Monosomy 7 and multipotential stem cell transformation

Monosomy 7 as the sole abnormality of an acute basophilic leukemia

We report the case of a 72-year-old man who had the very rare disease acute basophilic leukemia with the sole chromosomal finding of a monosomy 7. Most nuclear cells in the peripheral blood and bone marrow samples were either basophils or blasts. The blasts showed negative reaction with myeloperoxidase, periodic acid Schiff, chloroacetate esterase, alpha-naphthyl butyrate esterase, acid phosphatase, and Sudan black B. Metachromatic features of the blasts, however, were observed with toluidine blue stain. Electron microscopic evaluation showed the typical ultrastructure, with basophil and immature mast cell granules. Cytogenetic study revealed monosomy 7 in all metaphase cells, and this finding was confirmed by fluorescence in situ hybridization. The Philadelphia chromosome was absent. Review of the literature revealed abnormalities in cases of ABL. To our knowledge, the case reported here is the first to have basophilic leukemia with monosomy 7 as the only chromosome abnormality.

Myelodysplastic syndrome with monosomy 7 after immunosuppressive therapy in Behçet's disease

Only few cases of Behçet's and hematological malignancies have been reported until now. We recently observed a 39-year-old female patient with Behçet's disease developing a myelodysplastic syndrome (MDS) FAB subtype refractory anemia with excess of blasts in transformation [RAEB-t] with a monosomy 7 after being treated with cyclosporin A and chlorambucil for several years. This case is reported and the occurrence of hematological malignancies and Behçet's disease is reviewed.

Lineage switch in childhood leukemia with monosomy 7 and reverse of lineage switch in severe combined immunodeficient mice

Morphophenotypic lineage switches occur in a small percentage of those with acute leukemia, and the underlying mechanisms are not clear. In this study, we attempted to induce a lineage switch in acute myelocytic leukemia (AML) with monosomy 7, whose lineage had switched from acute T-lymphocytic leukemia (T-ALL) during chemotherapy, in severe combined immunodeficient (SCID) mice. Although the transplanted myeloid cells were engrafted in SCID mice without cytokine administration, T-ALL developed in SCID mice treated with recombinant human granulocyte-macrophage colony-stimulating factor or recombinant human interleukin 3. Analysis of the nucleotide sequences of the rearranged T-cell receptor gamma-chain (TCR-gamma) gene revealed that this lineage switch resulted from the selection of the T-lineage subclone in SCID mice, which had expanded at onset. In addition, we found that the T-lineage and myeloid cells belonged to the distinct subclones, which were different in TCR-gamma gene rearrangements, but were derived from a common clone with an identical N-ras gene mutation for both subclones. In in vitro cultures, only the myeloid subclone grew; the T-lineage subclone failed to grow even in the presence of recombinant human granulocyte-macrophage colony-stimulating factor or recombinant human interleukin 3. These results suggested that the initial diagnostic T-lymphoid subclone, whose growth was dependent on these cytokines and the hematopoietic microenvironment, emerged from a bipotential T-lymphoid/myeloid leukemic stem cell, and further genetic event(s) induced the myeloid subclone, which grew independently of these cytokines and the microenvironment.

Childhood myeloproliferative disorders

Disorders classified as paediatric myeloproliferative disorders (MPD), such as juvenile chronic myeloid leukaemia (JCML), and as paediatric myelodysplastic syndrome (MDS), are essentially diseases characterized by abnormal myeloproliferation and they share similar genetic events on chromosome 7. As such, the abnormalities of increased myeloproliferation in childhood (AIMC) should be considered under the same heading. Constitutional and other genetic factors play an essential role in children and include the NF1 gene, whereas toxic exposure is of greater importance in adults. The most common cytogenetic alteration is that of monosomy or deletion of the long arm of chromosome 7. Critical regions have been identified and mapped by fluorescence in situ hybridization (FISH). It appears that the similar critical regions on chromosome 7 are involved, and suggests that these regions may contain genes important in the pathogenesis of AIMC.

Establishment of a novel human myeloid leukaemia cell line (FKH-1) with t(6;9)(p23;q34) and the expression of dek-can chimaeric transcript

Translocation t(6:9)(p23;q34), resulting in a dek-can gene fusion, is a recurrent chromosomal abnormality mainly associated with specific subtypes of acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS). Patients with this type of chromosomal change are usually young and their prognosis is poor. The role of fusion protein generated from dek-can chimaeric transcript on the leukaemogenesis oft(6;9) AML or MDS is as yet unknown. We have established the first permanent cell line (FKH-1) with t(6;9). derived from the peripheral blood of a patient with t(6:9) AML transformed from Philadelphia chromosome (Ph1)-negative chronic myelocytic leukaemia (CML). The FKH-1 expressed myelomonocytic markers and dek-can chimaeric transcript. In the presence of 10 ng/ml recombinant human granulocyte colony-stimulating factor (G-CSF), the cells doubled every 54 h and showed multilineage myeloid differentiation, resulting in heterogenous morphologies such as macrophages, basophils, eosinophils and neutrophils. Thus, this cell line may be derived from a pluripotent myeloid stem cell and should be a useful tool for biomolecular studies on the pathogenesis of t(6;9) myeloid malignancies which have rarely been investigated because of the lack of continuously proliferating cells.

Constitutional inversion of chromosome 7 and hematologic cancers

Nonrandom aberrations of chromosome 7 have been described in various hematopoietic disorders. We describe here two unrelated families with the same constitutional inversion of chromosome 7 [inv(7)(q11.2q22)]. The probands in both families had acute leukemia and cytogenetic analysis revealed that the inversion was the sole cytogenetic abnormality in the bone marrow at diagnosis. There is a history of hematologic diseases in one of these families that included a son who is a carrier of this constitutional inversion. The distal inversion breakpoint lies within the common region of chromosome loss identified in some myeloid diseases. These observations raise the possibility that this inherited chromosome rearrangement could result in a mutation of a tumor suppressor gene and possibly represent a predisposing event for the development of leukemia in these individuals.

Monosomy 7 and 7q--associated with myeloid malignancy

An association between the complete or partial loss of chromosome 7 and preleukaemic myelodysplasia or acute myeloid leukaemia has been recognized from the early days of tumour cytogenetic analysis. Detection of such abnormalities usually heralds a poor prognosis. The loss of DNA on chromosome 7 has led to speculation that tumour-suppressor genes may play a significant role in this form of leukaemogenesis, although it may be part of a multistep process. A further association with leukaemia secondary to carcinogen exposure including previous chemotherapy or a number of congenital anaemias has increased the interest in discovering the gene or genes on chromosome 7. Banded chromosome analysis has suggested that there are two broad critical regions on the long arm of chromosome 7 at bands 7q22 and 7q34-q36 that may contain the relevant genes. Initial molecular analysis has confirmed these two regions to be of significance. The advent of fluorescence in-situ hybridization techniques has facilitated some definition of the 7q22 region, with identification of candidate genes for further functional analysis. It is becoming clear that there will be more than one gene on chromosome 7 involved in the leukaemic process and with the definition of these genes it may be possible to look for associations with different phenotypes and prognosis. As for the reason for chromosome 7 showing a particular predisposition to total or partial loss we may speculate that the DNA sequence and structure may confer a 'fragility' on the chromosome. A greater understanding of the DNA structure of the long arm may provide real insight into the mechanisms of leukaemia. We would like to speculate in the long term that this could lead to the ability to screen for leukaemia susceptibility and avoidance of 'inducers' in those at risk.

Chromosome 7 and Haematological Malignancies

Abnormalities of chromosome 7 are the most common clonal chromosomal changes observed in myelodysplasia (MDS) and the second most frequent in acute myeloid leukaemia (AML) [1-5]. These changes may consist of long arm deletion (7q-) or total loss of the whole chromosome (monosomy 7) from bone marrow cells [1, 4, 6-24] and was first reported in association with myeloid disease in 1964 with the report of 3 cases of refractory anaemia, granulocytic hyperplasia [25]. The association between chromosome 7 alterations, MDS and AML in children and adults is clear, however, a rare association with lymphoid malignancies has also been recently reported. The abnormalities may occur in de novo MDS/AML, secondary cases following exposure to drugs, radiotherapy and toxins and in addition in a range of constitutional disorders including Fanconi's anaemia, congenital neutropenia and neurofibromatosis type 1 (NF1). The broad spread of conditions in which this consistent genetic change can occur leads one to speculate that there is an underlying instability in chromosome 7 and that genes on this chromosome play a role in the development of malignancy. The loss of DNA associated with malignant progression suggests the presence of a tumour suppressor gene (or genes) [26, 27]. Patients with monosomy 7 usually present as classical MDS with abnormal erythroid, megakaryocyte and myeloid differentiation [7, 28]. From a mechanistic perspective, increased cell proliferation and apoptosis is a common feature possibly induced by the failure of normal haematopoietic maturation. In all groups the presence of chromosome 7 abnormalities defines a poor prognostic group [29]. The majority of patients with MDS transform to a form of acute leukaemia resistant to therapy, including bone marrow transplantation (BMT). Although fluorescence in situ hybridization (FISH) has accelerated the study of these disorders at the cytogenetic and molecular levels, [4, 30, 31, 32, 33] no gene has been clearly implicated. A few candidate genes are under investigation. While the loss of chromsome 7 material is crutial in the malignant process it is almost certainly not the primary molecular abnormality. An initiating event genetic event predisposing to chromosome breakage and loss probably occurs in haematopoietic cells permitting chromosome 7 loss and progression to clonal malignancy as a secondary event.

An abnormal clone with monosomy 7 and trisomy 21 in the bone marrow of a child with congenital agranulocytosis (Kostmann disease) treated with granulocyte colony-stimulating factor. Evolution towards myelodysplastic syndrome and acute basophilic leukemia

Cytogenetic analysis of bone marrow cells revealed an abnormal clone with monosomy 7 and trisomy 21 in a 12-year-old child with Kostmann disease (KD). The patient presented with anemia, thrombocytopenia, and splenomegaly after 5 years of treatment with granulocyte colony-stimulating factor (G-CSF). The bone marrow morphology was consistent with the diagnosis of myelodysplastic syndrome (MDS). Administration of G-CSF was discontinued at this point. Bone marrow studies 2 and 5 months later showed persistence of both myelodysplasia and the abnormal clone with monosomy 7 and trisomy 21. Monosomy 7 was also confirmed by fluorescence in situ hybridization (FISH). After 2 months of follow-up, the patient presented with acute basophilic leukemia, a very rare variant of acute myeloid leukemia (AML), expressing the same bone marrow chromosome abnormalities as observed earlier. This is a rare case of KD with prolonged survival and a cytogenetically abnormal clone evolving to MDS and acute basophilic leukemia. The significance of monosomy 7 and trisomy 21 in KD treated with G-CSF is discussed.

Possible evidence for genomic imprinting in childhood acute myeloblastic leukaemia associated with monosomy for chromosome 7

Monosomy or deletion of chromosome 7 is a frequent finding in both de novo and secondary acute myeloid leukaemia (AML) and myelodysplastic syndromes (MDS). Based on analysis of deletions of chromosome 7 in such patients, it has been suggested that there is a critical region of the chromosome lying within bands q21-q31. We have examined bone marrow and peripheral blood samples from 10 patients with MDS, AML and biphenotypic acute leukaemia who had monosomy for or rearrangement of chromosome 7, seeking evidence of non-random allele loss that might suggest the presence of imprinted genes on the chromosome. Bone marrow cells from one patient with the infant monosomy 7 syndrome had loss of maternal alleles as did two patients with biphenotypic leukaemia. Five out of five patients with MDS and both patients with de novo AML had loss of paternal alleles. One of the latter patients had a del(7) (q31q36) rather than monosomy 7. These findings suggest that imprinting of a gene(s) on chromosome 7, within the bands q31-q36, may be of importance in MDS and AML. Despite the reported increased incidence of AML amongst relatives of patients with cystic fibrosis (CF) the gene for which lies in chromosome region 7q31, none of the patients nor parents studied here appeared to be carriers of the most common gene mutation seen in patients with CF, the delta F508.

Monosomy 7 in multilineage and acute lymphoblastic leukaemia

Monosomy 7 as the sole cytogenetic abnormality was detected in five of 310 consecutive adult patients with acute leukaemia who were characterized by morphological, immunophenotypic and cytogenetic analyses. Morphologically, blast cells were myelomonocytic (FAB M4) in three and lymphoid (FAB L2) in two patients. By immunophenotyping, two M4 patients expressed terminal transferase (TdT) in 15-90% of myelomonoblasts (patients 3 and 1, respectively), and in the third M4 patient (no. 2), a 10% TdT+ component was present distinct from the bulk of myelomonoblasts. In one L2 patient (no. 4), the blast cells had an undifferentiated phenotype only expressing TdT and HLA-DR but lacking specific lymphoid and myeloid antigens, and patient 5 was typed as CD10+ ALL. Two patients had developed leukaemia following radiotherapy and/or chemotherapy for multiple myeloma or breast cancer. In two patients, induction chemotherapy induced a lineage switch in the immunophenotype without change in karyotype. These observations support the concept that monosomy 7 leukaemia results from the transformation of a multipotential stem cell.

Myelodysplasia and leukemia syndrome with monosomy 7: a genetic perspective

Acquired monosomy 7 is a frequent finding in myelodysplastic syndromes, including acute myelogenous leukemia. A subset of these patients has been described with an apparently distinct condition: myelodysplasia and leukemia syndrome with monosomy 7 (MLSM7). We report 2 brothers, 3 and 5 years of age, with MLSM7 and review other reports of familial occurrence. Genetic factors appear to be important in the cause of MLSM7, but the reported families do not fit neatly into any monogenic pattern. Recognition of the frequently familial nature of this condition requires hematological evaluation and genetic counseling for the families of patients with MLSM7.

Childhood monosomy 7 revisited

Monosomy 7 is found in acute myeloid leukaemia (AML) and myelodysplasia and is characteristic of a rare chronic myeloproliferative disease (MPD) of young children. We have seen 16 children with monosomy 7. Their clinical features and response to treatment are discussed. Monosomy 7 diseases appear to have a particularly poor prognosis. The AML is often resistant to treatment and relapse is common. Children with chronic MPD die of bone marrow failure or evolve to AML or myelofibrosis. We have treated these children intensively with combination chemotherapy and allogeneic bone marrow transplantation. Four children with MPD received supportive care and low dose chemotherapy alone. They all died, surviving between 4 months and 4 years. Six children with MPD received intensive chemotherapy: three remitted, one relapsing after 9 months, the others remaining in remission at 18 months and 3 years. One child with MPD has undergone successful BMT and survives 7 1/2 years after presentation. Remission was achieved in three of four cases of AML. They all relapsed within 9 months. Bone marrow transplantation was successful in one child with myelofibrosis. Intensive chemotherapy and early bone marrow transplantation is likely to offer these children their best chance of survival.

Disturbed patterns of globin chain synthesis in childhood monosomy 7 myeloproliferative syndrome

Two children with typical clinical and haematological features of monosomy 7 myeloproliferative syndrome are presented. Both children displayed decreased production of beta-globin chains and unbalanced high alpha/non-alpha synthetic ratios similar to those characteristic of homozygous beta-thalassaemia. These provide further evidence for the involvement of the erythroid line as part of the malignant clone, indicating neoplastic transformation of a pluripotential stem cell in this disease.

Multilineage cell involvement in Ph1-negative, bcr-negative chronic myeloid leukemia

We report a case of Ph1-negative, bcr-negative CML-BC, in which the primary leukemic cells displayed T-related antigens (CD7, CD4) in addition to HLA-DR and CD25 determinants. No B-lymphoid, myeloid and megakaryoblastic surface antigens were detected. In spite of this phenotype, DNA analysis revealed a germ-line configuration of the T-cell receptor beta chain gene region. Moreover, in-vitro culture studies demonstrated a proliferative response of the blast cell population to natural and recombinant myeloid-related factors, while no proliferative signal was observed in the presence of IL-2. The myeloid lineage was further demonstrated by the expression of myeloid-associated antigens on cultured blast cells, which still retained the CD7 antigen. Finally, cytogenetic analysis revealed a monosomy 7 which is usually associated with a stem cell leukemia. These results support the hypothesis that Ph1-negative, bcr-negative CML is characterized by the involvement of a multipotent stem cell capable of multilineage expression and indicate that differentiative and proliferative assays provide a further tool towards a more precise recognition of hematological disorders of uncertain origin.

Hybrid biphenotypic acute leukemia with extreme hypodiploidy

A patient diagnosed as having acute lymphoblastic leukemia (L2) relapsed 4 months later and was found to have morphologic and immunologic evidence of a biphenotypic hybrid acute leukemia. Chromosome analysis at relapse showed two abnormal clones, one with marked hypodiploidy and the other with exactly double the hypodiploid clone. It is considered that this is an example of a hybrid lymphoblastic/nonlymphoblastic leukemia with unique karyotype.

Familial myelodysplasia: progressive disease associated with emergency of monosomy 7

Two brothers developed hypoplastic anaemia with the development in one of refractory anaemia with excess blasts (RAEB) accompanied by emergence of monosomy 7. Both brothers have a constitutional inversion of chromosome 1. Neither shows the increased chromosomal fragility of Fanconi's anaemia or its variants. This family is the third reported in which monosomy 7 has been found when leukaemic or preleukaemic transformation has occurred in patients with familial hypoplastic anaemia.

Monosomy 7 and Ph-positive acute lymphoblastic leukaemia: cytogenetic and molecular aspects

A combination of monosomy 7 and translocation t(9;22) (q34;q11), rarely observed in acute lymphoblastic leukaemia (ALL), is here reported: a peculiarity of this case was that the "breakpoint cluster region" on chromosome 22 was not rearranged, as demonstrated by molecular analysis, and a new c-abl protein (p190) was found, instead of the usual p210 protein usually associated with the Ph chromosome; moreover a rearrangement of c-abl oncogene was found. The clinical course of this patient was, as expected, unfavorable: a few normal metaphases were observed during a short partial remission.

Juvenile monosomy 7 syndrome: evidence that the disease originates in a pluripotent hemopoietic stem cell

The present study was undertaken to investigate the hemopoietic cell from which malignant change evolves in juvenile dyshemopoiesis with monosomy 7. Two male patients, aged 18 and 5 months, were studied using progenitor assays combined with cytogenetics. Both had hepatosplenomegaly, cytopenias and a cellular marrow. The karyotype in direct marrow was 45,XY-7/47,XY,+8/46,XY in patient 1 and 45,XY,-7/46,XY in patient 2. Patient 1 received chemotherapy but developed acute nonlymphocytic leukemia after 17 months and died 20 months after diagnosis. During this time marrow metaphases with 45,XY,-7 increased to 100% (25/25). Patient 2 received an allogeneic marrow transplant 4 months after diagnosis which did not engraft. In both patients progenitors of both small (CFU-E) and large (BFU-E) erythroid colonies were present at normal frequencies. However, the colonies produced were small and poorly hemoglobinized with some erythropoietin-independent maturation. Progenitors of large granulocyte/macrophage colonies (CFU-GM) were present at an elevated frequency in the marrow of patient 1 and in the blood all progenitor classes were markedly increased. Cytogenetic analysis of colonies from this patient showed BFU-E to be 45,XY,-7 or 47,XY,+8 and CFU-GM to be 45,XY,-7 or 47,XY,+8 or 46,XY. In patient 2, most BFU-E were 45,XY,-7, although a few were 46,XY. These data indicate that malignant change in this disease involves hemopoietic stem cells capable of erythroid and in at least some cases, myeloid differentiation.