F. Lampert

Cloning and characterization of AFX, the gene that fuses to MLL in acute leukemias with a t(X;11)(q13;q23).

We report the cloning and characterization of the entire AFX gene which fuses to MLL in acute leukemias with a t(X;11)(q13;q23). AFX consists of two exons and encodes for a protein of 501 amino acids. We found that normal B- and T-cells contain similar levels of AFX mRNA and that both the MLL/AFX as well as the AFX/MLL fusion transcripts are present in the cell line and the ANLL sample with a t(X;11)(q13;q23). The single intron of the AFX gene consists of 3706 nucleotides. It contains five simple sequence repeats with lengths of at least 12 bps, a chi-like octamer sequence (GCA/TGGA/TGG) and several immunoglobulin heptamer-like sequences (GATAGTG) that are distributed throughout the entire AFX intron sequence. In the KARPAS 45 cell line the breakpoints occur at nucleotides 2913/2914 of the AFX intron and at nucleotides 4900/4901 of the breakpoint cluster region of the MLL gene. The AFX protein belongs to the forkhead protein family. It is highly homologous to the human FKHR protein, the gene of which is disrupted by the t(2;13)(q35;q14), a chromosome rearrangement characteristic of alveolar rhabdomyosarcomas. It is noteworthy that the t(X;11)(q13;q23) in the KARPAS 45 cell line and in one acute nonlymphoblastic leukemia (ANLL) disrupts the forkhead domain of the AFX protein exactly at the same amino acids as does the t(2;13)(q35;q14) in case of the FKHR protein. In addition, the 5′-part of the AFX protein contains a conserved hexapeptide motif (QIYEWM) that is homologous to the functionally important conserved hexapeptide QIYPWM upstream of the homeobox domain in Hox proteins. This motif mediates the co-operative DNA binding of Pbx family members and Hox proteins and, therefore, plays an important role in physiologic and oncogenic processes. In acute leukemias with a t(X;11)(q13;q23), this hexapeptide motif is separated from the remaining forkhead domain within the AFX protein. The predicted amino acid sequence of AFX differs significantly from the partial AFX protein sequence published previously (Genes, Chromosomes and Cancer, 1994, 11, 79 – 84). This discrepancy can be explained by the occurrence of two sequencing errors in the earlier work at nucleotide number 783 and 844 (loss of a cytosine residue or guanosine residue, respectively) that lead to two reading frame shifts.

A DNA damage repair mechanism is involved in the origin of chromosomal translocations t(4;11) in primary leukemic cells

Some chromosomal translocations involved in the origin of leukemias and lymphomas are due to malfunctions of the recombinatorial machinery of immunoglobulin and T-cell receptor-genes. This mechanism has also been proposed for translocations t(4;11)(q21;q23), which are regularly associated with acute pro-B cell leukemias in early childhood. Here, reciprocal chromosomal breakpoints in primary biopsy material of fourteen t(4;11)-leukemia patients were analysed. In all cases, duplications, deletions and inversions of less than a few hundred nucleotides indicative of malfunctioning DNA repair mechanisms were observed. We concluded that these translocation events were initiated by several DNA strand breaks on both participating chromosomes and subsequent DNA repair by ‘error-prone-repair’ mechanisms, but not by the action of recombinases of the immune system.

Comparative genomic hybridization (CGH) analysis of neuroblastomas--an important methodological approach in paediatric tumour pathology.

Comparative genomic hybridization (CGH) was applied to 35 neuroblastomas to obtain a global view of genetic imbalances. Results were validated by means of Southern blot hybridization (detection of N‐myc amplification), loss of heterozygosity (LOH) studies (detection of deletion 1p), and interphase cytogenetics [dual labelling fluorescence in situ hybridization (FISH) of centromeric 17 and erbB‐2]. CGH allowed sensitive detection of N‐myc amplification and chromosome 1p deletion, representing the most established prognostic markers of neuroblastoma. In addition, a high rate of chromosome 17 aberrations (63 per cent) with possible prognostic relevance was observed. Previously unreported high level copy number increases indicating oncogene amplification were mapped to chromosome subbands 2p13–14 and 3q24–26. Other recurrent regional chromosomal aberrations were localized on 11q, 12q, 13q, 14q, and 15q. CGH results were fully consistent with data of Southern blot analysis and LOH study, as well as interphase cytogenetics. These results show that CGH is a sensitive method for the detection of all prognostically relevant genetic alterations in neuroblastomas; that CGH considerably simplifies the detection of these alterations, resulting in a single methodological approach; and that CGH is a powerful tool to elucidate previously unknown genetic changes in neuroblastomas.

Down’s syndrome in childhood acute lymphoblastic leukemia: clinical characteristics and treatment outcome in four consecutive BFM trials

Clinical characteristics, treatment response and outcome were evaluated in children with Down’s syndrome (DS) and acute lymphoblastic leukemia (ALL) as compared to other children with ALL (NDS). Sixty-one DS and 4049 NDS patients, receiving intensive antileukemic treatment during four consecutive trials (ALL-BFM 81, 83, 86 and 90) of the Berlin–Frankfurt–Münster Group (BFM), were retrospectively analyzed. DS and NDS children did not differ with respect to sex, leukocyte count, CNS leukemia and cytogenetic translocations. The DS cohort was slightly older (P = 0.04), presented predominantly with the common while lacking the T immunophenotype (P = 0.005), had a lower frequency of hyperdiploidy (P = 0.004) and tended to have a better initial steroid response (P = 0.057). Therapy-associated morbidity especially during high-dose methotrexate and a subsequent need for treatment modification occurred in 43% of all DS patients. Event-free survival (EFS) was slightly worse in children with DS (58 ± 8% vs 70 ± 1%, P = 0.14), mainly due to rather late bone marrow recurrences. However, EFS in DS patients was comparable to the NDS group once they either received treatment with no major modifications (65 ± 9% vs 70 ± 1%, P = 0.66) or were <6 years of age, irrespectively of therapy modifications (73 ± 9% vs 74 ± 1%, P = 0.7). Cox regression analysis revealed that DS was an adverse prognostic factor for patients having completed therapy (P = 0.0107), but was not prognostic at diagnosis (P = 0.103). Age ⩾6 years, suboptimal treatment and infectious problems contributed to the slight inferior EFS in children with ALL and Down’s syndrome. Therefore, most of these patients can be successfully treated if receiving intensive antileukemic treatment with no major modifications, but they require more sophisticated management of toxicity.

Multicentre analysis of patterns of DNA gains and losses in 204 neuroblastoma tumors: how many genetic subgroups are there?

PROCEDURE Analysis of comparative genomic hybridization (CGH) data of 120 tumors from four different studies, and data of 84 previously unpublishied tumors, allowed delineation of at least six different genetic subsets of neuroblastomas. RESULTS AND CONCLUSIONS A small number of tumors show no detectable imballances. A second group of tumors presents with gains and losses of whole chromosomes and is found predominantly in prognostically favorable stage 1 and 2 tumors. The remaining groups are characterized by the presence of partial chromosome imbalances, and are found mostly in stage 3, 4, and 4S tumors. The third group shows 17q gain without 11q loss, 1p loss, or MYCN amplification (MNA). The fourth group has 1p deletion or MNA, and finally, a fifth group shows 11q loss without 1p deletion or MNA, and is found mainly in stage 4 tumors. The latter group is significantly associated with losses of 3p, 4p, and 14q.

Treatment of childhood idiopathic thrombocytopenic purpura with Rhesus antibodies (anti-D).

We have recently reported that a rise of platelet numbers in ITP can be induced by blockade of the RES with antibody-coated red blood cells. We now present a collaborative study in which 15 Rhesus-positive children with ITP (nine boys and six girls aged 1–15 years) were treated with low-dose anti-D. Ten patients had chronic ITP (duration 6–47 months), five had acute ITP. Doses of 28–50 μg anti-D/kg bodyweight per course were given intravenously. In all patients clinical signs of bleeding ceased and platelet counts were elevated. An excellent, good or fair response with platelet increments of >100, 50–100, or 20–50×109/l, respectively, was observed in 19, 7, and 12 out of 45 courses in chronic ITP, and in 4, 1, and 2 out of 8 courses in acute ITP. The platelet increase (>40×109/l) persisted for 10 to over 360 days in chronic ITP. There were no untoward side reactions. Haemoglobin values remained stable in all patients but laboratory signs of mild, compensated haemolysis ensued. The direct antiglobulin test became positive in all cases due to anti-D IgG. Previous therapy of patients with chronic ITP included high-dose immunoglobulins and prednisone. These regimens were both effective but remissions were short. We conclude that anti-D therapy is an effective and safe form of treatment in childhood ITP.

Trisomy 21 is a recurrent secondary aberration in childhood acute lymphoblastic leukemia with TEL/AML1 gene fusion.

TEL/AML1 gene fusion is the most frequent genetic lesion in pediatric acute lymphoblastic leukemia (ALL). It occurs as a consequence of the cryptic chromosomal translocation t(12;21)(p13;q22). In a cohort of 50 RT‐PCR–positive TEL/AML1 patients, karyotype examination by GTG banding and fluorescence in situ hybridization (FISH) allowed us to identify chromosome anomalies in addition to the already existing t(12;21). Secondary aberrations were found in 29 out of 41 patients (71%) at initial diagnosis and in all 9 patients with relapse. Structural rearrangements affected chromosome arms 2p, 2q, 5q, 9p, 12p (n = 2), 6q, 11p (n = 3), and 21q (n = 4). An extra chromosome 21 was found to be the most frequent anomaly. It was detected in 6 out of 41 patients at initial diagnosis (15%) and in 7 out of the 9 patients at relapse. No karyotype with trisomy 21 exceeded 47 chromosomes. Gain of chromosome 21 was the sole anomaly in GTG‐banding analysis in 2/41 patients at initial diagnosis and in 4/9 at relapse. Notably, chromosome painting analysis performed in 11 out of the 13 patients with an extra chromosome 21 revealed duplication of the normal chromosome 21 in 8, and duplication of der(21)t(12;21) in 3 patients. Furthermore, gain of der(21)t(12;21) chromosome was confined exclusively to the relapse patients. Genes Chromosomes Cancer 24:272–277, 1999.

Comparison of DNA aneuploidy, chromosome 1 abnormalities, MYCN amplification and CD44 expression as prognostic factors in Neuroblastoma

A comparison of the prognostic impact of five molecular variables in a large series was made, including tests of their nonrandom association and multivariate analysis. Molecular data were available for 377 patients and MYCN amplification, cytogenetic chromosome 1p deletion, loss of chromosome 1p heterozygosity, DNA ploidy and CD44 expression were investigated. Their interdependence and influence on event-free survival was tested uni- and multivariately using Pearsons chi 2-test, Kaplan-Meier estimates, log rank tests and the Coxs regression model. MYCN amplification was present in 18% (58/322) of cases and predicted poorer prognosis in localised (P < 0.001), metastatic (P = 0.002) and even 4S (P = 0.040) disease. CD44 expression was found in 86% (127/148) of cases, and was a marker for favourable outcome in patients with neuroblastoma stages 1-3 (P = 0.003) and 4 (P = 0.017). Chromosome 1p deletion was cytogenetically detected in 51% (28/55), and indicated reduced event-free survival in localised neuroblastoma (P = 0.020). DNA ploidy and loss of heterozygosity on chromosome 1p were of less prognostic value. Most factors of prognostic significance were associated with each other. By multivariate analysis, MYCN was selected as the only relevant factor. Risk estimation of high discriminating power is, therefore, possible for patients with localised and metastatic neuroblastoma using stage and MYCN.

Tumour karyotype may be important in the prognosis of human neuroblastoma.

SummaryWhen comparing clinical and tumour cytogenetic data on 14 neuroblastoma patients in different stages of disease we found a high incidence of 1p abnormalities (12/12), homogeneously staining regions/double minutes (9/12) and 2p abnormalities (4/12) in 12 unresectable and metastatic tumours (clinical stages III and IV). In contrast, these features were absent in clinical stage II tumours (2/2) with good prognosis. The coincidence of 1p aberrations with poor outcome of disease will be discussed.

Detection of a hepatitis B virus variant with a truncated X gene and enhancer II.

SummaryApproximately 15% of the viral genomes in the serum of a hepatitis B carrier were found to exhibit an 8 base-pair deletion within the enhancer II element, which would truncate the X protein by 26 amino acids at the carboxy-terminus.