The translocation t(8;16)(p11;p13) of acute myeloid leukaemia fuses a putative acetyltransferase to the CREB-binding protein.

The recurrent translocation t(8;16)(p11;p13) is a cytogenetic hallmark for the M4/M5 subtype of acute myeloid leukaemia. Here we identify the breakpoint-associated genes. Positional cloning on chromosome 16 implicates the CREB-binding protein (CBP), a transcriptional adaptor/coactivator protein. At the chromosome 8 breakpoint we identify a novel gene, MOZ, which encodes a 2,004-amino-acid protein characterized by two C4HC3 zinc fingers and a single C2HC zinc finger in conjunction with a putative acetyltransferase signature. In-frame MOZ-CBP fusion transcripts combine the MOZ finger motifs and putative acetyltransferase domain with a largely intact CBP. We suggest that MOZ may represent a chromatin-associated acetyltransferase, and raise the possibility that a dominant MOZ-CBP fusion protein could mediate leukaemogenesis via aberrant chromatin acetylation.

Hematologic malignancies with t(4;11)(q21;q23)--a cytogenetic, morphologic, immunophenotypic and clinical study of 183 cases. European 11q23 Workshop participants.

A total of 183 hematologic malignancies with t(4;11)(q21;q23), including five variant translocations, were collected by the Workshop. Clinical, morphologic and immunophenotypic features were compiled, and karyotypes with variant t(4;11) or secondary chromosomal aberrations were reviewed. All cases were acute leukemias (AL): 173 acute lymphoblastic leukemias (ALL), six acute myeloid leukemias (AML), three unclassifiable AL, and one biphenotypic AL. Ten patients had treatment-associated AL. Females were overrepresented (104 vs 79) and the age distribution was clearly nonrandom; 34% of the cases occurred in infants below the age of 12 months. The remaining AL were evenly distributed among the other age groups, with the oldest patient being 79 years old. An increased white blood cell count (WBC) was reported in more than 90% of the cases, with hyperleukocytosis (> or =100 x 10(9)/l) in 64%. Additional chromosomal changes were detected in 55 (30%) cases, most often gain of the X chromosome, i(7)(q10), and trisomy 8, with frequent breakpoints in 1p36, 1q21, 7q10, 11p15, 12p13, 17p11, and 17p10. All recurrent secondary changes resulted in genomic imbalances, in particular gains of 1q, 7q, 8, and X and losses of 7p and 17p. Event-free and overall survival (EFS and OS) could be ascertained in 170 and 171 patients, respectively. Kaplan-Meier estimates of EFS and OS showed no differences with regard to gender, WBC, or presence of secondary chromosomal abnormalities, and there was no increase of EFS or OS among the 55 cases that had undergone bone marrow transplantation. However, age had an important prognostic impact, with significantly (P < 0.0001) longer EFS and OS in children 2-9 years old than among infants and younger children, patients aged between 10 and 39 years and older adults.

Chromosomes in childhood acute lymphoblastic leukaemia: karyotypic patterns in disease subtypes.

To define further the clinical importance of cytogenetic analysis in acute lymphoblastic leukaemia (ALL) a prospective study was performed on 139 unselected children. Analyses were considered adequate in 104, of whom 35 were normal and 69 had clonal abnormalities. Abnormalities were categorised according to banded chromosome analysis as well as chromosome count. Karyotypes were correlated with clinical and laboratory features at diagnosis and with survival. Of the successful analyses, thirty five (34%) children had no abnormalities; this group contained an excess of T cell disease. Twenty five (24%) had a "characteristic" hyperdiploid karyotype and as a group had lower presenting white counts, a tendency to CD10, and periodic acid schiff positivity of the blast cells and smaller spleens. None was an infant and only one was over 10 years old. Seven (7%) children with t(9; 22), t(8; 14), or t(4; 11) translocations were grouped together as "specific" translocations. Collectively they had a significantly worse prognosis than the remainder. Nine children developed central nervous system relapse, six of whom had either t(4; 11) or abnormalities of 9p or 19p. A descriptive classification taking into account chromosome bonding pattern is cytogenetically more appropriate and may be more clinically useful than grouping children simply by chromosome number. As knowledge and techniques improve, the classification of cytogenetic abnormalities in ALL will need to be kept under frequent review.

Acute monocytic leukemia with a novel 10;11 rearrangement resolved by fluorescence in situ hybridization.

Fluorescence in situ hybridization analysis in an adult with acute monocytic leukemia revealed the complex nature of a rearrangement between chromosomes 10 and 11, which resulted in disruption of the MLL gene. Using a combination of chromosome 10 and 11 paints, a 10 centromere-specific sequence, and a probe for the MLL locus at 11q23, the rearrangement was deduced to have involved a reciprocal translocation between chromosomes 10 and 11, followed by an inversion within the short arm of the derivative 10. To our knowledge, this novel rearrangement has not been described previously.

Nonendemic Burkitt's lymphoma with complex chromosome abnormalities involving chromosomes 2 and 8.

A long surviving patient with nonendemic Burkitt's lymphoma and complex cytogenetic findings is presented. Chromosome abnormalities were seen as a minor clone in peripheral blood and were considered consistent with the t(2;8)(p12;q24) variant. The karyotype was 47,XY, -2, -8, + der2(8qter-8q24::2p12-2qter), + der8(8pter-8q23::2p12-2pter) + der8(8qter-8cen::1q21-1qter). This case illustrates the value of extensive chromosome analysis in hematologic disorders and, at the time of writing, is the first example in Britain of the t(2;8) variant in Burkitt's lymphoma.

Methotrexate and bone marrow metaphases.

The efficacy of a methotrexate (MTX) block/thymidine release synchronization technique has been assessed in bone marrow cultures from patients with acute nonlymphocytic leukemia and myelodysplasia. In contrast to cultures of stimulated lymphocytes from normal individuals, no improvement in mitotic index (MI) or metaphase quality could be detected using this technique. Demonstration of an unchanged level of division in bone marrow cultures in the presence of MTX suggests that the technique is unsuitable for synchronization purposes in this tissue. The influence of preincubation prior to MTX exposure and duration of exposure to colcemid on MI and metaphase quality have also been examined.

Value of cytogenetic studies in prediction of acute phase CML.

Twenty-five patients with Ph CML who eventually developed a blast crisis were karyotyped at regular intervals in order to correlate the evolution of abnormal clones with clinical changes. Persistent new clones appeared in the chronic phase, prior to either transition or transformation, or in the acute phase (the latter, particularly, where transformation was slow). In many patients, chromosome changes accumulated within a single abnormal clone as the disease progressed. In others, particularly where the simple Ph cell line was slow to be supplanted, new clones appeared from the remaining Ph cells at the time of transformation, perhaps reflecting the inability of certain chromosome abnormalities to coexist. We suggest that the occurrence of additional chromosome abnormalities is not reliable evidence of acute transformation, but that the nature and subsequent behavior of abnormal clones may provide more valuable indications.

Trisomy 15 associated with loss of the Y chromosome in bone marrow: a possible new aging effect.

Trisomy 15 as a single autosomal abnormality is a rare finding in hematological disorders and has not as yet been associated with any specific disease type. We report 20 cases of trisomy 15 observed in the bone marrow of patients referred for a suspected hematological malignancy. Most patients were elderly, and a marked male predominance was evident. Aneuploidy for the Y chromosome was observed in addition to +15 in 11 out of 15 male patients. A myelodysplastic disorder (MDS) was confirmed in six cases, and acute myeloid leukemia (AML) in one. There was no evidence of malignant hematological diseases in the remaining 13 patients. We propose that there may be an association between loss of the Y chromosome and trisomy 15 and that trisomy 15, like missing Y, may not always be a marker of malignancy, but may reflect an underlying age effect. The possibility that its presence may herald the development of a malignant condition cannot, however, be excluded.

Consistent fusion of MOZ and TIF2 in AML with inv(8)(p11q13).

We have recently cloned the inv(8)(p11q13) in a patient with acute myeloid leukemia (AML), and demonstrated a fusion between the MOZ and TIF2 genes at 8p11 and 8q13, respectively. We have partially characterized a further case of AML with the same karyotypic abnormality. Rearrangements were detected by Southern blotting with a TIF2 probe that was close to the breakpoint in the original inv(8) case and with a MOZ probe corresponding to the breakpoint cluster region in the t(8;16) (p11;p13). These findings indicate the existence of breakpoint cluster regions within both genes and demonstrate that the MOZ-TIF2 fusion is consistently associated with the inv(8)(p11q13).

Chromosome studies in eleven colorectal tumors.

Cytogenetic analysis is presented on seven freshly derived colorectal tumors and four established cell lines (SW 742, SW 480, SW 948, and HT 29). No chromosome change was common to all tumors, although previous nonrandom findings were confirmed. Single chromosome abnormalities were identified in two cases, 47,XX,+i(7p) and 46,XX,-17,+der(17),t(17;?)(p;?), and their relevance to tumor origin and development is discussed. The association of i(8q) with tumors of the rectosigmoidal region is confirmed, and it is suggested that other rearrangements involving loss of 8p may have the same association. Abnormalities resulting in loss of 20p and duplication of 20q, not previously reported as a nonrandom change, were seen in seven out of 11 cases.

Acute lymphoblastic transformation of essential thrombocythaemia.

Essential thrombocythaemia is a myeloproliferative disorder which may transform to acute myeloid leukaemia, especially following therapy with alkylating agents or radioactive phosphorus. We describe the rare occurrence of acute lymphoblastic leukaemia transformation in a patient with known essential thrombocythaemia.

Significance of non-standard Philadelphia chromosomes in chronic granulocytic leukaemia.

One hundred and nineteen unselected and similarly treated patients with Ph1-positive chronic granulocytic leukaemia (CGL) had the precise nature of their chromosome rearrangements producing the Ph1 studied to determine whether this had any clinical relevance. Eighteen (15%) did not have the usual 9/22 translocation and these, by life-table analysis, had a significantly shorter benign phase of their disease than the others (P less than 0.01). It further appeared that possession of a non-standard Ph1 was related to age, in that whereas only 24 patients were over 60 at diagnosis, 9 (33%) had a non-9/22 translocation (P less than 0.01). As the duration of the benign phase seemed to be shorter in those over 60 irrespective of Ph1 type (P less than 0.01), the questions arose whether non-standard PhI chromosomes were simply occurring in older patients or whether they were affecting prognosis independently. Their independent effect was suggested by the 11 patients under 60 with a non-9/22 Ph1 who still had a significantly shorter benign phase than the 84 of similar age with a standard Ph1 (P less than 0.01). It is concluded that the myeloid karyotype can provide prognostic as well as diagnostic information in patients with CGL.

Fluorescence in situ hybridization analysis of 25 cases of idiopathic myelofibrosis and two cases of secondary myelofibrosis: monoallelic loss of RB1, D13S319 and D13S25 loci associated with cytogenetic deletion and translocation involving 13q14.

To identify a commonly deleted region of 13q14 in idiopathic myelofibrosis (IMF), we used fluorescence in situ hybridization analysis to test for deletion of the RB1 and BRCA2 genes, and the microsatellite loci D13S319 and D13S25, in a series of 25 patients. A further two patients with myelofibrosis secondary to polycythaemia vera and essential thrombocythaemia with reciprocal 13q translocations were studied in an attempt to further define the CDR. Twenty out of 21 patients with a cytogenetically normal chromosome 13 failed to show allelic loss with any of the four probes. In contrast, all four cases with cytogenetic deletion of 13q14 and both cases with 13q translocations involving 13q14 exhibited loss of RB1, D13S319 and D13S25. Loss of the BRCA2 locus was present in a single case only. Our results indicate that cryptic deletions of the 13q14 in myelofibrosis are rare. In addition, the genetic loss associated with cytogenetic 13q14 deletions or reciprocal translocations involving 13q14 is large and encompasses the gene-rich region around RB1, D13S319 and D13S25.

Myeloid karyotype and the malignant phase of chronic granulocytic leukaemia.

During the course of a 30 month study period, 26 patients with typical chronic granulocytic leukaemia (CGL) developed karyotype abnormalities in addition to the Philadelphia (Ph1) chromosome. All cases had received at least 14 months continuous low dose busulphan, and the chromosome changes were found before clinical transformation in six patients and at the time this occurred in 20. Survival following the discovery of these additional abnormalities was short, with a median of 11 weeks for the whole group. Trisomy 8 was the commonest additional chromosome abnormality, but no one karyotype change was clearly associated with shorter survival than another. 23 of the 26 have died as a direct result of their disease, forming part of a total of 40 deaths from typical CGL encountered during the study period where karyotype analyses were performed during the terminal stages of disease. Of these 40, only two (5%) patients showed no chromosome abnormalities extra to the Ph1 prior to death. (The 17 non-study patients who died were similar in all respects to the 23 from the study group, but had no prior chromosome studies performed during the chronic phase of the disease.) It is suggested that an expanding aneuploid or pseudodiploid clone arising from the leukaemic cells during the benign phase of CGL can be used to mark the sometimes ill-defined onset of the malignant phase in all but a small proportion of cases.

Cytogenetically cryptic AML1-ETO and CBF beta-MYH11 gene rearrangements: incidence in 412 cases of acute myeloid leukaemia.

The rearrangements t(8;21)(q22;22) and inv(16)(p13q22) are two of the most frequently seen in acute myeloid leukaemia (AML), accounting for 8% and 4% of cases respectively. Detection of these abnormalities is important for disease management as both are associated with good responses to conventional chemotherapy and prolonged disease-free survival. Recent reports using reverse transcriptase polymerase chain reaction (RT-PCR) suggest that significant proportions of AML cases without a visible t(8;21) or inv(16) show expression of an abnormal fusion gene transcript and, consequently, they could not be detected using conventional cytogenetic analysis alone. We present here a four centre study involving 412 cases of AML screened using both standard cytogenetics and RT-PCR for AML1-ETO and CBF beta-MYH11. We detected a cytogenetic t(8;21) in 31 out of 412 (7.5%) cases and an inv(16) or t(16;16) variant in 27 out of 412 (6.6%) cases. RT-PCR detected only two cases (0.5%) of cryptic t(8;21) and no instances of cryptic inv(16). Both cryptic t(8;21) cases had the classic M2 FAB morphology for this type of disease. Our data concur with the established FAB type distribution of the rearrangements and indicate that cryptic t(8;21) and inv(16) may be much less frequent than reported elsewhere.