rearrangement pattern has been observed in 30% of ALL patients and was shown to be the result of ongoing rearrangement events. The extent and nature of these ongoing rearrangement processes in individual patients has so far remained obscure. We performed a detailed analysis of leukemic VHDJH rearrangements in three children with B-precursor ALL at diagnosis and one B-lymphoid blast crisis of a child with Ph+ chronic myeloid leukemia at diagnosis and relapse. The children were selected because they presented with multiple IgH rearrangements on Southern blot analysis. Polymerase chain reaction analysis of leukemic cells from two B-precursor ALL patients showed exclusively two groups of related sequences resulting from VH gene replacement events. Most VH gene replacements involved 3' located acceptor VH genes. Analysis of cells from the other B-precursor ALL patient showed exclusively related sequences as a result of VH gene joinings to a pre-existing DJH rearrangement. In the B-lymphoid blast crisis, a single germline precursor cell had generated multiple unrelated rearrangements and additional groups of related rearrangements resulting from VH to DJH joinings. Direct proof for the VH to DJH joining mechanism was obtained by amplification of the expected preexisting DJH rearrangements. Our findings suggest that the pattern of ongoing rearrangements in an individual patient reflects the IgH rearrangement status of the precursor cell at the time of malignant transformation. Sequence analysis of VHDJH rearrangements at diagnosis may therefore allow a prediction of the reliability of complementarity determining region 3 probes for the detection of minimal residual disease.     

Stochastic rearrangement of immunoglobulin variable-region genes in chicken B-cell development.

The molecular mechanism by which immunoglobulin (Ig) gene rearrangement occurs is highly conserved between mammalian and avian species. However, in avian species, an equivalent to the mammalian pre-B cell, which has undergone Ig heavy-chain gene rearrangement and expresses mu heavy chains in the absence of Ig light-chain rearrangement, has not been convincingly demonstrated. It is consequently unclear whether an ordered progression of gene rearrangement events leading to functional Ig expression occurs in avian species. To examine the sequence of Ig gene rearrangement events in chicken B-cell development, we transformed day 12 embryo bursal cells with the REV-T(CSV) retrovirus. More than 100 clones were analyzed by Southern blotting and polymerase chain reaction for the presence of Ig gene rearrangements. The majority of these clones contained only germline Ig sequences. Several clones contained complete heavy- and light-chain rearrangements and 13 clones contained only heavy-chain rearrangements analogous to stages of mammalian B-cell development. However, 5 clones contained rearrangements of light-chain genes in the absence of complete heavy-chain rearrangement. Consequently, we conclude that rearrangement of chicken Ig light-chain genes does not require heavy-chain variable-region rearrangement. This observation suggests that chicken Ig gene rearrangement events required for Ig expression occur stochastically rather than sequentially.     

Biologic and prognostic significance of the presence of more than two mu heavy-chain genes in childhood acute lymphoblastic leukemia of B precursor cell origin

We examined the arrangement of the mu heavy-chain immunoglobulin (Ig) genes in the leukemic blast cell DNA of 93 children with acute lymphoblastic leukemia (ALL). All cases met morphologic and cytochemical criteria for ALL, lacked detectable T cell surface antigens, and expressed HLA-DR (Ia) antigens. Eighty-three of the 93 patients (89%) were positive for the common acute lymphoblastic leukemia antigen (CALLA), and 20 of 91 (22%) tested had detectable cytoplasmic immunoglobulin. As expected, the heavy-chain lg gene was rearranged in all cases, and the pattern of rearrangements was variable; 23 had one allele rearranged and one in the germ line configuration; 15 had one rearranged and one deleted; and 37 had two rearranged. Unexpectedly, in 18 patients the presence of more than two mu gene-hybridizing bands was detected. Combinations of enzymes and heavy-chain gene probes were used to confirm that the extra bands were not the result of underdigestion of the DNA or DNA restriction site polymorphism. In eight of the 18 patients, we identified an extra chromosome 14 as a possible cause of the extra bands' hybridizing to the mu heavy-chain constant-region probe. In the remaining ten patients, the presence of three or four bands hybridizing with the mu probe suggests the presence of two populations of leukemic cells that may have arisen either by separate leukemic transformation events or by clonal evolution of one clone into two related lines. Although preliminary (2-year follow-up), our data suggest that childhood ALL of B lineage with more than two mu heavy-chain genes, but without extra copies of chromosome 14, may be more resistant to therapy.     

Acute mixed lineage leukemia: clinicopathologic correlations and prognostic significance

The frequency and clinical significance of acute leukemia displaying both lymphoid and myeloid characteristics was determined in 123 consecutive children using a panel of lineage-associated markers. The leukemic blasts from 18 of 95 children (19%) with the diagnosis of acute lymphoblastic leukemia (ALL) by standard diagnostic criteria expressed myeloid-associated cell surface antigens. Despite immunological evidence of lymphoid differentiation (17 CALLA + and one T cell-associated antigen +) and findings of immunoglobulin gene rearrangement, blasts from these patients reacted with one to five monoclonal antibodies identifying myeloid-associated cell surface antigens (My-1, MCS.2, Mo1, SJ-D1, or 5F1). Dual staining with microsphere-conjugated antibodies and analysis by flow cytometry confirmed that some blasts were simultaneously expressing lymphoid- and myeloid-associated antigens. Conversely, blasts from seven of 28 patients (25%) with acute nonlymphocytic leukemia (ANLL), diagnosed by otherwise standard morphological and cytochemical criteria, expressed lymphoid-associated surface antigens. Dual staining of individual blasts demonstrated simultaneous expression of myeloperoxidase (MPO) (including Auer rods) in association with either T-11, CALLA, or terminal deoxynucleotidyl transferase. Blasts from one patient with ANLL demonstrated T cell receptor gene rearrangement, while blasts from another patient demonstrated characteristics associated with T (T-11), B (CALLA and heavy-chain immunoglobulin gene rearrangement), and myeloid (MPO) lineage. There were no consistent cytogenetic abnormalities, and no patient demonstrated independent leukemic clones. Each patient with typical ALL, except for myeloid-associated antigens, achieved complete remission with conventional induction therapy for ALL. By contrast, three of the seven children with ANLL whose blasts expressed the T-11 surface antigen failed ANLL induction therapy. These three patients subsequently achieved remission with ALL therapy.     

Ultrastructural demonstration of peroxidase expression in acute unclassified leukemias: correlation to immunophenotype and treatment outcome.

The lineage affinity of 57 cases of acute unclassified leukemias (AUL) was reevaluated by ultrastructural analysis of peroxidase expression (POEM) in combination with immunophenotyping and analysis of immunoglobulin gene configuration. Twenty-three cases of myeloid and three cases of megakaryocytic differentiation were identified by detection of ultrastructural myeloperoxidase (UMPO) and platelet peroxidase (UPPO). No significant correlation was noted between myeloid marker expression and POEM positivity, whereas presence of CD 19 or CD 24 antigen significantly correlated with POEM negativity (P = .001 and .023, respectively). Ig gene rearrangements including oligoclonal patterns were also recorded in 8 of 14 UMPO+ patients tested. Fourteen UMPO+ patients responded poorly to an ALL/AUL chemotherapy regimen with a low complete remission (CR) rate of 29% and a short median remission duration (MRD) of 5 months. The POEM- patients proved very heterogenous with respect to immunophenotype and Ig gene rearrangement. Seventeen of 21 patients tested had Ig gene rearrangements, including oligoclonal patterns. Combined data suggest that a proportion of these cases probably derive from a very immature lymphoid progenitor cell, particularly because 15 POEM- AUL patients showed a response to ALL/AUL chemotherapy comparable to that observed in patients with definitive acute lymphoblastic leukemia (ALL) (CR rate 80%, MRD 20 months). Thus, ultrastructural analysis of peroxidase expression can provide decisive prognostic information in AUL patients.     

Infant leukemia: an analysis of nine Chinese patients

A study was made of the cellular and molecular characteristics of nine Chinese infants, consecutively presenting with acute leukemia. Five cases were acute lymphoblastic leukemia (ALL); four were acute nonlymphoblastic leukemia (ANLL). Hyperleukocytosis, hepatosplenomegaly, and poor response to conventional therapy were common features, and CNS involvement was detected at diagnosis in three cases. The blast cells from all five cases with ALL expressed early B-cell markers, i.e., HLA-DR+, CD19+, but CD10-. Terminal deoxynucleotidyl transferase (TdT) was present in blasts from four of the five cases and periodic acid-Schiff staining in blasts from two patients only. The leukemic cells of one patient also showed positive nonspecific esterase activity and expressed myeloid-associated antigens CD33 (My9), CD11 (OkM1), and CD14 (My4 and Mo2). Molecular analysis of leukemic cell DNA from this and two other patients showed rearrangement of the immunoglobulin (Ig) heavy-chain genes, but without any evidence of kappa light-chain gene rearrangement. T-cell receptor (TCR) genes remained in the germline configuration in these cases. Cytogenetic analysis showed translocation t(4;11) (q21;q23) in all four cases studied. In the group of ANLL, three cases belonged to the M4 and one to the M2 subtype. Chromosomal abnormality involving 11q23 was also detected in two patients: t(11;17)(q23;q11) and del(11)(q14q23) in each case respectively. Neither Ig nor TCR gene rearrangement was present in blast cells from patients with ANLL. The data indicate that chromosomal rearrangement of band 11q23 was quite common in Chinese infants with either form of leukemia, a finding that may have pathogenetic implications.     

Clinical and laboratory characteristics of acute leukemia with the 4;11 translocation

This report describes the clinical and laboratory features of seven cases of acute leukemia associated with the 4;11 chromosomal translocation. All seven children had acute lymphoblastic leukemia by standard morphologic and cytochemical criteria. Leukemic blasts from six of seven patients were terminal deoxynucleotidyl transferase- positive. Immunologic phenotyping suggested the leukemias were of B cell origin; blasts from five patients expressed HLA-DR and p24 (CD-9 antibody), blasts from three patients expressed B4 (CD-19), and blasts from two patients expressed the common acute lymphoblastic leukemia antigen (CD-10). One patient's leukemic blasts contained cytoplasmic immunoglobulin. Analysis of DNA from four of five patients demonstrated additional evidence of B cell differentiation with heavy-chain immunoglobulin gene rearrangement. When DNA from the four patients with heavy-chain immunoglobulin gene rearrangement was analyzed, one patient's DNA demonstrated light-chain immunoglobulin gene rearrangement. However, flow cytometric analysis of blasts from three patients showed the simultaneous expression of the lymphoid-associated antigen B4 (CD-19) and the myeloid-associated antigen My-1 (X-Hapten). Electron microscopic examination of blasts from one patient that expressed both lymphoid- and myeloid-associated antigens demonstrated ultrastructural characteristics of both lineages. These findings suggest that acute leukemia with the t(4;11) abnormality has mixed lineage characteristics as a result of leukemogenesis in a multipotential progenitor cell or aberrant gene expression later in differentiation. Furthermore, serial analysis of karyotype, immunophenotype, and heavy-chain immunoglobulin genes revealed changes in these biologic markers over time, suggesting continued chromosome rearrangement and gene modulation after the leukemogenic event in cells with the t(4;11).     

Rearrangement of immunoglobulin and T cell receptor genes in acute and chronic leukaemias.

The pattern of immunoglobulin (Ig) and T cell receptor (TCR) gene rearrangements was determined in 87 patients with acute and chronic leukaemias and myelodysplastic syndromes by Southern blot hybridisation. All 31 cases of common, B cell and null cell acute lymphoblastic leukaemia, and B cell chronic lymphocytic leukaemia showed Ig heavy chain (JH) rearrangement, and TCR (beta-chain) rearrangement was seen in all 5 cases of T cell acute lymphoblastic leukaemia. Inappropriate JH and TCR (beta) rearrangements were present in some cases of T-ALL (60%) and common acute lymphoblastic leukaemia (18%), respectively. For the 19 patients with acute leukaemias following chronic myeloid leukaemia, blastic transformation, all 4 with lymphoid transformation and 3 of the 15 with myeloid transformation had JH rearrangement, and 3 CD10-positive lymphoid transformation and 2 myeloid transformation had their TCR (beta) genes rearranged. In conclusion, the pattern of Ig and TCR gene rearrangements correlated well with the cell lineage. However, cross-lineage rearrangements were more commonly seen in patients with acute leukaemias following chronic myeloid leukaemia blastic transformation, as compared to the de novo cases.     

Myeloperoxidase gene expression in blast cells with a lymphoid phenotype in cases of acute lymphoblastic leukemia

By using a cDNA clone of the myeloperoxidase (MPO) gene, we have studied, by Northern blot analysis, the level of MPO mRNA in eight cases of acute lymphoblastic leukemia (ALL). The blast cell populations studied were characterized by morphologic, cytochemical, immunochemical, and molecular criteria. With all the methods used the populations were found to be highly homogeneous and showed a typical lymphoid phenotype. In particular, the Ig heavy-chain gene rearrangement was largely prevalent, and the germ line configuration was almost absent. However, in three of eight cases, high levels of MPO mRNA were detected. The remarkable homogeneity of the cell populations examined suggests that the MPO mRNA observed was present in cellular elements certainly identified as lymphoid. The absence of contamination by myeloid cells was confirmed by the results of Western blot analysis of the proteins of the cell population studied: no MPO protein was detectable. The levels of mRNA observed were high enough to be comparable to those observed in a promyelocytic cell population.     

Pre-B cell leukemia responds poorly to treatment: a pediatric oncology group study

Seventy-eight of 362 children with acute lymphocytic leukemia (ALL) had leukemic cells similar in phenotype to normal pre-B cells. When the clinical and laboratory features of patients with pre-B and "null" cell phenotypes of ALL were compared, no significant differences were noted, except that the pre-B cell ALL phenotype had a higher percentage of black children. In contrast, patients with T cell ALL had a higher median age at diagnosis, frequent thymic involvement, and higher WBC counts. Patients with pre-B and "null" cell ALL were treated identically and patients with T cell ALL differently. Although no difference in remission induction rates was noted between patient groups with pre-B and "null" cell ALL, the remissions were of shorter duration for patients with pre-B cell ALL (p = 0.004). Similarly, overt leukemic involvement of both the central nervous system (CNS) and bone marrow was noted sooner in the patient group with pre-B cell ALL. Univariate and multivariate Cox life table regression analyses demonstrate the independent prognostic significance of the pre-B phenotype and illustrate that the prognostic influence of potential relapse risk factors, such as WBC, sex, and age, are specific for leukemia phenotype. These findings may have importance for the design and tailoring of therapy for children with acute leukemia.     

Analysis of Ig and T-cell receptor genes in 40 childhood acute lymphoblastic leukemias at diagnosis and subsequent relapse: implications for the detection of minimal residual disease by polymerase chain reaction analysis

The rearrangement patterns of Ig and T-cell receptor (TcR) genes were studied by Southern blot analysis in 30 precursor B-cell acute lymphoblastic leukemias (B-ALLs) and 10 T-ALLs at diagnosis and subsequent relapse. Eight precursor B-ALLs appeared to contain biclonal/oligoclonal Ig heavy-chain (IgH) gene rearrangements at diagnosis. Differences in rearrangement patterns between diagnosis and relapse were found in 67% (20 cases) of precursor B-ALLs (including all eight biclonal/oligoclonal cases) and 50% (five cases) of T-ALLs. In precursor B-ALLs, especially changes in IgH and/or TcR-delta gene rearrangements were found (17 cases), but also changes in TcR-beta, TcR- gamma, Ig kappa, and/or Ig lambda genes (11 cases) occurred. The changes in T-ALLs concerned the TcR-beta, TcR-gamma, TcR-delta, and/or IgH genes. Two precursor B-ALLs showed completely different Ig and TcR gene rearrangement patterns at relapse, suggesting the absence of a clonal relation between the leukemic cells at diagnosis and relapse and the development of a secondary leukemia. The clonal evolution in the other 23 ALL patients was based on continuing rearrangement processes and selection of subclones. The development of changes in Ig and TcR gene rearrangement patterns was related to remission duration, suggesting an increasing chance of continuing rearrangement processes with time. These immunogenotypic changes at relapse occurred in a hierarchical order, with changes in IgH and TcR-delta genes occurring after only 6 months of remission duration, whereas changes in other Ig and TcR genes were generally detectable after 1 to 2 years of remission duration. The heterogeneity reported here in Ig and/or TcR gene rearrangement patterns at diagnosis and relapse might hamper polymerase chain reaction (PCR)-mediated detection of minimal residual disease (MRD) using junctional regions of rearranged Ig or TcR genes as PCR targets. However, our data also indicate that in 75% to 90% of ALLs, at least one major rearranged IgH, TcR-gamma, or TcR-delta band (allele) remained stable at relapse. We conclude that two or more junctional regions of different genes (IgH, TcR-gamma, and/or TcR-delta) should be monitored during follow-up of ALL patients for MRD detection by use of PCR techniques. Especially in biclonal/oligoclonal precursor B-ALL cases, the monitoring should not be restricted to rearranged IgH genes, but TcR-gamma and/or TcR-delta genes should be monitored as well, because of the extensive changes in IgH gene rearrangement patterns in this ALL subgroup.     

Comparative analysis of Ig and TCR gene rearrangements at diagnosis and at relapse of childhood precursor-B-ALL provides improved strategies for selection of stable PCR targets for monitoring of minimal residual disease

Immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements are excellent patient-specific polymerase chain reaction (PCR) targets for detection of minimal residual disease (MRD) in acute lymphoblastic leukemia (ALL), but they might be unstable during the disease course. Therefore, we performed detailed molecular studies in 96 childhood precursor-B-ALL at diagnosis and at relapse (n = 91) or at presumably secondary acute myeloid leukemia (n = 5). Clonal Ig and TCR targets for MRD detection were identified in 94 patients, with 71% of these targets being preserved at relapse. The best stability was found for IGK-Kde rearrangements (90%), followed by TCRG (75%), IGH (64%), and incomplete TCRD rearrangements (63%). Combined Southern blot and PCR data for IGH, IGK-Kde, and TCRD genes showed significant differences in stability at relapse between monoclonal and oligoclonal rearrangements: 89% versus 40%, respectively. In 38% of patients all MRD-PCR targets were preserved at relapse, and in 40% most of the targets (> or = 50%) were preserved. In 22% of patients most targets (10 cases) or all targets (10 cases) were lost at relapse. The latter 10 cases included 4 patients with secondary acute myeloid leukemia with germline Ig/TCR genes. In 5 other patients additional analyses proved the clonal relationship between both disease stages. Finally, in 1 patient all Ig/TCR gene rearrangements were completely different between diagnosis and relapse, which is suggestive of secondary ALL. Based on the presented data, we propose stepwise strategies for selection of stable PCR targets for MRD monitoring, which should enable successful detection of relapse in most (95%) of childhood precursor-B-ALL.     

Presence of more than two rearranged immunoglobulin heavy-chain genes in adult precursor B-cell acute lymphoblastic leukemia

Summary We examined the configuration of the immunoglobulin genes in the leukemic blast cell DNA of 20 adults with precursor B-cell acute lymphoblastic leukemia (ALL), treated according to the BMFT protocol. Sixteen of 20 (80%) patients expressed HLA-DR antigens and lacked detectable T-cell antigens. Eleven of the 20 patients (55%) were positive for the CD10 antigen and therefore classified as common ALL. Six patients were classified by immunological phenotyping as null-ALL (30%). Three patients (15%) expressed both immature B-cell markers CD19, CD22, or CD24 and myelomonocytic markers CDw65 or CD15, suggesting precursor B-ALL with cross-lineage expression of myeloid markers. In 18 of the 20 patients (90%), rearrangements and/or deletions of the immunoglobulin heavy-chain (IgH) gene locus were found. In none of the patients was a lightchain gene rearrangement observed. Two patients (10%) had a rearrangement of one allele for the J1 gene region of the TCR- gene. In four patients (20%) more than two hybridizing bands for the IgH genes were detected. Two of these four patients with multiple hybridizing bands for the IgH genes had a t (4; 11) translocation. Two of five patients with the t (4; 11) translocation co-expressed both B-cell antigens and the myeloid antigens CD15 or CDw65. No correlation was found between the immunophenotype of the ALL and the arrangement pattern of their IgH genes. Kaplan-Meier plot analysis revealed no significant difference between adult precursor B-ALL patients with monoclonal or oligoclonal IgH gene rearrangements and their disease-free survival rates.This work was supported by theDeutsche Forschungsgemeinschaft (Grant Ga 333/1-3).     

Presence of N regions in the clonotypic DJ rearrangements of the immunoglobulin heavy-chain genes indicates an exquisitely short latency in t(4;11)-positive infant acute lymphoblastic leukemia

Childhood acute lymphoblastic leukemia (ALL) is frequently initiated in utero at a time of developmentally regulated insertion of N regions into the DJ(H) rearrangements of immunoglobulin heavy-chain (Ig(H)) genes. Here it is shown that N regions are present in the clonotypic DJ(H) rearrangements in 11 of 12 infant ALLs with t(4;11). These data are compared with the 122 previously published DJ(H) sequences and were found to have a pattern similar to that of ALL in children older than 3 years at diagnosis but were unlike that in children younger than 3 years who predominantly lack N regions. These findings, therefore, indicate that t(4;11)-positive infant ALL is initiated later in fetal development than most B-cell precursor ALL from children younger than 3 years and that they have a shorter latency period already in utero.     

Clonal evolution as judged by immunoglobulin heavy chain gene rearrangements in relapsing precursor-B acute lymphoblastic leukemia.

Oligoclonality and ongoing clonal evolution are common features in patients with precursor-B (pre-B) acute lymphoblastic leukemia (ALL), as judged by immunoglobulin heavy chain (IgH) gene rearrangement analysis. These features are considered to be results of secondary rearrangements after malignant transformation or emergence of new tumor clones. In the present study we analyzed the IgH gene rearrangement status in 18 cases with relapsing pre-B ALL using variable heavy chain (V(H)) gene family specific polymerase chain reaction (PCR) amplification and single stranded conformation polymorphism (SSCP) analysis. Clonal IgH rearrangements were displayed in all leukemias but one, and altered rearrangement patterns occurred in five cases (29%), which were selected for detailed nucleotide sequence analysis. In one case, multiple subclones at diagnosis were suggested to be derived from a progenitor clone through joining of different V(H) germline gene segments to a pre-existing D-J(H) complex (V(H) to D-J(H) joining). Evidence for V(H) gene replacement with identical N-sequences at the V(H)-D junction and a common D-J(H) region was observed in one case. Diversification at the V(H)-D junction consisting of heterogeneous N-sequences were observed in one case. This molecular modification of the V(H)-D region could fit a hypothesized "open-and-shut" mechanism. Nevertheless, despite these ongoing events at least one IgH rearrangement remained unchanged throughout the disease in most patients, indicating that the immunoglobulin heavy chain locus can be a suitable marker for detection of minimal residual disease (MRD).